Syndio-and cis-1,4 dually selective copolymerization of polar fluorostyrene and butadiene using rare-earth metal catalysts

Abstract

Synthesizing functional butadiene–styrene rubber through coordination polymerization is a theoretical challenge for polymer science, since functional monomers usually deactivate to the applied catalyst. Herein, we report the coordination copolymerization of polar para-fluorostyrene (pFS) and butadiene (BD) using pyridyl–methylene–fluorenyl supported complexes [(Py-CH₂-Flu)Ln(CH₂SiMe₃)₂(THF)_n (Ln = Sc (1a), n = 0; Ln = Lu (1b), n = 1)] and pyridyl–cyclopentadienyl supported complexes [(Py-Cp)Ln(η³-C₃H₅)₂ (Ln = Sc (2a), Lu (2b))]. Strikingly, complexes 2a and 2b exhibited dually >99% syndio- and >95% cis-1,4 regio- selectivities and showed obvious characteristics of living polymerization. The insertion of pFS can be facilely tuned in the full range of 0–100% by changing the pFS-to-BD feed ratio. Diblock P(pFS-BD) copolymers were isolated by concurrent addition of monomers and the kinetics study of the copolymerization reaction revealed that BD had the privilege to coordinate to the active metal center. Interestingly, the polymerizations of BD and pFS via pulse loading of BD afforded multi-block copolymers of a novel type of fluoro styrene–butadiene rubber with high thermal stability (T_d = 368 °C). The microstructures of resultant copolymers were confirmed by ¹H and ¹³C NMR measurements and different phase morphologies of the di- and multi-block polymers were displayed through atomic force microscopy (AFM).