| 1. |
- Willgert, Markus, et al.
(författare)
-
Cellulose nanofibril reinforced composite electrolytes for lithium ion battery applications
- 2014
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 2:33, s. 13556-13564
-
Tidskriftsartikel (refereegranskat)abstract
- The present study describes the synthesis and characterization of a series of four composite electrolytes for lithium ion battery applications. The two-phase electrolytes are composed of a soft, ionic conductive poly(ethylene glycol) (PEG) matrix having stiff nanofibrillated cellulose (CNF) paper as reinforcement to provide mechanical integrity. The reinforcing CNF is modified in order to create covalent bonds between the phases which is particularly beneficial when swelling the composite with a liquid electrolyte to enhance the ionic conductivity. After swelling the composite polymer electrolyte, forming a gelled structure, values of ionic conductivity at 5 x 10(-5) S cm(-1) and an elastic modulus around 400 MPa at 25 degrees C are obtained.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Engström, Joakim, et al.
(författare)
-
Investigating the adsorption of anisotropic diblock copolymer worms onto planar silica and nanocellulose surfaces using a quartz crystal microbalance
- 2021
-
Ingår i: Polymer Chemistry. - : Royal Society of Chemistry (RSC). - 1759-9954 .- 1759-9962. ; 12:42, s. 6088-6100
-
Tidskriftsartikel (refereegranskat)abstract
- Electrostatic adsorption of cationic polyelectrolytes onto anionic cellulosic substrates is an attractive route for facile surface modification of biorenewable materials. Recently, attention has focused on adsorbing cationic spherical diblock copolymer nanoparticles onto model cellulose and/or nanocellulosic substrates. Herein, we investigate physical adsorption of highly anisotropic copolymer worms bearing either anionic or cationic charge onto planar silica, cellulose nanocrystal (CNC) or cellulose nanofibril (CNF) surfaces using quartz crystal microbalance with dissipation monitoring. Electrostatic interactions dominate in the case of anionic silica and CNC surfaces because the adsorbed mass of cationic worms was greater than that of anionic worms. However, either anionic or cationic worms could be adsorbed onto in situ generated CNF substrates, suggesting that additional interactions were involved: hydrogen bonding, van der Waals forces, and possibly covalent bond formation. Scanning electron and atomic force microscopy studies of the dried planar substrates after adsorption experiments confirmed the presence of adsorbed copolymer worms. Finally, composite worm/CNF films exhibited restricted swelling behavior when immersed in water compared to reference CNF films, suggesting that the worms reinforce CNF films by acting as a physical crosslinker. This study is the first investigation of the physical adsorption of highly anisotropic diblock copolymer worms onto cellulosic surfaces.
|
|
| 5. |
- Westlund, Robert, 1979-, et al.
(författare)
-
Efficient Nonlinear Absorbing Platinum(II) Acetylide Chromophores in Solid PMMA Matrices
- 2008
-
Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 18:13, s. 1939-1948
-
Tidskriftsartikel (refereegranskat)abstract
- Platinum(II) acetylides were incorporated into poly(methyl methacrylate) (PMMA) glasses to obtain solid-state nonlinear optical devices. We report on device fabrication, structural, chemical, and mechanical properties, as well as the optical limiting capabilities of the final solids. Two different guest-host systems are presented: 1) Dye molecules functionalized to be readily dispersed in methyl methacrylate (MMA) and subsequent in situ polymerization of the MMA yielding solid PMMA host matrices. 2) Dye molecules functionalized to copolymerize with MMA forming covalent bonds between the guest and the PMMA host matrix. A range of doped organic solids were prepared, reaching concentrations up to 13 wt% of the guest molecule. Raman spectra of the doped solid devices indicate that the chemical structure of the nonlinear dyes remains intact upon the polymerization of the solid matrix. Luminescence spectra confirm that the basic photophysical properties observed for the same solute molecules in THF are maintained also in the solid state. Optical power limiting (OPL) characterization reveal clamping levels for the dyes nonbonded to the solid host being less than 4 μJ at pulse energies up to 110 μJ at 532 nm (f/5 arrangement and 5 ns pulses), which is comparable to the performance of similar dyes in THF solutions. In contrast, the highly crosslinked solid possesses a higher clamping level (8 μj) at the same nominal concentration.
|
|
| 6. |
- Bergenudd, Helena, et al.
