A new class of thin film hydrogels produced by plasma polymerization

A simple, direct route to preparation of surface-immobilized hydrogel films is described. Specifically, low-pressure RF pulsed plasma polymerization of 1-amino-2-propanol and 2-(ethylamino)ethanol monomers produced thin hydrogel films deposited on substrates located in the plasma reactor. The successful syntheses were carried out under plasma conditions that not only yield the hydrogel but are also sufficiently energetic to produce films strongly grafted to the substrates. The polymer films obtained exhibit the thermoresponsive property of hydrogels, as shown by film color change with temperature. Additional evidence for the phase-transition properties of these films was obtained using water contact angle and capillary rise measurements. The plasma-polymerization approach provides an unusually simple route to synthesizing hydrogels in which the films are pinhole free and have easily controlled thickness. An important added advantage, particularly for applications involving biomaterials, is the conformal property of the plasma generated polymer films. The results obtained suggest that this approach should be applicable to a variety of other monomers and, on the basis of differences observed with the present two monomers, suggest synthesis of films that exhibit a range of phase-transition temperatures.