Novel Polymerization System of Acrylamides in the Presence of the Polymers having the Lower Critical Solution Temperature in Water

研究发现，丙烯酰胺（AAm）在聚（N-异丙基丙烯酰胺）（PNIPAAm）的存在下，在没有任何自由基引发剂的情况下，在水中聚合。PNIPAAm在水中的低临界溶解温度（LCST=32℃）是引发聚合的重要因素之一。在PNIPAAm的存在下，丙烯酰胺（AAm）与甲基丙烯酸甲酯（MMA）也进行了共聚反应，得到了分子量呈单峰分布的共聚物。在单体进料中MMA含量为50mol%的条件下得到的共聚物中MMA含量超过60%。这可能是由于PNIPAAm主链与MMA单体之间的疏水相互作用以及PNIPAAm上的酰胺基与MMA上的羰基之间的氢键作用所引起的单体浓缩效应。发现在单体进料中St为50mol%的条件下获得的共聚物显示出大于60%的St，但单体进料中St大于70%导致所得共聚物中St含量显著降低。这些结果合理地解释了AAm和St的单体浓缩过程分别进行的事实。即AAm单体通过PNIPAAm和AAm上的酰胺基团之间的特异性相互作用而集中在PNIPAAm聚合物基质中，而St单体仅通过PNIPAAm主链和St单体之间的疏水相互作用而集中在PNIPAAm聚合物基质中。

It has been found in this study that acrylamide(AAm) polymerizes in the presence of poly(N-isopropylacrylamide)(PNIPAAm) in water without any radical initiators. The mechanism of this polymerization is still not always clear at the presence, but the solution conditions of PNIPAAm in water at around its lower critical solution temperature(LCST=32℃) is one of the most important factors to induce the polymerization. In the presence of the resulting PNIPAAm, the coporlymerization of acrylamide(AAm) with methyl methacrylate(MMA) was also carried out, and found to give the corresponding copolymers which showed unimodal distributions in their molecular weights. The copolymer obtained under the condition of 50mol% of MMA in the monomer feed was found to show more than 60% of MMA content in the resulting copolymer. It is probably due to the monomer concentrating effect induced by the hydrophobic interaction between the PNIPAAm main chain and MMA monomers, and also by the hydrogen bondings between the amide groups on PNIPAAm and the carbonyl groups on MMA.The coporymerization of AAm with styrene(St) was also found to proceed in the presence of PNIPAAm in water. The copolymer obtained under the condition of 50mol% of St in the monomer feed was found to show more than 60% of St, but more than 70% of St in the monomer feed resulted in a remarkable decrease in the St content in the resulting copolymer. These results are reasonably explained by the fact that the monomer concentrationing processes of AAm and that of St proceed separately. Namely, the AAm monomers are concentrated in the PNIPAAm polyer matrix by the specific interaction between the amide groups on PNIPAAm and AAm, while the St monomers ony by the hydrophobic interaction between the PNIPAAm main chain and St monomers.