| 1. |
- Achtel, Christian, et al.
(författare)
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Dissolution capacity of novel cellulose solvents based on triethyloctylammonium chloride
- 2017
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 218:21
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Tidskriftsartikel (refereegranskat)abstract
- Dissolution of cellulose from various sources (microcrystalline cellulose and different dissolving grade pulp fibers) is investigated in solvent systems based on triethyl(n-octyl)ammonium chloride (N2228Cl). Clear cellulose solutions are obtained with N2228Cl in a variety of solvents, e.g., dimethyl sulfoxide, N,N-dimethylacetamide, and acetone. It is possible to prepare clear cellulose solutions from pulp fibers with concentrations up to 15 wt%. However, it is found that the cellulose is degraded, especially when neat (i.e., molten) N2228Cl is used as a solvent. The present work includes comprehensive rheological characterization of the cellulose solutions, both with shear and extensional rheology. In most cases, the viscosity values are low (complex viscosities below 100 Pa s for 5–10 wt% dissolved cellulose), and the solutions show more Newtonian than viscoelastic behavior.
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| 2. |
- Andersson, Mattias, 1985, et al.
(författare)
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Influence of Molecular Weight on the Creep Resistance of Almost Molten Polyethylene Blends
- 2018
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 219:3
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Tidskriftsartikel (refereegranskat)abstract
- The most common route to improve the creep resistance of low density polyethylene (LDPE) is crosslinking, which however results in volatile decomposition products that must be removed. Blends of LDPE and an additive-like amount of a linear polyethylene are found to offer improved creep resistance. Above the melting temperature of LDPE, T m ≈ 111 °C, a load-bearing network of higher-melting crystallites—connected through tie chains and trapped entanglements—provides additional form stability. The molecular weight of the linear polyethylene is found to be critical for the ability to arrest creep, which is correlated with the probability of tie chain formation as well as cocrystallization of the two polyethylenes. A number of high-density polyethylenes (HDPE) and one ultrahigh molecular weight polyethylene (UHMW-PE) are explored. For blends of LDPE and 2 wt% of the linear polyethylene, an HDPE with a weight-average molecular weight M w of 16 kg mol −1 is found to be sufficient to arrest creep at 115 °C. Further improvement in terms of creep resistance is obtained in case of UHMW-PE with creep fracture occurring only at a stress of 12 kPa at 115 °C. (Figure presented.).
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| 3. |
- Bini, Kim, 1987, et al.
(författare)
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Synthesis and Characterization of Isoindigo-Based Polymers with Thermocleavable Side Chains
- 2018
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 219:7
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Tidskriftsartikel (refereegranskat)abstract
- Stability of bulk heterojunction films for organic solar cells is a critical factor for commercial viability. One method to stabilize these films is to include cleavable side chains, which reduce the solubility of the polymers when removed. In order to study the stabilizing effect of cleavable side chains, a series of random copolymers using isoindigo with 0, 10, 20, 50, and 100% thermally cleavable side chains based on the tert-butyloxycarbonyl (t-BOC) group are synthesized. The polymers show a distinct one-step thermal cleavage of the side chains, with no separable dealkylation and decarboxylation steps. The thermal stability in film is studied with transmission electron microscopy and atomic force microscopy. The polymer with all t-BOC side chains on isoindigo significantly improves thermal stability with regard to crystal growth and phase separation in film. These results suggest BOC-substitution can be used for large scale processing to produce insoluble polymer films with a high degree of thermal stability.
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| 4. |
- Brännström, Sara, et al.
(författare)
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Tailoring Thermo-Mechanical Properties of Cationically UV-Cured Systems by a Rational Design of Vinyl Ether Ester Oligomers using Enzyme Catalysis
- 2018
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Ingår i: Macromolecular Chemistry and Physics. - : WILEY-V C H VERLAG GMBH. - 1022-1352 .- 1521-3935. ; 219:21
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Tidskriftsartikel (refereegranskat)abstract
- There is a demand for new sustainable polymeric materials. Vinyl ethers are, in this context, attractive oligomers since they polymerize fast, are non-toxic, and can be polymerized under ambient conditions. The availability of vinyl ether oligomers is, however, currently limited due to difficulties in synthesizing them without using tedious synthesis routes. This work presents the synthesis of a series of vinyl ether ester oligomers using enzyme catalysis under solvent-free conditions and the subsequent photoinduced cationic polymerization to form polymer thermosets with T(g)s ranging from -10 to 100 degrees C. The whole process is very efficient as the synthesis takes less than 1 h with no need for purification and the crosslinking is complete within 2 min.
