Thermal behavior and intermolecular interactions in blends of poly(3-hydroxybutyrate) and maleated poly(3-hydroxybutyrate) with chitosan
The thermal behavior and intermolecular interactions of blends of poly(3-hydroxybutyrate) (PHB) and maleated PHB with chitosan were studied with differential scanning calorimetry, Fourier transform infrared (FTIR), wide-angle X-ray diffraction (WARD), and X-ray photoelectron spectroscopy (XPS). The differences in the two blend systems with respect to their thermal behavior and intermolecular interactions were investigated. The melting temperatures, melting enthalpies, and crystallinities of the two blend systems gradually decreased as the chitosan content in the blend increased. Compared with that of the PHB component. with the same composition, the crystallization of the maleated PHB component. was more intensively suppressed by the chitosan component in the blends because of the rigid chitosan molecular chain and the intermolecular hydrogen bonds between the components. FTIR, WAXD and XPS showed that the intermolecular hydrogen bonds in the blends were caused by the carbonyls of PHB or maleated PHB and chitosan amino, and their existence depended on the compositions of the blends. The introduction of maleic anhydride group onto PHB chains promoted intermolecular interactions between the. maleated PHB and chitosan components. In addition, the intermolecular interactions disturbed the original crystal structures of the PHB, maleated PHB, and chitosan components; this was further proven by WAXD results.