The properties and reactivity of a series of iodonium salts with different anions were compared. The nucleophilicity of the anions in such compounds can be characterized by their melting points and NMR spectra. When using Quinaldine Red as indicator and CH3CN as solvent, the acid release rate of the iodonium salts correlated very well with their polymerization results in acid-sensitive epoxides.

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Several new iodonium salts containing weakly coordinating anions were synthesized and characterized. Upon UV irradiation, the rates of photoacid generation in acetonitrile and their preliminary activity in the photopolymerization of epoxy silicones were compared. Studies showed these salts to be excellent photoacid generators. The anions [(C 6F5)3B-C3H3N2-B(C6F5)3] -, B(C6F5)4 -, and Ga(C6F5)4were more active and the compounds made from them more soluble in most solvents. The [(C6F5)3B-C6F4-B(C6F5)3] 2anion was less active, and the compounds made from them were less soluble than compounds made from the three aforementioned anions. Compounds containing hexabromocarborane anion were quite similar to compounds containing SbF6in both photoactivity and solubility.

Direct photolysis of ((3-trimethylsilylpropoxy)phenyl)phenyliodonium salts with different counteranions (Cl(-), SbF(6)(-), and B(C(6)F(5))(4)(-)) in methanol leads to products by both heterolytic and homolytic processes. In the presence of 1-naphthol and 1-methoxynaphthalene, products formed by a heterolytic reaction disappear, suggesting an electron-transfer process occurs between excited 1-naphthol/1-methoxynaphthalene and the iodonium salts. In the case of 1-methoxynaphthalene, three phenylated methoxynaphthalene isomers are produced. These are produced as radical coupling products from the phenyl radical and 1-methoxynaphthalene radical cation.

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A series of iodonium tetrakis(pentafluorophenyl)gallate photoinitiators were employed to catalyze the photopolymerization of three typical epoxy resins. Rates of photoacid release were compared using Quinaldine Red as acid indicator in either acetonitrile or ethanol. A new fluorescence probe technique was successfully employed to follow the cross-linking kinetics of the epoxysilicone oligomer in real time.The results show that these new salts are the most soluble, most reactive photoinitiators with the desirable stability in monomer formulations in this family.