Facile Access to <i>gem</i>-Trifluoromethyl/Boron-Functionalized Polymers via Free-Radical Copolymerization and Cotelomerization
Yang Zeng, Yang Zhou, Qinzhi Quan, Mao Chen
Abstract
Functional fluoropolymers are important for various applications due to the integrated characteristics of functional groups and fluorocarbon segments. Herein, we developed (1) thermally initiated and visible-light-initiated copolymerization of (trifluoromethyl)vinyl boronic esters (CF3VBs) and unconjugated alkenes (18 examples, including vinyl ethers, esters, and amides), enabling the efficient synthesis of a broad scope of fluoropolymers in 71–92% yield and variable fractions of gem-CF3/B substituents (FCF3VB = 0.26–0.84) at different molar masses (Mn = 5.2–33.4 kDa) and (2) visible-light-initiated cotelomerization of CF3VB and unconjugated alkenes with p-tolyl disulfide as a telogen (Mn = 3.6–13.0 kDa). Reactivity ratios for copolymerization were determined by the Meyer–Lowry method at 65 °C (for BVE: rCF3VB = 1.254, rBVE = 0.006; for VAc: rCF3VB = 0.235, rVAc = 0.042; for NVP: rCF3VB = 1.067, rNVP = 0.063). The achieved high fractions of CF3VBs in copolymers are also confirmed by density functional theory (DFT) calculation results. Through post-polymerization modifications, gem-CF3/B units could transform into various copolymers and terpolymers with geminal functionalities (e.g., gem-CF3/OH, gem-CF3/vinyl, gem-CF3/furan). The increase of geminal functionalities enables clearly amplified chemical responsiveness toward pH variation, as demonstrated by fluoropolymers with gem-CF3/OH.