【作者】 彭懋；

【导师】 郑强； 长田义仁； 龚剑萍；

【作者基本信息】 浙江大学 ， 高分子材料， 2001， 博士

【摘要】 光学方法，如光散射、折射、干涉等，在不破坏材料内部结构的前提下可以获得有关材料微观结构的信息，并可对动态过程（如相分离、结晶及聚合等）进行实时和全程跟踪，因此在高分子材料物理性质的研究中具有重要作用。本论文用时间分辨的小角激光光散射（SALS）方法研究了低临界共溶温度（LCST）型高分子共混物热致相分离行为的温度依赖性；建立了实时激光光折射的方法，同时以该方法首次观察到了在疏水性基报表面合成聚合物水凝胶时溶液折光指数的空间分布，并研究了聚合过程中聚合物水凝胶与基板之间的界面处的非均匀聚合及其机理。 LCST型高分子共混物的热致相分离机理及动力学的研究具有重要的理论和实际意义。根据Cahn-Hilliard理论，对于发生旋节线（Spinodal）相分离的体系，在接近平衡Spinodal温度时，表观扩散系数与温度呈线性关系，因此将表观扩散系数线性外推至零可以得到平衡Spinodal温度。这样的线性区域能够在聚苯乙烯/聚乙基甲基醚（PS/PVME）等体系中观察到。但文献报道的其它LCST型高分子共混物，如聚碳酸酯/聚甲基丙烯酸甲酯（PC/PMMA）等，在实验温度范围内无法得到线性区域。无法用线性外推法得到平衡Spinodal温度。目前尚未对LCST型高分子共混物相分离行为的非线性温度依赖性进行系统研究。 本论文第一部分选择组成为60/40的LCST型聚甲基丙烯酸甲酯/苯乙烯-丙烯腈共聚物（PMMA/SAN）共混物为研究对象，用时间分辨的小角激光光散射方法研究了热致相分离行为的温度依赖性。发现PMMA/SAN（60/40）共混物在145℃到208℃之间的热致相分离行为均符合非稳态相分离（即Spinodal相分离）机理，但与PC/PMMA体系相似，在实验温度范围内表观扩散系数及相分离速度与温度的关系是非线性的，无法用线性外推方法得到平衡Spinodal温度。根据Cahn-Hilliard理论，可以认为，PMMA/SAN的平衡Spinodal温度可能远低于实验温度。论文进一步发现相分离初期的表观扩散系数及相分离速度的温度依赖性符合时温等效原理，并可用Williams-Landel-Ferry（WLF）方程描述。相分离后期，相分离速度也符合时温等效原理，并可用WLF方程描述。由上述WLF方程可以推算出平衡Spinodal温度，发现平衡Spinodal温度比PMMA／SAN的玻璃化转变温度还要低。但遗憾的是，从动力学上考虑，高分子链段在玻璃化温度以下被冻结，难以发生相分离，因此用WLF方程得到的平衡Spinodal温度难以用实验方法验证。 论文初步讨论了PMMA／SAN共混物相分离行为非线性温度依赖性的原因。根据文献报道，PSrpVME共混物的平衡Spinodal温度与实验温度范围较接近，在实验温度范围内熔体粘度对温度不敏感，相分离速度主要由相互作用参数决定。这是能够在PS／PVME 中观察到线性区域的原因。而本论文研究的PMMA／SAN 共混物的平衡Spinodal温度可能远低于实验温度范围。根据SALS实验的结果，在实验温度范围内，PMMA和SAN的相互作用参数对温度不敏感，因此相互作用参数对相分离速率的温度依赖性影响不大。在Spinodal相分离的初期和后期相分离速率分别主要由大分子的扩散速率及熔体的粘度控制。这是相分离行为服从时温等效原理的物理基础。在接近玻璃化转变温度时高分子链段的运动、扩散速度非常缓慢，相分离速度也非常缓慢，因此用恒温相分离方法确定LCST型高分子共混物的相图时，必须注意在较短的时间范围内可能无法正确判断样品在该温度下能否发生相分离。 讨论了用升温法测定高分于共混物浊点温度时浊点温度与升温速率的关系。发现在升温速率较大时，浊点温度与升温速率近似符合线性关系，但由此线性外推得到的温度远高于真实的平衡浊点温度，因为用恒温实验可以发现，在线性外推值以下较宽的温度范围内仍然可以观察到显著的Spinodal相分离行为。当升温速率进一步降低时，浊点温度急剧下降，与升温速率完全呈非线性关系。因此对于PMMA侣AN一类的高分子共混物体系，无法用简单的线性外推法获得准确的平衡浊点温度．同时发现，浊点温度和升温速率的非线性关系与恒温实验中发现的相分离速度对温度的非线性依赖性是一致的。 论文第二部分首先介绍了在疏水性基板（如聚四氟乙烯等）表面合成聚合物水凝胶时的基板效应。聚合物水凝胶的表面物理化学性质决定于合成时所使用基板的亲、疏水性。在疏水性基板表面聚合得到的凝胶表面具有较低的模量、摩橡系数和较高的溶胀度，与生物细胞的相互作用及生物细胞在凝胶表面的分裂、训展行为等也与在亲水性基板表血衍到的凝胶有显著不w。基板效应的另－个典型例子是在聚米乙烯试管中合成乡孔浆合物水凝胶时，所得到的材料具有明显的皮芯结构，凝胶表层通常不含微孔构巡。显然，蚀板效应及聚合物水凝胶的表面物埋化学性质的研究对于聚合物水敝胶在生物及工W 领域的应用具有重要的意义。 激光散斑干涉法曾被用来研究基板效应。激光散斑干涉法中通过样品池的光束与参 考光柬发生干涉。单体溶?更多还原

