Thermal and infrared spectroscopic studies on hydrogen-bonding interaction of biodegradable poly(3-hydroxybutyrate)s with natural polyphenol catechin

Thermal and infrared spectroscopic studies were performed on the hydrogen-bonding interaction in the blends of biodegradable atactic, highly syndiotactic and isotactic poly(3-hydroxybutyrate)s with catechin. From the analysis of Fourier-transform infrared spectra, it was found that the crystalline phase could greatly restrain the formation of inter-associated hydrogen-bonds. Moreover, the effect of the steric configuration on the formation of hydrogen-bonds was testified, and the results suggested that the higher tacticity benefited the formation of hydrogen-bonds, although its effect on the strength of hydrogen-bonds was small. The strong hydrogen-bonds between the two components in the blends promised their miscibility, which could be testified by differential scanning calorimetry measurements. All the poly(3-hydroxybutyrate)–catechin blends showed one glass transition temperature over the whole range of blend compositions and it increased rapidly with catechin content, indicating that poly(3-hydroxybutyrate)s and catechin are miscible in the amorphous phase.