| abstract |
Optically clear, reinforced cross-linked silicone elastomers of the invention contain 12 to 18 mol percent of aryl substituted siloxane units of the formula R4R5-SiO, end blockers containing siloxane units of the formula R1R2R3SiO.5, and dialkyl siloxane units of the formula R6R7-SiO. R1 and R2 are alkyl, aryl or substituted alkyl or substituted aryl groups, and R3 is an alkenyl group. R4 and R5 are phenyl or mono lower alkyl substituted phenyl groups. R6 and R7 are methyl or ethyl groups. The polymer has a degree of polymerization between 100 to 2000, and preferably approximately 250. The polymer also contains trimethyl silyl treated silica as a reinforcer in the weight ratio of approximately 15 to 45 parts of reinforcer to 100 parts of the polymer. After cross-linking, the polymer has properties of an optical refractive index which is at least 1.44, a type A durometer hardness of at least 35, tensile strength of at least 500 psi and tear strength of at least 20 pli. The foregoing properties render the cross-linked polymer especially suitable for forming the bodies of intraocular lenses. |