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| 5. |
- Feng, Zhaoxuan, et al.
(författare)
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Photocrosslinked Chitosan Hydrogels Reinforced with Chitosan-Derived no-Graphene Oxide
- 2019
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley-VCH Verlagsgesellschaft. - 1022-1352 .- 1521-3935. ; 220:13
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Tidskriftsartikel (refereegranskat)abstract
- Chitosan and chitosan-derived nano-graphene oxide carbon dots are successfully methacrylated and utilized for the fabrication of photocurable hydrogels. The addition of the nano-graphene oxide (nGO) does not significantly delay the polymer network build-up, but significantly reduces the storage modulus of the crosslinked network, with important detrimental effects on the mechanical performance. By replacing nGO with methacrylated M-nGO, the mechanical performance of the crosslinked polymer network is improved with an increase of the storage modulus as a function of increasing the M-nGO content in the photocurable formulation.
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| 6. |
- Finnveden, Maja, et al.
(författare)
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One-Component Thiol-Alkene Functional Oligoester Resins Utilizing Lipase Catalysis
- 2016
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Ingår i: Macromolecular Chemistry and Physics. - : John Wiley & Sons. - 1022-1352 .- 1521-3935.
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Tidskriftsartikel (refereegranskat)abstract
- Chemo-enzymatic methods are powerful tools for the synthesis of novel materials. By combining the flexibility of chemical synthesis and the high selectivity of enzymes, a variety of functional materials can be achieved. In the present study, a series of α,ω-thiol telechelic oligoesters with varying amount of internal alkenes are prepared using selective lipase catalysis and are subsequently cross-linked by thiol-ene chemistry yielding alkene functional networks. Due to the reactivity of thiols and alkenes almost all present thiol-ene systems consist of two components. This work demonstrates that selective lipase catalysis in combination with renewable monomers with internal alkenes is a promising system for achieving one-component thiol-alkene functional resins with good storage stability and a high degree of thiol end-groups. The developed chemo-enzymatic route yields polymer networks with tailored amount of alkene functionalities in the final thermoset, which facilitate further postmodification.
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| 7. |
- Golabi, Mohsen, et al.
(författare)
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Tuning the surface properties of polypyrrole films for modulating bacterial adhesion.
- 2016
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Ingår i: Macromolecular Chemistry and Physics. - : John Wiley & Sons. - 1022-1352 .- 1521-3935. ; 217:10, s. 1128-1135
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Tidskriftsartikel (refereegranskat)abstract
- Tuning the physical–chemical properties of polypyrrole (PPy) opens up potentially exciting new applications, especially in the area of bacterial adhesion. Polypyrrole is electrochemically synthesized under various conditions and the physical properties of the films and their effects on bacterial adhesion are characterized. Five types of dopants—chloride (Cl), perchlorate (ClO4), p-toluene-sulfonate (ToS), dodecylbenzene sulfonate (DBS), and poly sodium styrene sulfonate (PSS)—are used to fabricate PPy films at two different constant potentials (0.500 and 0.850 V) with and without Fe3+. Their thickness, roughness, and wettability are measured. The adhesion tendency of Escherichia coli, as a model bacterium, to the four polymers is studied. E. coli shows greater adhesion tendency to the hydrophobic, rough surface of PPy-DBS, and less adhesion tendency to the smooth and hydrophilic surface of PPy-PSS. The results facilitate the choice of appropriate electropolymerization conditions to modulate bacterial adhesion.
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| 8. |
- Jannasch, Patric, et al.
(författare)
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Configuring anion-exchange membranes for high conductivity and alkaline stability by using cationic polymers with side chains
- 2016
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1521-3935 .- 1022-1352. ; 217:10, s. 1108-1118
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Forskningsöversikt (refereegranskat)abstract
- Polymeric anion-exchange membranes (AEMs) are critical components for alkaline membrane fuel cells (AMFCs) which offer several attractive advantages including the use of platinum-free catalysts and a wide choice of fuel. The development of AMFCs and other electrochemical energy systems is currently severely limited by the lack of AEMs with sufficient alkaline stability. Still, significant advances have been made in recent years and one of the most promising approaches to emerge is the design and synthesis of cationic polymers with various side chain arrangements. Especially, synthetic strategies where the cationic ion exchange groups are placed on pendant alkyl spacer chains along the backbone seem to significantly improve microphase separation, hydroxide ion conductivity, and alkaline stability in relation to standard AEMs with cations placed in benzylic positions directly on the backbone. This article reviews recent approaches to high-performance cationic membrane polymers involving different side chain designs, and discusses some possible future directions.
