Photodegradation of poly(ether sulphone) Part 1. A time‐of‐flight secondary ion mass spectrometry study

Abstract

An extensive study of the surface chemical changes to poly(ether sulphone) (PES) ultrafiltration membranes is made for the first time by the use of time-of-flight secondary ion mass spectrometry (ToF-SIMS) after photoirradiation at 254 nm with irradiances varying from 10 to 300 mJ cm −2 in a nitrogen atmosphere. Complementary information is provided by analysis with x-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The versatility, superior specificity and sensitivity of using ToF-SIMS to investigate degradation phenomena are highlighted. The combined results demonstrate that photoirradiation causes a number of chemical changes to the surface: incorporation of oxygen; degradation of the benzene rings and formation of oxidized carbon species; depletion of carbon; reduction of -SO 2 -to some extent; formation of -OH, C O and -SO 3 H groups; and probable formation of -C 6 H 4 -O-C 6 H 5 end-groups. In addition, no -OSO 3 H groups are formed and no formation of SO 2 is detected. Also, it is shown that chain scission dominates below an irradiation dose of ∼200 mJ cm −2 (at 254 nm in a nitrogen atmosphere). At higher doses, cross-linking becomes dominant.

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

“…Nevertheless, -SO 3 H groups appear to be formed in a nitrogen atmosphere, suggestive of incomplete removal of ambient air, i.e. residual oxygen reacts with the -SO 2 ž radicals formed on the PES surface (consistent with conclusions made in the preceding article 8 ). This agrees with the fact that the SO 3 intensity curve for nitrogen lies between the curves for a vacuum and air.…”

“…In the preceding article 8 it was suggested based on ToF-SIMS data that -SO 3 H groups are formed as a consequence of photoirradiation and reaction with residual oxygen. In Fig.…”

“…It was postulated previously 8 for PES that the intensity ratio C n H 2n C /C n H C acquired from ToF-SIMS analysis can be used as a marker for loss of aromaticity, i.e. the ratio increases with an increase in the degree of benzene ring degradation.…”

“…One of the main differences is that the evolution of SO 2 is not an important process for photodegradation. 6,7 In the preceding article 8 it was demonstrated how timeof-flight secondary ion mass spectrometry (ToF-SIMS) 9 can be used as a tool for studying the photodegradation of PES. From the ToF-SIMS data alone it was possible to conclude that photoirradiation causes -OH and -SO 3 H group formation (the latter from reaction with residual oxygen), probable -C 6 H 4 -O-C 6 H 5 end-group formation and benzene ring degradation, and it was found that chain scission dominates over cross-linking for irradiation doses up to somewhere between 100 and 200 mJ cm 2 (at 254 nm in a nitrogen atmosphere).…”

Surface photomodification of flat-sheet PES membranes with improved antifouling properties by varying UV irradiation time and additive solution pH

“…UV-induced modification stands out among all the surface modification techniques developed to improve PES surface properties for many applications due to its simplicity, usefulness, versatility, and low cost, which make its use very widespread. Other researchers have demonstrated that all polyarylsulfone materials are intrinsically photosensitive at a wavelength higher than 254 nm [7,10]. Its main advantage is the ability to modify different properties on the PES surface by introducing functional groups from the selected monomer (or monomers) or by entrapping inorganic nanoparticles without affecting the bulk properties [7,11].…”