基于RAFT活性自由基聚合的具有一定立构规整性的聚丙烯腈合成

Preparation of Stereospecific Polyacrylonitrile via Reversible Addition Fragmentation Chain Transfer(RAFT) Polymerization

运用RAFT活性自由基聚合方法探索了具有一定立构规整性的聚丙烯腈的合成。合成得到RAFT聚合的链转移剂MESA，并以1H NMR进行了表征；以MESA作为链转移剂、碳酸乙烯酯为溶剂，在单体浓度为0.80 M、60℃、原料配比0/0/0为2500∶5∶1的聚合条件下，成功合成出较高分子量（Mn＝5.60×10^4g/mol）、窄分子量分布（PDI=1.15）的聚丙烯腈；进一步在各单体浓度的RAFT聚合中，加入单体摩尔量3%的AlCl3，得到聚丙烯腈数均分子量为6.1×10^4～6.5×10^4g/mol，全同立构组成为mm=32.1%～32.6%，聚合产物分子量分布宽度介于1.31～1.38之间，从而实现了在RAFT活性聚合体系中通过Lewis酸的作用合成得到具有一定立构规整性的聚丙烯腈。

Stereospecific Polyacrylonitrile was prepared via reversible addition fragmentation chain transfer （RAFT） polymerization. The chain transfer agent methyl （ethoxycarbonothioyl） sulfanyl acetate （MESA） was synthesized and characterized with 1H NMR. Polymerizations of acrylonitrile of different feeding ratio with MESA as the chain transfer agent and Ethylene carbonate as solvent were carried out at 60℃, affording polyacrylonitrile with higher molecular weight（Mn=5.60×10^4g/mol）and narrowerpolydispersity （PDI=1.15）. The RAFT polymerizations of acrylonitrile in presence of AlCl3 were further undertaken in order to synthesize PAN with simultaneously controlled molecular weight and tacticity. The influence of the amount of the added Lewis acids and different monomer concentration on the polymerization was studied. The addition of AlCl3 in RAFT of acrylonitrile led to polyacrylonitrile with higher molecular weight （Mn=6.1×10^4～6.5×10^4g/mol）, narrower polydispersity index（PDI=1.31～1.38）and an improved meso content （mm=32.1%～32.6%） under the optimum reaction condition used.