Stereospecific Living Radical Polymerization and Synthesis of Stereoblock Polymers

本研究旨在通过有效地结合活性自由基聚合和立体特异性自由基聚合来开发立体定向活性自由基聚合，以同时控制分子量和规整性。成功的关键是找到适当的组合，其中一个控件不应被另一个组件丢失。我们发现几种组合可以诱导不同单体如甲基丙烯酸酯、丙烯酰胺、乙酸乙烯酯和N-乙烯基吡咯烷酮的立体特异性活性自由基聚合。甲基丙烯酸甲酯与Ru(Cp^*)Cl(PPh_3)_2在(CF_3)_3COH中的自由基聚合得到了分子量分布窄、间规能力强(M_w/M_n=1.07，r=88%)的聚合物。对于甲基丙烯酸羟乙酯的聚合，以DMF为溶剂，在Ru(Cp^*)Cl(PPh_3)_2存在下引发间规活性自由基聚合，得到了立体嵌段聚合物。(2)铁催化丙烯酰胺在金属三元体系中的活性自由基聚合N，N-二甲基丙烯酰胺与[FeCp(CO)_2]_2在Y(OTf)_3存在下聚合，得到了相对分子质量可控的高等规度聚合物(M_w/M_n=1.87，(3)乙酸乙烯酯在m-C_6H_4{C(CF_3)_2OH}_2中进行碘转移自由基聚合，得到相对分子质量较窄、间规较高的聚合物(M_W/M_n=1.20，r=59%)。(4)黄原酸酯引发N-乙烯基吡咯烷酮在氟醇中的自由基聚合R=60%)。

This research is directed to developing the stereospecific living radical polymerization by effectively combining the living and stereospecific radical polymerizations for the simultaneous control of the molecular weights and tacticity. The key to the success is to find appropriate combinations where one of the controls should not be lost by the other component. We found that several combinations induced stereospecific living radical polymerizations of various monomers such as methacrylates, acrylamides, vinyl acetate, and N-vinylpyrrolidone. The followings summarize each system.(1) Ruthenium-catalyzed living radical polymerizations of methacrylates in fluoroalcohols and aprotic solventsMethyl methacrylate was polymerized with Ru(Cp^*)Cl(PPh_3)_2 in (CF_3)_3COH to give polymers with narrow molecular weight distributions (MWDs) and high syndiotacticity (M_w/M_n=1.07, r=88%). For the polymerization of 2-hydroxyethyl methacrylate, DMF as a solvent induced syndiospecific living radical polymerization in the presence of Ru(Cp^*)Cl(PPh_3)_2. By using the polymerizations, stereoblock polymers were obtained.(2) Iron-catalyzed living radical polymerizations of acrylamides in the presence of metal triflatesN,N-Dimethylacrylamide was polymerized with [FeCp(CO)_2]_2 in the presence of Y(OTf)_3 to result in the polymers with controlled molecular weights and high isotacticity (M_w/M_n=1.87, m=82%).(3) Iodine-transfer radical polymerizations of vinyl acetate in fluoroalcoholsIodine-transfer radical polymerization of vinyl acetate was done in m-C_6H_4{C(CF_3)_2OH}_2 to result in the polymers with narrow MWDs and relatively high syndiotacticity (M_W/M_n=1.20, r=59%).(4) Xanthate-mediated radical polymerizations of N-vinylpyrrolidone in fluoroalcoholsXanthate was employed for the control of molecular weight in radical polymerization of N-vinylpyrrolidone in (CF_3)_3COH to result in the polymer with controlled molecular weights and high syndiospecificity (M w/M_n=1.28, r=60%).