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| 2. |
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| 3. |
- Nicholls, Ian A., et al.
(författare)
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Rational design of biomimetic molecularly imprinted materials : theoretical and computational strategies for guiding nanoscale structured polymer development
- 2011
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 400:6, s. 1771-1786
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Forskningsöversikt (refereegranskat)abstract
- In principle, molecularly imprinted polymer science and technology provides a means for ready access to nano-structured polymeric materials of predetermined selectivity. The versatility of the technique has brought it to the attention of many working with the development of nanomaterials with biological or biomimetic properties for use as therapeutics or in medical devices. Nonetheless, the further evolution of the field necessitates the development of robust predictive tools capable of handling the complexity of molecular imprinting systems. The rapid growth in computer power and software over the past decade has opened new possibilities for simulating aspects of the complex molecular imprinting process. We present here a survey of the current status of the use of in silico-based approaches to aspects of molecular imprinting. Finally, we highlight areas where ongoing and future efforts should yield information critical to our understanding of the underlying mechanisms sufficient to permit the rational design of molecularly imprinted polymers.
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| 4. |
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| 5. |
- Wiklander, Jesper G., 1974-, et al.
(författare)
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Towards a synthetic avidin mimic
- 2011
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 400:5, s. 1397-1404
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Tidskriftsartikel (refereegranskat)abstract
- A series of streptavidin-mimicking molecularly imprinted polymers has been developed and evaluated for their biotin binding characteristics. A combination of molecular dynamics and NMR spectroscopy was used to examine potential polymer systems, in particular with the functional monomers methacrylic acid and 2-acrylamidopyridine. The synthesis of copolymers of ethylene dimethacrylate and one or both of these functional monomers was performed. A combination of radioligand binding studies and surface area analyses demonstrated the presence of selectivity in polymers prepared using methacrylic acid as the functional monomer. This was predicted by the molecular dynamics studies showing the power of this methodology as a prognostic tool for predicting the behavior of molecularly imprinted polymers.
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| 6. |
- Nyström-Larsson, Ingalill, 1969, et al.
(författare)
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Materialanalys av sydsvenskt bonadsmåleri
- 2007
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Ingår i: Rapport: Sammanfattning av Riksantikvarieämbetets seminarieserie 2007 kring pågående FoU-projekt. ; , s. 23-24
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Bonadsmåleriet hade sin storhetstid 1750-1850, och var influerat av medeltida kalkmåleri och bildvävnad i kyrkorna. Bonaderna var temporära och prydde stugorna till fest. Motiven kan vara både bibliska och profana. Materialet är tyger (återanvända och hopfogade) och senare även papper. Mot slutet av perioden övergår hantverket i massproduktion. Tidigare har bonaderna framför allt studerats inom humaniora (exempelvis etnologi) och ett naturvetenskapligt perspektiv har saknats. Därför finns mycket knapphändiga uppgifter om materialet. Syftet med projektet är att: • Kartlägga materialanvändningen • Tolka och förstå materialutvecklingen • Klarlägga innehållet i de otydliga trivialnamnen • Bygga upp ett referensmaterial Genomförande Ett antal frågeställningar har satts upp inför studiet: • Vilka materialval har man gjort? • Skiljer måleriteknik, färg, materialval mellan bonader, och går det att urskilja geografiska skillnader eller är det en tidsmässig utveckling? • Kan bonader attribueras utifrån materialval och färgval? • Vad är det för pigment som döljs i trivialnamnen? Skriftliga källor räcker inte för att svara på dessa frågor utan måste komplet-teras med naturvetenskapliga analyser. Diskussion kring RÄA-seminariets specifika frågeställningar På vad sätt bidrar ert projekt till kunskapsuppbyggnaden inom ert område? • Projektet är också ett pilotprojekt och den kunskap som vinns kan också appliceras på annat än bonadsmåleri. Utifrån resultaten kan man också gå vidare och titta på handelsvägar, infrastruktur etc. • En referensdatabas byggs upp och kan kanske också användas för an-nat material. På vilket sätt skulle resultaten från ert projekt kunna tillämpas mer konkret inom kulturmiljösektorn? • Ett viktigt mål är att hitta analysmetoder som inte förstör materialet, och som helst kan göras på plats så att materialet inte behöver flyttas (Raman spektroskopi). • Som konstaterades ovan kan resultaten från den kemiska analysen visa att en sådan kan komplettera traditionella historiska metoder också inom andra områden än bonadsmåleri. Frågor och öppen diskussion • Ännu har man inte hittat några speciella pigment eller färger, men analysen är inte klar. • Analysmaterialet som valts ut är signerade bonader. • Eftersom uppbyggandet av referensdatabaser är centralt i konserva-torns arbete är det viktigt att sprida resultaten av projektet.
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| 7. |
- Höglund, Odd, et al.
(författare)
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A new resorbable device for ligation of blood vessels - A pilot study
- 2011
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Ingår i: Acta Veterinaria Scandinavica. - : Springer Science and Business Media LLC. - 0044-605X .- 1751-0147. ; 53, s. 47-
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Tidskriftsartikel (refereegranskat)abstract
- Background: During surgery, controlled haemostasis to prevent blood loss is vital for a successful outcome. It can be difficult to ligate vessels located deep in the abdomen. A device that is easy to use and enables secure ligatures could be beneficial. Cable ties made of nylon have been used for ligation but the non-resorbable material caused tissue reactions. The objective of this study was to use a resorbable material to construct a device with a self-locking mechanism and to test its mechanical strength and ligation efficiency. Methods: The device was manufactured by injection moulding of polydioxanone, a resorbable polymer used for suture materials. Polydioxanone with inherent viscosities of 1.9 dL/g and 1.3 dL/g were tested. The device consisted of a perforated flexible band which could be pulled through a case with a locking mechanism. After a first version of the device had been tested, some improvements were made. The locking case was downsized, corners were rounded off, the band was made thicker and the mould was redesigned to produce longer devices. Tensile tests were performed with the second version. The first version of the device was used to ligate the ovarian pedicle in a euthanized dog and to test echogenicity of the device with ultrasound. Compression of vessels of the ovarian pedicle was examined by histology. Both versions of the device were tested for haemostasis of and tissue grip on renal arteries in six anaesthetised pigs. Results: The tensile strength of the flexible band of the devices with inherent viscosity of 1.9 dL/g was 50.1 +/- 5.5 N (range 35.2-62.9 N, n = 11) and the devices with inherent viscosity of 1.3 dL/g had a tensile strength of 39.8 +/- 8.1 N (range 18.6-54.2 N, n = 11). Injection moulding of the polymer with lower inherent viscosity resulted in a longer flow distance. Both versions of the device had an effective tissue grip and complete haemostasis of renal arteries was verified. The device attached to the ovarian pedicle could be seen with ultrasound, and vessel compression and occlusion were verified by histology. Conclusions: Tests of functionality of the device showed complete haemostasis and good tissue grip. Devices with a band of sufficient length were easily applied and tightened in tissue.
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| 8. |
- Martinez-Sanz, Elena, et al.
(författare)
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Bone reservoir : Injectable hyaluronic acid hydrogel for minimal invasive bone augmentation
- 2011
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Ingår i: Journal of Controlled Release. - : Elsevier BV. - 0168-3659 .- 1873-4995. ; 152:2, s. 232-240
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Tidskriftsartikel (refereegranskat)abstract
- A strategy has been designed to develop hyaluronic acid (HA) hydrogel for in vivo bone augmentation using minimal invasive technique. A mild synthetic procedure was developed to prepare aldehyde modified HA by incorporating an amino-glycerol side chain via amidation reaction and selective oxidation of the pendent group. This modification, upon mixing with hydrazide modified HA formed hydrazone-crosslinked hydrogel within 30 s that was stable at physiological pH. In vitro experiments showed no cytotoxicity of hydrogel with the controlled release of active bone morphogenic protein-2 (BMP-2). In vivo evaluation of this gel as a BMP-2 carrier was performed by injecting gels over the rat calvarium and showed bone formation in 8 weeks in correlation with the amount of BMP-2 loaded (0, 1 and 30 pig) within the gel. Furthermore, hydrogels with 30 Kg of BMP-2 induced less bone formation upon subcutaneous injection in comparison with subperiosteal implantation. Histological examination showed newly formed bone with a high expression of osteocalcin, osteopontin and with angiogenic bone marrow when higher BMP-2 concentration was employed. Our result suggests that novel HA hydrogels could be used as a BMP-2 carrier and can promote bone augmentation for potential orthopedic applications.
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| 9. |
- Yang, Xia, et al.
