Poly(acrylate-b-styrene-b-isobutylene-b-styrene-bacrylate) block copolymers via carbocationic and atom transfer radical polymerizations

摘要

A series of polyacrylate-polystyrene-polyisobutylene-polystyrene-polyacrylate (X-PS-PIB-PS-X) pentablock terpolymers (X = poly( methyl acrylate) (PMA), poly(butyl acrylate) (PBA), or poly( methyl methacrylate) ( PMMA)) was prepared from poly (styrene-b-isobutylene-b-styrene) (PS-PIB-PS) block copolymers (BCPs) using either a Cu(I) Cl/1,1,4,7,7-pentamethyldiethylenetriamine(PMDETA) or Cu(I) Cl/tris[2( dimethylamino) ethyl] amine (Me6TREN) catalyst system. The PS-PIB-PS BCPs were prepared by quasiliving carbocationic polymerization of isobutylene using a difunctional initiator, followed by the sequential addition of styrene, and were used as macroinitiators for the atom transfer radical polymerization ( ATRP) of methyl acrylate ( MA), n-butyl acrylate (BA), or methyl methacrylate (MMA). The ATRP of MA and BA proceeded in a controlled fashion using either a Cu( I) Cl/PMDETA or Cu( I) Cl/ Me6TREN catalyst system, as evidenced by a linear increase in molecular weight with conversion and low PDIs. The polymerization of MMA was less controlled. H-1-NMR spectroscopy was used to elucidate pentablock copolymer structure and composition. The thermal stabilities of the pentablock copolymers were slightly less than the PS-PIB-PS macroinitiators due to the presence of polyacrylate or polymethacrylate outer block segments. DSC analysis of the pentablock copolymers showed a plurality of glass transition temperatures, indicating a phase separated material.