Synthesis of amphiphilic amylose and starch derivatives

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

The effects of plasticizers on the dynamic mechanical and thermal properties of poly(lactic acid)

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

Preparation and properties of alkylated poly(styrene-graft-ethylene oxide)

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

Synthesis and Characterization of Anionic Graft Copolymers Containing Poly(ethylene oxide) Grafts

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

Preparation and properties of plasticized poly(lactic acid) films

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

Degradation of LDPE LLDPE and HOPE in film extrusion

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 28

Degradation of LDPE LLDPE and HDPE in film extrusion

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 28

Ionic Conductivity and Dielectric Properties of Poly(ethylene oxide) Graft Copolymers End-capped with Sulfonic Acid

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)

Thermomechanical film properties and aging of blends of poly(lactic acid) and malonate oligomers

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

Preparation and properties of alkylated poly(styrene-graft-ethylene oxide)

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