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温度响应性纳米胶束在脱缩醛/酮反应中的催化应用
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Abstract:
为制备在脱缩醛/酮反应中具有高催化效率且可多次利用的催化剂，首先以甲基丙烯酸N-琥珀酰亚胺酯(NMS)、聚乙二醇甲醚甲基丙烯酸酯(OEGMA)和甲基丙烯酸甲酯(MMA)为原料，通过可逆加成-断裂链转移(RAFT)聚合合成两亲嵌段聚合物P((NMS-co-OEGMA)-b-MMA)，然后利用活化酯功能化策略引入β-丙氨酸，最后将所得功能性两亲嵌段共聚物在水中自组装形成羧基催化型纳米胶束。采用GPC、1H NMR、DLS、UV-Vis等手段表征聚合物和纳米胶束的结构与性能，采用GC-MS研究了催化剂的催化性能。结果表明：含羧基的两亲嵌段共聚物的低临界溶解温度(LCST)随着OEGMA和NMS聚合度比例的变化而变化，所得纳米胶束的粒径为95 nm左右，在水中具有良好的分散性。纳米胶束在用量为5 mol%、室温条件下催化脱缩醛反应，缩醛/酮在1 h生成醛/酮的产率可达到85%以上，使用之后的催化剂可通过加热离心沉淀的方法进行回收。
To prepare catalyst with high catalytic efficiency and recyclability in deacetalization reaction, block polymers P((NMS-co-OEGMA)-b-MMA) were firstly synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using methacrylic acid N-hydroxysuccinimide ester (NMS), poly(ethylene glycol) methyl ether methacrylate (OEGMA) and methyl methacrylate MMA were used as the monomers. Next, β-alanine was introduced by an activated ester functionalization strategy. Finally, self-assembly of the resulting functionalized amphiphilic block copolymers in water afforded the carboxyl acid-containing nanomicelles. The structures of polymers and nanomicelles were characterized by means of GPC, 1H NMR, and DLS and UV-Vis. The recovery and catalytic performance of the catalysts were studied. The results showed that the lower critical solution temperature (LCST) of the carboxylic acid-containing amphiphilic block copolymers changed with the ratio of the polymerization degree of OEGMA and NMS, and the nanomicelles showed a particle size of 95 nm under LCST, showing good dispersibility in water. Nanomicelles catalyze the deacetalization reaction at room temperature at a dosage of 5 mol% catalyst, and the yield of aldehyde/ketone can reach more than 85% in 1 h. After use, the catalyst can be recovered by heating and centrifugal precipitation.
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