| 1. |
- Dérand, Helene, et al.
(author)
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Anionic Graft Copolymers Containing Poly(ethylene oxide)
- 1995
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In: Electrochimica Acta. - 0013-4686. ; 40:13-14, s. 2413-2416
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Journal article (peer-reviewed)abstract
- Anionic graft copolymers were prepared through ring-opening anhydride reactions between poly(ethylene oxide) monomethyl ethers (MPEG) and copolymers of maleic anhydride and styrene (SMA), methyl vinyl ether (MEMA) and ethylene (EMA), respectively. The carboxylic acid groups in the graft copolymers were neutralized with KOH, and films were prepared by solution casting. The materials were characterized by FTIR, NMR and DSC. Ionic conductivity and electrical relaxation have been studied as well. The EMA-MPEG 2000 graft copolymer showed the highest conductivity, sigma = 3 x 10(-5) S cm(-1) at 80 degrees C.
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| 2. |
- Dérand, Helene, et al.
(author)
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Ionic Conductivity and Dielectric Properties of Poly(ethylene oxide) Graft Copolymers End-capped with Sulfonic Acid
- 1998
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In: Electrochimica Acta. - 0013-4686. ; 43:10-11, s. 1525-1531
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Journal article (peer-reviewed)abstract
- Both anions and cations are mobile and carry the electrical charge in most polymer electrolytes. A single ion conductor with purely cationic conduction can be realized by incorporation of the anion into the polymer chain. In order to obtain pure lithium ion conductors we prepared two types of graft copolymers, namely poly(amide 12-graft-ethylene oxide) and poly(ethylene-co-vinyl alcohol-gr aft-ethylene oxide), respectively, and end-capped the poly(ethylene oxide) grafts with sulfonic acid groups. Lithium salts of the graft copolymers were made by neutralizing the sulfonic acid groups with lithium hydroxide. Films of the neutralized polymers were prepared by solution casting. The thermal properties of the films were evaluated from DSC measurements. Complex impedance spectroscopy gave information on the ionic conductivity and dielectric relaxations. The highest conductivity, at 80 degrees C, 2*10(-5) S/cm was obtained for poly(amide 12-graft-ethylene oxide).
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| 3. |
- Dérand, Helene, et al.
(author)
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Pol(ethylene glycol) Graft Copolymers Containing Carboxylic Acid Groups: Aggregation and Viscometric Properties in Aqueous Solution
- 1996
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In: Macromolecules. - 0024-9297. ; 29:27, s. 8770-8775
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Journal article (peer-reviewed)abstract
- Poly(ethylene glycol) monomethyl ethers (MPEG) were grafted on copolymers of maleic anhydride and styrene, methyl methacrylate, and ethylhexyl methacrylate, respectively. Hydrolysis of the remaining anhydride residues gave graft copolymers carrying a large number of carboxylic acid groups along the main chains. The properties in aqueous solutions of these graft copolymers were studied with respect to aggregation behavior and viscometric properties, Aggregation of the polymers was examined by quasi-elastic light scattering and now field-flow fractionation in water and KCl solution. Both methods showed that the anionic graft copolymers mainly were present as single molecules in pure water, with a minor fraction of aggregates. In KCI solution, aggregates with average sizes of approximately 30 nm were the dominant species. In aqueous solution, the polymers exhibited polyelectrolyte behavior, i.e., a dramatic increase of the viscosity upon neutralization. Graft copolymers with hydrophobic groups in the backbone had lower viscosities.
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| 4. |
- Wesslén, Bengt, et al.
(author)
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Synthesis of amphiphilic amylose and starch derivatives
- 2002
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In: Carbohydrate Polymers. - 0144-8617. ; 47:4, s. 303-311
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Journal article (peer-reviewed)abstract
- For non-food uses starch generally is modified in order to obtain products with properties suitable for various applications. In the present work, starch and amylose were hydrophobically modified through reactions with long-chain alpha -alkyl epoxides (C-6 and C-12) in DMSO solution, in the presence of NaH as a catalyst. The molar substitution (MS) was calculated from NMR spectra. Derivatives with high as well as low MS values were obtained. In order to reach MS values above 1.5, the reaction had to be run for 150-300 h. Viscosity and GPC measurements indicated that the polysaccharides were degraded in DMSO under the influence of methyl sulfinyl anion, which presumably is the active catalyst. The derivatives were also characterized by FTIR. The ratio between the peak areas for OH stretching and alkyl stretching vibrations, respectively, in the FTIR spectra, was found to be proportional to MS values determined from NMR spectra. The solubility of the hydrophobically modified polysaccharide in various solvents was tested. Samples having C-12-alkyl side chains and MS > 1 were soluble in toluene. The C6 derivatives were water soluble up to a MS value of 0.3.
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| 5. |
- Wittgren, Bengt, et al.
