Self-reinforcing hydrogels comprised of hydrophobic methyl methacrylate macromers copolymerised with either N-vinyl-2-pyrrolidone or 2-hydroxyethyl acrylate

Methyl methacrylate macromers have been synthesised by catalytic chain transfer polymerization with M(n) values ranging from 565 to 25 392. These macromers were subsequently copolymerized with either 2-hydroxyethyl acrylate or N-vinyl-2-pyrrolidone, in bulk, by λ-radiation to yield xerogel materials. Copolymerization was confirmed by NMR analyses and by subsequent aqueous extraction of the resultant copolymers. The xerogels containing 2- hydroxyethyl acrylate and macromers below 10 000 (M(n)) molecular weight yielded popcorn polymers. All other xerogel materials were transparent. On swelling in deionised water, compositions containing 2-hydroxyethyl acrylate became white and opaque indicating phase segregation. In contrast all of the hydrogels based on N-vinyl-2-pyrrolidone retained transparency. Hydrogels were formed that had significantly higher Young's moduli than hydrogels based on random copolymers of equivalent composition.