Facile Arm-First Synthesis of Star Block Copolymers via ARGET ATRP with ppm Amounts of Catalyst

Star polymers with block copolymer arms were prepared by atom transfer radical polymerization (ATRP) via an arm-first method. Several macroinitiators based on block copolymers (MIs), PBA-b-PtBA–Br, PtBA-b-PBA–Br, PSAN-b-PBA–Br, and PBA-b-PtBA–Br, were prepared by activators regenerated by electron transfer (ARGET) ATRP to maintain high chain-end functionality. Then the MIs were reacted with divinylbenzene as a cross-linker to form star-shaped polymers via ARGET ATRP. Several parameters including concentration of reducing agent, copper catalyst concentration, degree of polymerization (DP) of MIs, and composition of MIs were investigated. A high level of control was achieved by sequential feeding of the reducing agents for DPMI ≤ 100. Stars in >95% yield and with narrow molecular weight distributions (Mw/Mn < 1.3) were obtained under the optimized polymerization condition.