(författare)
-
Solvent Effects on ATRP of Oligo(ethylene glycol) Methacrylate. Exploring the Limits of Control
- 2009
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 42:9, s. 3302-3308
-
Tidskriftsartikel (refereegranskat)abstract
- Five copper complexes in combination with six monomer-solvent mixtures have been used to investigate the solvent effects oil ATRP of oligo(ethylene glycol) methacrylate (OEGMA). The redox properties of the copper complexes in OEGMA-solvent mixtures and the apparent rate constants (k(p)(app)) for ATRP of OEGMA were correlated to the degree of control over the polymerizations. Based on this correlation, a general discussion of the limits of control in ATRIP is carried out. One of the key parameters for control in ATRP is the propagation rate constant, making the choice of monomer essential for the design of ail ATRP system. Also, the solvent effects oil the ATRP equilibrium constant (K-ATRP) affect the limit of control (i.e., the apparent rate constant above which control is lost). The choice of copper complex is also more important than the choice of solvent for the design of a well-controlled ATRP system.
|
|
| 7. |
- Carlmark, Anna, et al.
(författare)
-
ATRP of dendronized aliphatic macromonomers of generation one, two, and three
- 2004
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 37:20, s. 7491-7496
-
Tidskriftsartikel (refereegranskat)abstract
- Atom transfer radical polymerization (ATRP) of dendritic, aliphatic macromonomers has been investigated. The macromonomers were based on acrylate functionalized 2,2-bis(methylol)propionic acid (bis-MPA) dendrons, with a flexible spacer of 10 carbons incorporated in the structure in between the polymerizable group and the dendritic wedge. Dendronized polymers of generation one, two, and three were successfully synthesized by ATRP. The polymerizations proceeded until over 80% conversion was reached, while maintaining control over polydispersity index (PDI). Plots of ln([M](0)/[M]) vs time for the polymerization of all three macromonomers showed a linear dependence, indicating that the number of propagating radicals in the reaction solution was constant throughout the reaction, when ethyl 2-bromopropionate (EBrP) was used as an initiator (i.e., radical termination was negligible). All of the resulting polymers had low PDI values and molecular weight close to the theoretical ones. The products were analyzed by H-1 and C-13 NMR spectroscopies, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF).
|
|
| 8. |
- Carlmark, Anna E, et al.
(författare)
-
Atom transfer radical polymerization of methyl acrylate from a multifunctional initiator at ambient temperature
- 2002
-
Ingår i: Polymer. - OXFORD, ENGLAND : ELSEVIER SCI LTD. - 0032-3861 .- 1873-2291. ; 43:15, s. 4237-4242
-
Tidskriftsartikel (refereegranskat)abstract
- A multifunctional initiator for ATRP has been synthesized by reacting a hyperbranched polyether, based on 3-ethyl-3-(hydroxymethyl)oxetane, with 2-bromo-isobutyrylbromide. The macroinitiator contained approximately 25 initiating sites per molecule. It was used for the atom transfer radical polymerization of methyl acrylate mediated by Cu(I)Br and tris(2-(dimethylamino)ethyl)amine (Me-6-TREN) in ethyl acetate at room temperature. This yielded a co-polymer with a dendritic-linear architecture. The large number of growing chains from each macromolecule increases the probability of inter-and intramolecular reactions. In order to control these kinds of polymerizing systems and prevent them from forming a gel, the concentration of propagating radicals must be kept low. The polymerizations under these conditions were well controlled. When a ratio of initiating sites-to-catalyst of 1:0.05 was used, the polymers from all of the reactions had a low polydispersity, ranging from 1.1 to 1.4. None of the polymerizations under these conditions gave gelation. Monomer conversions as high as 65% were reached while maintaining control over the polymerization. (C) 2002 Elsevier Science Ltd. All rights reserved.
|
|
| 9. |
- Claesson, Hans, et al.
(författare)
-
Rheological behaviour during UV-curing of a star-branched polyester
- 2002
-
Ingår i: Progress in organic coatings. - 0300-9440 .- 1873-331X. ; 44:1, s. 63-67
-
Tidskriftsartikel (refereegranskat)abstract
- Using a rheometer coupled with an UV-light generator, the viscoelastic behaviour during the fast cure of star-branched polyester is investigated. The 32 arm star polymers consist of a hyperbranched polyester core, Boltorn(TM) and linear grafts of poly(E-caprolactone) (degree of polymerisation: 20-52) with methacrylate end groups. The resins are crystalline and the melting points range from 34 to 50degreesC; films can be formed and cured below 80degreesC. The crossover of G' and G was used as the gel point. The time to reach the gel point, a few seconds, increases linearly with molecular weight.
|
|
| 10. |
- Eriksen, Jaran, et al.
