Diffusion and Segregation in Polymer Films

我们将继续我们关于聚合物薄膜中扩散和分离的实验，利用前向反冲光谱、核反应分析、动态二次离子质谱仪和中子反射仪对标有氘的聚合物分子进行补充的深度剖析能力。重点将放在了解球形微相分离的嵌段共聚熔体中的扩散，其中我们将研究单个嵌段共聚物链的扩散和胶束的扩散。重点还将放在了解聚合物模型混合物中的表面分离，平衡浓度分布的细节和接近这种平衡分布的动力学都是令人感兴趣的。最后，我们将进一步探讨表面引力对聚合物薄膜调幅分解相分离的影响。这项研究的目标是开发新的实验方法来研究聚合物中扩散的基本方面，并使用这些方法来严格测试这些过程的模型。一种聚合物向另一种聚合物中的扩散在各种工业过程中起着重要作用，从可混溶聚合物的熔融共混到塑料的摩擦焊接和热封。为了能够预测部分相容聚合物中的相分离动力学，并且能够比较聚合物结晶的理论和实验，还需要关于扩散速率的基本信息。在更基本的层面上，聚合物中的扩散测量是因为它们可以揭示聚合物熔体中粘弹性过程(“分子流变学”)的基本原理。

We will continue our experiments on diffusion and segregation in polymer films, exploiting the complementary depth profiling capabilities of forward recoil spectrometry, nuclear reaction analysis, dynamic secondary ion mass spectrometry and neutron reflectometry for polymer molecules labelled with deuterium. Emphasis will be placed on understanding diffusion in microphase- separated block copolymer melts with spherical morphologies, where we will investigate both the diffusion of individual block copolymer chains and the diffusion of micelles. Emphasis will also be placed on understanding surface segregation in model mixtures of polymers, with both the details of the equilibrium concentration profile and the kinetics with which such equilibrium profiles are approached being of interest. Finally the influence of a surface attraction on phase separation by spinodal decomposition in polymer films will be further explored. The goals of this research are to develop new experimental methods for investigating the fundamental aspects of diffusion in polymers and to use these methods to critically test models of these processes. Diffusion of one polymer into another plays an important role in a variety of industrial processes ranging for melt blending of miscible polymers to friction welding and heat sealing of plastics. Basic information on diffusion rates is also required to allow predictions on the kinetics of phase separation in partially compatible polymers and to permit comparison between theory and experiments on polymer crystallization. On an even more basic level, diffusion measurements in polymers are of interest for the light they can shed on the fundamentals of viscoelastic processes ("molecular rheology") in polymer melts.