Photodegradation behavior of nanosilica-filled PMMA composite: synergistic effect of mixed solvents and interfacial functional groups

Poly(methyl methacrylate) (PMMA) and its composites are widely used in industrial applications, therefore their durability is of great concern. In this work, we systematically investigate the photooxidative degradation behavior of nanosilica-filled PMMA composite films and the synergistic effect of mixed solvents of tetrahydrofuran (THF) and chloroform (TCM) and interfacial functional groups. The results indicated that the surface functional groups of nanosilica fillers—such as polar, aryl, and alkyl moieties—significantly affect the photodegradation kinetics and pathways of PMMA. The key mechanism lies in the modulation of solvent–solvent reaction selectivity at the polymer–filler interface. Functional groups that selectively promote the chlorination reaction between THF and TCM accelerate PMMA photodepolymerization, while those that suppress this reaction hinder degradation. This interfacial effect is validated by trends in molecular weight loss, volatile product profiles, and MMA yields during aging. Our findings reveal that the photodegradation behavior of PMMA composites is not only governed by environmental conditions but also critically influenced by interfacial chemistry. This study provides new insight into the interfacial aging mechanism of polymer nanocomposites and offers guidance for the rational design of PMMA-based materials with improved durability.