Diffusion in Polymer Melts

正向反冲光谱法（FRES）将用于确定氘化聚合物扩散到未氘化聚合物中的浓度与深度分布，反之亦然。通过研究具有不同臂数的聚苯乙烯（PS）星在以下矩阵中的扩散，将探讨分子拓扑结构的重要性：不同分子量的线性PS， PS微凝胶和γ辐照交联PS，以及PS星。结果将与目前的恒星不依赖矩阵和依赖矩阵的扩散理论进行比较。实验将开始跟踪聚苯乙烯和聚（乙烯吡啶）嵌段共聚物在嵌段共聚物基体中的扩散，以确定基体形态对扩散的作用。这些实验将根据该区块的域结构对小区块的捕获来解释。在混相聚合物共混物中，重点将放在确定二元聚合物共混物中两组分的示踪剂扩散行为，以及确定由于自由能中梯度项的平方而增加的相互扩散系数。相互扩散系数的测量也可以灵敏地测定混合物的负Flory参数。最后，实验将开始测量大分子沿表面的扩散，即在二维中。所有这些实验的结果都将用当前的理论来解释。

Forward recoil spectrometry (FRES) will be used to determine the concentration versus depth profiles of deuterated polymers diffusing into undeuterated ones or vice versa. The importance of molecular topology will be explored by investigating the diffusion of polystyrene (PS) stars with various arm numbers into matrices consisting of the following: linear PS of various molecular weights, PS microgels and gamma-irradiation crosslinked PS, and PS stars. Results will be compared with current theories of the matrix-independent and matrix-dependent diffusion of stars. Experiments will be initiated to follow the diffusion of block copolymers of polystyrene and poly(vinylpyridine) into block copolymer matrices to determine the role of the morphology of the matrix on the diffusion. These experiments will be interpreted in terms of the trapping of the minor block by the domain structure of this block. In miscible polymer blends, emphasis will be placed on determining the tracer diffusion behavior of the two components in binary polymer blends and on determining the enhancement of the mutual diffusion coefficient due to the square gradient term in the free energy. Measurements of the mutual diffusion coefficient will also permit a sensitive determination of the negative Flory parameter for the blend. Finally experiments will be initiated to measure the diffusion of macromolecules along surfaces, i.e., in two dimensions. The results of all these experiments will be interpreted in terms of current theory.