SWELLING AND MECHANICAL-PROPERTIES OF CROSS-LINKED HYDROGELS CONTAINING N-VINYLPYRROLIDONE

Copolymers of 2-hydroxyethyl methacrylate/N-vinyl-2-pyrrolidone (HEMA/ NVP) and methyl methacrylate (MMA)/NVP were prepared in the presence o f varying amounts of ethylene glycol dimethacrylate (EGDMA) and methyl ene diacrylamide (MDA) as crosslinkers by photopolymerisation. The res ultant solid polymers were swollen to equilibrium in water at 293 K to produce hydrogels. These hydrogels were characterised by soluble frac tion and equilibrium water content. The gels were also characterised b y compression-strain measurements, which enabled the calculation of Yo ung's modulus and effective crosslink density. The differences in thes e properties of HEMA/NVP and MMA/NVP polymer series and the effects of MDA versus EGDMA as a crosslinker were explained in terms of composit ional drift of polymerisation, heterogeneous crosslinking and hydrophi licity/hydrophobicity of the components involved. In comparison with E GDMA, MDA was found to be more effective in reducing the soluble fract ion of the polymers studied and to produce less rigid networks when sw ollen.