Comparison of various ATRP techniques for synthesis of polar block copolymers with polyolefins

The polyolefin active ester exchange (PACE) technique allows efficient integration of coordination-insertion polymerization (CIP) with atom transfer radical polymerization (ATRP) to synthesize polyolefin-polar block copolymers. In this study, the PACE strategy was extended from previously reported SARA (supplemental activators reducing agents) ATRP to ICAR (initiators for continuous activator regeneration) ATRP, ARGET (activator regenerated by electron transfer) ATRP, and photoinitiated ATRP. All approaches showed good compatibility with the PACE-prepared macroinitiators, yielding well-defined block copolymers with low dispersities and a good agreement of theoretical and experimental molecular weights. Each technique had some advantages and limitations. SARA ATRP minimized side reactions but was limited by heterogeneous reaction conditions. ICAR ATRP was simple to set up and inexpensive, yet it generated new chains from free-radical initiators and contaminated block copolymers. ARGET ATRP required a specific selection of reducing agents and copper catalysts. PhotoATRP achieved the fastest polymerization but required proper solvents. By expanding the compatible techniques, the PACE strategy can be applied to various conditions and monomers for polyolefin-polar block copolymers.