【作者】 周涛；

【导师】 张爱民；

【作者基本信息】 四川大学 ， 材料学， 2005， 硕士

【摘要】 本文采用了计算机模拟的方法对SEBS三嵌段共聚物的微观结构进行了初步的研究。模拟中采用了分子力学(MM)和分子动力学(MD)方法,其研究重点在于常温和本体状态下SEBS分子链中软段(EB)的侧乙基含量对SEBS分子链微观结构的影响;采用了非等温的多个扫描速率的热分析动力学方法,利用线性升温DSC数据,详细研究了SEBS在不同交联剂存在条件下热交联的机理模型。通过原位红外的二维相关分析详细研究了YH-503 SEBS在升温过程中的热氧化机理;通过原位红外的二维相关分析详细研究了YH-501 SEBS在升温过程中接枝马来酸酐(MAH)的机理。 通过以上研究得到了以下结论: 1、在计算机模拟中,我们发现随着SEBS分子链中EB段侧乙基含量的增加:软段与硬段的微相分离程度加大;SEBS分子链的均方末端距逐渐增大,本体中分子尺寸变大;SEBS本体的自由体积有逐渐减小的趋势;同时EB段侧乙基的存在对SEBS本体的稳定性起到了很大的作用,侧乙基含量越多SEBS本体体系愈稳定。通过径向分布函数的分析可知,随着EB段侧乙基含量的增加SEBS分子链远程无序度有增加的趋势,近程有序度无任何变化,也就是说SEBS本体的无规程度增加了。 2、通过热分析动力学方法,发现两种交联剂引发的SEBS交联都经过了明显的三步反应;同时得知由于交联剂A具有特殊结构而且产生自由基的需更多还原

【Abstract】 The computer simulation is employed to investigate the micro-structure of SEBS which is a kind of three-block copolymer in this thesis. Molecular Mechanics method (MM) and Molecular Dynamics method (MD) are used in our simulation. The key idea of this research is to disclose the influence of side ethyl with different content on SEBS molecular chain micro-structure; Non-isothermal analysis kinetics method with several scan speed rate is introduced in this paper and linear heating-up data of DSC is used to study the mechanism model of SEBS containing different cross-linking agent; The two-dimensional correlation spectrum method is also introduced. Through the two-dimensional correlation infrared spectrum, the thermal oxidative mechanism of YH-503 SEBS and the mechanism of YH-501 SEBS grafted by MAH are studied in details.The results in research are as follows:1. From the computer simulation results it can be found that, with the mole content of side -CH2CH3 of EB block in SEBS chains increasing, the micro-phase separation between soft-block (EB) and hard-block (PS) is increased, simultaneously, the mean square end to end distance of whole SEBS chainsincreases and therefore the size of SEBS chains enlarges. On the contrary, the Free Volume of SEBS amorphous decreases with the mole content of side -CH2CH3 increasing. We also find that, once the side -CH2CH3 is introduced in EB block, the SEBS bulk grows stable; The more content of side -CH2CH3, the more stabilization. Through the analysis of RDF of EB block, it can be proved that the degree of disorder of long-range increases and the degree of order of shorten-range has no variation with the mole content of side -CH2CH3 increasing. All results, which we obtain in simulation, are the most valuable information in designing thermoplastic elastomer of super-high performance, like SEBS.2. From the results of thermal analysis kinetics, it can be proved that, the reactions, which are initiated by two different cross-linking agents, both have three steps. Simultaneously, the activity energy of cross-linking agent A generating radicals is less than that of cross-linking agent B and there are about 80kJ/mol difference between two quantity. This is therefore proved that the control step of reaction which is initiated by cross-linking agent A is cross-linking reaction of SEBS and that of reaction which is initiated by cross-linking agent B is decompose of cross-linking agent B. We find that not only the initiation speed of cross-linking agent A is more fast, but also the cross-linking reaction have more inclination to take place than B in the identical temperature.3. Through two-dimensional correlation infrared spectrum analysis, we find that the reaction sequence of functional groups of EB block in thermal oxidation is like this: CHEB^CH2EB-?CH3EB and the reaction sequence of PS block is: CHPS—>CH2PS.We also discover that the oxidation of EB block is before that of PS block. A great many CH2 groups convert to C=O and C-0 groups in the course of oxidation of SEBS and partial CH3 convert to OO groups. But the generatingof C-0 has nothing with CH3 groups. There are three kinds of C=O structure produces in oxidation. The course of producing C-0 and C-O-C structure is more complex and there may be various paths and means.4. Through two-dimensional correlation infrared spectrum analysis, it finds that the main position of SEBS grafted by MAH is CH2 groups of fundamental chain. The number of PS block’s CH2 groups, which involves in reaction, is more than that of EB block. The grated reaction has nothing with CH2 groups that have asymmetric stretching vibration. On the contrary, it has much relationship with CH2 groups that have symmetric stretching vibration. Before MAH grafting on SEBS fundamental chain, MAH monomers firstly convert to -CH-- radicals and then participate in the reaction. Unexpectedly, MAH monomers grafting on PS block is easier than grafting on EB block. The reason, we think, is that MAH monomers maybe have inclination to aggregate in PS phase, so the form of diffusion determines the area of grafted reaction.更多还原