Surface adsorption of polar end-functionalised polystyrenes

Due to their inherently high surface energy, polar end-functionalised polymers do not normally adsorb to the external surfaces of blends. However, adsorption of polar functionalities can be induced rapidly by annealing in a polar environment such as glycerol prior to quenching to a glassy state. Blended films of carboxy end-functionalised deuteriopolystyrene (dPS-COOH) with hydrogenous polystyrene (hPS) were annealed at 150 °C under glycerol. Nuclear reaction analysis was used to quantify the surface excess of dPS-COOH retained at the surface after quenching the films to below the glass transition temperature. Incorporation of multiple COOH groups onto a single chain end greatly increases the affinity of these chains to the interface with glycerol. Here we have shown that even a difunctional material, dPS-2COOH, is much more surface active than either the singly functionalised dPS-COOH or the difunctional ester from which it was prepared. Self-consistent mean field theory yielded thermodynamic 'sticking energy' values per functionality at the polystyrene-glycerol surface of 1.3-1.7 for carboxy groups and 0.3 for ester groups.