Branched Structure Research Articles

Improvement of processability of poly(?-caprolactone) by radiation techniques

Improvement of processability of Poly(ε-caprolactone) (PCL) was achieved by introduction of a branch structure using gamma-irradiation from a 60Co source. Irradiated PCL has higher molecular weight by producting a branch structure. Hence, the irradiation at a lower dose, such as 3 Mrad, leads to a higher melt viscosity. The branched structure gave improved properties for dynamic viscoelasticity and elongational viscosity. High elongational viscosity was observed by entanglement due to branch chain formed during irradiation, and the elongational viscosity for 3 Mrad is higher than 1.5 Mrad. Due to a higher elongational viscosity, PCL foam can be produced by a molding process. Foam produced from irradiated PCL pellets at 3 Mrad has honeycomb-like structure, and the foam showed higher enzymatic degradation compared to film samples. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1815–1820, 1999

Shear flow properties of carbon fibre-filled polyethylene melts

Waxy cassava starch (WS) from a spontaneous mutation offer enough advantages to encourage the development of commercial varieties. However, breeding work is limited because only one source of WS was available. This article reports the discovery of five new sources of WS which were compared with commercial (CC) and high amylose (HA) cassava starches (19.9 and 30.2% amylose, respectively). Waxy starch gels were considerably clearer and had higher solubility and swelling power than those from CC. Pasting temperature and peak viscosity in WS were higher (68.5 °C and 1149 cP) than in CC (64.2 °C and 993 cP). No retrogradation or syneresis could be detected in refrigerated gels or after freeze/thaw cycles in any WS gel. Average λmax for WS, CC and HA were 540.2, 591.3 nm, and 607.0 nm, respectively. Amylopectins from WS displayed M¯w between 271 × 106 and 551 × 106 g mol−1, R¯G ranged between 229 and 298 nm and νG values ranged between 0.38 and 0.40 (between the sphere and the random coil). The apparent density distributions in all WS suggested close densities and branching structure. The corrected average number of glucosyl units in a linear chain averaged 21.2 in WS and 23.1 in CC. Amylopectins from WS showed a slightly more branched structure (average 4.8%) than in CC (average 4.3%), but lower than in HA (7.0%). WS exhibited larger average granule size (15.9 μm) compared with CC (14.3 μm). New sources of WS will contribute the breeding efforts to develop successful commercial varieties.

Effects of charge density and structure of side-chain branching on the composition of polyanion-polycation complexes

A combination of methods (turbidimetry and conductometry) was used to study polyanion-polycation complex formation and its stoichiometry. The influence of charge density on the polyelectrolyte complex (PEC) formation and the behaviour of PEC upon addition of salt (sodium chloride) was studied; the specific structure of the individual components was also investigated. As anionic polymer components modified poly(ethylene oxide) ionomers and poly(acrylamide-co-acrylic acid) of various charge densities were used. For the cationic polymer component, cationically modified polyacrylamides, poly(dimethyldiallylammonium chloride) and highly branched poly(ethylenimine) were used. By a variation of chemical structure of the individual polymers and their charge densities, the stoichiometry of the PEC formation could be very strongly influenced, as shown by turbidimetric and conductometric endpoint measurements; a 1:1 stoichiometry is the exception. In contrast to polyacrylamides with various amounts of carboxylate groups (polyacrylate copolymers), carboxylate-containing ethylene oxide comonomers, because of their highly branched structure, have a strong tendency towards immediate gel formation.

Studies of mannan and related compounds. V. Detailed examination of the branched structure of konjac glucomannan.

Konjac glucomannan, a reserve polysaccharide from Amorphophallus koniac tubers was isolated in a homogeneous state and is known to contain D-mannose and D-glucose in a molar ratio of 1.6:1. Survival of some monosaccharides after the periodata oxidation and subsequent reduction of knojac glucomannan suggested that it was composed mainly of β-1, 4 linkages, however, there was some branching in the polysaccharide. By analysis of the hydrolyzate of the permethylated sample by GC-MS, the branching structure through C3 of both D-mannose and D-glucose residues was confirmed. Yields of O-methyl mugars were also determined. The results indicate a branched structure for a native and non-denatured specimen of konjac glucomannan.