Grafting of styrene onto low molecular weight polymers and copolymers of butadiene

Abstract

AbstractThe grafting of styrene onto low molecular weight polybutadienes and butadiene–styrene co‐polymers was studied. A mathematical method was used for the design of experiments and for the determination of the optimum grafting conditions with respect to the conversion of styrene and the efficiency of grafting. The reaction parameters were temperature (65–105°C), time (2–10 hr), concentration of the initiator, polymer to monomer ratio (10/90–90/10) and dilution by solvent (toluene). The optimum grafting conditions were chosen under which 50–60 wt‐% of styrene was grafted onto backbone polymer at a high conversion of the monomer. It was found that the reactions producing graft copolymer prevailed over the styrene homopolymerization when the temperatures employed were lower (65–85°C), and the reaction time (8–10 hr), backbone polymer/monomer ratio, and the dilution by solvent were higher. The efficiency, density, and degree of grafting were found to increase with the increase in the molecular weight of the backbone polymer. The efficiencies and densities of grafting onto low molecular weight polybutedienes were higher than those of grafting onto low molecular weight butadiene–styrene copolymers. Grafting efficiencies and grafting densities were in the ranges 37.8–61.6 wt % and 0.06–0.26, respectively, in the studied range of number‐average molecular weights (M̄n = 2400–6000).