Abstract: Thermally reversible polyurethane hydrogels are formed by adding water to a gel forming hydrophilic polyurethane polymer produced by reacting under anhydrous conditions a non-aromatic organic diisocyanate with a glycol component in an NCO/OH mole weight ratio of from about 0.900/1 to about 0.980/1, the glycol component having a number average molecular weight of from about 1000 to 3500 wherein the percentage by weight of the diisocyanate in the reaction mixture is from about 7% to about 20%. The hydrogels are solids at room temperature but liquify at higher temperatures such as body temperature and therefore are useful as carriers for the protection, delivery and sustained release of a variety of active agents including pharmaceuticals, cosmetics, living cells and organisms.

Abstract: The coefficient of friction of surfaces of articles, wherein the surface comprises a hydrophilic polyurethane polymer, is reduced by treating the surface with a mixture of concentrated sulfuric acid and a low molecular weight organic polyhydroxy compound, and removing excess treating mixture. Typical low friction articles produced thereby are boat hulls having drag resistant coatings, conduits having low friction linings, and cannula or body implants having slippery surfaces.

Abstract: An article having a lower coefficient of friction in the wet state is produced by applying to a substrate an adherent isocyanate coating followed by a second coating of polyvinylpyrrolidone copolymerized with a minor amount of an ethylenic monomer having active hydrogens and curing the so-coated substrate to effect reaction between the active hydrogens and isocyanate groups. The article is useful in the manufacture of medical devices for insertion in the body.