The hydrotrope effect on the photopolymerization of styrenesulfonate initiated by Ru complexes

Styrenesulfonate (StyS) was photopolymerized in the presence of tris(2,2′-bipyridine)ruthenium(II) chloride and triethylamine (TEA) or triethanolamine (TEAOH). Polymerization observed in both cases is obtained, but the rate is faster with triethylamine. The results are correlated with the ability of the monomer to form hydrotropic domains at sufficiently high concentrations (>0.1 M). The emission intensity behaviour and the lifetimes of the [Ru(bpy)3]2+ MLCT state confirm that the positively charged Ru complex is placed in those domains. At the same time, the amount of the reduced complex transient, [Ru(bpy)3]+, in solutions containing toluenesulfonate points to the presence of TEA in the same domains. On the other hand, the lower rate observed for the photopolymerization in the presence of TEAOH is attributed to the preferential placing of this amine in the bulk of the aqueous solution, outside the hydrotropic environment.