Several hydrophilic, amphiphilic and thermoresponsive polymers are reported which can be attached to polymeric substrates by using macroinitiators, "grafting onto" processes or plasma and electron beam activation. Poly(acrylic acid) hydrogel layers grafted from a thin macroinitiator layer could be used to reduce the friction of polymeric catheters and to allow a better sliding of the tubes into the blood vessels without damaging tissue. A similar approach could be used to fix hydrogel layers on balloon catheters which are able to carry anticlotting drugs being released after the fixation of the catheter/stent within the blood vessel. A variety of amphiphilic graft copolymers and gels have been prepared based on oxazoline chemistry which allows to induce heterogeneity into the gel structure leading to specific swelling properties. Copolymerization with N-isopropylacrylamide (NIPAAm) allowed also to incorporated a thermoresponsive behavior in these gels. Copolymers of NIPAAm with poly(ethylene glycol) macromonomers allowed the preparation of cell compatible thermoresponsive materials immobilized on surfaces for cell release studies. Biactive and thermoresponsive block copolymers from NIPAAM and glycomonomers prepared via the RAFT process can be used for the control of cell adhesion and proliferation.