ENVIRONMENTALLY INDUCED MACROMOLECULAR REARRANGEMENT ON THE SURFACE OF POLYURETHANE-POLYSILOXANE GRAFT-COPOLYMERS

The surface of polyurethane-polysiloxane graft copolymers possessing a controlled polysiloxane graft segment length and a defined siloxane content was studied in both dry and wet states. The top surface of casted graft copolymer film was covered completely with the polysioloxane component in dry state and the thickness of hte top polysiloxane layer range from more than about 100 Å to less than about 20 Å depending both on the graft segment length and on the total siloxane content. Along with the change of contacting medium from dry to aqueous phase, a dynamic surface rearrangement was observed during a 3-h period from a polysiloxane-like surface to a polyurethane-like surface only when the top polysiloxane layer of graft copolymers in dry state was less than around 100 Å. © 1990.