Thermal and crystallization behavior of hydrogen-bonded miscible blend of poly(3-hydroxybutyrate) and enzymatically polymerized polyphenol

Enzymatically prepared novel polyphenol poly(4,4ʹ-dihydroxydiphenyl ether) (PDHDPE) is blended to modify the properties of biodegradable polyester poly[(R)-3-hydroxybutyrate] (PHB). Because the differential scanning calorimetry data show a single composition-dependent glass transition for each blend, PHB and PDHDPE are found to be miscible in the amorphous phase. The crystallization of PHB is depressed by PDHDPE because PDHDPE reduces the molecular mobility and the flexibility of molecular chains of PHB. The Fourier transform IR spectra clearly indicate that PHB and PDHDPE interact through strong intermolecular hydrogen bonds between the carbonyl groups of PHB and the hydroxyl groups of PDHDPE. However, when PHB is blended with DHDPE monomer, no obvious hydrogen bonds are observed because of the phase separation and strong self-intermolecular hydrogen bonds between DHDPE molecules.