Triblock copolymers via thermal “macroiniferters”: Block copolymers of ethyl acrylate with methyl methacrylate or styrene

The concept of macro iniferter (MI) was applied to realize the synthesis of triblock copolymers of ethyl acrylate (EA) with styrene (St) or methyl methacrylate (MMA), with EA forming the end blocks. The syntheses involved 3 steps. Secondary amine terminated poly(ethyl acrylate) was synthesisted by polymerization of EA in presence of butyl-(2-mercaptoethyl)ammonium chloride as a functional chain-transfer agent. The macroamine so obtained was converted to the macrothiuram disulfide by reaction with CS₂ and I₂. Thermal polymerization of MMA or St in presence of this macroiniferter led to the respective triblock copolymers. The kinetics of polymerization of MMA and styrene using MI and two different chain lengths was done in limited concentration ranges. The kinetic parameters indicated that the iniferter action was not affected by the incorporation of the thiuram disulfide groups in the polymer backbone. Triblock copolymers of differing block lengths of hard and soft segments could be prepared by varying the chain length of the macroamine and the concentration of the iniferter in the reaction system. The copolymers were characterized by GPC analysis and spectral or elemental analyses. In the case of St, analysis showed formation of perfect triblocks, whereas for MMA, tendencies to form diblocks were observed on increasing the chain length of the iniferter-forming block. DSC analyses showed demixing of the soft EA block and the hard central blocks.