Chem. and supramol. structures of polyurethanes and poly-siloxanes and a possibility of synthesis of polyurethane-polysiloxane copolymers were presented. Free surface energy, mech. and transport properties as well as thermal, chem. and biol. resistance of the polymeric materials were taken into consideration. Membranes for sepn. of gases, polymer coatings and elastomeric construction materials for electronics and medicine were described as examples of their uses.