silicone rubber seal of the mould the degree of swelling is a function of the concentration of polyhpma in the hydrogel with respect to the concentration of the crosslinker and the amount of solvent while strength and resistance depend primarily on the concentration of polyhema in the formed hydrogel after polymerization the hydrogels are removed from the moulds and washed in distilled water for 24 hours and allowed to equilibrate in distilled water for 1 week the invention is further illustrated by means of the foiling non limiting examples in a glass ampoule there was dissolved 0 136 grams of hema 0 15 grams of hpma and 0 0446 grams of ethylene glycol dimethacrylate egdma in 0 28 grams of water ethylene glycol 1 1 wt wt by heating and stirring until dissolution to the resultant solution there was added a redox system made of 0 0273 grams of 6 w w ammonium persulfate and 0 0273 grams of 12 w w sodium thiosulfate the reaction mixture was degassed with pure nitrogen for 5 minutes thoroughly homogenised and injected using a syringe into moulds having two pre heated plates that are pre heated with an internal system of circulating water connected to a thermostated water bath each plate being provided with a separation layer made of polypropylene care was taken not to introduce air bubbles into the reaction mixture during loading the space of the moulds the thickness of the gel membrane that is required for the desired application.