Photoinitiated living ionic polymerization

Photoinitiated living ionic polymerization 3.3.1. Living cationic photopolymerization 

Crivello and coworkers were the first to report the use of iodonium and sulfonium salts as photoinitiators in cationic pol5mierization back in the 1970s [CRI 78, CRI 77, CRI 79]. Since then, research into this field has led to the development of a variety of onium salts commonly known as 

Diagram 3.10. Photoinitiated living cationic polymerization of isobutyl vinyl ether by iodonium salts and zinc halides 

This concept was further extended to totally eliminate the use of iodonium salts as the component of the photoinitiating system [KAH 09]. The cationic polymerization of vinyl ethers was initiated upon irradiation at A = 350 nm with vinyl halides in the presence of zinc iodide. A mechanism involving the formation of an adduct between the monomer and the products yielded from the photoinduced homolysis of the vinyl halide followed by electron transfer is proposed. In the subsequent step, the terminal carbon-halide bond in this adduct is activated by the coordinating effect of zinc iodide. This polymerization exhibited some characteristics of pseudo-living cationic polymerization. 

In the second way, the addition of nucleophilic agents to the pol5merization media has been used to suppress side reactions. For example, when the polymerization is performed in the presence of dimethyl sulfide, the pol mers obtained display characteristics of living polymerization such as narrow polydispersity and well-defined chain end functionality due to suppression of side reactions [PER 87]. In this case, the polymerization 

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