Shape memory polyurethane or polyurethane-urea polymers

A biostable shape memory polyurethane or polyurethane-urea polymer comprising a reaction product of (a), (b) and (c) as set out below:

• (a) a silicon-based macrodiol and a polyether of formula (I) below;
• a silicon-based macrodiamine and a polyether of formula (I) below;
• or a silicon-based microdiol, a silicon-based macrodiamine and polyether of formula (I):
• A(CH2)m—On(CH2)m—A′ (I)
• wherein
• A and A′ are endcapping groups;
• m is an integer of 6 or more;
• and
• n is an integer of 1 or greater,
• (b) a diisocyanate;
• and
• (c) a chain extender,
• wherein the silicon-based macrodiol and macrodiamine are silicon-based polycarbonates having the formula (IV):
• wherein:
• R1, R2, R3 and R4 are the same or different and selected from hydrogen or an optionally substituted straight chain, branched chain and cyclic, saturated or unsaturated hydrocarbon radical;
• R5, R6, R8 and R9 are the same or different and selected from an optionally substituted straight chain, branched chain and cyclic, saturated or unsaturated divalent hydrocarbon radical;
• R7 is a divalent linking group or an optionally substituted straight chain, branched chain or cyclic, saturated or unsaturated hydrocarbon radical;
• A and A′ are as defined in formula (I);
• m, y and z are integers of 0 or more;
• and
• x is an integer of 0 or more
• said polymer having a glass transition temperature which enables the polymer to be transformed from its original shape into a first shape at a temperature higher than the glass transition temperature and maintained in said first shape when the polymer is cooled to a temperature lower than the glass transition temperature, said polymer then being capable of resuming its original shape on heating to a temperature higher than the glass transition temperature.