Improved oxygen permeability and mechanical strength of silicone hydrogels with interpenetrating network structure

 The interpenetrating polymer network (IPN) silicone hydrogels with improved oxygen permeability and mechanical strength were prepared by UV-initiated polymerization of monomers including methacryloxypropyl tris(trimethylsiloxy)silane (TRIS), 2-hydroxyethylmethacrylate (HEMA) and N-vinyl pyrrolidone (NVP) in the presence of free radical photoinitiator and cationic photoinitiator. The polymerization mechanism was investigated by the formation of gel network. The structure of IPN hydrogels was characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results showed that the IPN hydrogels exhibited a heterogeneous morphology. The mechanical properties, surface wettability and oxygen permeability were examined by using a tensile tester, a contact angle goniometer and an oxygen transmission tester, respectively. The equilibrium water content of the hydrogels was measured by the gravimetric method. The results revealed that the IPN hydrogels possessed hydrophilic surface and high water content. They exhibited improved oxygen permeability and mechanical strength because of the incorporation of TRIS.