Cyclo and cyclized diene polymers. XVII. Styrene–isoprene block and graft cyclopolymers

Abstract

AbstractThe cationic polymerization of isoprene in n‐heptane at 20°C. with ethylaluminum dichloride as catalyst gave cyclopolyisoprene in low conversion in equilibrium with unreacted monomer and catalyst. The addition of monomer resulted in renewed polymerization and re‐establishment of the equilibrium. Addition of styrene to the dormant polymerization system gave block copolymers and reinitiated isoprene polymerization. The second‐stage isoprene polymerization curve duplicated the initial curve, and an equilibrium was again established. The isoprene units in the block copolymer with styrene contained no linear forms and were present as saturated cyclic segments. The polymerization of isoprene in cyclohexane at 20°C. in the presence of polystyrene, with ethylaluminum dichloride–titanium tetrachloride as catalyst, resulted in cross‐linking of the polystyrene, the formation of isoprene–styrene graft copolymers, a decrease in the molecular weight, and an increase in the branching of the ungrafted polystyrene. The isoprene units in the graft copolymers were present as cyclic segments.