Fully Degradable Polyacrylate Networks from Conventional Radical Polymerization Enabled by Thionolactone Addition

We report the preparation of degradable polymer networks by conventional free radical copolymerization of n-butyl acrylate with a crosslinker (1 mol %) and dibenzo[c,e]oxepane-5-thione (DOT) as a strand-cleaving comonomer. Addition of only 4 mol % of DOT imparts the synthesized networks with full degradability by aminolysis, whereas gels with less DOT (2-3 mol %) cannot be degraded. This data confirms the recently proposed reverse gel-point model for networks prepared by free radical polymerization and demonstrates the importance of considering copolymerization kinetics when designing fully degradable gels. Notably, even though DOT significantly slows down the polymerization and delays gelation, it has a minimal effect on physical properties of the networks such as shear storage modulus, equilibrium swelling ratio, glass transition temperature, or thermal stability.