Infrared ellipsometry of interdiffusion in thin films of miscible polymers

A new application of infrared ellipsometry is reported. Specifically, the interdiffusion between thin films of miscible polymers-poly(methyl methacrylate) and poly(vinylidene fluoride)-is detected in a non-invasive measurement. A novel technique of data analysis for interdiffusion was developed and is described. The validity of the approach is supported by simulations of diffusion in a bilayer. The onset of extensive interdiffusion over a time period of 15 min occurs at a temperature of 160degreesC. At a temperature of 190degreesC, the data show that complete mixing of a bilayer (850 nm thick) occurs within 30 s, which is consistent with previously reported values of the mutual diffusion coefficient. Infrared ellipsometry is non-invasive, applicable at elevated temperatures and relatively fast and sensitive. Although, in these measurements, it was unable to determine a concentration profile at the interface, infrared ellipsometry was used successfully to detect when interdiffusion had occurred. Hence, it is a useful means for screening polymer pairs for miscibility. Copyright (C) 2004 John Wiley Sons, Ltd.