【Abstract】 Optical techniques play important roles in the study of physical properties of polymeric materials, because one can obtain large amount of valuable information about microstructure of the materials by using optical techniques without the needs of destroying it. Furthermore, one can study the dynamic process in real time by using optical methods. In this dissertation, the time-resolved small angle light scattering (SALS) technique was employed to study the temperature dependence of spinodal decomposition (SD) behavior of LCST type polymer blends and founded the real-time laser light refraction technique to study the spatial distribution of refractive index in hydrogels during polymerization. According to the Cahn-Hilliard theory, the apparent diffusion coefficient Dapp linearly depends on temperature when approaching the equilibrium spinodal temperature. The equilibrium spinodal temperature can be obtained by linear extrapolating Dapp into zero. This linear phase separation behavior could be observed in polystyrene/polyvinylmethylether (PS/PVME) blends. However, as reported in the literature, this linear regime couldn抰 be observed in some other systems such as PC/PMMA, PS/PMsC and other polymer blends. To better understand this nonlinear phase separation behavior, poly(methyl methacrylate)/poly (styrene-co-acrylonitrile) (PMMAISAN) blend system was selected in this dissertation and its phase separation behavior was investigated by using SALS method during isothermal annealing and heating process. It was found that phase separation of PMMA/SAN blends follows the SD mechanism over the temperature range from 1450C to 2080C. It was also found experimentally that no linear regime for apparent diffusion coefficient and phase separation rate can be observed over the experimental temperature range, which was much larger than that investigated by other authors. Therefore, it was impossible to obtain the equilibrium spinodal temperature by any linear extrapolation. This indicated that the experimental temperature is much higher than the equilibrium spinodal temperature. At lower temperatures, phase separation was too slow to be observed within a limited time because of thc poor motility of macromolecules at temperature close to glass transition temperature. Therefore, when determine the equilibrium phase diagram of polymer blends like PMMA/SAN by using the isothermal annealing method, it should be noted that when temperature is close to the glass transition temperature, phase separation rate is very slow and it is hard to observe obvious phase separation behavior within limited time. It was further found that the evolution of scattering intensity over a large temperature range follows the time-temperature superposition (TTS) principle could be described by the Williams-Landel-Ferry (WLF)-like function. In early stage of phase separation, time dependent scattering intensity 1(t) and temperature dependent apparent diffusion coefficient Dapp(T) can be related by WLF-like function. In coarsening process, the evolution of domain size can also be described by WLF-like function. The reason for the nonlinear phase separation behavior is that the interaction parameter between PMMA and SAN weakly depends on temperature and the phase separation kinetics within the temperature range under investigation is mainly controlled by the diffusion behavior of macromolecules and viscosity of the melts, which follows the well-known ITS principle. It is also found that the SD behavior of polystyrene/poly(methyl methacrylate-stat-c更多还原