(författare)
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beta-Cyclodextrin grafted polyethyleneimine hydrogel immobilizing hydrophobically modified glucose oxidase
- 2011
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 48:4, s. 661-666
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogels which release their contents in response to glucose concentration were prepared by immobilizing glucose oxidase (GOD) into beta-cyclodextrin grafted polyethyleneimine hydrogels (PEI-beta CD hydrogel). For the tight immobilization, hydrophobically modified GOD (HmGOD) was prepared by reacting GOD with palmitic acid-N-hydroxysuccinimide ester (PA-NHS) in the molar ratio of 1:40. According to trinitrobenzene sulfonic acid (TNBS) assay, five palmitic acids were covalently attached to one GOD molecule. The activity of HmGOD was about 76% of native enzyme. The swelling ratios of HmGOD loaded hydrogels increased from about 960% to 1190% in 24 h, when glucose concentration was varied from 0 to 100 mg/dl. The % release in 48 h of fluorescein isothiocyanate dextran increased from about 53% to 89%, when glucose concentration was varied in the same range. Gluconic acid, produced by the enzymatic reaction, would protonate and swell the PEI-beta CD hydrogel, leading to a higher release.
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| 10. |
- Yang, Xia, et al.
(författare)
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Effect of Hydrophobic Comonomer Content on Assembling of Poly (N-isopropylacrylamide) and Thermal Properties
- 2011
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 120:4, s. 2346-2353
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Tidskriftsartikel (refereegranskat)abstract
- Copolymers of N-isopropylacrylamide and octadecyl acrylate (PNO), of which the content of octadecyl acrylate (ODA) was 1.3% (PNO 1.5), 1.7% (PNO 2.0), and 3.0% (PNO 4.0), were prepared using a free radical reaction. Various assemblies were obtained depending on the concentration of PNOs and the contents of ODA. Hydrophobic interaction between ODA residues is likely to act as crosslinker. PNO 1.5 formed hydrogel at the concentration of 7%. With PNO 2.0, hydrogels were formed when the concentration was 5 and 7%. With PNO 4.0, the opaque gel was obtained when the concentration was 7%. Upon heating across the lower critical solution temperature, the hydrogels shrank but the opaque gel was broken down into a suspension. At 40 degrees C, the release degrees of fluorescein isothiocyanate-dextran were much smaller than those of release at 23 degrees C. The temperature-sensitive release is due to temperature-sensitive swelling ratio.
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| 11. |
- Tan, Semra, et al.
(författare)
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Poly(ether amine) and cross-linked poly(propylene oxide) diacrylate thin-film polymer electrolyte for 3D-microbatteries
- 2010
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Ingår i: Electrochemistry communications. - : Elsevier BV. - 1388-2481 .- 1873-1902. ; 12:11, s. 1498-1500
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a novel thin-film electrolyte of a 2:1 blend of polyetheramine (glyceryl poly(oxypropylene)) and cross-linked oligomeric poly(propylene oxide) diacrylate with LiTFSI. The polyetheramine acts as a surfactant, and can thereby be applied as a conformal coating on complex surfaces-here demonstrated for porous LiFePO4 cathodes-making it useful for 3D-microbatteries. The poly(propylene oxide) diacrylate blends with the surfactant and is easily UV cross-linked, thereby ensuring good mechanical stability. Electrolytes, ∼ 2 μm thick, were casted onto LiFePO 4 cathodes and cycled against metallic lithium, displaying stable discharge capacities of ∼ 8 mAh/g at room temperature and ∼ 120 mAh/g at 60 °C. The electrolyte showed conductivities of 3.45 × 10 - 6 and 5.80 × 10- 5 S cm- 1 at room temperature and 60 °C, respectively.
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| 12. |
- Bergenstråhle, Malin, 1977-, et al.
(författare)
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Dynamics of Cellulose-Water Interfaces : NMR Spin-Lattice Relaxation Times Calculated from Atomistic Computer Simulations
- 2008
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Ingår i: Journal of Physical Chemistry B. - Washington : ACS Publications. - 1520-6106 .- 1520-5207. ; 112:9, s. 2590-2595
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Tidskriftsartikel (refereegranskat)abstract
- Solid-state nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy has often been used to study cellulose structure, but some features of the cellulose NMR spectrum are not yet fully understood. One such feature is a doublet around 84 ppm, a signal that has been proposed to originate from C4 atoms at cellulose fibril surfaces. The two peaks yield different T1, differing by approximately a factor of 2 at 75 MHz. In this study, we calculate T1 from C4-H4 vector dynamics obtained from molecular dynamics computer simulations of cellulose Iβ-water interfacial systems. Calculated and experimentally obtained T1 values for C4 atoms in surface chains fell within the same order of magnitude, 3-20 s. This means that the applied force field reproduces relevant surface dynamics for the cellulose-water interface sufficiently well. Furthermore, a difference in T1 of about a factor of 2 in the range of Larmor frequencies 25-150 MHz was found for C4 atoms in chains located on top of two different crystallographic planes, namely, (110) and (10). A previously proposed explanation that the C4 peak doublet could derive from surfaces parallel to different crystallographic planes is herewith strengthened by computationally obtained evidence. Another suggested basis for this difference is that the doublet originates from C4 atoms located in surface anhydro-glucose units with hydroxymethyl groups pointing either inward or outward. This was also tested within this study but was found to yield no difference in calculated T1.
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| 13. |
- Byström, Emil, 1980-
(författare)
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Porous polymeric materials for chromatography : Synthesis, functionalization and characterization
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Separation science is heavily reliant on materials to fulfill ever more complicated demands raised by other areas of science, notably the rapidly expanding molecular biosciences and environmental monitoring. The key to successful separations lies in a combination of physical properties and surface chemistry of stationary phases used in liquid chromatographic separation, and this thesis address both aspects of novel separation materials.Methods: The thesis accounts for several approaches taken during the course of my graduate studies, and the main approaches have been i) to test a wild-grown variety of published methods for surface treatment of fused silica capillaries, to ascertain firm attachment of polymeric monoliths to the wall of microcolumns prepared in silica conduits; ii) developing a novel porogen scheme for organic monoliths including polymeric porogens and macromonomers; iii) evaluating a mesoporous styrenic monolith for characterization of telomers intended for use in surface modification schemes and; iv) to critically assess the validity of a common shortcut used for estimating the porosity of monoliths prepared in microconduits; and finally v) employing plasma chemistry for activating and subsequently modifying the surface of rigid, monodisperse particles prepared from divinylbenzene.Results: The efforts accounted for above have resulted in i) better knowledge of the etching and functionalization parameters that determine attachment of organic monoliths prepared by radical polymerization to the surface of silica; ii) polar methacrylic monoliths with a designed macroporosity that approaches the desired "connected rod" macropore morphology; iii) estab¬lishing the usefulness of monoliths prepared via nitroxide mediated polymerization in gradient polymer elution chromatography; iv) proving that scanning electron microscopy images are of limited value for assessing the macroporous properties of organic monoliths, and that pore measurements on externally polymerized monolith cocktails do not represent the porous properties of the same cocktail polymerized in narrow confinements; and v) showing that plasma bromination can be used as an activation step for rigid divinylbenzene particles to act as grafting handles for epoxy-containing telomers, that can be attached in a sufficiently dense layer and converted into carboxylate cation exchange layer that allows protein separations in fully aqueous eluents.
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| 14. |
- Nordborg, Anna, 1977-, et al.
(författare)
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Gradient polymer elution chromatography of methacrylate Telomers on monolithic capillary columns prepared by nitroxide-mediated polymerization
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Linear methacrylate telomers prepared by isopropylxanthic disulfide photoiniferted polymerization of 2-hydroxyethyl methacrylate, methyl methacrylate, and ethyl methacrylate have been separated from their precursor monomers using gradient polymer elution chromatography (GPEC) on a monolithic capillary column. The capillary monoliths were prepared by thermally initiated radical polymerization of styrene and divinylbenzene controlled by 1-carboxy-PROXYL stable free radicals, and characterized by nitrogen adsorption and mercury intrusion porosimetry. The separations in GPEC mode were performed using a mobile phase gradient from water to methanol, where water is the non-solvent and methanol the good solvent with respect to the telomers. Successful separation of telomers from their monomer was achieved for all tested telomers. In addition, it was observed that the retention times of the intact telomers were different from those of telechelic oligomers produced by hydrolysing the isopropylxanthic terminals. The current set-up is therefore promising both for monitoring of the progress of photoiniferted polymerizations and to monitor the hydrolysis of resulting polymerized oligomers into thiol-terminated telechelics.
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| 15. |
- Börjesson, Karl, 1982, et al.
(författare)
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Conjugated anthracene dendrimers with monomer-like fluorescence
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:38, s. 19846-19850
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Tidskriftsartikel (refereegranskat)abstract
- Two generations of highly emissive conjugated anthracene dendrimers containing up to 9 anthracene units are presented. In these dendrimers, anthracene-like absorption and emission properties are preserved due to the relatively weak electronic coupling between the anthracene units, while evidence of fast crosstalk within the molecular framework is still observed.
