Thermal Properties and Depth Profile Studies on Polymer Polymer Solvent Coatings

Abstract

The designing of the multi-polymer-solvent coatings is done by single thick layer and layer-by-layer techniques in order to minimize the residual solvent. The average concentrations of the polymers and solvent, change in coating thickness with time have been calculated from the gravimetric weight loss data. In the case of poly(styrene)-(poly(methyl methacrylate)-tetrahydrofuran (PS-PMMA-THF) and poly(styrene)-poly(methyl methacrylate)-toluene system, (PS-PMMA-TOL) the doubling the poly(styrene) mass fraction does not change the mass transfer mechanism within these coatings. However, doubling the poly(methyl methacrylate) mass fraction changes the mass transfer mechanism very significantly which leads to very slow diffusion process within these coatings. In case of poly(styrene)- poly(methyl methacrylate)-ethylbenzene (PS-PMMA-EB), doubling of both the polymer mass fraction does not change the mass transfer mechanism within these coatings. However, the drying time is much higher as compared to the other two systems, that is poly(styrene)- poly(methyl methacrylate)-tetrahydrofuran, and poly(styrene)- poly(methyl methacrylate)-toluene coatings. The effect of change of polymer and solvent has been studied. PMMA has been replaced by amorphous PEG to study the effect of its mass fraction on the residual solvent and morphology of the coatings. The results indicate that the single thick layer technique should be used to minimize the residual solvent in the coatings studied herein. However, these coatings are taking longer time to dry as compared to the layer-by-layer technique. Hence, higher energy demands for the drying operation. The morphological studies of poly(styrene)-poly(ethylene glycol)-chlorobenzene films have been performed using scanning electron microscopy. The average diameter of the holes present in the coatings decreased from 7.68 mm to 3.74 mm with the increase in the polymer content from 5% to 10%.