活性/可控自由基无皂乳液聚合

Soap-Free Living/Controlled Radical Emulsion Polymerization

活性自由基聚合与无皂乳液聚合都是近年来研究的热点课题,而活性自由基无皂乳液聚合兼具两种聚合方法的优点,有着重要的理论研究意义和广泛的工业应用前景。目前,实现活性自由基无皂乳液聚合主要通过两种途径:一是先利用活性自由基聚合方法制备含有活性引发基团的水溶性或两亲性聚合物,将这类聚合物溶解或分散在水中,无需加入其他乳化剂的条件下,进行疏水性单体的乳液聚合,新生成的共聚物同样具有两亲性,因而可以较稳定地分散在水体系中并形成乳液。这是较为常用的方法。二是直接利用具有引发活性的小分子乳化剂,对疏水单体进行无皂乳液聚合,反应后这些小分子乳化剂则成为大分子乳化剂继续发挥乳化作用。本文对近年来运用上述两种方法进行活性自由基无皂乳液聚合的文献进行了综述,并提出了存在的问题及可能的解决途径。

Living/controlled radical polymerization （L/CRP） and soap-free emulsion polymerization have attracted much interest in recent years due to their great significance both in academics and in industry. Polymers with topological architectures and controlled molecular weight as well as controlled molecular weight distribution can be prepared by L/CRP method. As an environmentally friendly polymerization approach, soap-free emulsion polymerization can overcome the drawbacks of conventional small molecular surfactants that have negative effects on the properties of polymer products. Soap-free living radical emulsion polymerization combines the advantages of both L/CRP and soap-free emulsion polymerization. The soap-free living radical emulsion polymerization can be usually implemented via two methods. The first one is that a water soluble or amphiphilic polymer with an initiating group is synthesized firstly by living radical polymerization, then the polymer is dissolved or dispersed in water, followed by emulsion polymerization of a hydrophobic monomer to form an amphiphilic polymer product. Thus, the amphiphilic polymer product can solely stabilize the latex as a macro-emulsifier without adding any other small emulsifiers. This is the major approach used in literature. The second is to utilize directly a surface-active small molecular initiator in a soap-free emulsion polymerization of a hydrophobic monomer,and a macro-emulsifier as the final polymer product can be formed after polymerization. The paper summarized recent progress of soap-free living radical emulsion polymerization,mainly including atom transfer radical polymerization （ATRP） and reversible addition-fragmentation chain transfer polymerization （RAFT） soap-free emulsion polymerizations. However,there are still some problems in soap-free living radical emulsion polymerization such as complex reaction systems, phenomena, and loss of latex stability under harsh conditions.