Browsing by Author "Sanguanchaipaiwong, V"
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- ItemBiosynthesis and characterization of deuterated polyhydroxyoctanoate(American Chemical Society, 2006-04) Foster, LJR; Russell, RA; Sanguanchaipaiwong, V; Stone, DJM; Hook, JM; Holden, PJThe synthesis of a polyhydroxyalkanoate with medium chain length alkyl substituents by Pseudomonas oleovorans was investigated using protonated and deuterated forms of octanoic acid in a minimal salts medium. Cultivation with deuterated octanoic acid resulted in a reduced rate of polymer accumulation compared to that with its protonated counterpart (107 and 207 mg of polymer L-1 of medium h-1 of cultivation, respectively). Nuclear magnetic resonance and gas chromatography coupled mass spectrometry of the derivatized polymer was used to establish the extent and distribution of deuterium in the biopolymer. A partially deuterated heteropolymer with 3-hydroxyoctanoic acid as the main constituent was produced. Deuteration is an important tool for contrast variation studies using neutron scattering, but predicates that the deuterated polymer is otherwise comparable in its physiochemical and material properties to its protonated counterpart. In studies reported here, the deuterated biopolymer exhibited an additional diffraction maximum at 7.55 Å and slight differences in its melting point (60 and 55 °C) and glass transition temperature (−39 and −36 °C) when compared to its protonated equivalent. While significant differences between the protonated and deuterated biopolymers were determined, our results support the use of this deuterated polyhydroxyalkanoate in its application in investigations using analytical neutron scattering techniques. © 2006, American Chemical Society
- ItemPolyhydroxyalkanoate-based natural–synthetic hybrid copolymer films: a small-angle neutron scattering study(Elsevier B. V., 2006-11-15) Foster, LJR; Knott, RB; Sanguanchaipaiwong, V; Holden, PJPolyhydroxyalkanoates have attracted attention as biodegradable alternatives to conventional thermoplastics and as biomaterials. Through modification of their biosynthesis using Pseudomonas oleovorans, we have manipulated the material properties of these biopolyesters and produced a natural–synthetic hybrid copolymer of polyhydroxyoctanoate-block-diethylene glycol (PHO-b-DEG). A mixture of PHO and PHO–DEG were solvent cast from analytical grade chloroform and analysed using small-angle neutron scattering. A scattering pattern, easily distinguished above the background, was displayed by the films with a diffraction ring at q∼0.12 Å−1. This narrow ring of intensity is suggestive of a highly ordered system. Analysis of the diffraction pattern supported this concept and showed a d-spacing of approximately 50 Å. In addition, conformation of the hybrid polymer chains can be manipulated to support their self-assembly into ordered microporous films. Copyright © 2006 Elsevier B.V.
- ItemPolyhydroxyalkanoate-based natural–synthetic hybrid copolymer films: a small-angle neutron scattering study(The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Foster, LJR; Knott, RB; Sanguanchaipaiwong, V; Holden, PJPHAs have attracted attention as biodegradable alternatives to conventional thermoplastics and as biomaterials. By modifying their bioprocessesing we have manipulated their PHA material properties and produced a a natural–synthetic hybrid copolymer of polyhydroxyoctanoate-block-diethylene glycol (PHO--DEG). While the molecular weight ratio of these hybrids is approximately 900:1, the polymer displays amphipillic properties, A mixture of PHO and PHO–DEG were solvent cast from analytical grade chloroform and analysed using small-angle neutron scattering. A scattering pattern, easily distinguished above the background, was displayed by the films with a diffraction ring at q∼0.12 Å−1. This narrow ring of intensity is suggestive of a highly ordered system. with d-spacing of approximately 50 Å. Once can speculate that the hydrophilic synthetic blocks of the polymer chains may group together when the polymer is dissolved in organic solvent. This speculative model is supported by the formation of microporous films by these hybrids when processed by sold solvent evaporation under a humid flow (92% rH). © The Authors