(författare)
-
High adherence to the 'Wise List' treatment recommendations in Stockholm : a 15-year retrospective review of a multifaceted approach promoting rational use of medicines
- 2017
-
Ingår i: BMJ Open. - London, UK : BMJ Publishing Group Ltd. - 2044-6055. ; 7:4
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To present the 'Wise List' (a formulary of essential medicines for primary and specialised care in Stockholm Healthcare Region) and assess adherence to the recommendations over a 15-year period.DESIGN: Retrospective analysis of all prescription data in the Stockholm Healthcare Region between 2000 and 2015 in relation to the Wise List recommendations during the same time period.SETTING: All outpatient care in the Stockholm Healthcare Region.PARTICIPANTS: All prescribers in the Stockholm Healthcare Region.MAIN OUTCOME MEASURES: The number of core and complementary substances included in the Wise List, the adherence to recommendations by Anatomic Therapeutic Chemical (ATC) 1st level using defined daily doses (DDDs) adjusted to the DDD for 2015, adherence to recommendations over time measured by dispensed prescriptions yearly between 2002 and 2015.RESULTS: The number of recommended core substances was stable (175-212). Overall adherence to the recommendations for core medicines for all prescribers increased from 75% to 84% (2000 to 2015). The adherence to recommendations in primary care for core medicines increased from 80% to 90% (2005 to 2015) with decreasing range in practice variation (32% to 13%). Hospital prescriber adherence to core medicine recommendations was stable but increased for the combination core and complementary medicines from 77% to 88% (2007 to 2015). Adherence varied between the 4 therapeutic areas studied.CONCLUSIONS: High and increasing adherence to the Wise List recommendations was seen for all prescriber categories. The transparent process for developing recommendations involving respected experts and clinicians using strict criteria for handling potential conflicts of interests, feedback to prescribers, continuous medical education and financial incentives are possible contributing factors. High-quality evidence-based recommendations to prescribers, such as the Wise List, disseminated through a multifaceted approach, will become increasingly important and should be developed further to include recommendations and introduction protocols for new expensive medicines.
|
|
| 11. |
- Glimsdal, E., et al.
(författare)
-
Two-photon absorption cross-section and triplet states of dendritic Pt-acetylides for OPL applications
- 2005
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE - The International Society for Optical Engineering.
-
Konferensbidrag (refereegranskat)abstract
- The photo-physical properties of bis((4-(phenylethynyl)phenyl)ethynyl) bis(tributylphosphine) platinum(II) with 2,2-bis(methylol)propionic acid (bis-MPA) dendritic substituents were studied. The introduction of dendrimer capping was found to give rise to protection from oxygen quenching of phosphorescent states with a considerably longer decay time of the phosphorescence (0.1 -0.4 ms range) for solvents with oxygen removed or dendrimers of larger size (G2-G4) or higher concentration. Presence of oxygen reduces the phosphorescence decay time to below 1 microsecond. Two-photon induced fluorescence and z-scan of fs pulses at low pulse repetition frequency at approximately 720 nm revealed that the two-photon absorption cross-section is in the order of 0.01 cm/GW, well below the 0.34cm/GW reported by Staromlynska et al [J. Staromlynska, T. McKay and P. Wilson, J. Appl. Phys. 88, 1726 (2000)] and similar for all dendrimer complexes as well as the non-capped Pt-acetylide. Z-scans performed at high pulse repetition frequency gives an apparent two-photon absorption cross-section that is higher due to the population of excited triplet states, and the contribution from incoherent multiphoton absorption involving the triplet states.
|
|
| 12. |
- Gode, Peter, et al.
(författare)
-
A novel sulfonated dendritic polymer as the acidic component in proton conducting membranes
- 2006
-
Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 177:7-8, s. 787-794
-
Tidskriftsartikel (refereegranskat)abstract
- The present study involves the synthesis of sulfonated poly(3-ethyl-3-(hydroxymethyl)oxetane), sPTMPO, by end-capping the hydroxy-groups in the PTMPO with 1,4-butane sultone. A series of the polymer with different degrees of substitution was investigated. Furthermore, the subsequent use of the sulfonated PTMPO as the acidic component in proton conducting membranes was explored. The membranes were prepared by either a) mixing the partly sulfonated PTMPO with hexamethoxymethyl melamine (HMMM) to form cross-links by ether formation between the methylol groups on HMMM and the remaining hydroxyl groups on the hyperbranched polyether or b) using the sulfonated polyether in conjunction with a pyridine functionalised polysulfone, PSU-pyridine, to produce acid-base blend membranes. Membrane properties such as proton conductivity, water uptake and mechanical properties are discussed.
|
|
| 13. |
- Harth, E. M., et al.
