Phase Morphology–Structure–Property–Recyclability Relationships of Dynamically Crosslinked Thiol-Ene Photopolymers

Abstract

Thiol–ene photopolymerization provides a versatile platform for constructing dynamic covalent adaptable networks through the incorporation of reversible or exchangeable bonds. However, in such dynamic thiol-ene photopolymers, the influence of phase separation on network properties remains poorly understood. In this study, dynamic thiol–ene photopolymer networks with distinct phase morphologies are prepared by photocuring nonpolar polybutadiene (PBD) with polar disulfide-containing dithiol oligomers (Thioplast G4). When mixed in the bulk state, PBD and G4 mixtures undergo phase separation due to their pronounced polarity mismatch, and subsequent photocuring yields morphologically heterogeneous networks comprising a PBD-rich continuous phase and G4-rich dispersed domains (noted as X series). In stark contrast, the addition of tetrahydrofuran leads to fully dissolved PBD/G4/tetrahydrofuran precursor mixtures, and subsequent photocuring in the solution state produces morphologically homogeneous, optically transparent networks (noted as HX series). Despite their identical PBD and G4 compositions in feed precursor mixtures, X and HX series exhibit pronounced differences in thiol–ene conversion, optical transparency, thermal transitions, mechanical extensibility, and chemical deconstruction kinetics. Across the varying G4 loadings employed to modulate crosslink density, these direct X and HX comparison results demonstrate how phase morphology can be tailored to tune the structure, property, and recyclability of thiol–ene photopolymer networks comprising dynamic disulfide bonds.