Poly(ether urethane) oligomers as poly(HEMA) crosslinkers

Hydrogels with improved mechanical properties and acceptable levels of water absorption were developed by crosslinking poly(hydroxyethyl methacrylate), P(HEMA), with isocyanate-terminated poly(ether glycols). The crosslinking agents consisted of polyethylene glycol) (PEG) and poly(tetramethylene glycol) (PTMG) chains end-capped with hexamethylene diisocyanate (HDI). PEG of molecular weight 600 and PTMG of molecular weight 650 were used. P(HEMA) was reacted with either of the two crosslinkers alone, at concentrations of 5-30%, or with various combinations of the two crosslinkers, at total crosslinker content of 10-30%. Generally, as the level of the PEG-containing crosslinker increased, the mechanical properties of the hydrogel, both dry and wet, decreased, whereas the equilibrium water content increased. Hydrogels with a good balance between mechanical properties and water content could be obtained by adjusting the amount and composition of the crosslinking agent.