Photodegradation of poly(ether sulphone) Part 2. Wavelength and atmosphere dependence

Abstract

The photodegradation of poly(ether sulphone) (PES) was investigated systematically by time-of-flight SIMS (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS). The effect of varying the irradiation dose, wavelength and the atmosphere was studied along with mechanistic photooxidation studies using 18 O 2 . Photoinduced -SO 3 H group formation was observed at 199, 260 and 315 nm for an oxygen-containing atmosphere only. Photoinduced -OH group formation is observed at all investigated wavelengths and atmospheres. Photoinduced cross-linking was an important process in a vacuum. The oxygen reacts quickly with the PES surface during photoirradiation and chain scission was found to be the dominant process, and oxygen incorporation was found to be non-specific but pronounced for -SO 3 H group formation. It was found that for conditions where processes are affected by photoirradiation the extent is observed to follow the UV absorption and showed little dependence on the wavelength. The wavelength only affects the extent of the process in question, which is ascribed to a fast equilibrium of the absorbed energy. The photoinduced processes are very sensitive towards the presence of the smallest amounts of oxygen in the atmosphere.

Controlling the surface wettability of poly(sulfone) films by UV‐assisted treatment: benefits in relation to plasma treatment

“…The present results on UV‐modified PSU films in the presence of oxygen did not show evidence of OSO 3 H or SO 3 H groups. By contrast, Bormashenko et al and Norrman and Krebs did present evidence of their presence. Norrman et al analyzed their samples a few minutes after photo‐irradiation in order to minimize possible time effects and possible contamination, i.e.…”

“…The emphases of past studies of UV irradiation of PES and PSU films were examinations of photodegradation and photo‐oxidation of the films; consequently, much higher UV doses were used. For example, Kuroda et al used an incident intensity of about 2.2 × 10 −8 E cm −2 s −1 , which is more than 10 times higher than our conditions . Rivaton and Gardette used monochromatic and high pressure Xe lamps, probably with a much higher photon flux than our experiments (the actual intensity was not provided).…”

“…UV irradiation of poly(ethersulfone) (PES) and PSU have been studied in the past, with particular attention given to understanding the photodegradation and photo‐oxidation mechanisms . Kuroda et al reported a series of studies of the photodegradation of PES and PSU.…”

Chemical degradation mechanisms of organic photovoltaics studied by TOF-SIMS and isotopic labeling

“…22,23 In the case of the 18 O 2 labeling studies the freshly prepared solar cell was introduced into the vacuum chamber in the dark and pumped to a pressure <10 -4 mBar. The entire system was then purged with nitrogen (99.9%) and pumped back down to <10 -4 mBar when 18 O 2 (97%, 500 mL at 1 atm., ~20 mmol) was introduced followed by nitrogen (99.9%, 2 L at 1 atm.).…”

Advanced Functional Polymers for Increasing the Stability of Organic Photovoltaics

“…Since this layer is responsible for absorbing the light, it is also subject to photodegradation with a great variation due to differences in the chemical structure 10–15. In most OPVs, the donor material is a conjugated polymer with alkyl side chains, and the dominant mode of degradation is reaction with oxygen 16–20. One previously popular type of polymer was the poly(phenylene vinylene) (PPV) class of materials that have been abandoned because it is very susceptible to attack from oxygen at the exocyclic vinylene bonds 21.…”