Photoinitiated Cationic Polymerization Using Diaryliodonium and Triarylsulfonium Salts

8 Photoinitiated Cationic Polymerization Using Diaryliodonium and Triarylsulfonium Salts 

In addition to the control which can be exercised over photoinitiated cationic polymerizations by manipulation of the structures of the diaryliodonium and triarylsulfonium salts, there are a number of additional factors which also influence these polymerizations. First, the emission spectrum of the irradiation source must be matched as closely as possible to the absorption characteristics of the specific photoinitiator. Fortunately, today there are available commercial light sources which provide intense bands in specific areas of any portion of the ultraviolet spectrum. Since the rate of photolysis of the photoinitiators varies as the first power of the light intensity, a simple doubling of the light intensity doubles the rate of photolysis of the photoinitiator. In practice it has also been observed that the rate of the polymerization of epoxy containing monomers is also doubled by a two fold increase in the light intensity 

As in the case of all cationic polymerizations, the rates of the photoinitiated polymerizations are markedly influenced by temperature, the reactivity of the specific 

1 General Characteristics of DialkylphenacylsuUoniiini and Dialkyl-4 ydrophenylsulfonium Salts 

Dialkylphenacylsulfonium salts (111) and dialkyl-4-hydroxyphenylsulfonium (IV) salts have recently been described as useful photoinitiators for cationic polymerization 1 2-123) 

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