Polymer blending is an important route to the creation of new polymeric materials with superior processing and tunability. The incorporation of associating end-groups influences the phase behavior of polymer blends. We are studying the effects of strong, site-specific, hydrogen-bonding groups on the behavior of traditional polymer blends. Ureidopyrimidinone (UPy) functional groups self-associate through the formation of four hydrogen bonds. When incorporated into a polymer blend system, these functional groups alter the miscibility of the blend.

To systematically study how end-group association affects polymer miscibility, we synthesized monofunctional and telechelic ureidopyrimidinone (UPy) functionalized polystyrene (PS) and poly(4-methylstyrene) (P4MS) using ATRP with a functionalized initiator. Ternary polymer₁-polymer₂-solvent blend phase space was examined. Polymer pairs were chosen that exhibit upper critical solution temperatures (UCST) and lower critical solution temperatures (LCST). The polymer pairs studied include PS/polybutadiene (PB) and PS/P4MS (UCST) and PS/PVME (LCST). The phase behavior and association of these systems were studied using laser light scattering and dilute solution viscometry. Data from PS/PB/toluene blends containing only one functionalized polymer, PS, indicate a reduction in miscibility relative to the corresponding parent blend. Blends where both polymer components contain UPy functionalities are also being studied.