| 1. |
- Dérand, Helene, et al.
(författare)
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Anionic Graft Copolymers Containing Poly(ethylene oxide)
- 1995
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Ingår i: Electrochimica Acta. - 0013-4686. ; 40:13-14, s. 2413-2416
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: Electrochimica Acta. - 0013-4686. ; 43:10-11, s. 1525-1531
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: Macromolecules. - 0024-9297. ; 29:27, s. 8770-8775
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Synthesis of amphiphilic amylose and starch derivatives
- 2002
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 47:4, s. 303-311
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: Langmuir. - 0743-7463. ; 12:25, s. 5999-6005
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Cation coordination in ion-conducting gels based on PEO-grafted polymers
- 2000
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Ingår i: Solid State Ionics. - 0167-2738. ; 135:1-4, s. 149-154
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Degradation of LDPE LLDPE and HDPE in film extrusion
- 2003
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Ingår i: TAPPI European PLACE Conference. ; 2, s. 333-359
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Konferensbidrag (refereegranskat)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.
(författare)
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Degradation of LDPE LLDPE and HOPE in film extrusion
- 2004
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Ingår i: TAPPI PLACE Conference. - 1595100628 ; , s. 77-92
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Konferensbidrag (refereegranskat)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.
(författare)
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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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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 95:3, s. 583-595
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Tidskriftsartikel (refereegranskat)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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| 11. |
- Andersson, Thorbjörn, et al.
(författare)
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Degradation of low density polyethylene during extrusion : III. Volatile compounds in extruded films creating off-flavor
- 2005
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 95:4, s. 847-858
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Tidskriftsartikel (refereegranskat)abstract
- This study was aimed at finding a correlation between the experienced off-flavor in packaged foods and the presence of specific degradation products in PE packaging films. The possibility to trap degradation products by chemical reactions with scavengers, that is, zeolites and maleic anhydride grafted LLDPE, were investigated. This trapping would prevent the degradation products from migrating to the polymer film surface and further into food in contact with the film. This work concludes that off-flavor in water packed in LDPE-films depends on extrusion temperature and the content of oxidation products in the polymer film. At lower extrusion temperatures, reactive additives to the LDPE material could control the release of off-flavor giving compo nents. Adsorbents, such as zeolites, which are able to adsorb degradation products, are effective also at higher extrusion temperatures. The amount of oxidized degradation products in the films correlated well to the perceived off-flavor in the packed water. The presence of aldehydes and ketones have a clear impact on the off-flavor. The best correlation between off-flavor and oxidized components were found for C7-C9 ketones, and aldehydes in the range of C5 to C8.
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| 12. |
- Andersson, T, et al.
(författare)
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Degradation of low density polyethylene during extrusion. I. Volatile compounds in smoke from extruded films
- 2002
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 86:7, s. 1580-1586
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Tidskriftsartikel (refereegranskat)abstract
- Many problems with odor and taste in food packaging can be traced to degradation of the packaging materials during processing. From this starting point, the degradation of polyethylene in a commercial extrusion coating process was studied by analyzing degradation products present in smoke sampled at the extruder die orifice. Two low-density polyethylenes, A and B, with similar melt flow indexes and densities and obtained from different producers, were investigated. A third polymer, C, consisting of recycled material B, was also investigated. More than 40 aliphatic aldehydes and ketones, together with 14 different carboxylic acids, were identified in the smoke. The highest concentration was found for acetaldehyde, regardless of polymer and processing conditions. Increasing the extrusion temperatures in the range 280-325 degreesC increased the amounts of the oxidized products in the smoke. The extruded film thickness, 12 and 25 mum, influenced the concentrations of degradation products, With the thicker film giving higher amounts of product. The recycled polymer C generally gave lower concentrations of degradation products compared with the virgin polymer B. Difference ill the product spectrum between the two virgin polymers may be related to differences in the manufacturing process, Many of the identified compounds have very characteristic taste and smell and are consequently of interest fron on odor and taste point of view in food packaging applications. (C) 2002 Wiley Periodicals, Inc.
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| 13. |
- Andersson, T, et al.
(författare)
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Degradation of low-density polyethylene during extrusion. VI. Effects of oxygen content in air gap
- 2005
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 96:5, s. 1767-1775
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Tidskriftsartikel (refereegranskat)abstract
- In our previous papers polyethylene degradation during extrusion coating has been studied and the type of degradation products that are formed and from which step they originate have been discussed. A trained sensory panel has rated the off-flavor intensities in water samples that have been in contact with various extruded films. Encouraged by the results from these investigations and the documented synergism between aldehydes and ketones and aldehydes and carboxylic acids in off-flavor intensity, the present study was aimed at confirming the belief that the off-flavor depends on the presence of oxidative degradation products that have migrated from the film into the water. By decreasing the oxygen concentration in the atmosphere surrounding the extruded melt presence of the highly oxidized species (i.e., carbonyl compounds and carboxylic acids) would decrease and thus the off-flavor in the water should decline. From this study it could be concluded that the extrusion temperature and the oxygen content in the atmosphere nearest the molten film before quenching are the most important parameters for oxidative degradation and residence time in the air gap influence the amount of oxidative degradation products formed. Furthermore we concluded that the off-flavor intensity is strongly correlated to the surface oxidation index of the film. Carboxylic acids are present in the water extracts of extruded films and are related to the off-flavor intensities. (c) 2005 Wiley Periodicals, Inc.
