A novel sequential dual-curable thermosetting system with a custom-tailorable structure based on a click thiol–epoxy reaction and excess epoxy is presented.

Diglycidyl ether of bisphenol A (DGEBA) was cured with γ‐butyrolactone (γ‐BL) with ytterbium triflate as a catalyst. The curing was studied with differential scanning calorimetry, Fourier transform infrared (FTIR), and thermomechanical analysis. FTIR studies confirmed that four elemental reactions took place during the curing process: the formation of a spiroorthoester (SOE) by the reaction of DGEBA with γ‐BL, the homopolymerization of SOE, the homopolymerization of DGEBA, and the copolymerization of SOE and DGEBA. Moderate proportions of γ‐BL produced materials with higher glass‐transition temperatures, and the curing occurred with lower shrinkage after gelation because of the polymerization of SOE, with near‐zero shrinkage during the final stages of the curing. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2794–2808, 2003

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A new dual-curing, solvent-free process is described for the preparation of tailor-made materials from off-stoichiometric amine-acrylate formulations. The first stage reaction is a self-limiting click aza-Michael addition between multifunctional amine and acrylate monomers with an excess of acrylate groups. The second stage reaction is a photoinduced radical polymerization of the unreacted acrylate groups. By selecting the structure of the monomers and the stoichiometry of the formulations, mechanical and thermal characteristics of the intermediate and final materials can be tuned. The materials obtained after the first curing stage can be gelled or ungelled and loosely or tightly crosslinked at the end of the second curing stage. The methodology used allows to obtain storable and procesable intermediate polymers and final networks with optimum properties for different applications. The presence of amines in the reaction medium overcomes the intrinsic oxygen inhibition of acrylate free-radical polymerizations, resulting in a quasi complete cure. Dual curing processing, combining different and compatible polymerization mechanisms, can be used in many applications to obtain a stable material after the first stage that maintains the ability, upon application of a second stimulus, to further react and achieve the final properties desired. Nair et al. 6 developed new two-stage reactive systems based on the combination of base-catalyzed thiol-acrylate Michael addition and UV-induced free radical polymerization of excess acrylates. Peng et al. 7 prepared