Synthesis and properties of polydimethylsiloxane-containing block copolymers via living radical polymerization

Abstract

Polydimethylsiloxane (PDMS) block copolymers were synthesized by using PDMS macroinitiators with copper-mediated living radical polymerization. Diamino PDMS led to initiators that gave ABA block copolymers, but there was low initiator efficiency and molecular weights are somewhat uncontrolled. The use of mono- and difunctional carbinol-hydroxyl functional initiators led to AB and ABA block copolymers with narrow polydispersity indices (PDIs) and controlled number-average molecular weights (Mn's). Polymerization with methyl methacrylate (MMA) and 2-dimethyl-aminoethyl methacrylate (DMAEMA) was discovered with a range of molecular weights produced. Polymerizations proceeded with excellent first-order kinetics indicative of living polymerization. ABA block copolymers with MMA were prepared with between 28 and 84 wt% poly(methyl methacrylate) with Mn's between 7.6 and 35 K (PDI <1.30), which show thermal transitions characteristic of block copolymers. ABA block copolymers with DMAEMA led to amphiphilic block copolymers with Mn's between 9.5 and 45.7 K (PDIs of 1.25-1.70), which formed aggregates in solution with a critical micelle concentration of 0.1 g dm-3 as determined by pyrene fluorimetry experiments. Mono-carbinol functional PDMS gave AB block copolymers with both MMA and DMAEMA.