在无皂乳液聚合体系中,通过使用两亲性RAFT试剂可以解决传统RAFT乳液聚合乳液稳定性差、分子量不可控和分子量分布宽等问题.从聚合特点、成核机理以及常用的两亲性RAFT试剂等方面总结了RAFT无皂乳液聚合技术的研究现状.两亲性RAFT试剂作用下的无皂乳液聚合符合RAFT活性聚合的一般特征.两亲性RAFT试剂浓度在其CMC值以上时主要通过胶束成核机理成核,在其CMC值以下则按均相成核机理成核的几率增大.常用的两亲性RAFT试剂主要是双硫酯或三硫酯.目前该方法已经成功应用于均聚物和嵌段共聚物的制备,今后可用于制备梯度共聚物等更多精细结构的聚合物.%Reversible addition-fragmentation chain transfer (RAFT) polymerization in conventional emulsion systems have reported some problems, such as poor colloidal stability, poor molecular weight control, or high polydispersity. These problems can be avoided by the application of amphiphilic RAFT agents via surfactant-free emulsion system. This paper mainly summarizes the polymerization characteristics, nucleation mechanism, and the application progress of amphiphilic RAFT agents in the RAFT surfactant-free emulsioi polymerization. This polymerization is consistent with the classical characteristics of RAFT polymerization. Above the critical micelle concentration of the amphiphilic RAFT agents, the nucleation mechanism is mainly micelle nucleation. A homogeneous nucleation mechanism is most likely to operate below the CMC of the amphiphilic RAFT agents. The amphiphilic RAFT agent is mainly dithioester or trithioester. At present, the method has been successfully applied in the preparation of homopolymers and block copolymer. In the future, this method is expected to prepare more fine polymers such as gradient polymers.
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