Kationische Photopolymerisation von Isobutylglycidether mit Benzoinderivat/Aryloniumsalz‐ bzw. Benzildimethylketal/Aryloniumsalz‐Initiatorsystemen

Cationic Photopolymerization of Isobutylglycidyl Ether with Benzoine Derivatives/Arylonium Salts‐ or Benzildimethyl Ketal/Arylonium Salts‐Initiator Systems Radicals produced by photolysis of benzoine derivatives and benzile dimethylketale decompose arene diazonium salts (ArN2⊕), diphenyliodonium salts (Ph2I⊕) and triphenylsulfonium salts (Ph3S⊕), respectively. The carbenium ions or protons formed in this way can be used for the cationic polymerization of isobutylglycidyl ether (IBGE). The efficiency of this polymerization depends on the quantum yields of the onium salts decomposition. A reactivity ArN2⊕ > Ph2I⊕ > Ph3S⊕ was found. In the case of ArN2⊕ the salt decomposition is caused by electron transfer between the photolytically produced substituted benzylic radicals and the diazonium ions. It is assumed that by the decomposition of Ph2I⊕ and Ph3S⊕ intermediates occur, which give rise to some reversible reactions. Therefore, the quantum yields of onium salt decomposition are less than those of initiator photolysis. The rate of cationic polymerization of IBGE is also influenced by the anion of onium compounds. A sequence PF6⊖ >SbF6⊖ >BF4⊖ was found.