Hydrogels based on copolymers of N-(2-hydroxyethyl)methacrylamide, 2-hydroxyethyl methacrylate, and 4-t-butyl-2-hydroxycyclohexyl methacrylate

A nonionic, high water content, high-strength hydrogel based on N-(2-hydroxyethyl)methacrylamide (HMA), 2-hydroxyethyl methacrylate (HEMA), and a strengthening agent, 4-t-butyl-2-hydroxycyclohexyl methacrylate (TBCM). The HMA was prepared by the reaction of methacryloyl chloride with ethanol amine. The copolymerization of HMA with varying concentrations of HEMA and TBCM resulted in transparent hydrogel films possessing a wide range of mechanical and physical properties. A copolymer composition of 79 parts HMA, 20.7 parts TBCM, and 0.3 parts ethylene glycol dimethacrylate (EGDMA) gave a transparent, flexible film possessing a water content of 72.6%, a Young's modulus of 0.45 MPa, oxygen permeability of 28 barriers, and a tear strength of 28 N/m. In contrast, a copolymer composition of 40 parts HMA, 59.7 parts TBCM, and 0.3 parts EGDMA gave a hard, transparent film possessing a water content of 33% and a modulus of 504 MPa.