A cross-linkable and cross-linked organosilicon polymer which is prepared from a mixture of a reactive polysiloxane resin having both reactive carbon-carbon double bonds and silicone-hydrogen groups, characterized by alternating structures of polycyclic polyene residue and cyclic (or tetrahedral) polysiloxane residue, and either vinyl terminated fluorine-containing polysiloxane or vinyl terminated phenyl-substituted siloxane. In an alternative embodiment, the polymer comprises a mixture of vinyl terminated phenyl-substituted polysiloxane and vinyl functional fluorosilicone elastomer with the cross-linkable and cross linked organosilicon polymer. In an alternative embodiment, the polymer comprises vinyl functional polydimethyl siloxane, and preferably high molecular weight methyl divinyl siloxane, with or without phenyl substituted siloxane.