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The depletion of alkylamine terminal groups at the vacuum-polymer interface is measured for a,@-difunctional poly(dimethylsi1oxane) oligomers by X-ray photoelectron spectroscopy. The driving force for this depletion is the high relative surface energy of the amine terminal groups compared to that of the low surface energy poly(dimethylsi1oxane) backbone. The degree of surface end group depletion, within the maximum sampling depth probed (ca. 7 nm), is found to be on the order of 40% for a 960 molecular weight oligomer and decreases slightly with an increase in the oligomer molecular weight. Angle-dependent measurements are applied to determine end-group concentration depth profiles. End-group depletion is largest at the shallowest sampling depths and decays rapidly toward the bulk. The decay profiles cannot be explained by simple monotonic decay functions, consistent with the expected effects of connectivity between the end groups and the chain backbone, but the data are insufficient to prove whether the profiles are oscillatory in nature, as expected from theoretical considerations.

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For differential equations exhibiting steep gradients and large curvature of the solution. the arc-length transformation has been proposed. The transformed differential equations can be accurately represented by a small number of equally spaced mesh points. The transformation can be used both for initial and boundary value problems. This transformation proved to be useful for reactor, flame and combustion problems. calculation of dissipative structures and transient behavior of certain autocatalytic reactions. Three sample examples are solved.

We demonstrate the use of computer vision techniques and optical microscopy to follow the kinetics and microstructure during spinodal decomposition of a polymer blend. Among other features, the mean of the population of the local maxima of the gradients in each image is computed; this global feature is shown to co‐develop with the phase separation of the blend. An algorithm is presented which employs the gradient magnitude technique to analyze optical images of spinodally decomposing polymer blends. This algorithm has been used to extract the Cahn‐Hilliard spinodal growth rates for a binary blend of polystyrene with poly(vinyl methyl ether). We show that the spinodal temperature can be found from the temperature dependence of this growth rate. We also show how additional shape features such as compactness might be used to study, the same binary blend.

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