Abstract
Time-dependent infrared (IR) spectral variations during isothermal melt-crystallization process of poly(3-hydroxybutyrate) (PHB) have been analyzed for different wavenumber regions (C−H, CO, C−O−C, and C−C stretching vibration regions) by difference spectra, second derivatives, and two-dimensional (2D) correlation analysis, and the bands characteristic of crystalline and amorphous parts are identified in each region. By the 2D correlation analysis, it has been found that the intensity changes in the 1731 cm-1 band, which may be due to the intermediate state, and in the 1722 cm-1 band due to the crystal packing occur out of phase with each other, whereas those in the two amorphous CO stretching bands (1747 and 1739 cm-1) ascribed to the different conformations of the main chain are synchronous, which represents a cooperative conformational rearrangement for the CO groups in the amorphous state during the crystallization process. Meanwhile, a distinct delay between the intensity change rates of bands at 118...
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