Linear and Star Block Copolymers of Styrenic Macromonomers by Anionic Polymerization

Abstract

We describe the synthesis of a number of linear and star block copolymers where at least one block consists of a polymacromonomer (molecular brush). The key to this general technique is the use of styrene-tipped macromonomers, which polymerize in a manner similar to styrene monomer. By this means well-defined styrenic macromonomers of polyisoprene, PI (sMMI), polybutadiene, PB (sMMB), and poly(styrene-b-isoprene), PSI (sMMSI), have been prepared by selective reaction of PILi, PBLi, and PSILi with the chlorine of 4-(chlorodimethylsilyl)styrene. These macromonomers and conventional monomers (styrene, isoprene, and butadiene) were homopolymerized or block copolymerized, by anionic polymerization high-vacuum techniques, to synthesize the following structures: PsMM-b-PM, PS-b-PsMM-b-PM, and PsMM1-b-PsMM2 where PsMM is PsMMI or PsMMB and PM is PS, PI, or PB. Furthermore, by utilizing the chlorosilane method, star polymers of the (PS)2(PsMMB) and (PsMMI-b-PI)3 type were synthesized. Attempts to prepare A3 and A4 star polymers with polymacromonomer arms were not entirely successful. All materials were characterized by size exclusion chromatography (SEC) with DRI and UV detectors, SEC with two-angle-laser-light-scattering detector (SEC/TALLS), and NMR spectroscopy. It was concluded that macromonomers can be used much like the conventional monomers under appropriate experimental conditions.