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| 14. |
- Andersson, T, et al.
(författare)
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Degradation of polyethylene during extrusion. II. Degradation of low-density polyethylene, linear low-density polyethylene, and high-density polyethylene in film extrusion
- 2004
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 91:3, s. 1525-1537
-
Tidskriftsartikel (refereegranskat)abstract
- The degradation of different polyethylenes-low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (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 online rheometry, size exclusion chromatography, surface oxidation index measurements, and gas chromatography-mass spectrometry. The degradations start in the extruder where primary radicals are formed, which are subject to the auto-oxidation when oxygen is present. In the extruder, crosslinking or chain scissions reactions are dominating at low and high melt temperatures, respectively, for LDPE, and chain scission is overall 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 280degreesC give a dominating surface oxidation, which increases with the exposure time to air between die orifice and quenching too. A number of degradation products were identified-for example, alclehydes and organic acids-which were present in homologous series. The total amount of aldehydes and acids for each number of chain carbon atoms were appeared in the order of C5>C4>C6>C7much greater thanC2 for LDPE, C5>C6>C4> C7much greater thanC2 for LLDPE, and C5>C6>C7>C4much greater thanC2 for HDPE. The total amounts of oxidized compounds presented in the films were related to the processing conditions. Polymer melts exposed to oxygen at the highest temperatures and longest times showed the presence dialdehydes, in addition to the aldehydes and acids. (C) 2003 Wiley Periodicals, Inc. J Appl Polyrn Sci 91: 1525-1537, 2004.
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| 15. |
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| 16. |
- Dérand, Helene, et al.
(författare)
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Graft Copolymers Prepared by Ethoxylation of Polyamide 12 and Poly(ethylene-co-vinyl alcohol)
- 1998
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Ingår i: Journal of Polymer Science. Part A, Polymer Chemistry. - 0887-624X. ; 36:5, s. 803-811
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Tidskriftsartikel (refereegranskat)abstract
- Graft copolymers consisting of polyamide 12 or poly(ethylene-co-vinyl alcohol) as backbone polymers and side chains of poly(ethylene oxide) have been synthesized. The amide and hydroxyl groups of the backbone polymers were used as initiation sites for the polymerization of ethylene oxide (EO). Potassium tert-butoxide was used for ionization of the active groups, and the polymerization of EO was carried out in dimethyl sulfoxide. The graft copolymers were characterized with respect to molecular weight and composition using elemental analysis, H-1-NMR, gel permeation chromatography, and FTIR. The size of the side chains varied between 300 and 1000 g/mol. Thermal properties were examined by DSC. The graft copolymers showed increasing crystallinity and increasing melt temperature with increasing molecular weight of the side chains.
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| 17. |
- Dérand, Helene, et al.
(författare)
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Synthesis and Characterization of Anionic Graft Copolymers Containing Poly(ethylene oxide) Grafts
- 1995
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Ingår i: Journal of Polymer Science. Part A, Polymer Chemistry. - : Wiley. - 0887-624X .- 1099-0518. ; 33:3, s. 571-579
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Tidskriftsartikel (refereegranskat)abstract
- Anionic graft copolymers were synthesized through grafting of poly(ethylene glycol) monomethyl ether (MPEG) onto terpolymers containing succicinic anhydride groups. The backbone polymers were prepared through radical terpolymerization of maleic anhydride, styrene, and one of the following monomers: methyl methacrylate, ethylhexyl methacrylate, and diethyl fumarate. MPEG of different molecular weights were grafted onto the backbone through reactions with the cyclic anhydride groups. In this reaction one carboxylic acid group is formed together with each ester bond. The molecular weights of MPEG were found to influence the rate of the grafting reaction and the final degree of conversion. The graft copolymers were characterized by IR, GPC, and IH-NMR. Thermal properties were examined by DSC. Graft copolymers containing 50% w/w of MPEG 2000 grafts were found to be almost completely amorphous, presumably because of crosslinking, and hydrogen bonding between carboxylic acid groups in the backbone and the ether oxygens in MPEG grafts.
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| 18. |
- Eklind, H, et al.
(författare)
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Characterization of the interphase in PPO/PMMA blends compatibilized by P(S-g-EO)
- 1996
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 29:3, s. 984-992
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Tidskriftsartikel (refereegranskat)abstract
- The influence of a poly(styrene-graft-ethylene oxide) (P(S-g-EO)) copolymer on poly(2,6-dimethyl-p-phenylene oxide)/poly(methyl methacrylate) (PPO/PMMA) blends was studied by a number of different techniques in order to characterize the properties of the interphase. Scanning electron microscopy shows that the copolymer reduces the dispersed phase size, and dynamic mechanical spectroscopy (DMS) reveals a new micromechanical transition in the ternary blends. These effects are shown to be caused by a copolymer-rich interphase with a certain volume fraction and with its own characteristic properties. Solid-state nuclear magnetic resonance (NMR) relaxation times indicate that the poly(ethylene oxide) side chains of the copolymer are partially miscible with PMMA in the ternary blends, which suggests that the interphase does not only consist of pure copolymer.
