Hydrogen bonding, miscibility, crystallization, and thermal stability in blends of biodegradable polyhydroxyalkanoates and polar small molecules of 4-tert-butylphenol

The hydrogen bonding, miscibility, crystallization, and thermal stability of poly(3-hydroxybutyrate) (PHB)/ 4-tert-butylphenol (BOH) blends and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-3HHx)]/BOH blends were investigated by Fourier transform infrared (FTIR) spectroscopy, solid-state C-13-NMR, differential scanning calorimetry, wide-angle X-ray diffraction (WAXD), and thermogravimetric analysis. The results of FTIR spectroscopy and solid-state C-13-NMR show that intermolecular hydrogen bonds existed between the two components in the blends and that the interaction was caused by the carbonyl groups in the amorphous phase of both polyesters and the hydroxyl groups of BOH. With increasing BOH content, the chain mobility of both the PHB and P(3HB-3HHx) components was improved. After the samples were quenched, the detected single glass-transition temperatures decreased with composition, indicating that both PHB/BOH and P(3HB-3HHx)/BOH were miscible blends in the melt. Moreover, as BOH content increased, the melting temperatures of PHB and P(3HB-3HHx) clearly decreased, which implied that their crystallization was suppressed by the addition of BOH. Although the crystallinity of PHB and P(3HB-3HHx) components decreased with increasing BOH content in the blends, their crystal structures were hardly affected after they were blended with BOH, which was further proven by WAXD results. In addition, the thermal stability of PHB was improved by a smaller amount of BOH. (c) 2005 Wiley Periodicals, Inc.