Visible-light mediated synthesis of main-chain-type semifluorinated alternating terpolymers by NaI catalyzed START polymerization
Fluorinated polymers are a class of fascinating materials due to their unique features; however, they have not been applied widely in daily life because of the restricted synthetic methodology and limited availability of various monomers. In this work, main-chain-type semifluorinated alternating terpolymers (SFATs) (AB1)n-co-(AB2)m are prepared by a step transfer-addition and radical-termination (START) polymerization strategy using NaI as the catalyst under irradiation with visible light at room temperature. Herein, 1,6-diiodoperfluorohexane and two α,ω-unconjugated dienes with different structures are used as A, B1 and B2 monomers, respectively. Interestingly, a dual alternating polymerization process can be possible at the beginning of terpolymerization by using dienes with flexible and rigid chains as B1 and B2, respectively. In addition, compared to binary copolymers (AB)n previously synthesized by START polymerization, facile regulation of Tg of the SFATs can be achieved easily either by adjusting the feed ratio of two B monomers or by the removal of the periodic iodine atoms formed in SFATs. Overall, this work provides a guide for the synthesis of a broad range of fluorinated polymers by increasing participating monomers, allowing easier adjustment of the chemical composition and facilitating the integration of desirable properties into fluoropolymers to fulfill diverse requirements in practical application.
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