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| 19. |
- Freij-Larsson, Christina, et al.
(författare)
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Adsorption behaviour of amphiphilic polymers at hydrophobic surfaces: Effects on protein adsorption
- 1996
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Ingår i: Biomaterials. - : Elsevier BV. - 1878-5905 .- 0142-9612. ; 17:22, s. 2199-2207
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of four different amphiphilic polymers to a model surface has been studied, and the effects of the adsorbed amphiphiles on the subsequent adsorption of fibrinogen (Fg) and human serum albumin (HSA) at the surfaces were investigated. The amphiphilic polymers were one commercially available ABA block copolymer, Pluronic PE9400 (PE94), composed of poly(ethylene oxide) (A-blocks) and poly(propylene oxide) (B-block), and three graft copolymers, two with backbones of poly(styrene-co-acrylamide) (STY) and one with a backbone of poly(methyl methacrylate-co-ethylhexyl methacrylate) (ACRY). The backbones carried poly(ethylene oxide) (PEG) grafts, The model surface was a hydrophobic methylated silica surface (HMS). The amphiphilic polymers were adsorbed at the HMS surface from an ethanol/water solution. The adsorption process was monitored by ellipsometry. After rinsing with phosphate buffered saline (PBS), protein was added and the continued adsorption measured by ellipsometry. Surfaces modified by adsorption of the amphiphilic polymers were also characterized by contact angle measurements and X-ray photoelectron spectroscopy (XPS). According to these measurements the amphiphilic polymers adsorbed in significant amounts at the HMS surface. A limited study by atomic force microscopy (AFM), as well as the XPS measurements, suggests that both single molecules and micellar aggregates adsorb at the surface. ACRY and PE94 gave the highest levels of adsorption. As compared to the Pluronic block copolymer the graft copolymers were more strongly attached to the HMS surface, as shown by less desorption on rinsing with solvent. The ellipsometric results show that the adsorption of HSA and Fg at HMS surfaces containing preadsorbed amphiphilic polymer was significantly reduced as compared to the bare HMS surface. ACRY and PE94 showed the largest effects. Both polymers gave more than a 20-fold reduction of the Fg adsorption and a 10-fold reduction of the HSA adsorption. The STY polymers reduced the protein adsorption by a factor of 2-3.
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| 20. |
- Freij-Larsson, Christina, et al.
(författare)
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Grafting of Polyurethane Surfaces with Poly(Ethylene Glycol)
- 1993
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 50:2, s. 345-352
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Tidskriftsartikel (refereegranskat)abstract
- Films of a commercial poly (ether urethane), Pellethane 2363-80AE, were prepared through solvent casting from dimethyl formamide. The films were grafted with poly (ethylene glycol) (PEG) by a two-step procedure. In the first step, the film surfaces were treated with hexamethylene diisocyanate in toluene in the presence of triethylamine as a catalyst. In the second step, PEG 1500 was allowed to react in toluene with surface bound isocyanate groups. It was shown by ATR-IR, XPS, and contact angle measurements that the grafted surfaces were mainly composed of PEG, and that they were strongly hydrophilic. It was also shown that unreacted PEG was entrapped in the material, which influenced its mechanical and thermal properties. Extraction of the films with toluene eliminated the entrapped PEG, and the hydrophilicity as well as the PEG coverage of the surface decreased. However, a subsequent treatment with aqueous NaCl solution induced a molecular restructuring of the surface, increasing the amount of grafted PEG at the surface to a value close to the original one.
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| 21. |
- Freij-Larsson, Christina, et al.
(författare)
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Polyurethane surfaces modified by amphiphilic polymers: effects on protein adsorption
- 2000
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Ingår i: Biomaterials. - 1878-5905. ; 21:3, s. 307-315
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Tidskriftsartikel (refereegranskat)abstract
- Surface modification of polyurethane (PUR) surfaces was carried out by using three different amphiphilic polymers. Two of the polymers were graft copolymers, having backbones consisting of poly(methyl methacrylate-co-ethylhexyl acrylate) and poly(styrene-co-acrylamide), respectively, and poly(ethylene oxide) PEO 2000 grafts. The third polymer was a commercially available poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) block copolymer, Pluronic 9400. The polymers were designated ACRY, STY2, and PE94, respectively. Surface modification was achieved by adsorption of the amphiphilic polymers at PUR surfaces from an aqueous solution, or by blending the amphiphiles into a PUR solution, followed by solution casting of films. The accumulation of the amphiphilic polymers at the PUR surfaces was observed by XPS and contact angle measurements. The ACRY and PE94 polymers were shown to adsorb poorly at the PUR surface, but gave strong surface effects when present in the PUR matrix. Protein adsorption was measured under static as well as under flow conditions. The modified surfaces had generally lower adsorption of blood proteins (HSA, Fg and IgG) than the unmodified PUR surfaces. ACRY blend modified surfaces had the lowest adsorption.
