Synthesis and Characterization of BAB and CBABC Tri- and PentaBlock Copolymers via Atom Transfer Radical Polymerization

摘要

Atom transfer radical polymerization (ATRP) technique was applied successfully for the synthesis of poly(n-butyl methacrylate-b-styrene-b-n-butyl methacrylate) (PBMA-b-PS-b-PBMA), (BAB) and poly(methyl methacrylate-b-n-butyl methacrylate-b-styrene-b-n-butyl methacrylate-b-methyl methacrylate) (PMMA-b-PBMA-b-PS-b-PBMA-b-PMMA), (CBABC) linear tri- and pentablock copolymers, respectively, in solution for the first time. Difunctional polystyrene macroinitiator that contains a bromide end-group was prepared by ATRP of styrene with dimethyl-2,6-dibromoheptanedioate (DMDBHD). The formation of block copolymers was confirmed by gel permeation chromatography (GPC), nuclear magnetic resonance (~1H NMR) spectroscopy, and differential scanning calorimetry (DSC). Good agreement was observed between the theoretical and experimental molecular weights. The molecular weight distribution (MWD) was narrow and did not change much with the progress of the reaction. A linear increase in the number average molecular weight (M_n) with conversion was observed indicating that the polymerizations followed a 'living'/controlled process. Both BAB and CBABC block copolymers showed core-shell type flower-like micellar structures when toluene is used as a selective solvent for A block (polystyrene).