STRUCTURE OF AN IRREVERSIBLY ADSORBED POLYMER LAYER IMMERSED IN A SOLUTION OF MOBILE CHAINS

We discuss the structure of an irreversibly adsorbed layer made of neu tral, flexible polymer chains (degree of polymerization N) exposed to a solution of mobile chains (degree of polymerization P). We assume th at the mobile chains are chemically identical to the adsorbed chains a nd that their length is shorter (or comparable). According to the valu e of the bulk volume fraction, phi(b), the mobile chains may, or may n ot, penetrate into the layer and may, or may not, affect the layer con formation. Using scaling laws, we locate the domains of existence of t hese different regimes in terms of the variables phi(b), P, and N. In particular, we expect the mobile to penetrate into the layer if the bu lk volume fraction phi(b) is greater than a critical value phi(bM) giv en by phi(bM) congruent to (P/N)(4/7) for P > N-5/12 and by phi(bM) co ngruent to N--1/3 for P < N-5/12.