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| 22. |
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| 23. |
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| 24. |
- Gavelin, Patrik, et al.
(författare)
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Amphiphilic polymer gel electrolytes. 3. Influence of the ionophobic-ionophilic balance on the ion conductive properties
- 2001
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Ingår i: Electrochimica Acta. - 0013-4686. ; 46:10-11, s. 1439-1446
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Tidskriftsartikel (refereegranskat)abstract
- Gel electrolytes based on amphiphilic copolymethacrylates containing ethylene oxide (EO)(n) side chains as ionophilic units and fluorocarbon (CF,), side chains as ionophobic units showed a substantial increase in ion conductivity, as compared to corresponding gels based on homopolymers of (EO),, methacrylate. The highest ion conductivity was found for a gel based on a copolymer composed of 24 wt% of (EO)(9) methacrylate and 76 wt% of fluorocarbon methacrylate. This gel contained 70 wt% of 1 M LIPF6 gamma -butyrolactone, and had an ion conductivity of 4.0 mS/cm at 20 degreesC, and 1.0 mS/cm at - 20 degreesC. It was found that gels based on fluorocarbon-containing copolymers having (EO), side chains had higher ion conductivities than gels based on copolymers containing (EO), side chains. The study showed that it is important to control the ionophobic-ionophilic balance of the amphiphilic copolymer in order to achieve high ion conductivities in the gel electrolyte. It is very likely that the ionophobic side chains of the copolymer associated to form microdomains in the electrolyte. It is also likely that longer EO chains increased the stability of these microdomains in the electrolyte. However, strong lithium ion coordination to EO chains above a critical chain length may have suppressed the ion conductivity of the gels.
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| 25. |
- Gavelin, Patrik, et al.
(författare)
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Amphiphilic polymer gel electrolytes. I. Preparation of gels based on poly(ethylene oxide) graft copolymers containing different ionophobic groups
- 2001
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Ingår i: Journal of Polymer Science. Part A, Polymer Chemistry. - : Wiley. - 0887-624X. ; 39:13, s. 2223-2232
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Tidskriftsartikel (refereegranskat)abstract
- Amphiphilic graft copolymers were prepared via the radical copolymerization of poly(ethylene oxide) (PEO) macromonomers with fluorocarbon or hydrocarbon acrylates in toluene with 2,2 ' -azobisisobutyronitrile (AIBN) as an initiator. H-1 NMR spectroscopy confirmed that the composition of the graft copolymers corresponded well to the monomer feed. For gel electrolytes prepared from the amphiphilic copolymers, the nature of the ionophobic parts of the amphiphilic graft copolymers had a great influence on the ion conductivity. Gel electrolytes based on graft copolymers containing fluorocarbon side chains showed significantly higher ion conductivity than electrolytes based on graft copolymers containing hydrocarbon groups. The ambient-temperature ion conductivity was about 2.6 mS/cm at 20 degreesC for a gel electrolyte based on an amphiphilic graft copolymer consisting of an acrylate backbone carrying PEO and fluorocarbon side chains. Corresponding gels based on graft copolymers with PEO side chains and hydrocarbon groups showed an ambient-temperature ion conductivity of about 1.2 mS/cm. The gel electrolytes contained 30 wt % copolymer and 70 wt % 1 M LiPF6 in an ethylene carbonate/gamma -butyrolactone (2/1 w/w) mixture.
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| 26. |
- Gavelin, Patrik, et al.
(författare)
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Amphiphilic polymer gel electrolytes. II. Influence of the ethylene oxide side-chain length on the gel properties
- 2001
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Ingår i: Journal of Polymer Science. Part B, Polymer Physics. - : Wiley. - 0887-6266 .- 1099-0488. ; 39:13, s. 1519-1524
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Tidskriftsartikel (refereegranskat)abstract
- Amphiphilic polymers consisting of copolymethacrylates carrying about 26 wt % ethylene oxide [(EO)(n)] side chains of different lengths were used as matrices in gel electrolytes. The gel electrolytes were composed of 30 wt % copolymer and 70 wt % 1 M LiPF6 in a mixture of ethylene carbonate and gamma -butyrolactone (2/1 w/w). The coordination of lithium ions by the (EO)(n) side chains in competition with the solvent was studied by Raman spectroscopy. A significantly stronger lithium coordination was observed when the gel electrolyte was based on a copolymer carrying (EO)(9) units in comparison with copolymers having (EO)(1), (EO)(2), and (EO)(4) units. Despite the observed stronger lithium coordination by (EO)(9) units in the gel, the ion conductivity was not significantly lower with respect to the gels based on the other copolymers.
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| 27. |
- Gavelin, Patrik, et al.
