US Patent 7423074 Polysiloxane prepolymers for biomedical devices

A polysiloxane copolymer that is useful for forming biomedical devices comprises blocks (I) and (II) and is terminated at each end with an ethylenically unsaturated radical:(*Dii*Diol*Dii*PS)x   (I)(*Dii*PS)y   (II)wherein:each Dii is independently a diradical residue of a diisocyanate;each Diol is independently a diradical residue of a diol having 1 to 10 carbon atoms;each PS is independently a diradical residue of a polysiloxane-containing diol or diamine;each * is independently —NH—CO—NH—, —NH—COO— or —OCO—NH—:x represents the number of blocks (I) and is at least 2, andy represents the number of blocks (II) and is at least 1.