Atom transfer radical polymerization with different halides (F, Cl, Br, and I): Is the process "living" in the presence of fluorinated initiators?

Abstract

Atom transfer radical polymerization (ATRP) is often used for grafting from fluorinated polymers. Nevertheless, the possibility to initiate an ATRP from a C-F functionality and the activity of the catalysts in the presence of fluoride anions are essentially unexplored. Therefore, we investigated the thermodynamics and kinetics of C-F bond activation by ATRP catalysts and compared it with other halide systems. The ATRP equilibrium constant was estimated to be small for the reaction between [CuITPMA]+ and benzyl fluoride (TPMA = tris(2-pyridylmethyl)- amine). However, [CuITPMA] + could react with the more active initiator diethyl fluoromalonate (DEFM). With DEFM as initiator and CuIBr/TPMA as catalyst, ATRP of methyl acrylate and styrene displayed initiation efficiencies of 73% and 95%, respectively. ATRP deactivation by [F-CuIITPMA] + was slow and followed by even slower activation of newly formed C-F bonds, leading to limited conversion. Comparison with other halides indicates that Br- and Cl-based ATRP systems are more efficient that I- and F-based systems.