Graphene oxide-reinforced poly(2-hydroxyethyl methacrylate) hydrogels with extreme stiffness and high-strength

Designing hydrogels with high-strength and stiffness remains a challenge, limiting their usage in several applications that involve load-bearing. In this work, in situ incorporation of different amounts of graphene oxide (GO) into poly(2-hydroxyethyl methacrylate) (pHEMA) was used to create hydrogels with outstanding stiffness (Young's modulus of up to 6.5 MPa, 8.3x higher than neat pHEMA) and tensile resistance (ultimate tensile strength of up to 1.14 MPa, 7.4x higher than neat pHEMA) without affecting the water absorption capacity, surface wettability and cytocompatibility of pHEMA. Such magnitude of improvement in Young's modulus and ultimate tensile strength was never before described for GO incorporation in hydrogels. Moreover, these stiffness and tensile resistance values are higher than the ones of most hydrogels (few hundred kPa), achieving a stiffness comparable to polydimethylsiloxane (PDMS), cartilage and artery walls and a tensile resistance similar to rigid foams, PDMS and cork. These new materials open a wide range of applications for pHEMA in different fields.