POLY(1-VINYL-2-PYRROLIDINONE) HYDROGELS AS VITREOUS SUBSTITUTES - A RHEOLOGICAL STUDY

In order to develop an artificial vitreous, a large series of hydrogel s have been previously produced by polymerization of 1-vinyl-2-pyrroli dinone, with or without crosslinking. Based on the assumption that a f unctional vitreous substitute should possess viscoelastic properties a fter its delivery, a number of selected gels were characterized theolo gically by both oscillatory shear stress analysis and shear creep anal ysis, using a controlled stress rheometer in the cone/plate configurat ion. The experiments demonstrated a dramatic effect of injecting the g els through small-gauge needles, as many lost their viscoelasticity to become free-flowing fluids, probably because of the cleavage of chain s and crosslinks. It was also found that the increase of comonomer con tent (2-hydroxyethyl methacrylate) and of crosslinking level generally had a strengthening effect. However, the effects of hydrophilic cross linking agents (diallyl ether and divinyl glycol) were irregular. Even tually, only four hydrogels in this series showed viscoelastic charact eristics after injection through a 30-gauge (0.13 mm diameter) needle, maintaining behaviour typical of crosslinked networks and warranting further assessment as potential vitreous substitutes. (C) 1998 SCI.