(författare)
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Amphiphilic solid polymer electrolytes
- 2002
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Ingår i: Solid State Ionics. - 1872-7689 .- 0167-2738. ; 147:3-4, s. 325-332
-
Konferensbidrag (refereegranskat)abstract
- Amphiphilic graft copolymers consisting of methacrylate backbones carrying approximately 48 wt.% of ethylene oxide [(EO)(9) or (EO)(23)] side chains as ionophilic groups and fluorocarbon or hydrocarbon side chains as ionophobic groups were prepared. Solid polymer electrolytes based on the copolymers and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) were characterized by DSC and the impedance spectroscopy. A maximum ion conductivity of 8 x 10(-5) S cm(-1) at 60 degreesC was found for a polymer electrolyte based on a copolymer having hydrocarbon side chains and (EO)(23) side chains, despite an EO content of only 50 wt.%. No (EO)(n) side chain crystallinity in the electrolytes was detected by calorimetry. The hydrocarbon side chains, on the other hand, were found to form a crystalline phase in the electrolytes. The melting of this phase was not reflected in the shape of the Arrhenius conductivity plot. This indicated that the segmental mobility in the ion conducting phase did not decrease as a result of the presence of the crystalline hydrocarbon phase.
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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
- Jannasch, Patric, et al.
(författare)
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Compatibilizing effects of poly(styrene-graft-ethylene oxide) in blends of polystyrene and butyl acrylate polymers
- 1996
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Ingår i: Journal of Applied Polymer Science. - 1097-4628. ; 59:4, s. 619-626
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Tidskriftsartikel (refereegranskat)abstract
- The compatibilizing effect of poly(styrene-graft-ethylene oxide) in polystyrene (PS) blends with poly(n-butyl acrylate) (PBA) and poly(n-butyl acrylate-co-acrylic acid) (PBAAA) was investigated. No significant effects of the graft copolymer on the domain size were found in the PBA blends. By functionalizing PBA with acrylic acid, the average size of the polyacrylate domains was reduced considerably by the graft copolymer. Thermal and dynamic mechanical analysis of the PS/PBAAA blends revealed that the PBAAA glass transition temperature (T-g) decreased with increasing graft copolymer content. The effect of the graft copolymer in the PS/PBAAA blends can be explained by interactions across the interface due to the formation of hydrogen bonds between the poly(ethylene oxide) (PEO) side chains in the graft copolymer and the acrylic acid segments in the PBAAA phase. Hydrogen bonding was confirmed by IR analysis of binary blends of PEO and PBAAA. Partial miscibility in the PEO/PBAAA blends was indicated by a PEO melting point depression and by a T-g reduction of the PBAAA phase. The thermal properties of the PEO/PBA blends indicated only very limited miscibility.
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| 34. |
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| 35. |
- Jannasch, Patric, et al.
(författare)
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On the macro- and microphase separation of compatibilizers in immiscible polymer blends
- 1996
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Ingår i: Journal of Polymer Science. Part B, Polymer Physics. - 0887-6266. ; 34:7, s. 1289-1299
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Tidskriftsartikel (refereegranskat)abstract
- Macro- and microphase separation of compatibilizing graft copolymers in melt-mixed polystyrene/polyamide-6 blends was studied by transmission electron microscopy and thermal analysis. Three different graft copolymers with main chains of polystyrene and side chains of poly(ethylene oxide) were used as additives at various concentrations. The polyamide-6 domain sizes decreased with increasing amounts of compatibilizing graft copolymers in the blends up to a saturation concentration, after which no further reduction was noted. Macrophase separation of the graft copolymers into discrete macrodomains 20-200 nm in size occurred at concentrations equal to or slightly lower than the saturation concentration. The macrodomains of the graft copolymers were microphase separated, and the sizes and shapes of the microdomains were found to largely depend on the graft copolymer structure and composition. As a consequence of microphase separation, poly(ethylene oxide) crystallinity was noted in blends with sufficiently high macrophase contents. Observations of a graft copolymer interphase between the polystyrene matrix and the polyamide-6 domains confirmed that the graft copolymer was present at the blend interfaces in some of the compatibilized blends.
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| 36. |
- Jannasch, Patric, et al.
(författare)
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Poly(styrene-graft-ethylene oxide) as a compatibilizer in polystyrene/polyamide blends
- 1995
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 58:4, s. 753-770
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Tidskriftsartikel (refereegranskat)abstract
- Polystyrene (PS) blends containing a dispersed phase of either polyamide-6 (PA-6) or polyamide-12 (PA-12) were compatibilized by additions of 1, 3, or 5 wt % poly(styrene-graft-ethylene oxide). The graft copolymers were found to have a stabilizing effect on the domain sizes. Weight average radii of PA-6 domains in compression molded samples were reduced by a factor of 5 with 3 wt % graft copolymer added. The corresponding size reduction for PA-12 domains was by a factor of 3. Also, the domain sizes were more uniformly distributed in blends containing the graft copolymers. Thermal analysis of the blends revealed that compatibilization retarded the PA crystallization, with some PA crystallizing at the PS glass transition. This retarded crystallization is explained as a result of the domain size reduction and by the presence of graft copolymer at the interface. The graft copolymers had a toughening effect on the blends and the impact strength of a PS/PA-12 blend was improved by 65% by adding 3 wt % of graft copolymer. Binary blends of the PA and poly(ethylene oxide) (PEO) were investigated in a separate study to verify miscibility of the graft copolymer side chains and the PA. Hydrogen bonding between PA-6 and PEO was confirmed by IR spectroscopy and partial miscibility was indicated by melting point depressions.
