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 degrees 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.