Published in Surface and Interface Analysis (2005) 37(1):33-41 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 160 oC. At a temperature of 190 °C, 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. IR 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, IR ellipsometry was successfully used to detect when interdiffusion had occurred. Hence, it is a useful means for screening polymer pairs for miscibility. Running head: Infrared Ellipsometry of Polymer Interdiffusion