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4-Hexyloxysubstituted diazonium salts with complex anions are thermostable compounds in several solvents (dioxane: 12 d; 1,2-dichloroethane: 410 d; 40degreesC; salt as hexafluoroantimonate). These salts efficiently initiate the photocrosslinking of vinyl ethers and epoxides. Interestingly, oxygen influences the efficiency of this cationic process. EPR-experiments prove that radicals possess a key function for the production of the initiating species. a-Ether radicals induce a secondary radical induced cation formation. Such reactions are always possible if E,d of the onium salt is lower than -1V. Oxygen inhibits this radical induced cation formation. On the other hand, the decay of peroxides results in a branched radical reaction. The reaction rate is faster under air with respect to inert conditions. The high thermostability of the used salt decreases by addition of a small amount of monomer. A bimolecular dediazoniation mechanism explains the observed effects. This mechanism produces directly initiating cationic species, which start the cationic polymerization. The monomer and its by-products are the cause of the poor thermal stabilifity of the diazonium salts and not the inherent thermal instabilifity of the salt used.

4-Hexyloxysubstituted diazonium salts with complex anions are thermostable compounds in several solvents (dioxane: 12 days; 1,2-dichloroethane: 410 days; 40°C; salt as SbF6−).