Simultaneous scission and crosslinking of polystyrene chains on irradiation by ultraviolet light in CCl₄ and CHCl₃ solutions

Abstract

This work is the continuation of the investigations of changes in the structure of polystyrene initiated by radiation of wavelengths λ ≥ 270 nm in oxygen‐free solutions in CCl4 and CHCl3. Coupled integral and quasielastic light scattering techniques have been applied, enabling observations of changes in the molecular weight distribution function w(M). On the basis of the experimental data and application of Saito and Inokuti's theoretical results, it is shown that in the irradiated solutions polystyrene undergoes simultaneous chain scission and crosslinking. The average number of scissions and crosslinks per macromolecule as a function of irradiation time is calculated. The effect of macromolecular mobility on both photochemical processes is also discussed.

Near-Field Optical Drilling of Sub-λ Pits in Thin Polymer Films

“…Moreover, such optical drilling does not work on PMMA films unless much higher powers (>12 mW/μm 2 ) are applied for longer irradiation times (30 s), and even then the pits produced are much shallower (SI, Figure S3). This evidence of chemical selectivity suggests that the degradation of PS is likely to be a photochemical process, , in which free radicals break vinyl bonds and benzyl rings in the presence of oxygen at the surface . Further evidence suggesting subsequent photochemical changes is that irradiated regions of PS film close to the substrate cannot be dissolved in toluene, leaving arrays of thin polymer pads (35 nm in height) on the gold (SI, Figure S4).…”