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| 16. |
- Howe, Andrew, 1995-
(författare)
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Immobilisation of Ru-Based Molecular Catalysts for Electrochemical Water Oxidation
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Artificial photosynthesis requires catalysts for efficient and selective conversions of small molecules. Molecular catalysts are advantageous to use in these instances as they offer precise control over chemical reactivity. They are synthetically tuneable, and their catalytic mechanisms are often well documented and more readily understood than those of solid-state catalysts. In this thesis, the synthetic incorporation of molecular catalysts into heterogenised molecular anodes for water oxidation are evaluated. The catalysts are incorporated as structural linkers into porous metal-organic framework (MOF) structures, and as coordination oligomers stacked onto graphitic surfaces. The preparation of MOF/molecular catalyst hybrid materials of two topologies, UiO (UiO = Universitet i Oslo) and NU-1000 (NU = Northwestern University), were investigated. Multiple synthetic methods for the incorporation of molecular ruthenium-based catalysts into MOFs were examined in papers I and II. In paper III of this thesis, a Ru-bda type molecular complex was successfully used in the solvothermal synthesis of a new MOF. The resulting material is the first of its kind that is built exclusively from molecular water oxidation catalyst linkers. It is shown that MOF incorporation greatly enhances the structural stability of the catalyst linker in chemical water oxidation experiments, giving rise to higher turnover numbers compared to that of a homogenous reference system. Finally, paper IV describes a stable and inert molecular ruthenium complex, which possesses a flexible adaptative multidentate equatorial (FAME) type equatorial ligand with a carbanion on the equatorial ligand that forms a C-Ru bond. This molecular complex is studied in homogeneous phase, and subsequently incorporated into a coordination oligomer, which can be activated for water oxidation catalysis. This finding broadens the field of molecular catalysis significantly, and proves that supramolecular interactions can be used to promote electrocatalysis in complexes which are otherwise too inert and stable to engage in electrocatalytic reactions.
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| 17. |
- Heydari, Golrokh, 1982-, et al.
(författare)
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Temperature-Dependent Deicing Properties of ElectrostaticallyAnchored Branched Brush Layers of Poly(ethylene oxide)
- 2016
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32:17, s. 4194-4202
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Tidskriftsartikel (refereegranskat)abstract
- The hydration water of hydrophilic polymersfreezes at subzero temperatures. The adsorption of suchpolymers will result in a hydrophilic surface layer that stronglybinds water. Provided this interfacial hydration water remainsliquidlike at subzero temperatures, its presence could possiblyreduce ice adhesion, in particular, if the liquidlike layer isthicker than or comparable to the surface roughness. Toexplore this idea, a diblock copolymer, having one branchedbottle-brush block of poly(ethylene oxide) and one linear cationic block, was electrostatically anchored on flat silica surfaces. Theshear ice adhesion strength on such polymer-coated surfaces was investigated down to −25 °C using a homebuilt device. Inaddition, the temperature dependence of the ice adhesion on surfaces coated with only the cationic block, only the branchedbottle-brush block, and with linear poly(ethylene oxide) was investigated. Significant ice adhesion reduction, in particular, attemperatures above −15 °C, was observed on silica surfaces coated with the electrostatically anchored diblock copolymer.Differential scanning calorimetry measurements on bulk polymer solutions demonstrate different thermal transitions of waterinteracting with branched and linear poly(ethylene oxide) (with hydration water melting points of about −18 and −10 °C,respectively). This difference is consistent with the low shear ice adhesion strength measured on surfaces carrying branchedbottle-brush structured poly(ethylene oxide) at −10 °C, whereas no significant adhesion reduction was obtained with linearpoly(ethylene oxide) at this temperature. We propose a lubrication effect of the hydration water bound to the branched bottlebrushstructured poly(ethylene oxide), which, in the bulk, does not freeze until −18 °C.
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| 18. |
- Dunér, Gunnar, et al.
(författare)
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Surface-confined photopolymerization of pH-responsive acrylamide/acrylate brushes on polymer thin films
- 2008
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:14, s. 7559-7564
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic acrylamide/acrylate polymeric brushes were synthesized at gold-plated quartz crystal surfaces. The crystals were initially coated with polystyrene-type thin films, derivatized with photolabile iniferter groups, and subsequently subjected to photoinitiated polymerization in acrylamide/acrylate monomer feeds. This surface-confined polymerization method enabled direct photocontrol over the polymerization, as followed by increased frequency responses of the crystal oscillations in a quartz crystal microbalance (QCM). The produced polymer layers were also found to be highly sensitive to external acid/base stimuli. Large oscillation frequency shifts were detected when the brushes were exposed to buffer solutions of different pH. The dynamic behavior of the resulting polymeric brushes was evaluated, and the extent of expansion and contraction of the films was monitored by the QCM setup in situ in real time. The resulting responses were rapid, and the effects were fully reversible. Low pH resulted in full contractions of the films, whereas higher pH yielded maximal expansion in order to minimize repulsion around the charged acrylate centers. The surfaces also proved to be very robust because the responsiveness was reproducible over many cycles of repeated expansion and contraction. Using ellipsometry, copolymer layers were estimated to be similar to 220 nm in a collapsed state and similar to 340 nm in the expanded state, effectively increasing the thickness of the film by 55%.
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| 19. |
- Liu, Yanfeng, et al.
(författare)
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In Situ Optical Spectroscopy Demonstrates the Effect of Solvent Additive in the Formation of All-Polymer Solar Cells
- 2022
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 13:50, s. 11696-11702
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Tidskriftsartikel (refereegranskat)abstract
- 1-Chloronaphthalene (CN) has been a common solvent additive in both fullerene- A nd nonfullerene-based organic solar cells. In spite of this, its working mechanism is seldom investigated, in particular, during the drying process of bulk heterojunctions composed of a donor:acceptor mixture. In this work, the role of CN in all-polymer solar cells is investigated by in situ spectroscopies and ex situ characterization of blade-coated PBDB-T:PF5-Y5 blends. Our results suggest that the added CN promotes self-aggregation of polymer donor PBDB-T during the drying process of the blend film, resulting in enhanced crystallinity and hole mobility, which contribute to the increased fill factor and improved performance of PBDB-T:PF5-Y5 solar cells. Besides, the nonradiative energy loss of the corresponding device is also reduced by the addition of CN, corresponding to a slightly increased open-circuit voltage. Overall, our observations deepen our understanding of the drying dynamics, which may guide further development of all-polymer solar cells.
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| 20. |
- An, N., et al.
(författare)
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Mechanistic insight into self-propagation in organo-mediated Beckmann rearrangement: A combined experimental and computational study.
- 2013
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Ingår i: Journal of Organic Chemistry. - 0022-3263 .- 1520-6904. ; 78:9, s. 4297-4302
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Tidskriftsartikel (refereegranskat)abstract
- Organo-mediated Beckmann rearrangement in the liquid phase, which has the advantage of high efficiency and straightforward experimental procedures, plays an important role in the synthesis of amides from oximes. However, the catalytic mechanisms of these organic-based promoters are still not well understood. In this work, we report a combined experimental and computational study on the mechanism of Beckmann rearrangement mediated by organic-based promoters, using TsCl as an example. A novel self-propagating cycle is proposed, and key intermediates of this self-propagating cycle are confirmed by both experiments and DFT calculations. In addition, the reason why cyclohexanone oxime is not a good substrate of the organo-mediated Beckmann rearrangement is discussed, and a strategy for improving the yield is proposed.
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| 21. |
- Engelhardt, Eva-Maria, et al.
(författare)
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A collagen-poly(lactic acid-co-epsilon-caprolactone) hybrid scaffold for bladder tissue regeneration
- 2011
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 32:16, s. 3969-3976
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Tidskriftsartikel (refereegranskat)abstract
- Scaffold materials should favor cell attachment and proliferation, and provide designable 3D structures with appropriate mechanical strength. Collagen matrices have proven to be beneficial scaffolds for tissue regeneration. However, apart from small intestinal submucosa, they offer a limited mechanical strength even if crosslinking can enhance their mechanical properties. A more cell-friendly way to increase material strength is to combine synthetic polymer meshes with plastic compressed collagen gels. This work describes the potential of plastic compressed collagen poly(lactic acid-co-epsilon-caprolactone) (PLAC) hybrids as scaffolds for bladder tissue regeneration. Human bladder smooth muscle and urothelial cells were cultured on and inside collagen PLAC hybrids in vitro. Scaffolds were analyzed by electron microscopy, histology, immunohistochemistry, and AlamarBlue assay. Both cell types proliferated in and on the hybrid, forming dense cell layers on top after two weeks. Furthermore, hybrids were implanted subcutaneously in the backs of nude mice. Host cell infiltration, scaffold degradation, and the presence of the seeded bladder cells were analyzed. Hybrids showed a lower inflammatory reaction in vivo than PLAC meshes alone, and first signs of polymer degradation were visible at six months. Collagen PLAC hybrids have potential for bladder tissue regeneration, as they show efficient cell seeding, proliferation, and good mechanical properties.
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| 22. |
- Londero, Elisa, 1982, et al.
