This article reports on the curing behavior and adhesion performance of ultraviolet (UV)-curable, polystyrene-polyisoprene-polystyrene (SIS)-based pressure-sensitive adhesives (PSAs) blended with dior tri-functional monomers and a photoinitiator. The curing reaction was achieved by direct excitation of PSAs by irradiation with a 100 W high-pressure mercury lamp at different UV doses. The curing behavior of the PSAs was studied by gel fraction determination, rigid-body pendulum type physical properties test (RPT) and Fourier transform-infrared-attenuated total reflection (FT-IR-ATR) spectroscopy. The adhesion performance was determined by probe tack, peel strength and shear adhesion failure temperature (SAFT) measurements. The reaction rate and extent of UV curing reaction were found to be strongly dependent on the curing rate for the following five multifunctional monomers studied: three di-functional monomers, ethylene/glycol dimethacrylate (EGDMA), triethylene glycol dimethacrylate (TEGDMA) and poly(ethylene/glycol)(400) dimethacrylate (PEG(400)DMA), and two tri-functional monomers, trimethylolpropane triacrylate (TMPTA) and trimethylolpropane ethoxylated (6) triacrylate (TMPEOTA). In addition, the adhesion performance was affected by the semi-interpenetrating polymer network (IPN) structure formed depending on the curing rate and degree of cross-linking. (C) Koninklijke Brill NV, Leiden, 2008