Measurement of concentration profiles using confocal Raman spectroscopy in multicomponent polymeric coatings-model validation

Concentrations of the solvents were measured using confocal laser Raman Spectroscopy for two ternary systems, poly(styrene)tetrahydrofuranp-xylene and poly(methyl methacrylate)ethylbenzenetetrahydrofuran, during drying at room temperature. The concentrations were compared with predictions of drying models, which utilize several existing theories for mutual diffusion coefficients for polymer solvent systems. Of the nine free volume parameters required to predict diffusion coefficients of binary systems, four for each of the four pairs studied here were estimated as suggested by the literature. Estimation was done by minimizing the difference between predictions of the model and experimental weight loss data for each binary pair. It is found that the predictions of the models which include cross term diffusion coefficients are in better agreement with measured concentrations than those which ignore the cross terms. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 201