Diffusion in Polymer Melts

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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.