Adsorption of branched homopolymers on a solid surface

Simulation calculations are reported for single-chain polymer-wall conforma tion-averaged potentials of mean force and segment-density profiles for hom opolymers of different structures as a function of the segment-wall attract ive potential. When there is no attraction between the wall and the polymer segments, the presence of the wall generates a polymer-segment depletion l ayer whose thickness depends on polymer structure and on surface roughness. Segment-density profiles are characterized by three regions. In the proxim al region, the segment density is determined by surface roughness and by po lymer flexibility. In the distal region, the segment density approaches uni ty asymptotically. In the central region, the segment density depends on ge ometric characteristics of the polymer in the bulk solution. When the wall- segment attractive potential is sufficiently large, the depletion layer thi ckness is reduced and the polymers are adsorbed. When attraction is weak, c ompact polymers (e.g., dendrimers of high generation) are readily adsorbed. Due to their globular shape, high-generation dendrimers, at weak attractiv e interactions, are at contact with the surface with numerous segments; glo bular polymers experience a relatively small entropic penalty for adsorptio n. By contrast, linear polymers, due to their flexibility at good solvent c onditions, pay a high entropic penalty for each segment at contact with the surface. Therefore, at weak attractive interactions, globular polymers are readily adsorbed, whereas linear polymers are more readily adsorbed at str onger attractive interactions. With rising surface roughness, flexible poly mers tend to spread on the surface, whereas branched polymers are repelled at larger distances. (C) 2001 American Institute of Physics.