Characterisation of polystyrene microspheres surface-modified using a novel UV-ozone/fluidised-bed reactor

A fluidised-bed apparatus equipped with UVand oxygen sources has been developed and used for controlled surface oxidative modification of polystyrene microspheres. The composition and wettability of the microspheres modified using this method were characterised by X-ray photoelectron spectroscopy and a ‘‘floating’’ contact angle technique respectively. X-ray photoelectron spectroscopy data indicate an increase in surface oxygen concentration to 27 at.% after 1200 s UV-ozone treatment. This was accompanied by a decrease in the measured water contact angle from that of the unmodified surface, which gave a value of 87, to 248 after a similar UV-ozone treatment. Force–distance plots obtained from atomic force microscopy showed that the treatment resulted in an increase in the adhesion force measured between tip and surface which correlated well with the surface oxygen content. The experimental results demonstrate that this fluidised-bed apparatus is a convenient and reliable method for the modification of polymeric microparticles and that the resulting changes can be effectively studied and understood using the techniques applied here. # 2003 Elsevier B.V. All rights reserved.