an oil bath to reflux under a nitrogen blanket after two hours the reaction is complete and the contents stripped under vacuum 5 6 mmhg for 4 hours the ir spectrum shows two kinds of peaks for carbonyl groups u2014 both acid chloride and ester the flask contents is then added with 16 64 g 0 04 mole of the reactive nvp oligomer and 100 ml of methylene chloride and continued heating the contents under reflux until all acid chloride group disappeared by ir 1769 cm 1 then the mixture is cooled and 5 41 grams of sodium bicarbonate was added to neutralize the content while kept on stirring overnight 600 ml of methylene chloride was then added and the solution was filtered and extracted with 100 ml of water the organic layer is separated and the solvent is stripped to give a viscous fluid product this prepolymer is prepared in the same fashion as described in example 3 using dma in place of nvp a monomer mix derived from the components listed in the following table is prepared a monomer mix containing the above components at the same parts as those listed in table 1 is mixed with 0 5 part of nvp oligomer terminated fumarate prepolymer of polytetrafluoroethylene glycol the monomer mixture of example 6 is injected onto a clean polypropylene anterior mold half and covered with the complementary polypropylene posterior mold half the mold halves.