Enzyme-Initiated Devulcanization of Silicone–Gelatin Elastomers

Silicone elastomers are valued for their resilience, particularly in stressful environments. Commercial cross-linking processes lead to covalent bonds based on Si–C or Si–O links, which, like all conventional rubbers, make degradation of the elastomer difficult at the end of life. We show that hydrated gelatin, a natural protein, can be covalently incorporated into silicone elastomers to produce hydrogels; the protein serves as both a diluent for silicone and a handle for devulcanization. Diacrylated cross-linkers based on poly­(ethylene glycol) or triglycerol led to homo- and heteropolymer cross-linking between silicone and gelatin; the homogeneity of the elastomer products was dependent upon mixing prior to cure. Reactions occurred over a few hours at 80 °C to give hydrogels initially or, after drying, elastomers that exhibited the properties of both constituents. The cross-linked materials were stable during use, dry or after swelling in water, but very susceptible to enzymatic degradation to give silicone oils when treated with the enzymes bromelain and lipase.