二维傅里叶变换红外(2D FTIR)相关光谱技术研究聚羟基丁酸酯(PHB)的熔融与结晶

应用新型二维傅里叶变换红外(2DFTIR)相关光谱研究细菌合成聚羟基丁酸酯(PHB)在升温时的预熔行为以及降温后的重结晶过程.在25～220℃的变温过程中测得动态红外光谱.着重讨论了在热力学干扰导致红外谱图中羰基峰(1700～1770cm^-1)和醚键(1230～1310cm^-1)吸收强度的波动.结果表明,这种影响来自样品中PHB的结晶态和非晶态之间的相态变化.二维谱图分析表明,在热熔过程中,结晶态的消失并不同时引起完全非晶态的出现,暗示在分子排列高度有序的晶态和非晶态之间存在某种中间态,PHB晶体向非晶态转变时必须经过一个预熔过程.在红外谱图上这个中间态很可能对应着由二维分析显示出来的位于1730cm^-1的吸收峰.同时,在PHB熔体从非晶态逐渐生成晶体的过程中也探测到了中间态的存在.

Studies on Pre-melting and Crystallization Process of Biosynthesized Poly(3-hydroxybutyrate) Using Two-dimensional Fourier-transform Infrared Spectroscopy

The pre melting behavior and the crystallization process of bacterially synthesized polyester poly(3 hydroxybutyrate), abbreviated as the PHB, was investigated by generalized two dimensional Fourier Transform Infrared(2D FTIR) correlation spectroscopy. The temperature dependent dynamic spectra were measured from 25 to 220 ℃. The thermally induced intensity fluctuations of bands for C=O (1700-1770cm^-1) and C-O-Cgroups (1230-1310cm^-1) stretching vibrations were discussed. 2Dcorrelation analysis on changes of the crystalline and amorphous conformation indicated that the appearance of fully amorphous component did not accur simultaneously with the disappearance of crystalline component, suggesting that there is an intermediate state between the ordered crystalline and amorphous states in PHB, which may probably responsible for the band near 1730cm^-1. Also the intermediate state was observed in the crystallization process of melted amorphous PHB.