US Patent 7632876 Polysiloxane prepolymers for biomedical devices

A polysiloxane prepolymer that is useful for forming biomedical devices has the formula:M(*Dii*PS)x*Dii*M  (I)wherein:each M is independently a polymerizable ethylenically unsaturated radical;each Dii is independently a diradical residue of a diisocyanate;each PS is independently a diradical residue of a polysiloxane-diol or a polysiloxane-diamine;each * is independently —NH—CO—NH—, —NH—COO— or —OCO—NH—; andx is at least 2.