To homogenize light emitted from fiber optic diffusers for photodynamic therapy (PDT), novel coating materials with tunable properties were designed. A class VI medical grade UV-curable acrylic resin for biomedical applications was used for the polymer matrix, and titanium dioxide (TiO2) was added to the resin as a scattering agent. UV-curability of coatings containing TiO2 was significantly influenced by the grade and Surface treatment of the TiO2 studied. Despite using a free-radical system without inert gas protection, all samples demonstrated considerable thermal postcuring. A novel TiO2 surface treatment methodology was developed based on unsaturated alkoxyorganosi lanes combined with unsaturated carboxylic acids for compatibilizing TiO2 for use in the resin material studied. By adjusting the concentration of the surface-modifying agent, the scattering efficiency and UV curability can be controlled by decreasing the effective particle size and enhancing the dispersibility of the powder filler within the resin. This modification will enable fine-tuning of the effective size of TiO2 particles to the wavelength of laser light to be scattered to maximize scattering efficiency in photodynamic cancer therapy and possibly also in other forms of cancer treatment (interstitial laser hyperthermia or interstitial laser photocoagulation). (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 1516-1523, 2009