Effect of the C-H…O=C Hydrogen Bondings of Biodegradable Polymers on the Crystal Structures and Thermal Behaviors

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The purpose of this study is to investigate C-H…O=C hydrogen bondings and thermal behavior of biodegradable polyhydroxyalkanoates by using IR and Raman spectroscopy and quantum chemical calculation studies. It is very likely that the C-H…O=C hydrogen bondings break much more easily in P(HB-co-HHx) copolymer than in PHB because of the bulkiness of large amounts of amorphous parts. However, the polymer chains still keep the lamella structure even in the copolymers with the HHx (long side chain unit) content of more than several percent. The crystal structure of PHB remains almost unchanged until 140℃, but that of P(HB-co-HHx) decreases gradually from fairly low temperature (～50℃).