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Intermolecular hydrogen bondings in the poly(3-hydroxybutyrate) and chitin blends: Their effects on the crystallization behavior and crystal structure of poly(3-hydroxybutyrate)

Publication date: 28 September 2015
Source:Polymer, Volume 75

Author(s): Khasanah, Kummetha Raghunatha Reddy, Harumi Sato, Isao Takahashi, Yukihiro Ozaki

Crystallization behavior and intermolecular hydrogen-bonding interactions of poly(3-hydroxybutyrate) (PHB)/chitin blends on as-solution cast films were studied as a function of composition and temperature by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and infrared (IR) spectroscopy. The significant changes were observed in the DSC curves, WAXD patterns and IR spectra of the blends with PHB ?50†wt%. We found that the crystallinity of PHB decreases in the blends, however, its crystal structure is not much affected by blending with chitin. The appearance of a new band at around 1710?1714†cm?1 clearly reveals the formation of intermolecular hydrogen bondings between the CO groups of PHB and the O?H and N?H groups of chitin (CO?H?O and CO?H?N). It is very likely that these intermolecular CO?H?N and CO?H?O hydrogen bondings occur in the amorphous phase because of the reduction in the chain mobility in the blends with increasing chitin content, even above the melting temperature of PHB. The CO?H?N and CO?H?O hydrogen bondings are formed upon the cleavage of weak CO?H3C hydrogen bondings of PHB. Thus, the formation of the CO?H?N and CO?H?O hydrogen bondings is accompanied by the decrease in the crystallinity of PHB in the blends.
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This project has received funding from the European Unionís Seventh Framework Programme for research, technological development and demonstration