Abstract
Light Induced Polymer and Polymerization Reactions. 14. Radical Photopolymerization by Potassium Trisoxalato Cobaltate Arylonium Salts Systems.The photopolymerization of acrylamide (AA) by trisoxalato cobaltate ([Co(ox)3]3⊖) is inefficient because the produced nucleophilic ·CO2⊖‐radicals are oxidized or they terminate with polymer radicals. If onium compounds are added to this system the initiation efficiency is increased as follows : p‐CH3OC6H4N2⊕>Ph2I⊕>PhCOCH2S(CH3)2⊕>Ph3S⊕. By means of quantum yield measurements a mechanism was proposed including the electron transfer from ·CO2⊖ to onium compounds. The produced radicals also initiate the polymerization of AA. The exponent m of the polymerization rate (vp ≈︁ [AA]m) is decreased from 1.4 to 1.1 in the presence of Ph2I⊕, deciding the decrease of termination reaction between ·CO2⊖ and polymer radicals. In comparison with K3[Fx(ox)3] the corresponding cobalt complex possesses higher polymerization quantum yields for AA.
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