Probing Interdomain Mixing Effects via Specific Interactions: A Model System Approach

The feasibility of applying specific interactions to promote interdomain adhesion in multicomponent materials was investigated using a model bicomponent system. Polystyrene (with either phenolic or sulfonic functionality at variable levels) and poly(ethyl acrylate) form the basis of our system, with adhesion arising from intercomponent mixing at the domain interface. The driving force for mixing was confirmed via infrared spectroscopy to be hydrogen bonding between the styrene acidic functions and the acrylate carbonyl. We demonstrate that the degree of mixing can be varied continuously in these multiphase materials via systematic control of the polystyrene functionalization level, and we probe the macroscopic effects of enhanced intercomponent adhesion via thermal, thermomechanical, and uniaxial tensile stress-strain analyses. At high functionalization levels, contrasting trends are evident in the activity of the two compatibilizing functions used. Component segregation is observed when the polystyrene is sulfonated, with adverse consequences on blend mechanical properties, but not when the polystyrene contains phenolic units. Free energy computations based upon the association model of Coleman, Painter, and co-workers suggest the observed segregation is driven by the dominance of dispersive interactions.