B. Tech, Chemical Engineering, IIT Bombay
Copolymerization and polymer blending are versatile routes to tailor the property spectrum of a polymeric material. My work aims to investigate the compatibility of polyisoprene (PI) with an ethylene-based elastomer, hydrogenated medium-vinyl polybutadiene (hPB), through a block copolymer approach, and study a pathway to enhance their miscibility. PI/hPB forms a diene/olefin pair, resulting in large inter-block incompatibility. The regular solution model suggests that the incorporation of modest amounts of styrene (S) into the hPB block through monomer randomization should enhance the inter-block miscibility, owing to S’s high solubility parameter. In my work, block-random copolymers of isoprene with (butadiene-co-styrene) – PI-SBRs, with targeted molecular weights and compositions - are anionically synthesized, and the butadiene units are selectively hydrogenated using a homogeneous ruthenium-based catalyst. Chemical incompatibility between PI and the random copolymer blocks drives microphase separation, forming self-assembled nanoscale domains enriched in one component. This incompatibility is quantified by the interaction energy density X (proportional to the Flory interaction parameter), which can be determined via a measurement of the order-disorder transition temperature – the temperature at which the diblock goes from an ordered state to a disordered state. My work aims to tune the miscibility of the selectively saturated SBRs with PI through compositional control (S content in the SBR block) and quantify it through the measurement of X, thus identifying materials that are compatible with polyisoprene.