Dithiolane-Ene Copolymerization: Enabling Tunable, Dynamic, Dual-Cure Networks via Real-Time UV–Vis/FTIR Kinetics and Compositional Analysis

The radically mediated dithiolane-ene copolymerization enables efficient incorporation of dynamic disulfide bonds into vinyl polymers, facilitating control over dynamic disulfide bond integration. However, the reactivity of various vinyl monomers and the nature of their copolymerization with the dithiolane remains largely uninvestigated. This study employs a simultaneous FTIR/ultraviolet–visible (FTIR/UV–vis) apparatus in combination with other techniques such as NMR to examine the real-time kinetics, composition, and structure of copolymers formed with 1,2-dithiolanes and various vinyl monomers, including acrylates, methacrylates, vinyl ethers, vinyl sulfides, norbornenes, and allyl ethers. All vinyl monomers, except allyl ether, readily copolymerized with the methyl ester of lipoic acid (LipOMe), showing significant conversion within seconds to minutes of irradiation. Acrylates and vinyl ethers reacted most rapidly, each achieving greater than 82% conversion within 30 s while methacrylates reacted more slowly. Vinyl sulfides reached a final conversion of 48%, surpassing previous reactivity with linear disulfides and showing promise for dithiolane-yne copolymerizations. Additionally, acrylates and vinyl ethers exhibited complementary behavior, integrating with dithiolanes in 2:1 and 1:2 vinyl: dithiolane functional group ratios, respectively, while norbornene displayed a secondary mechanistic pathway that is hypothesized to result from disulfide bond exchange, yielding nearly 1:1 stoichiometric dithiolane:ene integration. Thermal reversion studies confirmed random incorporation of reducible disulfide bonds in acrylates. Utilizing this complementary behavior in acrylates and vinyl ethers, networks were formed and subjected to stress relaxation studies, which revealed divinyl ether networks relaxed 90% of stress in 3 min, compared to 50% for diacrylate networks in 10 min, demonstrating the ability to tune the amount of dynamic bonds and dynamic behavior based on the vinyl/monomer choice. Finally, a sequential, dual-cure organogel (10 wt % in DMSO) system utilizing both anionic and radical initiation mechanisms with norbornene achieved a modulus of 10 4 Pa upon anionic cure and subsequent 10-fold modulus increase following radical generation, demonstrating the potential to design materials with tunable material properties.