Irreversible vs. reversible coating

We discuss theoretically the composition of a coating, formed by polymers that can adsorb by both ends, in terms of loops (double-bounded chains) and tails (single-bounded chains) as a function of surface coverage and concentration of the adsorbing solution. Both irreversible adsorption (e.g., by chemical surface reaction) and reversible adsorption (e.g., by van der Waals interactions) are considered. Tails are found to be scarce but their amount controls surface properties such as roughness, dewetting or early bridging interactions. The population of tails is a non-monotonic function of coverage. We show that for irreversible adsorption the composition as a function of (the time-dependent) coverage follows a universal (independent of sample history) law at high coverage. This law is similar to, but qualitatively different from, the Mass Action Law describing coatings at equilibrium.