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| 9. |
- Lobov, Gleb S., et al.
(författare)
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Size Impact of Ordered P3HT Nanofibers on Optical Anisotropy
- 2016
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Ingår i: Macromolecular Chemistry and Physics. - : John Wiley & Sons. - 1022-1352 .- 1521-3935. ; 217:9, s. 1089-1095
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Tidskriftsartikel (refereegranskat)abstract
- Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline structures with semiconductor properties. When P3HT nanofi bers are dispersed in nonconducting solvent, they react to external alternate electric field by aligning along the field lines. This can be used to create layers of ordered nanofi bers and is referred to as alternating current poling method. P3HT nanofi bers with three different size distributions are fabricated, using self-assembly mechanism in marginal solvents, and used for the alignment studies. Anisotropic absorption of oriented 2 mu m long nanofi bers exponentially increases with the magnitude of applied field to a certain asymptotic limit at 0.8 V mu m(-1), while 100-500 nm long nanofi bers respond to electric field negligibly. Effective optical birefringence of oriented 2 mu m long nanofi bers is calculated, based on the phase shift at 633 nm and the average layer thickness, to be 0.41. These results combined with further studies on real-time control over orientation of P3HT nanofi bers in liquid solution or host system are promising in terms of exploiting them in electroabsorptive and electrorefractive applications.
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| 10. |
- Valencia, Luis, et al.
(författare)
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Tuning the LCST of PNIPAM via Random Oxidation-Sensitive Thioether Functionalities
- 2017
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 218:9
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Tidskriftsartikel (refereegranskat)abstract
- In this work, an oxidation-responsive thioether-functionalized poly(N-isopropylacrylamide) is reported, which is synthesized via reversible-addition fragmentation transfer (RAFT) polymerization using 6-(methylthio)hexyl acrylate or 2-(methylthio)ethyl acrylate as comonomers and S-ethyl-S-(a,a-dimethyl-a-acetic acid)trithiocarbonate as RAFT agent, investigating the influence over the lower critical solution temperature (LCST) of the random thioether functionalities, prior and upon oxidation. The hydrophobic thioethers shift the LCST values of the resulting copolymers to very low temperatures, but the value could be regulated upon oxidation due to the huge increase in dipolar moment. The resulting copolymers containing hydrophilic sulfoxides show much higher LCST values, reaching a difference of up to 23 degrees C after oxidation. Results are supported by H-1 NMR, size exclusion chromatography, and turbidimetry measurements.
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| 11. |
- Woo, Euntaek, et al.
(författare)
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Polyimide‐PEG Segmented Block Copolymer Membranes with High Proton Conductivity by Improving Bicontinuous Nanostructure of Ionic Liquid‐Doped Films
- 2019
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley-Blackwell Publishing Inc.. - 1022-1352 .- 1521-3935. ; 220:9
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Tidskriftsartikel (refereegranskat)abstract
- The structure and properties of segmented block copolymer films of aromatic polyimide (PI) and poly(ethylene glycol) (PEG) doped with an ionic liquid are studied for potential polymer electrolyte membrane applications for fuel cells. Poly(amic acid) precursors of PI-PEG copolymers of 4,4-(hexafluoroisopropylidene) diphthalic anhydride, 4,4-(1,3-phenylenedioxy) dianiline, and bis(3-aminopropyl) terminated PEG (M-n approximate to 1500) are synthesized and then thermally imidized in membrane films, followed by swelling in ethylammonium nitrate (EAN) ionic liquid. The small-angle X-ray scattering results from the EAN-doped PI-PEG copolymer films show disordered bicontinuous phase-separated nanostructures described by Teubner-Strey theory, with the interface fractal dimension determined from the Porod equation. Thermal annealing of the EAN-doped membranes at 100-140 degrees C results in increased correlation lengths and smoother interfaces of the bicontinuous nanostructures. Such improved nanostructures lead to the increased ionic conductivity by two to five times with the maximum conductivity of 210 mS cm(-1) at 60 degrees C and 70% RH, much greater (nearly fivefold) than that of Nafion films, while maintaining the mechanical stability possibly up to 140 degrees C. Moreover, the investigation of the disordered bicontinuous phase-separated nanostructure of EAN-doped PI-PEG copolymer membranes is highly relevant to understanding the nanostructures of hydrated Nafion membranes and segmented block copolymers in general.
