The effect of specific interactions on dye transport in polymers above the glass transition

Abstract

The transport of a functionalised dye solute has been studied in various amorphous polymers above the glass transition temperature. An azo dye containing two hydroxyalkyl groups was transferred from a constant dye-donor polymer matrix to a variety of dye-acceptor polymer matrices using dye diffusion thermal transfer printing. Using the solution–diffusion model of permeability as the starting point, equations were developed to correlate solute transport with dye and polymer structural characteristics. Diffusivity is strongly influenced by polymer T g whereas solubility is controlled by the balance of physical forces and specific interactions between dye and dye-acceptor polymer. An excellent correlation was established for permeability as a function of polymer T g, dye–polymer solubility parameter difference and dye–polymer specific interaction as characterised by the infrared shift of solute O–H vibration. This predicted that maximum permeability would be obtained via a combination of low T g, matched dye–polymer solubility parameters and strong specific acid–base dye–polymer interactions.