【作者】 李润明；

【导师】 周持兴；

【作者基本信息】 上海交通大学 ， 材料科学与工程， 2007， 博士

【摘要】 聚合物共混材料的性能不仅与共混体系各组分的物理、化学特性以及组成配比等有关,而且与其内部结构也密切相关,因此,掌握结构与性能的关系并在此基础上通过加工有目的地控制其内部结构是设计高性能材料过程中的关键环节。在结构与性能关系的研究中,材料的流变性能一直倍受关注,这是因为它不仅能为加工成型提供必要的材料参数,而且还可提供材料内部结构方面的信息。加工成型的精密化、自动化也迫切要求深入了解动态加工条件下聚合物共混体系的热力学特征和动力学行为。聚合物加工成型是一个远离平衡热力学的动态过程,这使得在平衡条件下得到的热力学理论不再有效,因此,研究流动条件下共混体系相结构形成和演变的规律,是实现有目的地加工成型的必要条件。可以看出,对部分相容共混体系的流变性能以及流场影响相行为的研究不仅是多组分、多相聚合物共混体系的流变学、热力学和动力学研究中极具挑战性的课题,而且对聚合物材料的加工成型有着重要的指导意义。本论文报告了应用小角激光散射仪(SALS)、旋转流变仪结合透射电子显微镜(TEM)对具有低临界共容温度(LCST)相行为的苯乙烯-马来酸酐共聚物(SMA)/聚甲基丙烯酸甲酯(PMMA)共混体系的平衡热力学、粘弹性、相形态、相分离过程以及流场中的相行为进行的系统研究,主要内容如下:1)应用小角激光散射技术测定了SMA/PMMA共混体系的热力学相图并应用Flory-Huggins模型对其进行了分析,得到了该共混体系相互作用参数对温度的关系表达式;应用Helfand等的方法计算得到了不同温度下SMA/PMMA相分离体系的界面张力,发现随着温度的升高,界面张力增加,与不相容体系界面张力对温度的依赖性刚好相反;探索了该共混体系经由亚稳态分裂的相分离过程,并应用Cahn-Hilliard等的理论对相分离的初期、中期和后期阶段进行了分析。2)系统研究了不同组成的共混体系在均相区和相分离区的粘弹性质,结果表明,在均相区,不同温度下共混体系的动态模量利用时温叠加规则仅通过水平位移就可以很好地叠加在一起,无论是储能模量还是损耗模量在低频末端均近似地符合经典的低频末端标度关系;而在相分离区,动态模量偏离了经典的低频末端标度关系,其中储能模量的偏离尤为明显,从而导致了时温叠加的“失效”;相应地Han图、vGP图和Cole-Cole图也表现出不同于均相体系的特征;这些特更多还原

【Abstract】 Mixing different polymers can lead to a wide range of phase behavior that directly influences the associated physical properties and ultimate applications. For a partially miscible polymer pair, phase behavior is determined by composition and temperature. For a mixture of certain composition, thermally induce phase separation can proceed by two different mechanisms: nucleation and growth (NG), or spinodal decomposition (SD), which result in different types of morphologies: droplet-matrix or co-continuous morphology, respectively. And the associated properties are often very complex. One of these properties, the viscoelasticity is of great interest for both scientific and practical industrial reasons, since the characteristic rheological responses might give not only helpful information on the internal structure of such materials, but also useful instruction for polymer processing. Thus the direct correlation between rheological functions and phase behavior, morphology is of significance. In addition, the blend system approaches the phase boundary; there is strong interaction between the rheology and thermodynamics. It is well known the phase behavior can be markedly changed by processing flow, in turn, once the phase behavior changes, the viscoelastic properties of polymer blend show inevitably some characteristic responses. Therefore, the prediction of phase behavior of polymer blend subjected to flow is also very important.In the thesis, the linear viscoelastic behavior of partially miscible blend of poly(styrene-co-maleic anhydride) (SMA) and poly(methyl methacrylate) (PMMA) in homogenous and phase-separated regions measured by small amplitude oscillatory shear (SAOS), and the phase behavior of the blend without flow and with flow determined by small angle light scattering (SALS), SAOS and modeled based on polymer reference interaction site model (PRISM) and polymer conformation tensor rheological model (PCTRM) are reported. The main aim is to manifest the relationship between rheological responses of the phase-separated blend and the internal structure, and to establish a model for describing and predicting the phase behavior of partially miscible blend subjected to shear flow.更多还原