C. Chen, and L.-S. Dong*
Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022,. China
Keywords: Poly(hydroxyalkanoates), Modification, Blending, Copolymerization, Transesterification
In order to overcome their shortcomings and obtain news biomaterials with promising properties, poly(hydroxyalkanoates) (PHAs) were modified by physical and chemical methods, for example, blending, graft copolymerization and transesterification. The blends based on PHAs included two parts: 1. the blends containing hydrogen bonds, such as poly(3-hydroxybutyrate) (PHB)/poly(p-vinylphenol) (PVPh); 2. the blends containing similar structure, such as PHB/poly(methyl acrylate) (PMA). Both blend systems were miscible because a single composition-depend glass transition temperature and a depression of the equilibrium melting point were observed by DSC. Moreover, the interaction parameters of both blend systems were negative values, suggesting that the blends were thermodynamically miscible in the melt. The presence of amorphous components (PVPh and PMA) resulted in the decrease in the rate of spherulite growth of PHB. The long period of the blends obtained by SAXS increased as amorphous components increased, implying that amorphous components were squeezed into the interlamallar region of PHB. By grafting maleic anhydride (MA) onto PHB, the thermal stability of maleated PHB was obviously improved, compared with that of pure PHB. Its thermal decomposition temperature was enhanced by about 20 °C. The introduction of MA groups promoted biodegradability and solubility of PHB. The transesterification of PHB and poly(ε-caprolactone) (PCL) was carried out in liquid phase to synthesize their copolyesters. The reacted products were confirmed to the block copolymers, whose PCL content was from 0.86 mol % to 3.58 mol %. With the increase in PCL content in the copolyesters, the thermal behavior of the copolyesters changed evidently. However, PCL segments onto PHB chains did not affect the crystalline structure.
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論文來源：International Symposium on Biological Polyesters ,Auguest 22-27, 2004
