Fluorescent Visualization of Bond Breaking in Polymer Glasses

Abstract

Mechanofluorescent polymer probes were used to visualize stresses and bond scission in polystyrene and polycarbonate. Sonication of polystyrene probes with a molar mass of 1.1 × 105 g·mol–1 in solution resulted in 30% activation after 1 h, while shorter probes showed lower activation percentages. Single-asperity sliding friction tests were performed on mechanophore-containing polystyrene and polycarbonate films. Polystyrene showed clearly visible crack formation with a correlated pattern in the friction force, penetration depth, and fluorescent activation of the mechanophore. Significant mechanophore activation in polystyrene was observed for an applied normal load of 100 mN, whereas in polycarbonate, activation only occurred at a normal load higher than 400 mN. The different degrees of activation correlate well with the toughness of polycarbonate compared to polystyrene.