A microcapsule system with polyurethane acrylate (PUA) shell is prepared by interfacial polymerization between acrylic polyurethane diisocyanate and water to achieve controlled release via UV irradiation. The size of the microcapsule is influenced by the concentration of protecting colloid and property of acrylic polyurethane diisocyanate. When concentration of polyvinyl alcohol (PVA) is 5% and molar ratio of TDI and acrylic ethoxylated pentaerythritol (acrylic PP50) rises to 1.50, average diameter of the microcapsule is only 3.3223 mu m. Delivery of 4-hydroxy-4'-isopropoxydiphenylsulfone (D-8) encap-suled by PUA microcapsule in solution can be prevented effectively by 30-min UV irradiation. Lightness (L*) is used to measure color changes of reaction between D-8 in PUA microcapsule and 2-amino-6-dibutylamino-3-methylfluoran (ODB-2) under thermal treatment. In dry state, irradiated PUA microcapsules are much harder to release D-8 than those not irradiated. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1008-1016, 2009