Study of C-H…O Hydrogen Bond for Biodegradable Polymer using Infrared Spectroscopy and X-ray Diffraction -Role of the “Weak Hydrogen Bond” toward Crystal Structure Stabilization and Thermal Behavior —

By: Harumi Sato*

28 February 2007

*Kwansei Gakuin University Graduate School of Science and Technology

This study focuses attention on the typical biodegradable polymer, PHB (poly (3-hydroxybutyrate) ) using Infrared (IR) Spectroscopy and X-ray Diffraction in combination. The study shows research into the crystalline structure and thermal behavior of PHB, culminating in confirmation of C-H・・・O=C interaction in the PHB crystalline structure for the first time. The C-H・・・O=C interaction is one of the famous "Weak Hydrogen Bond" situations that have gained much attention recently. We studied the variation of intensity and temperature by considering the slight shift and intensity change between the C-H stretching vibration band and C=O stretching vibration band. For the band analysis, second order derivative and differential spectra were fully applied. Results of quantum chemistry calculation were also taken into consideration. From the stretching vibration band wavenumbers of C-H and C=O, we have investigated the intensity of C-H・・・O=C hydrogen bond, and researched how the hydrogen bond started breaking along with the temperature rise brought about by intensity change. The C-H・・・O=C hydrogen bond is said to stabilize the crystal structure by combining two polymer chains each of which has a helical structure. We confirmed the crucial role of C-H・・・O=C interaction toward the unique "folded" structure of the PHB molecule chain, the crystalline structure stabilization, and the high copolymer crystallization.

(Same content in Japanese is in Readout No.32-Japanese edition-.)

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