(författare)
-
The effect of macromolecular architecture in nanomaterials : A comparison of site isolation in porphyrin core dendrimers and their isomeric linear analogues
- 2002
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 124:15, s. 3926-3938
-
Forskningsöversikt (refereegranskat)abstract
- The influence of macromolecular architecture on the physical properties of polymeric materials has been studied by comparing poly(benzyl ether) dendrons with their exact linear analogues. The results clearly confirm the anticipation that dendrimers are unique when compared to other architectures. Physical properties, from hydrodynamic volume to crystallinity, were shown to be different, and in a comparative study of core encapsulation in macromolecules of different architecture, energy transduction from the polymer backbone to a porphyrin core was shown to be different for dendrimers as compared to that of isomeric four- or eight-arm star polymers. Fluorescence excitation revealed strong, morphology dependent intramolecular energy transfer in the three macromolecular isomers investigated, Even at high generations, the dendrimers exhibited the most efficient energy transfer, thereby indicating that the dendritic architecture affords superior site isolation to the central porphyrin it surrounds.
|
|
| 14. |
- Hedfors, Cecilia, et al.
(författare)
-
Thiol end-functionalization of poly(epsilon-caprolactone), catalyzed by Candida antarctica lipase B
- 2005
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 38:3, s. 647-649
-
Tidskriftsartikel (refereegranskat)abstract
- The use of Candida antarctica Lipase B (CALB) chemoselective catalyst in the Thiol End-Functionalization of Poly(ε-caprolacetone) was discussed. Thiol-functionalization of poly(ε-caprolacetone)(PCL) was made by an initiation reaction catalyzed by CALB in bulk. 2-Mercaptoethanol (1) was used to initiate the enzyme-assisted ring opening polymerization of ε-caprolacetone(2) to give the desired thiol-functionalized polymer. The structure of the terminated PCL was confirmed by 13C nuclear magnetic resonance .
|
|
| 15. |
- Hong, Y., et al.
(författare)
-
Film blowing of linear low-density polyethylene blended with a novel hyperbranched polymer processing aid
- 2000
-
Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 41:21, s. 7705-7713
-
Tidskriftsartikel (refereegranskat)abstract
- The use of hyperbranched polymer (HBP) as a processing aid for linear low-density polyethylene (LLDPE) in the tubular film blowing process was investigated. Through the addition of HBP, sharkskin was successfully eliminated without significantly changing the overall physical properties of LLDPE films. Also, there was a minimum of 40% enhancement in processing rate with addition of 0.5 wt% HBP. The study showed that HBP and LLDPE are immiscible, and HBP has a tendency to migrate to the surface, subsequently, it seems to form a lubricating layer between the metal surfaces and the bulk material. This phase separation between HBP and LLDPE results in an HBP-rich surface, which has a high potential to create unique surface properties tailored to various applications. Rheological analysis indicated that excessive slip was present in HBP/LLDPE suggesting that the onset of slip is not the cause of sharkskin. On the contrary, it may be partially responsible for the elimination of sharkskin.
|
|
| 16. |
- Jesberger, M., et al.
(författare)
-
Hyperbranched polymers as scaffolds for multifunctional reversible addition-fragmentation chain-transfer agents : A route to polystyrene-core-polyesters and polystyrene-block-poly(butyl acrylate)-core-polyesters
- 2003
-
Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 41:23, s. 3847-3861
-
Tidskriftsartikel (refereegranskat)abstract
- Polydisperse hyperbranched polyesters were modified for use as novel multifunctional reversible addition-fragmentation chain-transfer (RAFT) agents. The polyester-core-based RAFT agents were subsequently employed to synthesize star polymers of n-butyl acrylate and styrene with low polydispersity (polydispersity index < 1.3) in a living free-radical process. Although the polyester-core-based RAFT agent mediated polymerization of n-butyl acrylate displayed a linear evolution of the number-average molecular weight (M.) up to high monomer conversions (>70%) and molecular weights [M-n > 140,000 g mol(-1), linear poly(methyl methacrylate) equivalents)], the corresponding styrene-based system reached a maximum molecular weight at low conversions (approximate to30%, M-n = 45,500 g mol(-1), linear polystyrene equivalents). The resulting star polymers were subsequently used as platforms for the preparation of star block copolymers of styrene and n-butyl acrylate with a polyester core with low polydispersities (polydispersity index < 1.25). The generated polystyrene-based star polymers were successfully cast into highly regular honeycomb-structured microarrays.
|
|
| 17. |
- Johansson, Mats K. G., et al.