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| 37. |
- Jannasch, Patric, et al.
(författare)
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Preparation and properties of alkylated poly(styrene-graft-ethylene oxide)
- 1995
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Ingår i: Journal of Polymer Science. Part A, Polymer Chemistry. - : Wiley. - 0887-624X .- 1099-0518. ; 33:9, s. 1465-1474
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Tidskriftsartikel (refereegranskat)abstract
- Poly(styrene-graft-ethylene oxide), having alkyl chains (C-12 or C-18) on the polystyrene main chain or on the poly(ethylene oxide) (PEO) side chains, were synthesized. The main chain was alkylated by first ionizing amide groups in a styrene/acrylamide copolymer with tert-butoxide, and then using the amide anions as sites for reactions with 1-bromoalkanes. An excess of amide anions was used in the reaction, and the remaining anions were subsequently utilized as initiator sites for the anionic polymerization of ethylene oxide (EO). Synthesis of poly(styrene-graft-ethylene oxide) with alkylated side chains was accomplished by polymerization of EO onto the ionized styrene/acrylamide copolymer, followed by an alkylation of the terminal alkoxide anions with 1-bromoalkanes. The alkylated graft copolymers were structurally characterized by using elemental analysis, H-1 NMR, GPC, and IR spectroscopy. DSC analysis showed that only graft copolymers with PEO contents exceeding about 50 wt % had side chain crystallinities comparable to those of homo-PEO. Main chain alkylated graft copolymers generally had higher crystallinities, as compared to nonalkylated and side chain alkylated samples. The graft copolymers absorbed water corresponding to one water molecule per EO unit at low PEO contents. The water absorption increased progressively at PEO contents above 30 wt % for main chain alkylated samples and above 50 wt % for non-alkylated samples.
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| 38. |
- Jannasch, Patric, et al.
(författare)
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Stress-strain behavior and impact strength of polystyrene/polyamide-6 blends compatibilized with poly(styrene-g-ethylene oxide)
- 1998
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Ingår i: Journal of Applied Polymer Science. - 1097-4628. ; 70:10, s. 1887-1891
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical properties of polystyrene/polyamide-6 (50/50 wt/wt) blends were improved by additions of small amounts of poly(styrene-g-ethylene oxide) (SEO) during compounding by extrusion. Tensile testing of injection-molded samples revealed that the blends developed a yield point after addition of 1 wt % SEO. The elongation at break increased by almost a factor of 6, and the impact strength increased by a factor of 1.5 after adding 3 wt % SEO. Morphological analysis by electron microscopy showed that additions of SEO resulted in decreased domain sizes, and seemed to promote interfacial adhesion. The morphologies of the compatibilized blends also had a higher degree of anisotropy, as compared with the uncompatibilized blend.
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| 39. |
- Jannasch, Patric, et al.
(författare)
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Synthesis of poly(styrene-graft-ethylene oxide) by ethoxylation of amide group containing styrene copolymers
- 1993
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Ingår i: Journal of Polymer Science. Part A, Polymer Chemistry. - : Wiley. - 0887-624X .- 1099-0518. ; 31:6, s. 1519-1529
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Tidskriftsartikel (refereegranskat)abstract
- Graft copolymers containing poly(ethylene oxide) side chains on a polystyrene backbone have been synthesized. Styrene copolymers synthesized by free radical mechanism and containing between 5 and 15 mol % acrylamide or methacrylamide were used as backbones. The amide groups in the copolymers were ionized by using potassium tert-butoxide or potassium naphthalene, and grafting was achieved by utilizing the amide anions as initiator sites for the polymerization of ethylene oxide in 2-ethoxyethyl ether at 65°C. The graft copolymers were characterized with respect to molecular weight and composition using elemental analysis, NMR, gel permeation chromatography, IR, and viscosity measurements. The size of the side chains were between 600 and 2000 g/mol. GPC results from a hydrolyzed graft copolymer sample suggest a narrow size distribution for the poly(ethylene oxide) grafts. Solution properties of the graft copolymers were investigated in different toluene/methanol mixtures. The intrinsic viscosities of the graft copolymers were found to depend primarily on the poly(ethylene oxide) content rather than the graft density or the poly(ethylene oxide) chain length.
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| 40. |
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| 41. |
- Karlsson, Lina, et al.
