A controlled synthesis method of polystyrene-b-polyisoprene-b-poly(methyl methacrylate) copolymer via anionic polymerization with trace amounts of THF having potential of a commercial scale

Abstract

A controlled synthesis method for the polystyrene-b-polyisoprene-b-poly(methyl methacrylate) (PS-b-PI-b-PMMA) tri-block copolymer using the anionic copolymerization was innovated, in which being differ from previous researches for the anionic polymerization of polar monomers, nonpolar cyclohexane was used as solvent and only trace amounts tetrahydrofuran (THF) was adopted as a polar regulator. The sequential anionic copolymerization could be smoothly conducted at 0 °C and the conversion of all monomers reached 100%. The copolymer was characterized by gel permeation chromatography (GPC), proton nuclear magnetic resonance (¹H-MNR), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). It was found that the number average molecular weights (M_n) of PS, PI and PMMA were 12 760, 26 340 and 13 600 respectively. The 1,4-addition structure in PI block occupied 93% and its forming mechanism was explained. Furthermore, the produce of tri-block copolymers with PMMA block of different lengths confirmed this synthesis method controlled for definite structures, fewer side reactions and a appropriate temperature. Based on these results, the anionic block copolymerization containing polar monomer MMA at a commercial scale starts to become possible.