Novel hard-block polyurethanes with high strength and transparency for biomedical applications.

Novel hard-block-only polyurethanes are prepared from 1,4-butanediol (BDO) and a pre-polymer synthesized separately from 1,3-bis (4-hydroxybutyl) tetramethyl disiloxane (BHTD) and 4,4'-diphenylmethane diisocyanate (MDI). Three (co)polymers using different proportions of these chain extenders were synthesized using reaction injection moulding, and their microstructure, mechanical properties and in vitro oxidative biostability were evaluated. These materials were found to form a single-phase system, and exhibit optical transparency, high elastic modulus and tensile strength, as well as significant in vitro oxidative biostability. By controlling the BDO/BHTD composition, the ductility can be tuned over orders of magnitude. These polyurethanes may be potentially suitable for biomedical applications, like electronic headers for defibrillators, pacemakers and neurostimulators, and orthopedic nail encapsulation.