A thermoplastic elastomer, polystyrene-block-polybutadiene-block-polystyrene (SBS) with a high vinyl content (59%), was crosslinked within a fraction of a second by UV-irradiation in the presence of a trifunctional thiol and an acylphosphine oxide photoinitiator. The curing process was followed by LR spectroscopy, insolubilization and hardness measurements. Both the thiol and the photoinitiator concentrations were shown to affect the kinetics of the thiol-ene polymerization. Insolubilization was found to occur even at very low concentrations in thiol (less than or equal to 1 wt%) and in photoinitiator (0.1 wt%). The heat resistance of the photosensitive formulation is high enough at 150 degrees C to allow this system to be used for hot-melt adhesive applications. (C) 2000 Elsevier Science Ltd. All rights reserved.