Multi-component polymer systems exhibit a rich variety of useful mechanical, electrical, and optical properties. The nature of the interface and free surface boundary regions is a central problem to the understanding and predicting of their complex behavior. This ROW research-initiation grant will deal with composition-vs-distance profiles in the model systems of partially miscible polymers; (a) polystyrene/polybromostyrene (b) polystyrene/deuterated polystyrene. The measurements will be performed by several complementary techniques; (a) secondary ion mass spectroscopy, (b) forward recoil elastic scattering with simultaneous measurement of time-of-flight and energy measurements, (c) neutron and x-ray reflectivity and fluorescence. The first two techniques have resolutions of 120A and 240A, respectively, and the advantage that the measured energy spectra can be converted simply and unambiguously into concentration profiles. The reflectivity techniques have resolutions of approx. 20A but obtain data in inverse space and the interpretation is difficult without preliminary information from other methods. The experimental program will focus on investigation of the equilibrium and dynamical properties of interfaces and surfaces as functions of chain length, interaction parameter, segment deuteration, and blend composition. Of special interest are surface wetting and pre-wetting phase transitions and their relationship to bulk critical phenomena as predicted by various theoretical models.
