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Polyethersulfone (PES) films are widely employed in the construction of membranes where there is a desire to make the surface more hydrophilic. Therefore, UV photo-oxidation was studied in order to oxidize the surface of PES and increase hydrophilicity. UV photo-oxidation using low pressure mercury lamps emitting both 253.7 and 184.9 nm radiation were compared with only 253.7 nm photons. The modified surfaces were characterized using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and water contact angle (WCA) measurements. Both sets of lamps gave similar results, showing an increase of the oxygen concentration up to a saturation level of ca. 29 at.% and a decrease in the WCA, i.e., an increase in hydrophilicity, down to ca. 40°. XPS detected a decrease of sp2 C-C aromatic group bonding and an increase in the formation of C-O, C=O, O=C-O, O=C-OH, O-(C=O)-O, and sulphonate and sulphate moieties. Since little change in surface roughness was observed by AFM, the oxidation of the surface caused the increase in hydrophilicity.

Poly(ethylene 2,6-naphthalate) (PEN) was treated with ozone in the absence of radiation and the results were compared with ultraviolet (UV) photooxidation using 253•7 and 184•9 nm radiations. The surface modification of the top 2-5 nm was analyzed by X-ray photoelectron spectroscopy (XPS) for chemical changes. Higher saturation levels of oxidation were achieved using UV photooxidation than ozonation. Both treatment methods increased the amounts of CO -C, C=O and O-C=O bondings while UV photooxidation also increased the concentration of the anhydride/carbonate moieties on the surface. Atomic force microscopy detected smoother surfaces with increasing treatment time for both the treatments. The changes in functional groups and surface roughness with both treatments contributed to an increase in hydrophilicity as determined by advancing water contact angle measurements. A greater increase in hydrophilicity was observed for the UV photooxidized PEN samples. Initial results showed a slight increase in hydrophilicity when acrylic acid was grafted onto ozone-treated PEN surfaces, although, the ester group in the PEN structure made it difficult to detect poly(acrylic acid) by XPS.