Thiol–Ene and Thiol–Yne Photopolymerisation in VPP: Stoichiometry, Oxygen Response and Network Architecture
Segurola, Juan
2026-08-27 · Informe · Versión 1.1
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Vat photopolymerisation is dominated by chain-growth acrylate and methacrylate chemistry. Thiol-ene and thiol-yne reactions provide a different network-forming route in which thiyl-radical addition and rapid hydrogen transfer create a step-growth-like reaction cycle. Under appropriate functionality and stoichiometry, this can delay gelation to higher conversion, reduce oxygen sensitivity, limit early microgel formation and produce more uniform network connectivity. These advantages are conditional. Ene identity determines whether chain transfer or homopolymerisation dominates. Thiol-acrylate formulations contain a mixed step- growth/chain-growth mechanism rather than a pure thiol-ene network. Thiol-yne systems can consume two thiol equivalents per alkyne through a vinyl-sulfide intermediate, increasing potential connectivity while tightening stoichiometric control. Residual thiol, oxidation, odour, dark reaction, radical stabilisation, optical confinement and diffusion-limited conversion remain formulation-specific risks. Published light-based additive-manufacturing systems include tomographic thiol-ene VAM resins with TEMPO-defined thresholds, unmodified polybutadiene and polychloroprene elastomers, visible-light photoredox thiol-yne resins, degradable aliphatic-polycarbonate networks and CO2-derived copolymer elastomers. These studies demonstrate broad chemistry access but also show that oxygen tolerance can weaken volumetric thresholding, solvent-assisted feedstocks can undergo very large drying shrinkage, and high conversion does not remove transport or network-state limitations. This review develops a reaction-classification and qualification framework for thiol-ene, thiol-yne and mixed thiol-acrylate VPP. It separates functional-group stoichiometry from monomer mass ratio, distinguishes oxygen tolerance from oxygen independence, and requires both thiol and ene/yne conversion, gelation, dark reaction, residual-functionality and dimensional evolution to be reported.