(författare)
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Desorption of n-alkanes from graphene: a van der Waals density functional study
- 2012
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Ingår i: Journal of Physics Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 24:42, s. 424212-
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Tidskriftsartikel (refereegranskat)abstract
- A recent study of temperature-programmed desorption (TPD) measurements of small linear alkane molecules (n-alkanes, with formula CNH2N+2) from C(0001) deposited on Pt(111) shows a linear relationship of the desorption energy with increasing n-alkane chain length N. We here present a van der Waals density functional study of the desorption barrier energy of the ten smallest n-alkanes (of carbon chain length N = 1–10) from graphene. We find linear scaling with N, including a non-zero intercept with the energy axis, i.e. an offset at the extrapolation to N = 0. This calculated offset is quantitatively similar to the results of the TPD measurements. From further calculations of the polyethylene polymer we offer a suggestion for the origin of the offset.
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| 23. |
- Nilsson, Robin, 1993
(författare)
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Interactions Between Water and Cellulose Esters
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biopolymers, which are produced from natural sources, are gaining interest as a potential replacement for fossil-based polymers. As such, they are already widely used in several industries, including the food, healthcare, and personal care industries. To harness the full potential of biopolymers as materials in new products designed for specific tasks, an ability to accurately predict their properties and how these properties change in different environments, is desirable. Hansen Solubility Parameters (HSP) combine dispersive, polar, and hydrogen bonding energies to understand interactions between molecules. This thesis explores the potential use of HSP as predictors of glass transition temperatures (Tg) and water interactions. It also focuses on elucidating the effect of an increased side-chain length of cellulose esters on their thermal properties, structural properties, and water interactions, together with how these properties are affected by the absorption of water. The cellulose esters studied here were cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. The HSP showed that the dispersive energy dominates the total cohesive energy, followed by the hydrogen bonding and then the polar energy. Counter-intuitively, the Tg decreased with an increased total cohesive energy. The HSP explained this phenomenon, namely, that the increased length of the substituents screened the short-range hydrogen bonds. A similar effect was observed for water solubility and penetration into the cellulose esters, which decreased with increasing side-chain lengths despite the approximately constant hydrogen bonding energies. This indicates the importance of focusing on each of the different interaction parameters instead of only the total HSP.
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| 24. |
- Palma, Carlos-Andres, et al.
(författare)
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Photo-induced C-C reactions on insulators towards photolithography of graphene nanoarchitectures
- 2014
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 136, s. 4651-4658
-
Tidskriftsartikel (refereegranskat)abstract
- On-surface chemistry for atomically precise sp2 macromolecules requires top-down lithographic methods on insulating surfaces in order to pattern the long-range complex architectures needed by the semiconductor industry. Here, we fabricate sp2-carbon nm-thin films on insulators and under ultra-high vacuum (UHV) conditions from photo-coupled brominated precursors. We reveal that covalent coupling is initiated by C-Br bond cleavage through photon energies exceeding 4.4 eV, as monitored by laser desorption ionization (LDI) mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) gives insight into the mechanisms of C-Br scission and C-C coupling processes. Further, unreacted material can be sublimed and the coupled sp2-carbon precursors can be graphitized by e-beam treatment at 500°C, demonstrating promising applications in photolithography of graphene nanoarchitectures. Our results present UV-induced reactions on insulators for the formation of all sp2-carbon architectures, thereby converging top-down lithography and bottom-up on-surface chemistry into technology.
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| 25. |
- Yang, Xia, et al.
(författare)
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Preparation of hyaluronic acid nanoparticles via hydrophobic association assisted chemical cross-linking : an orthogonal modular approach
- 2011
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 7:16, s. 7517-7525
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to develop an efficient and stable drug delivery nanocarrier based on a dually functionalized hyaluronic acid (HA) derivative which could be used as a long circulating drug delivery vehicle. Self-assembled HA nanoparticles (HA NPs) were prepared by attaching pyrene to the HA backbone and the obtained physical NPs were stabilized by chemical cross-linking of the HA chains to form hydrophobic core-hydrophilic shell NPs. Orthogonal chemoselective reactions were applied for conversion of HA into its amphiphilic derivative and subsequent cross-linking of the formed micellar-type associates. Chemical stabilization of the physical HA associates afforded therefore very stable nanoparticles that could easily be re-suspended in aqueous media after freeze-drying. In contrast, freeze-drying of the uncross-linked physically associated particles resulted in a non-soluble material. Doxorubicin (DOX), a typical anticancer drug, was entrapped into HA NPs via ionic and/or hydrophobic interactions and used for in vitro drug release. Higher loading efficiency and the slower release profile of DOX from HA NPs were obtained with the hydrophobically encapsulated drug. We have shown that free HA NPs were readily taken up by NIH 3T3 cells without causing any toxicity to the cells, while the DOX-loaded HA NPs resulted in increased cell death comparable to the free drug. This study clearly showed the applicability of orthogonal chemoselective modifications for the synthesis of stable HA nanogel particles as a potential cancer-targeted drug delivery system.
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| 26. |
- Asfaw, Habtom Desta
(författare)
-
Multifunctional Carbon Foams by Emulsion Templating : Synthesis, Microstructure, and 3D Li-ion Microbatteries
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbon foams are among the existing electrode designs proposed for use in 3D Li-ion microbatteries. For such electrodes to find applications in practical microbatteries, however, their void sizes, specific surface areas and pore volumes need be optimized. This thesis concerns the synthesis of highly porous carbon foams and their multifunctional applications in 3D microbatteries. The carbon foams are derived from polymers that are obtained by polymerizing high internal phase water-in-oil emulsions (HIPEs).In general, the carbonization of the sulfonated polymers yielded hierarchically porous structures with void sizes ranging from 2 to 35 µm and a BET specific surface area as high as 630 m2 g-1. Thermogravimetric and spectroscopic evidence indicated that the sulfonic acid groups, introduced during sulfonation, transformed above 250 oC to thioether (-C-S-) crosslinks which were responsible for the thermal stability and charring tendency of the polymer precursors. Depending on the preparation of the HIPEs, the specific surface areas and void-size distributions were observed to vary considerably. In addition, the pyrolysis temperature could also affect the microstructures, the degree of graphitization, and the surface chemistry of the carbon foams.Various potential applications were explored for the bespoke carbon foams. First, their use as freestanding active materials in 3D microbatteries was studied. The carbon foams obtained at 700 to 1500 oC suffered from significant irreversible capacity loss during the initial discharge. In an effort to alleviate this drawback, the pyrolysis temperature was raised to 2200 oC. The resulting carbon foams were observed to deliver high, stable areal capacities over several cycles. Secondly, the possibility of using these structures as 3D current collectors for various active materials was investigated in-depth. As a proof-of-concept demonstration, positive active materials like polyaniline and LiFePO4 were deposited on the 3D architectures by means of electrodeposition and sol-gel approach, respectively. In both cases, the composite electrodes exhibited reasonably high cyclability and rate performance at different current densities. The syntheses of niobium and molybdenum oxides and their potential application as electrodes in microbatteries were also studied. In such applications, the carbon foams served dual purposes as 3D scaffolds and as reducing reactants in the carbothermal reduction process. Finally, a facile method of coating carbon substrates with oxide nanosheets was developed. The approach involved the exfoliation of crystalline VO2 to prepare dispersions of hydrated V2O5, which were subsequently cast onto CNT paper to form oxide films of different thicknesses.
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| 27. |
- Bergenstråhle, Malin, 1977-, et al.
(författare)
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Thermal Response in Crystalline Iβ Cellulose : A Molecular Dynamics Study
- 2007
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Ingår i: Journal of Physical Chemistry B. - Washington : ACS Publications. - 1520-6106 .- 1520-5207. ; 111:30, s. 9138-9145
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of temperature on structure and properties of the cellulose Iβ crystal was studied by molecular dynamics simulations with the GROMOS 45a4 force-field. At 300 K, the modeled crystal agreed reasonably with several sets of experimental data, including crystal density, corresponding packing and crystal unit cell dimensions, chain conformation parameters, hydrogen bonds, Young's modulus, and thermal expansion coefficient at room temperature. At high-temperature (500 K), the cellulose chains remained in sheets, despite differences in the fine details compared to the room-temperature structure. The density decreased while the a and b cell parameters expanded by 7.4% and 6%, respectively, and the c parameter (chain axis) slightly contracted by 0.5%. Cell angles α and β divided into two populations. The hydroxymethyl groups mainly adopted the gt orientation, and the hydrogen-bonding pattern thereby changed. One intrachain hydrogen bond, O2'H2'···O6, disappeared and consequently the Young's modulus decreased by 25%. A transition pathway between the low- and high-temperature structures has been proposed, with an initial step being an increased intersheet separation, which allowed every second cellulose chain to rotate around its helix axis by about 30°. Second, all hydroxymethyl groups changed their orientations, from tg to gg (rotated chains) and from tg to gt (non-rotated chains). When temperature was further increased, the rotated chains returned to their original orientation and their hydroxymethyl groups again changed their conformation, from gg to gt. A transition temperature of about 450 K was suggested; however, the transition seems to be more gradual than sudden. The simulated data on temperature-induced changes in crystal unit cell dimensions and the hydrogen-bonding pattern also compared well with experimental results.
