Spatial and Temporal Control of Photomediated Disulfide-Ene and Thiol-Ene Chemistries for Two-Stage Polymerizations

A new strategy is reported for the design and synthesis of high sulfur-containing materials for potential use in covalent adaptable networks and optical materials by combining photomediated thiol-ene- and disulfide-ene-based polymerization reactions. Taking advantage of the relative reaction rates to differentiate sequentially between the thiol-ene and disulfide-ene conjugations, these reactions were performed semiorthogonally to produce polymer networks of controlled architecture. Kinetic analysis demonstrates that the thiol-ene reaction is approximately 30 times faster than the disulfide-ene reaction, enabling spatial and temporal manipulation of material properties via dual-cure networks and photopatterning. A two-stage polymerization approach was implemented with increases in modulus in the second stage of 2-3 orders of magnitude accompanied by increases in the glasstransition temperature of more than 15 degrees C. Additionally, the thiol-ene reaction in the presence of a disulfide yields materials capable of simultaneous network development and stress relaxation through dynamic bond exchange during in situ polymerization.