Stability of polystannanes towards light

The influence of pendant side groups on the stability of polystannanes against light was studied; more specifically poly[bis(4-butylphenyl)stannane] and poly(dibutylstannane) in solutions of tetrahydrofuran and dichloromethane. In both solvents, the poly(diarylstannane) was found to be more resistant towards light than the poly(dialkylstannane). Degradation was particularly rapid in tetrahydrofuran (THF) but was markedly retarded in presence of the radical scavenger 2,6-di-tert-butyl-4-methylphenol (BHT). Experiments with laser flash photolysis indicated that the superior stability of poly[bis(4-butylphenyl)stannane] was not a result of more stable Sn-Sn bonds but due to recombination of relatively long-living radicals. By contrast there was no evidence for such a process in the case of poly(dibutylstannane). Different reaction pathways of the degradation of polymer molecules themselves were identified by gel permeation chromatography (GPC) analysis of irradiated polymer solutions, leading to the conclusion that two different decomposition mechanisms can occur: i.e. either random scission of polymer chains or unzipping, depending on the polymer architecture and the nature of the solvent.