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| 28. |
- Özeren, Hüsamettin Deniz, et al.
(författare)
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Role of Hydrogen Bonding in Wheat Gluten Protein Systems Plasticized with Glycerol and Water
- 2021
-
Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 232, s. 124149-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Many biopolymers are stiff and brittle and require plasticizers. To optimize the choice and amount of plasticizer, the mechanisms behind plasticization need to be understood. For polar biopolymers, such as polysaccharides and proteins, plasticization depends to a large extent on the hydrogen bond network. In this study, glycerol-plasticized protein systems based on wheat gluten were investigated, in combination with the effects of water. The methodology was based on a combination of mechanical tests and molecular dynamics simulations (MD). The simulations accurately predicted the glycerol content where the experimental depression in glass transition temperature (Tg) occurred (between 20 and 30 wt.% plasticizer). They also predicted the strong water-induced depression in Tg. Detailed analysis revealed that in the dry system, the main effect of glycerol was to break protein-protein hydrogen bonds. In the moist system, glycerol was partly outcompeted by water in forming hydrogen bonds with the protein, making the glycerol plasticizer less effective than in dry conditions. These results show that MD can successfully predict the plasticizer concentration at which the onset of efficient plasticization occurs. MD can therefore be an important tool for understanding plasticizer mechanisms, even in a complex system, on a level of detail that is impossible with experiments.
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| 29. |
- Karlsson, Therese, 1987, et al.
(författare)
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Hyperspectral imaging and data analysis for detecting and determining plastic contamination in seawater filtrates
- 2016
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Ingår i: Journal of Near Infrared Spectroscopy. - Chichester, England : SAGE Publications. - 0967-0335 .- 1751-6552. ; 24:2, s. 141-149
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Tidskriftsartikel (refereegranskat)abstract
- One possible way of monitoring plastic particles in sea water is by imaging spectroscopic measurements on filtrates. The idea is that filters from seawater sampling can be imaged in many wavelengths and that a multivariate data analysis can give information on (1) spatial location of plastic material on the filter and (2) composition of the plastic materials. This paper reports on simulated samples with spiked reference plastic particles, and real seawater filtrates containing microplastic pollutants. These real samples were previously identified through visual examination in a microscope. The samples were imaged using three different imaging systems. The different wavelength ranges were 375–970nm, 960–1662nm and 1000–2500nm. Data files from all three imaging systems were analysed by hyperspectral image analysis. The method using the wavelength span 1000–2500nm was shown to be the most applicable to this specific type of samples and gave a 100% particle recognition on reference plastic, above 300 µm and an 84% pixel recognition on household polyethylene plastic. When applied to environmental samples the technique showed an increase in identified particles compared with visual investigations. These initial tests indicate a potential underestimation of microplastics in environmental samples. This is the first study to demonstrate that hyperspectral imaging techniques can be used to study microplastics down to 300µm, which is a common size limit used in microplastic surveys.
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| 30. |
- Kolavali, Reddysuresh, 1983, et al.
(författare)
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The sorption of monovalent cations onto wood flour and holocelluloses of Norway spruce: molecular interactions during LiCl impregnation
- 2017
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 71:5, s. 373-381
-
Tidskriftsartikel (refereegranskat)abstract
- Active functional groups and interactions involved in the sorption of Li+ ions from an aqueous LiCl solution onto the Norway spruce sapwood (sW) flour have been investigated. To this purpose, sW was delignified by peracetic acid (PAA) treatments and the resulting holocelluloses (HC6 h, HC24 h, HC51 h, HC72 h, where the lower case data indicate the PAA treatment time) with various lignin contents were immersed in aqueous solution of LiCl and the sorption effects were studied by flame atomic emission spectroscopy (FAES), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). The Brunauer- Emmett-Teller (BET) specific surface area increased from 1.5±0.0 m2g−1 to 2.4±0.1 m2g−1 for HC6 h, and from 1.6±0.03 m2g−1 to 2.7±0.6 m2g−1 for HC72 h upon LiCl treatment. It was found that Li+/Cl− retention occurs predominantly via O-containing functionalities and the carbohydrate-rich samples sorbed more Li+. Upon LiCl treatment, the mobility and accessibility of the wood matrix was enhanced, possibly by interference of the introduced ions with the existing intermolecular bonds.
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| 31. |
- Valencia, Luis, et al.
(författare)
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Multivalent ion-induced re-entrant transition of carboxylated cellulose nanofibrils and its influence on nanomaterials' properties
- 2020
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 12:29, s. 15652-15662
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we identify and characterize a new intriguing capability of carboxylated cellulose nanofibrils that could be exploited to design smart nanomaterials with tuned response properties for specific applications. Cellulose nanofibrils undergo a multivalent counter-ion induced re-entrant behavior at a specific multivalent metal salt concentration. This effect is manifested as an abrupt increase in the strength of the hydrogel that returns upon a further increment of salt concentration. We systematically study this phenomenon using dynamic light scattering, small-angle X-ray scattering, and molecular dynamics simulations based on a reactive force field. We find that the transitions in the nanofibril microstructure are mainly because of the perturbing actions of multivalent metal ions that induce conformational changes of the nanocellulosic chains and thus new packing arrangements. These new aggregation states also cause changes in the thermal and mechanical properties as well as wettability of the resulting films, upon water evaporation. Our results provide guidelines for the fabrication of cellulose-based films with variable properties by the simple addition of multivalent ions.
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| 32. |
- Rundlöf, Torgny, et al.
(författare)
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Survey and qualification of internal standards for quantification by 1H NMR spectroscopy
- 2010
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Ingår i: Journal of Pharmaceutical and Biomedical Analysis. - : Elsevier BV. - 0731-7085 .- 1873-264X. ; 52:5, s. 645-651
-
Tidskriftsartikel (refereegranskat)abstract
- In quantitative NMR (qNMR) selection of an appropriate internal standard proves to be crucial. In this study, 25 candidate compounds considered to be potent internal standards were investigated with respect to the ability of providing unique signal chemical shifts, purity, solubility, and ease of use. The 1H chemical shift (δ) values, assignments, multiplicities and number of protons (for each signal), appropriateness (as to be used as internal standards) in four different deuterated solvents (D2O, DMSO-d6, CD3OD, CDCl3) were studied. Taking into account the properties of these 25 internal standards, the most versatile eight compounds (2,4,6-triiodophenol, 1,3,5-trichloro-2-nitrobenzene, 3,4,5-trichloropyridine, dimethyl terephthalate, 1,4-dinitrobenzene, 2,3,5-triiodobenzoic acid, maleic acid and fumaric acid) were qualified using both differential scanning calorimetry (DSC) and NMR spectroscopy employing highly pure acetanilide as the reference standard. The data from these two methods were compared as well as utilized in the quality assessment of the compounds as internal standards. Finally, the selected internal standards were tested and evaluated in a real case of quantitative NMR analysis of a paracetamol pharmaceutical product.
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| 33. |
- Asplund, Basse, et al.
(författare)
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Effects of hydrolysis on a new biodegradable co-polymer
- 2006
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Ingår i: Journal of Biomaterials Science. Polymer Edition. - : Informa UK Limited. - 0920-5063 .- 1568-5624. ; 17:6, s. 615-630
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to examine the feasibility of using a new low-modulus biodegradable thermoplastic elastomer for in vivo application as a stent cover. The new polymer, a thermoplastic elastomer, consists of a three-armed co-polymer of poly(lactide)acid (PLLA), poly(trimethylene carbonate) (PTMC) and poly(caprolactone) (PCL). A degradation study was performed in a buffer solution at 37 degrees C for 4 and 6 weeks. The effect of degradation on mechanical properties was studied by stress-strain measurements and explained by using modulated DSC, GPC and mass measurements. A tapered block of PLLA and trimethylene carbonate connecting the crystalline outer part and the inner elastic part was highly susceptible to hydrolysis and caused rapid degradation and subsequent loss of mechanical properties. Random chain scission and homogenous hydrolysis resulted in a loss in mass and molecular weight. After 6 weeks of in vitro hydrolysis the molecular weight had decreased 54% and the elongation-at-break dropped from more than 300% to 90%. A medium free cell seeding study showed that endothelial cells adhered well to the polymeric material. An indicative animal study with the polymer acting as a stent cover showed very low levels of inflammation however, pronounced neointima thickening was observed which was probably due to the premature failure of the material.
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| 34. |
- Asfaw, Habtom Desta, Dr. 1986-, et al.
