Solute diffusion in relation to the glass transition temperature of solute-polymer blends

The transport of various dye solute molecules from amorphous donor polymer films to an amorphous acceptor polymer film has been investigated. Dye diffusion was studied by laminating dye-donor and dye-acceptor films under controlled pressure and temperature. The acceptor medium was kept constant, whereas a wide range of polymer structures were used as binders in the donor system. At constant dye concentration, the transport of the dye molecules from the donor sheet was found to be controlled by the glass transition temperature of the dye-polymer mixture in the donor film. This relationship was ubiquitous for all types of chromophore and polymer studied. The data was found to fit well with free volume considerations and the Williams-Landel-Ferry equation by using the glass transition as that of the dye-polymer blend in the donor matrix.