(författare)
-
Novel concept for low temperature curing powder coatings based on hyperbranched polyesters
- 2000
-
Ingår i: JCT. - 0361-8773. ; 72:906, s. 49-54
-
Tidskriftsartikel (refereegranskat)abstract
- The concept of using hyperbranched polymers as scaffolds for solid thermoset resin applications is described. A series of semi-crystalline methyacrylate-functional aliphatic polyesters has been synthesized and characterized for applications as solid thermoset resins, e.g., powder coating resins. The polyester resins have been crosslinked by UV irradiation producing either amorphous or semi-crystalline crosslinked films depending on the initial structure. The resins are based on hyperbranched aliphatic polyester chains have been grafted and end-capped with methacrylate moieties. The resins exhibit a rheological behavior suitable for low temperature curing powder coatings, i.e., films that can be readily formed and UV cured at temperatures below 80 degrees C.
|
|
| 18. |
- Lange, J., et al.
(författare)
-
Barrier coatings for flexible packaging based on hyperbranched resins
- 2001
-
Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 42:17, s. 7403-7410
-
Tidskriftsartikel (refereegranskat)abstract
- Hyperbranched resins have been evaluated for use as barrier coatings. Different types of modified hydroxy-functional hyperbranched polyester resins were prepared and partially end-capped with acrylate or methacrylate units. Crystalline end-groups (poly(epsilon -caprolactone) were grafted onto some resins. The coatings were applied on poly(ethylene terephthalate) and polypropylene substrates and crosslinked by UV light and their barrier against oxygen and water vapour determined. The results show that hyperbranched coatings give a pronounced improvement in oxygen barrier on both substrates. Expressed in terms of oxygen permeability coefficient, the improvement was a factor of up to 60 times compared to polypropylene and up to 2.2 times compared to poly(ethylene terephthalate). As for other hydroxy-functional barrier polymers, the amount of hydroxyl groups in the hyperbranched resins was found to play a major role concerning the oxygen barrier, controlling both performance and water sensitivity. It was seen that humidity led to a decrease in barrier at the highest hydroxyl group concentration, whereas the barrier performance of coatings with lower concentration of hydroxyl groups instead improved under humid conditions. It was also found that crystalline end-groups did not improve the oxygen barrier and that none of the synthesised resins gave any improvement in water vapour barrier.
|
|
| 19. |
- Lindqvist, Josefina, et al.
(författare)
-
Intelligent Dual-Responsive Cellulose Surfaces via Surface-Initiated ATRP
- 2008
-
Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 9:8, s. 2139-2145
-
Tidskriftsartikel (refereegranskat)abstract
- Novel thermo-responsive cellulose (filter paper) surfaces of N-isopropylacrylamide (NIPAAm) and pH-responsive cellulose surfaces of 4-vinylpyridine (4VP) have been achieved via surface-initiated ATRP. Dual-responsive (pH and temperature) cellulose surfaces were also obtained through the synthesis of block-copolymer brushes of PNIPAAm and P4VP. With changes in pH and temperature, these "intelligent" surfaces showed a reversible response to both individual triggers, as indicated by the changes in wettability from highly hydrophilic to highly hydrophobic observed by water contact angle measurements. Adjusting the composition of the grafted block-copolymer brushes allowed for further tuning of the wettability of these "intelligent" cellulose surfaces.
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
- Nilsson, Camilla, et al.
(författare)
-
Dendrimers in Thiol-ene Crosslinked Networks and the Effect on Subsequent Generations on Thermoset Properties
- 2009
-
Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 47:2, s. 589-601
-
Tidskriftsartikel (refereegranskat)abstract
- A series of well-defined allyl-ether functionalized polyester dendrimers has been synthesized via the divergent approach using traditional esterification reactions. Two commercially available trifunctional thiols, trimethylolpropane tri(3-mercaptopropanoate) (TRIS) and ethoxylated trimethylolpropane tri(3-mercaptopropanoate) (ETTMP), were incorporated with the dendrimers into the thiol-ene polymer networks. The thiol-ene reactions were conducted at room temperature and cured by UV light without the addition of photoinitiatior. Highly crosslinked films were obtained and characterized with respect to mechanical (DMA) and thermal (DSC and TGA) properties.
|
|
| 23. |
- Nilsson, Camilla, et al.
