B. Zhu, Y. He, J. Li, and Y. Inoue
Department of Biomolecular Engineering, Tokyo Institute of Technology, Nagatsuta 4259-B55, Midori-ku, Yokohama 226-8501, JAPAN.
This study has focused on the physical properties and morphology of biodegradable polyester materials. Some low-molecular weight polyphenols have been blended with biodegradable polyesters. The effects of the side group, steric structure and comonomer unit of polyesters on the hydrogen-bond between polyesters and low-molecular-weight polyphenol have been evaluated. The miscibility behaviors, thermal and mechanical properties of the blends were characterized with comparison with the strength and the number of hydrogen-bonds. Moreover, the restricted crystallization of polyesters by hydrogen-bonds and the resulted partial phase segregation have been studied carefully.
The chemical as well as the stereochemical structures of polyesters determine the strength and the number of hydrogen-bonds in the blends of polyesters with low-molecular-weight polyphenols. The side group adjacent to the carbonyl in the backbone will give some steric hindrance to the formation of hydrogen-bonds. The high tacticity endows polyesters with high crystallinity, which prevents the carbonyl from interacting with hydroxyls of phenols, however, in the amorphous phase the high tacticity of polyesters seems to benefit the formation of hydrogen-bonds. The introduction of the second monomer units into polyesters will result in a low crystallinity, and the increased amount of chains in amorphous phase obviously can lead to an increase in the number of hydrogen-bonds between two components. The stronger and more numerous hydrogen-bonds will prevent the two components in the amorphous phase from phase separation. The glass transition temperature of the blends increases and the melting temperature of polyesters decreases with increasing the content of phenols. In the blends of polyester with phenols, the reduction of chain mobility, the changes in free nucleation energy due to the specific interaction, and further the dilution of polyesters by low molecular dihydric phenols will alter the crystallization kinetics of polyesters. Moreover, the depressed crystallization for polyesters with the introduction of phenols will permit the phenols to segregate out, finally leading to a gradient distribution of phenols within spherulites.
論文來源：International Symposium on Biological Polyesters ,Auguest 22-27, 2004
