Radical Copolymerization Behavior of Macromonomers; Incompatibility Effect

Abstract

Copolymerizations of methacrylate terminated styrene macromonomer (MSt, Mn=12400) and dimethylsiloxane macromonomers (MDMS, Mn=1020, 8670) with methyl methacrylate (MMA) were investigated in benzene (Bz), cyclohexane (Ch), and phenetol (Pht) to clarify the incompatibility effect between the macromonomer and the propagating comonomer chain on copolymerization behavior of the macromonomers. In the MSt/MMA/Bz copolymerization system i.e., copolymerization in mutual good solvent, it was observed that the relative copolymerization reactivity of macromonomer is almost the same as that of the small monomer corresponding to the polymerizable end group under homogeneous solution reaction conditions. On the other hand, in the MDMS/MMA/Bz copolymerization system, decrease in the reactivity of macromonomer was observed even under homogeneous solution conditions. These results were considered in terms of differences in the degree of interpenetration of unlike polymers in the reaction medium due to the different effects of incompatibility between the macromonomer and the propagating comonomer chain. Furthermore, in the case of copolymerizations in a preferential solvent, MSt/MMA/Ch and MDMS/MMA/Pht systems, the copolymerization system became heterogeneous as copolymerization proceeded and polymer particles of considerably uniform size were produced due to stabilization by the graft copolymers produced. In these cases, appreciable decrease in the relative copolymerization reactivity of macromonomer was observed due to much decrease in the interpenetration of unlike polymer species.