(författare)
-
Methacrylated Dendrimers in Thiol-Methacrylate Networks and the Effect of Conversion on the Thermoset Properties
- 2009
-
Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 47:21, s. 5815-5826
-
Tidskriftsartikel (refereegranskat)abstract
- A series of well-defined methacrylate-functionalized polyester dendrimers based on 2,2-bis(methylol)propionic acid (bis-MPA) has been synthesized divergently. The thermal properties and conversion of the methacrylate functional dendrimers are investigated along with the structure-property relationship of networks composed of the methacrylate dendrimers and two commercially available trifunctional thiols, trimethylolpropane tri(3-mercaptopropanoate) (TRIS) and ethoxylated trimethylolpropane tri(3-mercaptopropanoate) (ETTMP). The thiol-methacrylate reactions were conducted at room temperature, under ambient conditions, and triggered by UV light in the presence of a photoinitiator. Crosslinked films were obtained and characterized with respect to conversion (FT-Raman) and thermal (DSC and TGA) properties.
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
- Nilsson, Camilla, 1979-, et al.
(författare)
-
Synthesis and Thiol-Ene Photopolymerization of Allyl Ether Functionalized Dendrimers
- 2008
-
Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 46:4, s. 1339-1348
-
Tidskriftsartikel (refereegranskat)abstract
- Well-defined, allyl-ether functional, first-generation dendrimers have been synthesized. The convergent growth approach was utilized, using the anhydride of the allyl-ether terminated building block. Three different core moieties were used: trimethylolpropane, trisphenol, and ditrimethylolpropane. The coupling reactions proceeded in good yields and all compounds were characterized by NMR, MALDI-TOF, and SEC. The allyl-terminated dendrimers were crosslinked by thiol-ene chemistry, using a multifunctional thiol, TriThiol, to give clear and smooth films. The photopolymerization was conducted in the presence of a photoinitiator, Irgacure 651, and no traces of either allyl-ether groups or thiols were observed by FT-Raman after cure. All crosslinked films were characterized with respect to mechanical (DMA) and thermal (DSC) properties. It was found that homogeneous networks were formed and that the core functionality and structure had little effect on the network properties.
|
|
| 27. |
- Núñez, Eugenia, et al.
(författare)
-
Crystal structure, melting behaviour and equilibrium melting point of star polyesters with crystallisable poly(ε–caprolactone) arms
- 2004
-
Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 45:15, s. 5251-5263
-
Tidskriftsartikel (refereegranskat)abstract
- Star polymers consisting of poly(ε-caprolactone), PCL, attached to third generation dendrimer, hyperbranched and dendron cores have been studied by differential scanning calorimetry and wide-angle X-ray scattering. The degree of polymerisation of the PCL arms of the star polymers ranged from 14 to 81. The crystal unit cell was the same for the star polymers as for their linear PCL analogues. The star polymers showed a lower degree of crystallinity than the linear PCL, suggesting that the dendritic cores imposed restriction on PCL crystallisation. Slow heating of rapidly cooled samples led to crystal rearrangement - a gradual increase in melting point with decreasing heating rate and recrystallisation followed by additional high temperature melting. The tendency for crystal rearrangement was less pronounced in star polymers based on dendrimer or hyperbranched cores, suggesting that the dendritic cores constitute an obstacle to crystal rearrangement. The star polymers showed higher equilibrium melting points than the linear PCL analogues. It is suggested that covalent attachment of the PCL arms to the dendritic core reduced the positional freedom and the entropy of the melt with respect to that of linear PCL.
|
|
| 28. |
|
|
| 29. |
- Nyström, Daniel, et al.
(författare)
-
Highly-ordered hybrid organic-inorganic isoporous membranes from polymer modified nanoparticles
- 2005
-
Ingår i: Macromolecular rapid communications. - : Wiley. - 1022-1336 .- 1521-3927. ; 26:7, s. 524-528
-
Tidskriftsartikel (refereegranskat)abstract
- Organic-inorganic hybrid materials consisting of nanosized silica particles with surface grafted PS or PS-b-PMMA were synthesized using ATRP. These hybrid materials were used in the fabrication of highly-ordered isoporous membranes. Optical characterization revealed that the membranes consisted of hexagonally ordered pores of uniform size. The combination of an open pore structure and high surface area makes isoporous membranes into materials of high interest in fields as biotechnology and photonics.
|
|
| 30. |
|
|
| 31. |
- Risén, Emma, et al.