(författare)
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Facile synthesis of hard carbon microspheres from polyphenols for sodium-ion batteries : insight into local structure and interfacial kinetics
- 2020
-
Ingår i: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 18
-
Tidskriftsartikel (refereegranskat)abstract
- Hard carbons are the most promising negative active materials for sodium ion storage. In this work, a simple synthesis approach is proposed to produce hard carbon microspheres (CMSs) (with a mean diameter of ~1.3 μm) from resorcinol-formaldehyde precursors produced via acid-catalyzed polycondensation reaction. Samples prepared at 1200, 1400, and 1500 oC showed different electrochemical behavior in terms of reversible capacity, initial coulombic efficiency (iCE), and the mechanism of sodium ion storage. The specific capacity contributions from the flat voltage profile (<0.1 V) and the sloping voltage region (0.1–1 V) showed strong correlation to the local structure (and carbonization temperature) determined by the interlayer spacing (d002) and the Raman ID/IG ratio of the hard carbons (HCs) and the rate of cycling. Electrochemical tests indicated that the HC synthesized at 1500 oC performed best with an iCE of 85–89% and a reversible capacity of 300–340 mAh g−1 at 10 mA g−1, with the majority of charge stored below 0.1 V. The d002 and the ID/IG ratio for the sample were ~3.7 Å and ~1.27, respectively, parameters indicative of the ideal local structure in HCs required for optimum performance in sodium-ion cells. In addition, galvanostatic tests on three-electrode half-cells cells revealed that sodium metal plating occurred as cycling rates were increased beyond 80 mA g−1 leading to considerably high capacity and poor coulombic efficiency, a point that must be considered in full-cell batteries. Pairing the hard CMS electrodes with Prussian white positive electrode, a proof-of-concept cell could provide a specific capacity of almost 100 mAh g−1 maintained for more than 50 cycles with a nominal voltage of 3 V.
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| 35. |
- Andersson Trojer, Markus, et al.
(författare)
-
Elastic strain-hardening and shear-thickening exhibited by thermoreversible physical hydrogels based on poly(alkylene oxide)-grafted hyaluronic acid or carboxymethylcellulose
- 2020
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 22:26, s. 14579-14590
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of strongly elastic physical gels based on poly(alkylene oxide)-grafted hyaluronan or carboxymethylcellulose, exhibiting both shear-thickening and strain-hardening have been studied using rheometry and explained using a slightly different interpretation of the transient network theory. The graft copolymers were prepared by a quantitative coupling reaction. Their aqueous solutions displayed a thermoreversible continuous transition from Newtonian fluid to viscoelastic solid which could be controlled by the reaction conditions. The evolution of all material properties of the gel could be categorized into two distinct temperature regimes with a fast evolution at low temperatures followed by a slow evolution at high temperatures. The activation energy of the zero shear viscosity and the relaxation time of the graft inside the interconnecting microdomains were almost identical to each other in both temperature regimes. This suggests that the number of microdomains remained approximately constant whereas the aggregation number inside the microdomains increased according to the binodal curve of the thermosensitive graft.
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| 36. |
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| 37. |
- Asfaw, Habtom Desta, 1986-, et al.
(författare)
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Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries : a study of structure and electrochemical performance
- 2014
-
Ingår i: Nanoscale. - Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 6:15, s. 8804-8813
-
Tidskriftsartikel (refereegranskat)abstract
- In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sol–gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material. The major benefits of the carbon foam used in our work are closely connected with its high surface area and the plenty of space suitable for sequential coating with battery components. After coating with a cathode material (LiFePO4nanoparticles), the 3D electrode presents a hierarchically structured electrode in which a porous layer of the cathode material is deposited on the rigid and bicontinuous carbon foam. The composite electrodes exhibit impressive cyclability and rate performance at different current densities affirming their importance as viable power sources in miniature devices. Footprint area capacities of 1.72 mA h cm−2 at 0.1 mA cm−2 (lowest rate) and 1.1 mA h cm−2 at 6 mA cm−2(highest rate) are obtained when the cells are cycled in the range 2.8 to 4.0 V vs. lithium.
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| 38. |
- Bandara, T M W J, 1968, et al.
(författare)
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Characterization of poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) nanofiber membrane based quasi solid electrolytes and their application in a dye sensitized solar cell
- 2018
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 266, s. 276-283
-
Tidskriftsartikel (refereegranskat)abstract
- The electrolyte plays a major role in dye sensitized solar cells (DSSCs). In this work a quasi-solid state (gel) electrolyte has been formed by incorporating a liquid electrolyte made with KI dissolved in ethylene carbonate (EC) and propylene carbonate (PC) co-solvent in poly (vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) co-polymer nanofiber membrane prepared by electrospinning. SEM images of the electrolyte membrane showed the formation of a three-dimensional network of polymer nanofibers with diameters between 100 and 300 nm and an average membrane thickness of 14 mu m. The electrolyte was characterized by FTIR and differential scanning calorimetry (DSC) measurements. The DSSCs fabricated with this electrolyte were characterized by current-voltage and Electrochemical Impedance Spectroscopy (EIS) measurements. DSC thermograms revealed that the crystallinity of the PVdF-HFP nanofiber is 14% lower than that of the pure PVdF-HFP polymer while the FTIR spectra showed a reduced polymer-polymer interaction in the nano fiber based gel electrolyte. The DSSCs fabricated with nanofiber based gel electrolyte showed an energy conversion efficiency of 5.36% under 1.5 a. m. solar irradiation, whereas the efficiency of the DSSC made with the liquid electrolyte based cell was 6.01%. This shows the possibility of replacing the liquid electrolyte in DSSCs by electro-spun polymer nanofiber based gel electrolyte and thereby minimizing some major drawbacks associated with liquid electrolyte based solar cells while maintaining a reasonably high efficiency.
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| 39. |
- Hosseini, Seyedehsan, 1994
(författare)
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Additive-Driven Improvements in Interfacial Properties and Processing of TMP-Polymer Composites
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Efforts to address environmental concerns have resulted in new regulations designed to plan the reduction of plastic and synthetic polymer usage, necessitating the search for sustainable natural alternatives with comparable cost-effectiveness and mechanical performance. Thermomechanical pulp (TMP) fibres are one of the most affordable natural fibres that have no chemical refining in production, production have a high yield of 90-98% and TMP fibres have been demonstrated to improve the mechanical characteristics (strength, stiffness and toughness) of wood-polymer composites (WPCs) compared to the pure polymer. The integration of TMP fibres with non-polar synthetic polymers remains a challenge due to surface polarity differences. This PhD thesis aims to ease the processing of TMP fibre composites through the incorporation of additives. The hypothesis posits that incorporating magnesium stearate (MgSt), molybdenum disulfide (MoS2) and alkyl ketene dimer (AKD) as additives in TMP composites will enhance interfacial properties, resulting in improved processability and flow behaviour at high temperatures. MoS2 is known for its interaction with lignin, which exists in TMP and MgSt is recognised for its ability to improve flow in pharmaceutical processing when combined with cellulose, also a component of TMP. AKD modifies the hydrophilic properties of lignocellulosic surfaces. The experimental work explores the effect of these additives on the properties of TMP composites of ethylene acrylic acid copolymer (EAA) and polypropylene (PP) matrices. The dynamic mechanical analysis (DMA) and mechanical analysis results reveal that MoS2 exhibits superior interaction with TMP fibres, yielding enhanced interfacial properties compared to MgSt in between EAA and TMP fibres. Rheological studies elucidate the transition from a fluid-like state to a network-like structure upon the incorporation of TMP into the PP matrix. The incorporation of AKD with C18 reduces the viscosity of TMP-PP composites and PP itself, and, as determined through theoretical Hansen solubility parameter (HSP) calculations, increases compatibility between cellulose in TMP fibres and PP. The addition of AKD influences both the colour (lighter) and shape (smoother surface) of the extrudate filaments in the TMP-PP composites, indicative of improved processing. In addition, frictional analysis demonstrates the reduction of the coefficient of friction (COF) between metal and TMP fibre by MgSt and AKD treatments.
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| 40. |
- Hosseini, Seyedehsan, 1994, et al.
(författare)
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Alkyl ketene dimer modification of thermomechanical pulp promotes processability with polypropylene
- 2024
-
Ingår i: Polymer Composites. - 1548-0569 .- 0272-8397. ; 45:1, s. 825-835
-
Tidskriftsartikel (refereegranskat)abstract
- Alkyl ketene dimers (AKDs) are known to efficiently react with cellulose with a dual polarity in their structure: a polar component and a nonpolar component. AKD of three different carbon chain lengths, 4, 10, and 16 carbons have been synthesized, and thermomechanical pulp (TMP) fibers were modified by them. The modification of TMP fibers with AKD resulted in an increased water contact angle, showing the presence of the AKDs on the TMP fibers and a new carbonyl peak in the IR spectra, suggesting modification of the TMP fibers with AKD groups. Calculating the Hansen solubility parameters of AKD and AKD conjugated to TMP in polypropylene (PP) indicates improved compatibility, especially of longer chain AKD and TMP AKD. The rheological studies of the composites showed that the AKD with the longest carbon chain decreases the melt viscosity of the PP-TMP-AKD composite, which combined with the shape and the color of the extruded composite filaments indicates improved flow properties and reduced stress build up during processing. The research findings demonstrate the ability of AKD to enhance the dispersibility and compatibility of natural fibers with PP.