(författare)
-
Preparation and solution properties of amphiphilic sulfonated acrylamide copolymers
- 2002
-
Ingår i: Macromolecular Chemistry and Physics. - 1521-3935. ; 203:4, s. 686-694
-
Tidskriftsartikel (refereegranskat)abstract
- Copolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and N-tert-butylacryl-amide has been carried out in methanol at 60degreesC using AIBN as initiator. Both IR and H-1 NMR spectroscopy indicated that monomer conversions exceeding 95% were reached in the copolymerizations. Copolymers containing more or equal to approximate to 15 mol-% AMPS were soluble in water and had an amphiphilic character. Analysis by dilute solution viscometry, quasi-elastic light scattering, and size exclusion chromatography in water and aqueous KCl solution showed that the AMPS homopolymer and the copolymers behave as polyelectrolytes. Light scattering analysis and atomic force microscopy indicated the presence of aggregates in aqueous solutions of a copolymer containing 15 mol-% AMPS. Gravimetrical measurements showed that the water absorption of the copolymers in humidified air increases almost linearly with the AMPS content of the copolymers.
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| 42. |
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| 43. |
- Karlsson, Lina, et al.
(författare)
-
Water absorption and proton conductivity of sulfonated acrylamide copolymers
- 2002
-
Ingår i: Electrochimica Acta. - 0013-4686. ; 47:20, s. 3269-3275
-
Tidskriftsartikel (refereegranskat)abstract
- Copolymers of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and N-tert-butylacrylamide (tBAA) have been evaluated as proton conducting materials. The water absorption of copolymers with varying equivalent weights (EW), i.e. g polymer/mol sulfonic acid groups, was studied at different relative humidities (rh) by gravimetry and calorimetry. Melt endotherms for water were detected by DSC in copolymers containing greater than or equal to 45 mol% AMPS when equilibrated at 93% rh, and greater than or equal to 36 mol% AMPS when equilibrated at 98% rh. A study of the kinetics of the water absorption at 98% rh showed that equilibration was faster for the copolymers than for the homopolymer PAMPS. The proton conductivity (Q) of the samples was investigated as a function of temperature, water content, and EW. ac Impedance measurements between -20 and 70 degreesC showed a value of sigma as high as 0.2 S/cm at 70 degreesC for a copolymer containing 54 mol% AMPS equilibrated at 98% rh. It was concluded that both the EW and the amount of water in the polymers controlled the conductivity at all temperatures. For example, increasing amounts of water in the polymers generally gave increasing sigma above the melting point of the water, but decreasing Q below the same temperature.
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| 44. |
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| 45. |
- Ljungberg, Nadia, et al.
(författare)
-
Film Extrusion and Film Weldability of Poly(lactic acid) Plasticized with Triacetine and Tributyl Citrate.
- 2003
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 88:14, s. 3239-3247
-
Tidskriftsartikel (refereegranskat)abstract
- Film extrusion and welding of biodegradable polymer films are important processes that must be considered in the development of compostable packaging materials. Film extrusion of poly(lactic acid) (PLA) has proved to be rather difficult because of its brittleness, but the flexibility of PLA can be improved by incorporation of a plasticizer in the material. PLA was plasticized with triacetine (TAc) and tributyl citrate (TbC). The blended materials and neat PLA were film extruded and the films were welded with constant heat (CH) welding. The films were analyzed by means of gas chromatography (GC), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), contact angle measurements, and tensile testing. Storage of the plasticized films resulted in an increased crystallinity and changes in the film properties, rendering CH welding difficult. The welding process had no influence on thermal properties, such as cold crystallization temperature, melting temperature, crystallization temperature, and degree of crystallinity, of neat PLA but caused significant changes in the crystallinity of the plasticized materials. © 2003 Wiley Periodicals, Inc.
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| 46. |
- Ljungberg, Nadia, et al.
(författare)
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Plasticization of poly(lactic acid) with oligomeric malonate esteramides: Dynamic mechanical and thermal film properties
- 2005
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 96:4, s. 992-1002
-
Tidskriftsartikel (refereegranskat)abstract
- Two oligomeric malonate esteramides and an oligomeric malonate ester were synthesized with the intention to plasticize poly(lactic acid), PLA. The synthesis was performed by reacting diethyl bishydroxymethyl malonate (DBM) with adipoyl dichloride and one of two diamines, that is, triethylene glycol diamine (TA) and polyoxypropylene glycol diamine (PA), or triethylene glycol (TEG), giving three platicizing agents denoted as DBMATA, DBMAPA, and DBMAT, respectively. The synthesis products were characterized by size exclusion chromatography and Fourier transform infrared spectroscopy, and blended with PLA at a concentration of 15 wt %. Dynamic mechanical analysis, differential scanning calorimetry, and tensile testing were used to investigate the physical properties of films from the resulting blends. All three plasticizers decreased the glass transition temperature of PLA, and the largest decrement was observed for PLA/DBMATA. Films of DBMATA and DBMAT showed enhanced flexibility in strain at break as compared to neat PLA. Subsequently, it was found that thermal annealing of the plasticized materials (4 h at 100 degrees C) encouraged cold crystallization, inducing phase separation in the blends, and caused them to regain the brittleness of neat PLA. On the other hand, by aging (6 weeks) the blends at ambient conditions, cold crystallization could be avoided and the flexibility in the films maintained. (c) 2005 Wiley Periodicals, Inc.
