【作者】 郭文娟；

【导师】 黄鹤；

【作者基本信息】 武汉理工大学 ， 材料学， 2011， 硕士

【摘要】 随着石油资源的日益枯竭,以及人们对环境保护意识的加强,生物降解高分子已成为人们竞相研发的热点,加快生物降解材料的研究和应用,符合当今高分子材料绿色化的潮流。聚合物的熔融和结晶行为一直是高分子科学中一个非常重要的课题,因为材料的性能与结构息息相关,熔融和结晶会直接影响材料的机械性能、热加工性能、降解性能等。近几年来用广义二维红外相关光谱(2D IR)研究生物降解高分子的熔融和结晶行为,引起了人们的关注。广义二维相关光谱是上世纪90年代初发展起来的一种新的分析、表征技术。一般认为,二维相关分析技术有两大主要优势：(1)有效提高了光谱的分辨能力,能将重叠峰或者被掩盖的小峰及弱峰清晰地分辨出来；(2)通过对同步和异步谱图的分析,根据所谓的“序列顺序”法可判断出各个基团发生变化的先后次序。然而,我们现有的理论分析和实验结果表明,由“序列顺序”法则得到的信息不一定完全可靠；同时,由广义二维相关光谱分辨出的新峰大多是不真实的。本文选用可生物降解的结晶性高分子中的左旋聚乳酸(PLLA)、聚羟基丁酸酯(PHB)及其共聚物P(HB-co-HHx)为研究体系,以C=O伸缩振动区为研究对象,结合原位红外光谱分析(差谱、二阶导、傅里叶自去卷积、曲线拟合等)及二维相关分析方法,研究了几种典型的可生物降解的结晶性高分子的熔融或结晶过程。主要内容如下：1.探讨了PHB随溶剂1,1,2,2-四氯乙烷(TCM)挥发结晶的过程。原位光谱分析结果表明,PHB的C=O伸缩振动区内包含有5个子峰,且在结晶过程中,结晶态和无定形态组分的吸收峰同时发生变化,没有观察到明显的局部序列顺序。通过分析5个子峰的面积相对百分含量随时间的变化规律,发现结晶态和无定形态组分对外扰有协同响应。2.研究了P(HB-co-HHx)随溶剂三氯甲烷挥发的等温结晶过程,及P(HB-co-HHx)的非等温熔融结晶行为。常温下P(HB-co-HHx)随溶剂挥发结晶的过程中,同PHB一样,C=O伸缩振动区域内可能包含有5个子峰,“局部”序列顺序如下：1722 cm-1≈1736 cm-1>1712 cm-1≈1729 cm-1>1746 cm-1。P(HB-co-HHx)的非等温熔融结晶过程,没有观察到明显的“局部”序列顺序。通过分析这两个不同的结晶过程中,5个子峰的面积相对百分含量随时间的变化规律,同样都发现结晶态和无定形态组分对外扰有协同响应。3.研究了PLLA在78℃下的冷结晶过程,从分子构象的角度归属C=O伸缩振动区内的子峰。原位光谱分析得到4个子峰的“局部”序列顺序：1760 cm-1(gt)≈1768 cm-1(tg)>1753 cm-1(tt)>1778 cm-1(gg)4.二维红外相关光谱提供的信息与原位光谱分析得到的结果不一致。总之,本文结合原位红外光谱及二维相关分析的方法,通过对原位红外光谱进行一系列的分析处理,探讨了几种可生物降解的结晶性高分子的熔融或结晶过程,找到了相变过程的真实规律。另一方面,验证了广义二维相关分析方法提供的信息可能缺乏物理意义。更多还原

【Abstract】 Melting and crystallization behaviors of polymers have long been an important and fundamental issue in polymer science because the properties and structure of polymers are closely related. The mechanical properties, thermal processing performance and biodegradability are largely controlled by the crystallinity and crystal structures of biodegradable polymers. The application of generalized two-dimensional infrared (2D IR) correlation spectroscopy in the melting and crystallization behaviors of polymers has been paid much attention in recent years. The wide application of this technology in various fields due to its two major features. One is the enhanced spectral resolution by spreading peaks along the second dimension. The other is the determination of sequential order of band intensity changes using the so-called "sequential order" rules. However, our theoretical analysis and experimental studies show that conclusions derived from the "sequential order" rules of generalized 2D correlation spectroscopy may lack physical significance. In addition, many new bands resolved by 2D IR are artifacts. In this work, the crystallization or melting behaviors of some biodegradable polymer such as PLLA, PHB and its copolymers P(HB-co-HHx) were studied, by analyzing the C=O stretching regions with a series of data processing methods, including calculation of difference spectrum, second derivative spectrum, fourier self-deconvolution, and curve-fitting, combined with 2D correlation analysis. The objective of this work is to investigate and better understand the melting and crystallization behavior of these polymers and, at the same time, to test the reliability of the information provided by 2D IR correlation spectroscopy. The main contents are as follows:l.The crystallization behavior of biosynthesized PHB film cast from 1,1,2,2-tetrachloromethane(TCM) was studied by in situ FTIR spectroscopy and 2D correlation analysis. In situ spectral analysis results reveal that there are probably five component bands under the C=O band profile, and the crystalline and amorphous band intensities change simultaneously during the crystallization process, with no local sequential order. Further analysis on the relative area percentage changes of the five component bands suggests that the crystalline component only changes in a fully cooperative manner with part of the amorphous component at the initial crystallization period.2.The crystallization behavior of solution-cast P (HB-co-HHx) film and the non-isothermal melt crystallization process of P (HB-co-HHx) were studied by in situ FTIR spectroscopy and 2D correlation analysis. There are probably five component bands under the overlapped C=O band profile of P (HB-co-HHx), as PHB. During the crystallization of solution-cast film, the following local sequential order has been obtained:1722cm-1≈1736cm-1>1712cm-1≈1729cm-1>1746cm-1. Further analysis on the relative area percentage changes of the five component bands also suggests that the crystalline component only changes in a fully cooperative manner with part of the amorphous component. In the non-isothermal melt crystallization process, no significant (local) sequential order was found for the intensity variation of each component band. That’s to say, all the sub-bands change in a fully cooperative manner.3.The isothermal cold-crystallization process of PLLA was studied by in situ FTIR and 2D correlation analysis. The individual component bands in the C=O stretching region are attributed to the different molecular conformations. The local sequential order obtained from the in situ spectral analysis results is:1760cm-1(gt)≈1768cm-1(tg)>1753cm-1(tt)>1778cm-1(gg)4.The information provided by the generalized 2D IR correlation spectroscopy disaccords with the in situ spectral analysis results.In summary, in situ FTIR spectroscopy and 2D correlation analysis are applied to the study the crystallization and melting behaviors of a few typical biodegradable polymers and some interesting results have been obtained. In addition, the applicability of generalized 2D IR correlation spectroscopy is tested, and the results from our experiments indicate that the information provided by the generalized 2D IR correlation spectroscopy may lack physical significance.更多还原