(author)
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Size characterization of a charged amphiphilic copolymer in solutions of different salts and salt concentrations using flow field-flow
- 1996
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In: Langmuir. - 0743-7463. ; 12:25, s. 5999-6005
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Journal article (peer-reviewed)abstract
- The aggregation behavior of a charged amphiphilic graft copolymer, prepared from poly(styrene-co-methyl methacrylate-co-maleic anhydride) and poly(ethylene oxide) monomethyl ether, was studied using flow field-flow fractionation (flow FFF). This method determines the hydrodynamic size of aggregates. The polymer was shown to have a complex aggregation behavior in aqueous solutions containing salt. This was expressed in the formation of differently sized structures, from single polymer chains to large polymolecular aggregates. The polymer changed its aggregation ability in the presence of different salts and salt concentrations, as reflected by changes in hydrodynamic size. Three different salts were tested: potassium chloride, sodium sulfate, and sodium phosphate. Even at micromolar concentrations of sodium sulfate, a pronounced aggregation was observed, probably due to reduced charge repulsion. At higher concentrations of the ''salting-out'' salts, the hydrodynamic size increased rapidly, reflecting the reduced solubility of the hydrophilic parts of the polymer, i.e. the poly(ethylene oxide) grafts. Sodium sulfate, and sodium phosphate in particular, had a stronger influence on polymer aggregation than potassium chloride. This agrees with current knowledge of electrolytic effects on poly(ethylene oxide) solutions. Flow FFF was found to be a suitable characterization technique for these complex systems, rapidly and efficiently separating different polymer aggregate populations ranging from a few nanometers up to 0.1 mu m.
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| 6. |
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| 7. |
- Adebahr, Josefina, et al.
(author)
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Cation coordination in ion-conducting gels based on PEO-grafted polymers
- 2000
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In: Solid State Ionics. - 0167-2738. ; 135:1-4, s. 149-154
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Journal article (peer-reviewed)abstract
- Ionic conducting polymer gels prepared from PEG-grafted acrylates, ethylene carbonate (EC), dimethyl carbonate (DMC), and LiPF6 are studied by means of infrared and Raman spectroscopy. It is found that the presence of grafted PEO chains substantially changes the coordination of lithium cations from 'cation-solvent' to 'cation-polymer'. Spectroscopic studies show that Li+-PEO coordination is strongly favored in competition with the solvent molecules and dominates completely at ether oxygen to Li-cation ratios (O:Li) of 10:1 and 5:1. At an O:M of 4:1 a solvent-cation interaction arises, in agreement with previously reported MD calculations of a preferred coordination number of 5 in similar systems. The results suggest that the complex interactions which determine long time stability and ionic transport properties can be designed by functionalization of the polymer backbone in PMMA-based gel electrolytes.
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| 8. |
- Andersson, Thorbjorn, et al.
(author)
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Degradation of LDPE LLDPE and HDPE in film extrusion
- 2003
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In: TAPPI European PLACE Conference. ; 2, s. 333-359
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Conference paper (peer-reviewed)abstract
- The degradation of different polyethylenes, LDPE, LLDPE, and HDPE, with and without antioxidants and at different oxygen concentrations in the polymer granulates have been studied in extrusion coating processing. The degradation was followed by On Line Rheometry, Size Exclusion Chromatography, Surface Oxidation Index measurements, and GC-MS Chromatography. The degradations starts in the extruder where primary radicals are formed which are subject the auto oxidation when oxygen is present. In the extruder, cross-linking and chain scission reactions are dominating at low and high melt temperatures, respectively, for LDPE, and chain scission is over all dominating for the more linear LLDPE and HDPE resins. Additives such as antioxidants react with primary radicals formed in the melt. Degradation taking place in the film between the die orifice and the quenching point is mainly related to the exposure time to air-oxygen. Melt temperatures above 280
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| 9. |
- Andersson, Thorbjörn, et al.
(author)
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Degradation of LDPE LLDPE and HOPE in film extrusion
- 2004
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In: TAPPI PLACE Conference. - 1595100628 ; , s. 77-92
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Conference paper (peer-reviewed)abstract
- The degradation of different polyethylenes, LDPE, LLDPE, and HDPE, with and without antioxidants and at different oxygen concentrations in the polymer granulates have been studied in extrusion coating processing. The degradation was followed by On Line Rheometry, Size Exclusion Chromatography, Surface Oxidation Index measurements, and GC-MS Chromatography. The degradations starts in the extruder where primary radicals are formed which are subject the auto oxidation when oxygen is present. In the extruder, cross-linking and chain scission reactions are dominating at low and high melt temperatures, respectively, for LDPE, and chain scission is over all dominating for the more linear LLDPE and HDPE resins. Additives such as antioxidants react with primary radicals formed in the melt. Degradation taking place in the film between the die orifice and the quenching point is mainly related to the exposure time to air-oxygen. Melt temperatures above 280
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| 10. |
- Andersson, Thorbjörn, et al.
(author)
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Degradation of low density polyethylene during extrusion. : IV. Off-flavor compounds in extruded films of stabilized LDPE
- 2005
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In: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 95:3, s. 583-595
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Journal article (peer-reviewed)abstract
- This study was aimed at finding a correlation between the experienced off-flavor in packed foods and the presence of specific degradation products in LDPE pack-aging films. The possibility to trap degradation products by chemical reactions with scavengers, i.e., a zeolite additive or antioxidants, was investigated This would prevent degradation products from migrating to the polymer film surface and further into food in contact with the film. It was found that off-flavor noted in water packed in LDPE films depended on extrusion temperature and exposure time for the melt to oxygen, that is, the parameters that influence the contents of oxidation products that are able to migrate from the polymer film. It was also found that adsorption of oxidative degradation products in a zeolite additive or protection of LDPE by using antioxidants could prevent off-flavor in the packed product (water). However, the antioxidant should be selected with regard to extrusion temperature because thermal instability in the additive might jeopardize the intended effect. Multifunctional antioxidants seem to provide improved protection, the most effective one evaluated in this work being Irganox E201, i.e., vitamin E. Concentrations of oxidized degradation products are well correlated to the perceived off-flavor in the packed water. The highest correlation between off-flavor and oxidized components was found for ketones in the range of C 7 to C9 and aldehydes in the range of C6 to C9.
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