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| 12. |
- Xu, Huan, et al.
(författare)
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Stereocontrolled Entanglement-Directed Self-Alignment of Poly(lactic acid) Cylindrites
- 2016
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Ingår i: Macromolecular Chemistry and Physics. - : John Wiley & Sons. - 1022-1352 .- 1521-3935. ; 217:23, s. 2567-2575
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Tidskriftsartikel (refereegranskat)abstract
- The concept of stereocontrolled entanglements, in which the tunable H-bonded chiral pairs serve as crosslinks to create topological constraints on the local chain dynamics, is introduced to tailor the crystalline morphology of stereocomplex poly(lactic acid). For the entanglements to be interconnected and activated, poly(d-lactic acid) with statistical branched architecture is incorporated, enabling the construction of 3D association with linear poly(l-lactic acid) chains. With thermodynamically graded disentanglement relaxation for the blends, the profound influence of entanglements on the crystalline morphology is revealed during isothermal crystallization. Orderly aligned cylindrites some with an exceptional length of over 500 μm, resembling the structural features of the classical shish-kebab superstructure, are observed in the blends penetrated with dense entanglement constraints. By contrast, only dendritic spherulites are formed in the highly disentangled blends. The selectively suppressed homo-crystallization by the entanglements offers insights into the contribution of constraints. This bottom-up strategy opens up pathways to engender oriented crystals of long-range order under quiescent conditions, which has potential implications for other chiral polymers.
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| 13. |
- Bagan Navarro, Hector, et al.
(författare)
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Thermoresponsive Polymer Brushes on Organic Microspheres for Biomolecular Separation and Immobilization
- 2017
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352. ; 218:3
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Tidskriftsartikel (refereegranskat)abstract
- A new method is developed to synthesize organic microsphere-supported polymer brushes for affinity separation of saccharides and glycoproteins. In the first step, crosslinked polymer microspheres are synthesized using atom transfer radical polymerization (ATRP). The terminal ATRP initiators on the microspheres are used to graft polymer brushes from propargyl acrylate and N-isopropyl acrylamide. The microsphere-supported polymer brushes are conjugated with an azide-tagged phenylboronic acid to complete the material synthesis. The microsphere-supported, boronic acid-containing polymer brushes are able to bind not only low molecular weight cis-diol compounds but also glycoproteins. The synthetic procedure developed in this work provides a convenient means for preparing all-organic microsphere-supported polymer brushes that have high alkaline stability. Using the surface-attached polymer brushes to immobilize a catalytic glycoprotein (horseradish peroxidase), it is possible to retain on-particle enzyme activity due to the open structure of the polymer brushes and the oriented immobilization. (Figure presented.).
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| 14. |
- Jiang, Lingdong, et al.
(författare)
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Temperature and pH Controlled Self-Assembly of a Protein-Polymer Biohybrid
- 2018
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352. ; 219:7
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Tidskriftsartikel (refereegranskat)abstract
- A novel pH and temperature dual-responsive bioconjugate is prepared by grafting thermoresponsive polymer chains from a pH-responsive protein amelogenin via atom transfer radical polymerization. To the best of our knowledge, this is the first time that amelogenin is exploited to prepare a hybrid biomaterial with new stimuli-responsive property. In both basic and acidic solutions the protein-polymer bioconjugate is able to self-assemble into uniform and stable nanoparticles when heated to above the lower critical solution temperature of the polymer. The amelogenin-based stimuli-responsive bioconjugate may be of great use in the fields of bioseparation and drug/gene delivery, and the synthetic approach reported here should provide a convenient means to preparing amelogenin-based functional biohybrid materials.
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| 15. |
- Tas, Sinem, et al.
(författare)
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Chain End-Functionalized Polymer Brushes with Switchable Fluorescence Response
- 2019
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352. ; 220:5
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Tidskriftsartikel (refereegranskat)abstract
- Herein is described the switchable fluorescence response of poly(methyl methacrylate) (PMMA) brushes. Chain end fluorescein labeled PMMA brushes are prepared by combining surface-initiated atom transfer radical polymerization (SI-ATRP) with a copper-catalyzed alkyne-azide cycloaddition (CuAAC) click reaction. Successful attachment of fluorescein is confirmed by measuring fluorescence of the as-prepared films. Utilizing co-solvency of PMMA in isopropanol-water mixtures, responsive behavior of the end-functionalized brushes is demonstrated by measuring the changes in fluorescence intensity between the swollen and collapsed states.
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