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| 47. |
- Ljungberg, Nadia, et al.
(författare)
-
Preparation and properties of plasticized poly(lactic acid) films
- 2005
-
Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 6:3, s. 1789-1796
-
Tidskriftsartikel (refereegranskat)abstract
- Poly(lactic acid), PLA, was blended with monomeric and oligomeric plasticizers in order to enhance its flexibility and thereby overcome its inherent problem of brittleness. Differential scanning calorimetry, dynamic mechanical analysis, transmission electron microscopy, and tensile testing were used to investigate the properties of the blends. Monomeric plasticizers, such as tributyl citrate, TbC, and diethyl bishydroxymethyl malonate, DBM, drastically decreased the T-g of PLA, but the blends showed no morphological stability over time since rapid cold crystallization caused a size reduction of the amorphous domains in PLA. Consequently, the ability of PLA to accommodate the plasticizer diminished with the increase in crystallinity and migration of the plasticizer occurred. Increasing the molecular weight of the plasticizers by synthesizing oligoesters and oligoesteram ides resulted in blends that displayed T-g depressions slightly smaller than with the monomeric plasticizers. The compatibility with PLA was dependent on the molecular weight of the oligomers and on the presence or not of polar amide groups that were able to positively interact with the PLA chains. Aging the materials at ambient temperature revealed that the enhanced flexibility as well as the morphological stability of the films plasticized with the oligomers could be maintained as a result of the higher molecular weight and the polar interactions with PLA.
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| 48. |
- Ljungberg, Nadia, et al.
(författare)
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The effects of plasticizers on the dynamic mechanical and thermal properties of poly(lactic acid)
- 2002
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 86:5, s. 1227-1234
-
Tidskriftsartikel (refereegranskat)abstract
- Poly(lactic acid) (PLA) was blended with five plasticizers in a batchwise mixer and pressed into films. The films were analyzed by means of dynamic mechanical analysis and differential scanning calorimetry to investigate the properties of the blends. Triacetine and tributyl citrate proved to be effective as plasticizers when blended with PLA. The glass transition temperature of PLA decreased linearly as the plasticizer content was increased. Both plasticizers were miscible with PLA to an extent of similar to 25 wt %. At this point, the PLA seemed to be saturated with plasticizer and the blends tended to phase separate when more plasticizer was added. There were also signs of phase separation occurring in samples heated at 35, 50, and 80degreesC, most likely because of the material undergoing crystallization. The presence of the plasticizers induced an increased crystallinity by enhancing the molecular mobility.
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| 49. |
- Ljungberg, Nadia, et al.
(författare)
-
Thermomechanical film properties and aging of blends of poly(lactic acid) and malonate oligomers
- 2004
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 94:5, s. 2140-2149
-
Tidskriftsartikel (refereegranskat)abstract
- Malonate oligomers were synthesized as plasticizers for poly(lactic acid) (PLA). Esterification reactions were performed between diethyl bishydroxymethyl malonate (DBM) and either adipoyl dichloride or succinyl dichloride. Two molar masses were obtained within each series. Blending was carried out with PLA and the four oligomers as well as the monomeric unit from the syntheses (DBM). Dynamic mechanical analysis and differential scanning calorimetry were used to investigate the viscoelastic mechanical and thermal film properties of the blends. All the investigated plasticizers reduced the glass-transition temperature of PLA, and the plasticization effect was better for the plasticizers of low molar mass. However, the amorphous domains of PLA became saturated with plasticizer at a certain concentration, and phase separation occurred. A higher molar mass of the plasticizer caused this saturation to occur at lower plasticizer concentrations. Subsequently, the aging of the blends at the ambient temperature for 4 months induced phase separation in the blends containing DBM, whereas those with an oligomeric plasticizer were stable and remained compatible with PLA within the aging period. (C) 2004 Wiley Periodicals.
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| 50. |
- Ljungberg, Nadia, et al.
(författare)
-
Tributyl Citrate Oligomers as Plasticizers for Poly (lactic acid): Thermo-mechanical Film Properties and Aging
- 2003
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 44:25, s. 7679-7688
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Tidskriftsartikel (refereegranskat)abstract
- Poly (lactic acid), PLA, is a biodegradable thermoplastic that can be produced from renewable resources. The polymer is of interest for production of films for packaging applications. However, plasticization of PLA is required in order to obtain films with sufficient flexibility. PLA was blended with tributyl citrate (TbC) and two oligomers of TbC that were synthesized by transesterification of tributyl citrate (TbC) and diethylene glycol (DEG). Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were used to investigate the dynamic mechanical and thermal properties of the blends. All the plasticizers investigated decreased the glass transition temperature of PLA, and the reduction was the largest with the plasticizer having the lowest molecular weight. The PLA matrix became saturated with plasticizer at a certain concentration and phase separation occurred; the higher the molecular weight of the plasticizer, the lower the saturation concentration. Aging of the blends at room temperature for several months induced partial phase separation in the material. It was observed that the morphological stability of the blends was enhanced when the plasticizer concentration was reasonably low, i.e. 10–15 wt%.
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