Cationic Living Polymerization of Vinyl Ethers with a Polar Pendant

活性聚合是迄今为止合成端基、分子量和分子量分布明确的聚合物的唯一方法，这些都是具有精细功能的特种聚合物所不可缺少的。虽然阴离子聚合可以得到活性聚合物，但除了我们使用碘化氢/碘（HI/ <I_2>）引发体系制备烷基乙烯基醚的方法外，还没有阳离子乙烯基聚合的方法。本研究项目旨在研究具有极性垂坠的乙烯基单体活性阳离子聚合的可能性，以及由此获得的聚乙烯醚的离子传输特性。我们发现，在精心选择的条件下，HI/ <I_2> -引发的聚合可以使乙烯基醚在吊坠中具有酯（2-乙酰氧乙基）、聚（氧乙烯）或苯氧乙烯基的活性聚合物。这些生物过程使我们能够首次通过阳离子聚合合成具有极性垂坠、设计良好的端基和窄分子量分布的聚合物。其他乙烯基单体的阳离子活性聚合活性聚合的范围已扩展到乙烯醚以外的乙烯基单体。我们展示了单体和反阴离子的合适组合来提供活聚合物；例如，n-乙烯基咔唑的亲核性碘离子带有一个强给电子链，对甲基苯乙烯的不亲核性高氯酸盐阴离子带有一个弱给电子取代基。聚乙烯醚对碱金属离子的运输研究发现，每个垂坠有四个氧乙烯单位的聚乙烯醚能有效地结合和运输钾离子（通过液膜）。

Living polymerization is, thus far, the only method to synthesize polymers with well- defined end groups, molecular weight, and narrow molecular weight distribution, all of which are indispensable for specialty polymers with fine functions. Although living polymers can be obtained by anionic polymerization, there have been none by cationic vinyl polymerization except our process for alkyl vinyl ethers using the hydrogen iodide/iodine (HI/ <I_2> ) initiating system. This research project aimed at investigating the possibility of living cationic polymerization of vinyl monomers having a polar pendant and the ion transport property of the poly(vinyl ethers) thus obtained.1. Living Cationic Polymerization of Vinyl Ethers with a Polar PendantWe found that HI/ <I_2> -initiated polymerizations under carefully selected conditions lead to living polymers from vinyl ethers with an ester (2-acetoxyethyl), poly(oxyethylene), or phenoxyethylene group in the pendant. These living processes enabled us to synthesize polymers that have polar pendants coupled with well-designed end groups and narrow molecular weight distribution, for the first time via cationic polymerization.2. Cationic Living Polymerization of Other Vinyl MonomersThe scope of living cationic polymerization was extended to vinyl monomers other than vinyl ethers. We showed suitable combinations of a monomer and a counteranion to provide living polymers; e.g., the nucleophilic iodide anion for N-vinylcarbazole that carry a strongly electron-donating pendant, and the less nucleophilic perchlorate anion for p-methylstyrene that has a weakly electron-donating substituent.3. Transport of Alkali Metal Ions by Poly(vinyl ethers)A poly(vinyl ether) with four oxyethylene units per pendant was found to bind and transport (through a liquid membrane) the potassium ion effectively.