Enhanced Photo-Oxidative Degradation of Polyethylene Films Using Piperonyl-Functionalized TiO2

This study presents a surface-engineered TiO2 photocatalyst that significantly accelerates the early stages of polyolefin oxidation. Piperonyl maleate (PipM) was synthesized and grafted onto surface hydroxyl groups of TiO2, producing a hybrid photocatalyst (TiO2–Pip) enriched in highly labile hydrogens. This modification enhances radical generation and enables a hydrogen-abstraction pathway that proceeds much faster than the spontaneous autoxidation typically observed in polyolefins. As a result, LDPE films containing TiO2–Pip undergo markedly accelerated oxidation during UV aging. Hydroxyl radicals generated on the modified TiO2 surface abstract the labile hydrogens of the piperonyl moiety, forming alkyl radicals that react with oxygen to produce peroxyl species. These peroxyl radicals promote rapid hydroperoxide formation and intensify chain-scission reactions. Gel permeation chromatography confirmed deep oxidative fragmentation, showing a reduction in Mw from 88,000 to 3300 g/mol after accelerated UV exposure. The oxidized oligomers were evaluated in fungal exposure assays, and the UV-aged films showed visible colonization by Aspergillus niger and Penicillium sp., indicating susceptibility to biodegradation. By driving LDPE oxidation to molecular weights within the range reported as microbially assimilable, the TiO2-Pip system offers a potential strategy for reducing the environmental persistence of plastic waste; further work using microplastic-relevant particle geometries is needed to confirm its relevance to environmental microplastic mitigation.