DIFFUSION OF SMALL MOLECULES IN GLASSY POLYMER THIN-FILMS STUDIED BY WAVE-GUIDE RAMAN TECHNIQUES

Waveguide Raman spectroscopy (WRS) allows one to monitor the spectrum of a polymer film in contact with a liquid phase. A unique advantage of WRS is its ability to monitor as a function of time all of the molecular species involved in the diffusion process simultaneously with minimal interference from the bulk solvents or substrate. Combining the linear Raman response with the integrated optical field in the polymer waveguide allows the mass sorption to be measured. If an adequate model is available, diffusion profiles, at any particular time in the experiment, can be calculated. The system studied in the present work consists of a polystyrene waveguide on a fused quartz substrate in contact with a binary solvent mixture of ethanol and perdeuteriotoluene. In this case the diffusion takes place over a distance of approximately 1 μm Finally, experimental results will be compared to several diffusion models. © 1990 American Chemical Society.