(författare)
-
Assessment of biomethane production from maritime common reed
- 2013
-
Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526 .- 1879-1786. ; 53, s. 186-194
-
Tidskriftsartikel (refereegranskat)abstract
- Several ongoing projects are harvesting maritime biomass from the Baltic Sea for eutrophication mitigation and utilisation of the recovered biomass. Some of this biomass comprises common reed (Phragmites australis), one of the most widespread vascular plants on Earth. Reed utilisation from eutrophied coastal areas needs to be evaluated. Therefore, a system analysis was performed of reed harvesting for biofuel and biofertiliser production. The specific objectives of the analysis were to: investigate the methane yield associated with anaerobic co-digestion of reed; make a primary energy assessment of the system; quantify Greenhouse Gas (GHG) savings when a fossil reference system is replaced; and estimate the nutrient recycling potential of the system. The results from energy and GHG calculations are highly dependent on conditions such as system boundaries, system design, allocation methods and selected indicators. Therefore a pilot project taking place in Kalmar County, Sweden, was used as a case study system. Laboratory experiments using continuously stirred tank reactor digesters indicated an increased methane yield of about 220 m3 CH4/t volatile solids from co-digestion of reed. The energy balance for the case study system was positive, with energy requirements amounting to about 40% of the energy content in the biomethane produced and with the non-renewable energy input comprising about 50% of the total energy requirements of the system. The net energy value proved to be equivalent to about 40 L of petrol/t reed wet weight. The potential to save GHG emissions compared with a fossil reference system was considerable (about 80%). Furthermore an estimated 60% of the nitrogen and almost all the phosphorus in the biomass could be re-circulated to arable land as biofertiliser. Considering the combined benefits from all factors investigated in this study, harvesting of common reed from coastal zones has the potential to be beneficial, assuming an appropriate system design, and is worthy of further investigations regarding other sustainability aspects.
|
|
| 32. |
- Sanchez, Carmen, et al.
(författare)
-
Characterization of Reduced and Surface-Modified Graphene Oxide in Poly(Ethylene-co-Butyl Acrylate) Composites for Electrical Applications
- 2019
-
Ingår i: Polymers. - : MDPI. - 2073-4360. ; 11:4
-
Tidskriftsartikel (refereegranskat)abstract
- Promising electrical field grading materials (FGMs) for high-voltage direct-current (HVDC) applications have been designed by dispersing reduced graphene oxide (rGO) grafted with relatively short chains of poly (n-butyl methacrylate) (PBMA) in a poly(ethylene-co-butyl acrylate) (EBA) matrix. All rGO-PBMA composites with a filler fraction above 3 vol.% exhibited a distinct non-linear resistivity with increasing electric field; and it was confirmed that the resistivity could be tailored by changing the PBMA graft length or the rGO filler fraction. A combined image analysis- and Monte-Carlo simulation strategy revealed that the addition of PBMA grafts improved the enthalpic solubility of rGO in EBA; resulting in improved particle dispersion and more controlled flake-to-flake distances. The addition of rGO and rGO-PBMAs increased the modulus of the materials up to 200% and the strain did not vary significantly as compared to that of the reference matrix for the rGO-PBMA-2 vol.% composites; indicating that the interphase between the rGO and EBA was subsequently improved. The new composites have comparable electrical properties as today's commercial FGMs; but are lighter and less brittle due to a lower filler fraction of semi-conductive particles (3 vol.% instead of 30-40 vol.%).
|
|
| 33. |
|
|
| 34. |
- Utsel, Simon, et al.
(författare)
-
Synthesis, adsorption and adhesive properties of a cationic amphiphilic block copolymer for use as compatibilizer in composites
- 2012
-
Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 48:7, s. 1195-1204
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, the objective was to synthesize a compatibilizer that can electrostatically adsorb onto cellulose fibers, in fiber-based composites, to enhance the interaction between the fibers and non-polar polymer matrices. This physical route to attach the compatibilizer onto and thereby modify a fiber surface is convenient since it can be performed in water under mild conditions. Polystyrene (PS) was used for the high molecular weight, non-polar, block and poly(dimethylamino)ethyl methacrylate (PDMAEMA) was used as the polar block, which was subsequently quaternized to obtain cationic charges. The block copolymer self-assembles in water into cationic micelles and the adsorption to both silicon oxide surfaces and cellulose model surfaces was studied. The micelles spread out on the surface after heat treatment and contact angle measurements showed that the contact angles against water increased significantly after this treatment. AFM force measurements were performed with a PS probe to study the adhesive properties. The adhesion increased with increasing contact time for the treated surfaces, probably due to entanglements between the polystyrene blocks at the treated surface and the probe. This demonstrates that the use of this type of amphiphilic block copolymer is a promising route to improve the compatibility between charged reinforcing materials, such as cellulose-based fibers/fibrils, and hydrophobic matrices in composite materials.
|
|
| 35. |
- Utsel, Simon, et al.
