Q. Zhao, L. Zhang, and G. Cheng*

School of Materials Science and Engineering, Tianjin University, Tianjin, 300072, China

In recent years, Poly(3-hydroxybutyrate) (PHB) has been intensively studied due to its special properties, such as biocompatibility, biodegradability, piezoelectric properties and so on ^[1-2]. Meanwhile, PHB is a polymer with high degree of crystallinity, which gives rise to its brittleness, poor hydrophilicity and relatively slow degradation rates. All these restrict the application areas of PHB, especially the applications in medical field. PEG is a synthetic soluble polymer known to be highly hydrophilic, biocompatible and flexible. It has been used to the PHB modification^[3]. In this paper, PEGs as block segments were introduced into the molecular chain of PHB, and PHB/PEG multiblock copolymers were prepared. The molecular structures and chemical compositions of copolymers were ascertained by fourier transform infrared spectra (FTIR), ¹³C nuclear magnetic resonance spectra (NMR) and gel permeation chromatography (GPC) ^[4].

The thermal properties were investigated by differential scanning calorimetry (DSC). The results showed that two components were both able to form crystalline phases. When compared with PHB precursors (PHB-diol), the melting temperature (T_m) and the degree of crystallinity (X_c) of the PHB phase in the copolymers decreased apparently, and they all decreased moderately with the increase of PEG content. The glass transition can be clearly observed in the thermograms. The corresponding transition temperature (T_g) lied between those of the two prepolymers and was much lower than that of PHB. The tensile properties of copolymers were determined at ambient temperature by stress-strain experiments. This material is characteristic of elastomers with remarkable tensile strength and elongation. Because the introduction of PEG segment can increase the availability of water within the matrix, the hydrophilicity of the materials was apparently improved. And the equilibrium water content (EWC) increased with the increase in PEG content. The degradation of this polymer proceeded faster than that of homopolymer PHB. This acceleration can be explained by the improvement of the hydrophilicity and the decrease in the crystallinity of PHB phase.

The Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of MOE (2002-123) and the Key Research Project of MOE(02041) support this research work.

[1]   Freier T, et al., 2002. Biomaterials 23, 2649-2657.

[2]   Zhijiang C, Guoxiang C, 2003. J. Mater. Sci. Lett. 22, 153-155.

[3]   Guoxiang C, et al., 2003. J. Mater. Sci. Mater. Med. 14, 1073-1078.

[4]   Qiang Z., Guoxiang C.,2004. J. Mater. Sci. 39, 3829-383.

        论文来源：International Symposium on Biological Polyesters ,Auguest 22-27, 2004