High modulus hydrogels for ophthalmic and related biomedical applications

This paper presents three families of semi‐interpenetrating polymer network (SIPN) hydrogels based on an ester‐based polyurethane (EBPU) and hydrophilic monomers: N,N‐dimethylacrylamide (NNDMA), N‐vinyl pyrrolidone (NVP) and acryloylmorpholine (AMO) as potential materials for keratoprosthesis, orthokeratology and mini‐scleral lens application. Hydrogels sheets were synthesized via free‐radical polymerization with methods developed in‐house. SIPN hydrogels were characterized for their equilibrium water content, mechanical and surface properties. Three families of optically clear SIPN‐based hydrogels have been synthesized in the presence of water with >10% of composition attributable to EBPU. Water contents of SIPN materials ranged from 30% to 70%. SIPNs with ≤15% EBPU of total composition showed little influence to mechanical properties, whereas >15% EBPU contributed significantly to an increase in material stiffness. In the hydrated state, SIPNs with ≤15% EBPU of total composition show little difference in polar component (γp) of surface free energy, whereas for >15% EBPU there is a decrease in γp. The EBPU SIPN hydrogels display complementary material properties for keratoprosthesis, orthokeratology, and mini‐scleral applications