(författare)
-
Thermoresponsive nanocomposites from multilayers of nanofibrillated cellulose and specially designed N-isopropylacrylamide based polymers
- 2010
-
Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 6:2, s. 342-352
-
Tidskriftsartikel (refereegranskat)abstract
- In this work positively charged polymers based on N-isopropylacrylamide (NIPAAm) have been synthesised and investigated in solution, on surfaces and in polyelectrolyte multilayers (PEMs) in combination with nanofibrillated cellulose (NFC). Polymers having thermoresponsive properties at low salt concentrations in solution and when adsorbed onto surfaces were obtained by separating the charged groups from the thermoresponsive part in different blocks within the polymer. The polymers have been synthesised using atom transfer radical polymerisation (ATRP) of NIPAAm and (3-acrylamidopropyl)trimethylammonium chloride (APTAC), which is the cationic monomer. All the block copolymers exhibited a lower critical solution temperature (LCST) in water between 35 and 39 degrees C and a positive correlation was found between the LCST and the charge densities of the polymers. It is shown that electrostatic interactions control the adsorption of the prepared polyelectrolytes to SiO2 surfaces and that the block copolymers are thermoresponsive when adsorbed at the solid-liquid interface. PEMs were also assembled with the synthesised polymers and NFC which is a renewable, fibrillar nanomaterial with interesting strength and biocompatibility properties. Even more interestingly it has been found that the formation of the layer-by-layer (LbL) structures of NFC and the block copolymers were demonstrated to have thermal responsivity. This type of thermoresponsive nanocomposite could be used as nano-containers for controlled release or for example in membranes where the permeability could be controlled by the temperature.
|
|
| 36. |
|
|
| 37. |
|
|
| 38. |
- Westlund, Robert, et al.
(författare)
-
Click Chemistry for Photonic Applications : Triazole-Functionalized Platinum(II) Acetylides for Optical Power Limiting
- 2008
-
Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 18:2, s. 166-175
-
Tidskriftsartikel (refereegranskat)abstract
- Three different triazole-containing platinum(ii) acetylide compounds were synthesized by click chemistry and evaluated for their use in optical power limiting (OPL) applications. The triazole unit was incorporated at three different positions within, or at the end of, the conjugation path of the chromophore. The aim is to explore the possibilities of using click chemistry to prepare dendronized chromophores, and to evaluate how the triazole structure affects the photophysical properties and the optical power limiting abilities of these acetylide compounds. It is shown that the concept of click chemistry can be used to attach branched monomer units to ethynyl-phenyl arms by Huisgen 1,3-dipolar cycloaddition, forming triazole units within the chromophore. Photophysical characterization of these triazole-containing materials shows an absorption maximum within the UV-A region and emission through both fluorescence and phosphorescence. Bright phosphorescence was emitted from argon purged samples, and decay measurements thereof showed triplet lifetimes of up to 100 μs. The results from the photophysical characterization suggest that the triazole does break the conjugation path, and in order to gain maximum optical limiting the triazole needs to be placed at the end of the conjugation. All three investigated triazole-containing platinum(ii) acetylides show good optical power limiting at 532 nm (10 ns pulse, f/5 set-up, 2 mm cells). The most efficient compound, with the triazole positioned at the end of the conjugation, reaches a defined clamping level of 2.5 μJ for a sample with a concentration of 50 mM in THF and a linear transmission above 80% at 532 nm. These data can be compared to the OPL properties of Zn-based porphyrins or derivatized thiophenes, reaching clamping levels of 6-15 μJ.
|
|
| 39. |
|
|
| 40. |
- Willgert, Markus, et al.
(författare)
-
Copper-based dye-sensitized solar cells with quasi-solid nano cellulose composite electrolytes
- 2016
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:61, s. 56571-56579
-
Tidskriftsartikel (refereegranskat)abstract
- The study presented describes the preparation of solvent-free nano composite gel electrolytes in combination with copper(I)-based dye-sensitized solar cells (DSSCs). The electrolytes comprise poly(ethylene oxide) (PEO) and cellulose nano crystals (CNCs) and an I-3(-)/I- redox shuttle. The quasi-solid-state DSSCs show increased photoconversion performance with increased amount of CNC in the electrolyte. DSSC performances measured on the day that the devices are fabricated show that when the electrolyte is composed of 80% CNC, a cell efficiency of 1.09% is reached compared to 1.16% using a standard liquid I-3(-)/I- electrolyte. DSSCs containing the nano composites and the copper(I)-based dye show robust stability over time, and after 60 days, DSSCs with the PEO/CNC/I-3(-)/I- electrolyte outperform those containing the liquid electrolyte.
|
|
| 41. |
|
|
