writer：Qiyuan Wang , Zhen Zhang, Yang Jiang, Yanfeng Zhang, Shihui Li* and Dongmei Cui*
keywords：isospecific polymerization，halostyrene，amino-substituted styrene，titanium complex
source：期刊
Issue time：2022年

Isospecific polymerization of polar styrenes is a challenge of polymer science. Particularly challenging are monomers bearing electron-withdrawing substituents or bulky substituents. Here, we report the coordination polymerization of halide- and amino-functionalized styrenes including para-fluorostyrene (pFS), para-chlorostyrene (pClS), para-bromostyrene (pBrS), and para-(N,N-diethylamino)styrene (DMAS) using 2,2'' -sulfur-bridged bis(phenolate) titanium precursor(1). The combination of 1 and [Ph₃C][B(C₆F₅)₄] and AlⁱBu₃ provides crystalline poly(pFS)s with perfect isotacticity (mmmm > 95%) and high molecular weights (≤16.0×10⁴ g mol^-1). Upon activation with a large excess of DMAO, 1 reaches polymerization activity of 5.58×10⁵ g mol Ti^-1h^-1 producing isotactic poly(pFS)s featuring higher molecular weights (≤39.6 10⁴ g mol^-1). The distinguished performance of the 1/DMAO system has been extended to the polymerization of pClS and pBrS, both usually involve halogen abstraction during the polymerization, to produce isotactic and high molecular weight (M_n = 32.2×10⁴ vs. 13.7×10⁴ g mol^-1) polymers in good activities (2.18×10⁵ vs. 1.31×10⁵ g molTi^-1h^-1). Surprisingly, 1/DMAO is nearly inactive for DMAS polymerization, on contrary, the system 1/[Ph₃C][B(C₆F₅)₄]/Alⁱ Bu₃ displays isoselectivity (mmmm > 95%) albeit in a moderate activity.