Macromolecules, Vol.33, No.12, 4561-4567, 2000
Interaction forces between adsorbed layers of associative polymer
We have measured normal quasi-equilibrium forces between adsorbed layers formed on hydrophilic surfaces in aqueous solutions of telechelic poly(ethylene oxide) end-terminated with octadecyl groups. At low polymer concentrations, c(pol), a monolayer adsorbs, which has properties similar to the monolayer of adsorbed nonhydrophobized poly(ethylene oxide). At moderate concentrations of ca. c(pol) approximate to c(cmc), a multilayer adsorbs onto the surface, which is presumably formed by micelles adsorbed onto the top of a monolayer. The adsorbed layers exhibit repulsion on approach and attraction on separation of the surfaces; the latter evolves after several/decompression cycles. The adhesion energy increases with the time that the compressed layers are maintain ed in contact and with the extent of compression of the adsorbed layers. We attribute the attraction between the adsorbed layers to bridging between the hydrophobic groups of molecules adsorbed onto opposite surfaces.
Keywords:CAPPED POLY(ETHYLENE OXIDE);MICA SURFACES;WATER;BRUSHES;FLUORESCENCE;AGGREGATION;DISPERSIONS;COPOLYMERS