Kinetics of formation of interfaces between immiscible polymers

The kinetics of the formation of the interfacial width between immiscible p olymer pairs are studied using neutron reflectivity. Bilayers of deuterated polystyrene (d-PS) and poly(methyl methacrylate) of high molecular weight are used. The time dependence of the formation of the interface in both cas es where the thickness of the top d-PS layer is thin (less than 200 Angstro m) and thick (greater than 1000 Angstrom) is investigated. Following an ini tial rapid increase, a logarithmic dependence of the interfacial width on t ime is observed. We interpret this result as arising fi om the slow equilib ration of long-wavelength capillary-wave fluctuations; comparison of our re sults with theory yields a value of the interfacial tension in good agreeme nt with the self-consistent field theory prediction.