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| 41. |
- Iurchenkova, Anna A., 1997-, et al.
(författare)
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MWCNT buckypaper/polypyrrole nanocomposites for supercapasitor application
- 2020
-
Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 335
-
Tidskriftsartikel (refereegranskat)abstract
- In this work MWNT/polypyrrole nanocomposites were synthesized and investigated as electrode materials for supercapasitor application. The MWNT were synthesized by CCVD-method and precipitated as buckypaper film (NTBP). The polypyrrole was precipitated on the NTBP surface by chemical (sample NTBP_PPy_Chem) and electrochemical (sample NTBP_PPy_Elect) polymerization. The morphology and functional composition of individual and hybrid materials were investigated by microscopic and spectroscopic methods. It was obtained that the deposition method and presence of NTBP affects the polymer morphology. It was shown that PPy chemical deposition leads to the precipitation of a large amount of an amorphous polymer on a buckypaper surface. At the same time electrochemical deposition method promotes the synthesis of uniform polymer layers. In the second case, the mass of the precipitated polymer is smaller. It was found that both deposition methods are suitable for the polypyrrole deposition and can increase the buckypaper capacity almost twice. The material long cycling showed that the NTBP_PPy_Elect sample has the greatest stability. Thus, in this study, the relationship between morphology, functional composition and electrochemical properties of materials was studied. It was shown that the synthesis method allows controlling the morphology and/or functional composition of the materials. Also it was demonstrated that the synthesized structures are promising for use as supercapacitor electrodes due to the high specific capacitance and stability.
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| 42. |
- Liu, Shungang, et al.
(författare)
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The role of connectivity in significant bandgap narrowing for fused-pyrene based non-fullerene acceptors toward high-efficiency organic solar cells
- 2020
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 8:12, s. 5995-6003
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Tidskriftsartikel (refereegranskat)abstract
- Great attention has been paid to developing low bandgap non-fullerene acceptors (NFAs) for matching wide bandgap donor polymers to increase the photocurrent and therefore the power conversion efficiencies (PCEs) of NFA organic solar cells, while pyrene-core based acceptor-donor-acceptor (A-D-A) NFAs have been mainly reported via the 2,9-position connection due to their bisthieno[3′,2′-b']thienyl[a,h]pyrene fused via a five-membered ring bridge at the ortho-position of pyrene as the representative one named FPIC5, which has prohibited further narrowing their energy gap. Herein, an acceptor FPIC6 was exploited by creating the 1,8-position connection through fusing as bisthieno[3′,2′-b′]thienyl[f-g,m-n]pyrene linked at the bay-position via a six-membered bridge, with enhanced push-pull characteristics within such A-D-A structure. As a structural isomer of FPIC5, FPIC6 exhibited a much lower bandgap of 1.42 eV (1.63 eV for FPIC5). Therefore, the photocurrent and PCE of PTB7-Th:FPIC6 cells were improved to 21.50 mA cm-2 and 11.55%, respectively, due to the balanced mobilities, better photoluminescence quenching efficiency and optimized morphology, which are both ∼40% better than those of PTB7-Th:FPIC5 cells. Our results clearly proved that a pyrene fused core with 1,8-position connection with electron-withdrawing end groups instead of 2,9-position connection is an efficient molecular design strategy to narrow the optical bandgap and improve the photovoltaic performance of NFA based OSCs.
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| 43. |
- Murto, Petri Henrik, 1984
(författare)
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Synthesis of Conjugated Polymers and Small Molecules for Organic Light-Emitting Devices and Photodetectors
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Production cost and environmental impact are the two major concerns that are related to the conventional optoelectronic devices. It is desirable for the modern semiconductors that they are free of toxic/costly metals, they can be processed with low-cost solution-based methods, and their optical, electronic, and mechanical properties can be easily tuned depending on the target application. In this thesis, a range of different conjugated polymers and small molecules are designed and synthesized as semiconductors for organic light-emitting diodes (OLEDs), light-emitting electrochemical cells (LECs), and organic photodetectors (OPDs). In organic light-emitting devices, the emissive molecule is commonly mixed with a charge transporting host matrix, which can be either a small molecule or a conjugated polymer. The latter is beneficial since it does not require deposition of the emitter and matrix components in high vacuum and high temperature conditions. The polymeric materials can be dissolved and printed on a substrate of any desired size and production scale, at room temperature, and even under ambient air. The specific wavelength range of near-infrared (NIR) at λ >700 nm is of interest for a wide range of applications spanning from optical communication to biosensing. However, the low energy of NIR range poses challenges for the materials design, in terms of emission efficiency and light intensity, which are further addressed in this thesis, allowing the fabrication of high-performance NIR-OLEDs and NIR-LECs. For photodetectors, absorption of a wide spectrum of light is beneficial in biosensing and imaging applications. Low noise and fast charge extraction are necessary for the detection of light at high speeds even at low intensities. These aspects are studied in this thesis by designing new polymers with different absorption, charge transport, and morphological properties in the photoactive layer. Two polymers enabled the fabrication of visible (red) OPDs with a low dark current (the main constituent in the noise), high detectivity, and high photoresponse speed.
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| 44. |
- Nilsson, Robin, 1993
(författare)
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An Investigation of Mixed Cellulose Esters and Acyclic Polyacetates: Effects of Side-Chain Lengths and Degrees of Ring-Opening
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bio-based polymers produced from natural sources are gaining an increased interest as potential replacement for today’s conventional fossil-based plastic polymers. Their use is already wide in many large-scale industrial areas such as healthcare, personal care, and food. To widen the potential of biopolymers in new applications such as plastics, their properties need to be tuned by modification to handle factors like relative humidity, which is especially important for gas barriers in food packaging. This thesis explores the effect of two structural variations of cellulose esters, one where the average side-chain length is increased, going from cellulose acetate to cellulose acetate propionate and then cellulose acetate butyrate, and another where the polymer backbone of cellulose acetate is ring-opened. These two modifications affect the glass transition temperature, an important structural factor. The effect of the average side-chain length is explored to a greater extent where they are studied for impact on mechanical properties, water content, water sorption at different RH, the kinetics of water sorption at different RH, mechanical properties at different RH and oxygen permeation at different RH. The focus is on how water interacts with the different esters with regard to the average side-chain length and how water affects their properties. An increase of average sidechain length and the ring-opening were shown to decrease the glass transition temperature. Together with the water sorption and Hansen solubility parameter, it was concluded that longer average side-chain length screens out hydrogen bonding between the polymers. The studies on the average side-chain length and water sorption indicated that water entering the cellulose acetate creates clusters. These formed water clusters create cavities in the polymer which makes the polymer hold more water than before introducing of the water clusters. Oxygen permeation studies on prewetted films prove that these cavities created by water clustering are still present after drying the material at 0% RH and thus resulted in a higher oxygen permeation compared to films that had not been exposed to higher than 50% RH.
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| 45. |
- Pipertzis, Achilleas, 1992, et al.
(författare)
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Ion transport, mechanical properties and relaxation dynamics in structural battery electrolytes consisting of an imidazolium protic ionic liquid confined into a methacrylate polymer
- 2023
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Ingår i: Energy Materials: Materials Science and Engineering for Energy Systems. - 1748-9237. ; 3
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of confining a liquid electrolyte into a polymer matrix was studied by means of Raman spectroscopy, differential scanning calorimetry, temperature-modulated differential scanning calorimetry, dielectric spectroscopy, and rheology. The polymer matrix was obtained from thermal curing ethoxylated bisphenol A dimethacrylate while the liquid electrolyte consisted of a protic ionic liquid based on the ethyl-imidazolium cation [C2HIm] and the bis(trifluoromethanesulfonyl)imide [TFSI] anion, doped with LiTFSI salt. We report that the confined liquid phase exhibits the following characteristics: (i) a distinctly reduced degree of crystallinity; (ii) a broader distribution of relaxation times; (iii) reduced dielectric strength; (iv) a reduced cooperativity length scale at the liquid-to-glass transition temperature (Tg); and (v) up-speeded local Tg-related ion dynamics. The latter is indicative of weak interfacial interactions between the two nanophases and a strong geometrical confinement effect, which dictates both the ion dynamics and the coupled structural relaxation, hence lowering Tg by about 4 K. We also find that at room temperature, the ionic conductivity of the structural electrolyte achieves a value of 0.13 mS/cm, one decade lower than the corresponding bulk electrolyte. Three mobile ions (Im+, TFSI-, and Li+) contribute to the measured ionic conductivity, implicitly reducing the Li+ transference number. In addition, we report that the investigated solid polymer electrolytes exhibit the shear modulus needed for transferring the mechanical load to the carbon fibers in a structural battery. Based on these findings, we conclude that optimized microphase-separated polymer electrolytes, including a protic ionic liquid, are promising for the development of novel multifunctional electrolytes for use in future structural batteries.
