Microstructured poly(2-hydroxyethyl methacrylate)/poly(glycerol monomethacrylate) interpenetrating network hydrogels: UV-scattering induced accelerated formation and tensile behavior

Methacrylate hydrogels are unique synthetic materials known for their capability to serve as multifunctional eye implants, practically without duration and compatibility limits. We introduce a novel strategy consisting in toughening of a macroporous microstructure using the interpenetrating network concept, which improves the commonly preferred preparation way of hydrogel based on photopolymerization. The method proceeds at ambient temperature and can be used in situ. Scattering of irradiation generated by the microstructure considerably enhances the polymerization rate. This acceleration effect was quantified by careful optical analysis and is important for in situ applications. Crosslinked IPN hydrogels of 2-hydroxyethyl methacrylate (HEMA) as the first network and glycerol methacrylate (GMA) as the second network based on this new design were studied and compared with IPNs prepared from non-porous PHEMA gels. Surprisingly, a relatively high swelling capacity was achieved with this new design and the Young's modulus increased from 4 kPa for parent PHEMA network to 380 kPa for the PHEMA-PGMA IPNs and to 980 kPa for the PHEMA-PHEMA IPNs. The IPN hydrogels were strong and resisted mechanical load. The reinforcement of the mechanically poor macroporous network by swelling in another hydrophilic monomer and subsequent polymerization presents a new concept of preparation of strong microstructured IPNs (MIPNs).