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| 46. |
- Santos, Denys E. S., et al.
(författare)
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Conformational Dynamics and Responsiveness of Weak and Strong Polyelectrolyte Brushes : Atomistic Simulations of Poly(dimethyl aminoethyl methacrylate) and Poly(2-(methacryloyloxy)ethyl trimethylammonium chloride)
- 2019
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Ingår i: Langmuir. - Washington : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 35:14, s. 5037-5049
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Tidskriftsartikel (refereegranskat)abstract
- The complex solution behavior of polymer brushes is key to control their properties, including for biomedical applications and catalysis. The swelling behavior of poly(dimethyl aminoethyl methacrylate) (PDMAEMA) and poly(2-(methacryloyloxy)ethyl trimethylammonium chloride) (PMETAC) in response to changes in pH, solvent, and salt types has been investigated using atomistic molecular dynamics simulations. PDMAEMA and PMETAC have been selected as canonical models for weak and strong polyelectrolytes whose complex conformational behavior is particularly challenging for the development and validation of atomistic models. The GROMOS-derived atomic parameters reproduce the experimental swelling coefficients obtained from ellipsometry measurements for brushes of 5–15 nm thickness. The present atomistic models capture the protonated morphology of PDMAEMA, the swollen and collapsed conformations of PDMAEMA and PMETAC in good and bad solvents, and the salt-selective response of PMETAC. The modular nature of the molecular models allows for the simple extension of atomic parameters to a variety of polymers or copolymers.
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| 47. |
- Spiliopoulos, Panagiotis, 1987, et al.
(författare)
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Cellulose modified to host functionalities via facile cation exchange approach
- 2024
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 332
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Tidskriftsartikel (refereegranskat)abstract
- Properties of cellulose are typically functionalized by organic chemistry means. We progress an alternative facile way to functionalize cellulose by functional group counter-cation exchange. While ion-exchange is established for cellulose, it is far from exploited and understood beyond the most common cation, sodium. We build on our work that established the cation exchange for go-to alkali metal cations. We expand and further demonstrate the introduction of functional cations, namely, lanthanides. We show that cellulose nanocrystals (CNCs) carrying sulfate-half ester groups can acquire properties through the counter-cation exchange. Trivalent lanthanide cations europium (Eu3+), dysprosium (Dy3+) and gadolinium (Gd3+) were employed. The respective ions showed distinct differences in their ability of being coordinated by the sulfate groups; with Eu3+fully saturating the sulfate groups while for Gd3+ and Dy3+, values of 82 and 41 % were determined by compositional analysis. CNCs functionalized with Eu3+ displayed red emission, those containing Dy3+ exhibited no optical functionality, while those with Gd3+revealed significantly altered magnetic relaxation times. Using cation exchange to alter cellulose properties in various ways is a tremendous opportunity for modification of the abundant cellulose raw materials for a renewable future.
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| 48. |
- Swensson, Beatrice, 1992
(författare)
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Dissolution of cellulose in aqueous hydroxide base solvents
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As we move towards a circular bioeconomy, new and advanced materials based on cellulose are constantly developed. Unlike most plastics or metals, cellulose cannot be melted, and therefore dissolution is an important tool for processing of cellulose but also for analytical purposes. There is, however, both a knowledge gap in understanding the mechanisms behind dissolution as well as a continued search for new and improved solvents. Aqueous solutions of hydroxide bases are a group of solvents with considerable variation in both dissolution capacity and stability of cellulose solutions, and their properties need to be improved to be useful solvents. Despite this, they are interesting because they have the potential to be cheap and non-toxic, depending on the base of choice. Therefore, the purpose of this thesis has been to further understand the interactions governing cellulose dissolution and properties in aqueous solutions of hydroxide bases, so that in the future, new and improved solvents can be designed. In order to achieve this, cellulose dissolution at low temperatures in aqueous solutions of NaOH and selected quaternary ammonium hydroxide bases has been investigated. The effect of combining NaOH with a quaternary ammonium hydroxide was also investigated, along with the influence of the commonly used additive urea. Results based on light scattering measurements revealed that dissolution in NaOH(aq) is poor, with relatively large aggregates present already at very dilute concentrations and a fraction of undissolved cellulose always present. Upon comparing NaOH to more hydrophobic quaternary ammonium hydroxides, it was observed that the dissolution capacity of the bases increased with increasing hydrophobicity of the cation, alongside their ability to act as hydrogen bond acceptors. Rheology measurements showed that compared to pure NaOH(aq) or pure tetramethylammonium hydroxide (TMAH)(aq), combining NaOH with TMAH improved the stability of the solutions over time and against increasing temperature. It was therefore proved that combining bases can have a similar effect as an additive, but the results were highly dependent on the base pair employed and indicated that both bases need to be able to dissolve cellulose on their own, within the same temperature interval and be miscible with each other in order to improve solution properties.
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| 49. |
- Xu, Husen, et al.
(författare)
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Synergistically boosting performances of organic solar cells from dithieno[3,2-b]benzo[1,2-b;4,5-b′]dithiophene-based copolymers via side chain engineering and radical polymer additives
- 2024
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Ingår i: Journal of Materials Chemistry C. - 2050-7526 .- 2050-7534. ; 12:10, s. 3644-3653
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Tidskriftsartikel (refereegranskat)abstract
- As a notable analogue of benzo[1,2-b:4,5-b′]dithiophene (BDT), dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene (DTBDT) is expected to be a more promising building block for polymer photovoltaic donor materials due to its larger coplanar core and extended conjugation length as well as a similar electron donor ability to BDT. However, the performance of organic solar cells (OSCs) from DTBDT-based copolymers is much lower than that of OSCs from BDT-based copolymers, which is attributed to the higher voltage loss of the OSCs from DTBDT-based polymers as compared to that from BDT-based polymers. In this study, approaches such as increasing the donor (D) and acceptor (A) spacing by lengthening the side chains of the polymer donors and use of radical conjugated polymer additives are synergistically employed in OSCs from 2-alkyl-3-chlorothiophene flanked DTBDT-alt-1,3-bis(thiophen-2-yl)-5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-4,8-dione (BDD) polymers paired with Y6. Compared to the OSCs from the DTBDT-alt-BDD polymer with 2-ethylhexyl side chains (PBDT-Cl) paired with Y6, the power conversion efficiencies (PCEs) of the counterpart OSCs from the DTBDT-alt-BDD polymer with 2-butyloctyl side chains (PDBT-Cl-BO) increased from 12.67% to 14.58%, with a remarkable improvement of the open circuit voltage (VOC). The reduction of non-radiative energy loss of the OSCs from PBDT-Cl-BO:Y6, ascribed to the increase of the DA spacing by lengthening the side chains, is supported through detailed studies such as Fourier-transform photocurrent spectroscopy external quantum efficiency (FTPS-EQE), electroluminescence (EL), electroluminescence external quantum efficiency (EQEEL), and molecular dynamics simulations (MD). Afterwards, the PCEs of the OSCs from the blends of PDBT-Cl-BO:Y6 were further improved from 14.58% to 15.93% with a notable improvement of short circuit densities (JSCs) and fill factors (FFs), along with a small improvement in VOC upon the addition of the radical conjugated polymer GDTA as an additive. For comparison, the PCEs of the OSCs from the blends of PDBT-Cl:Y6 remained almost unchanged upon the addition of GDTA. This work suggests a wise strategy to synergistically utilize side-chain engineering and radical conjugated polymer additives to reduce the non-radiative energy loss, thus improving the performance of OSCs from DTBDT-based polymer donors.
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| 50. |
- Yang, Yi, et al.
(författare)
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Using an ionomer as a size regulator in γ-radiation induced synthesis of Ag nanocatalysts for oxygen reduction reaction in alkaline solution
- 2023
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 646, s. 381-390
-
Tidskriftsartikel (refereegranskat)abstract
- Ag nanoparticles (Ag NPs) are among the most promising candidates to replace Pt as the catalyst for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs). However, synthesizing size-controlled Ag NPs with efficient catalytic performance is still challenging. Herein, uniform Ag NPs are produced through a γ-radiation induced synthesis route in aqueous solutions, using the ionomer PTPipQ100 as both an efficient size regulator in the synthesis and a conductor of hydroxide ions during the ORR process. The origin of the size control is mainly attributed to the affinity of the ionomer to metallic silver. The resulting Ag NPs covered with ionomer layers can be applied as model catalysts for ORR. The nanoparticles that were prepared using 320 ppm ionomer in the reaction solution turned out to be coated with a ∼1 nm thick ionomer layer and exhibited superior ORR activity as compared to other Ag NPs of similar size studied here. The improved electrocatalytic performance can be attributed to the optimal ionomer coverage that enables fast oxygen diffusion, as well as interactions at the Ag-ionomer interface which promote the desorption of OH intermediates from the Ag surface. This work demonstrates the advantage of using an ionomer as the capping agent to produce efficient ORR catalysts.
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