Mechanisms of Irreversible Polymer Adsorption

Controlling polymer/substrate interfaces without modifying chemistry is nowadays possible by finely tuning the formation of adsorbed layers. The complex processes leading to irreversible attachment of chains onto solid substrates are governed by two mechanisms: molecular rearrangement and potential-driven adsorption. Here we describe an analytical method to differentiate these two mechanisms. By analyzing experiments and simulations, we investigate how changes in thermal energy and interaction potential affect equilibrium and non-equilibrium components of the adsorption kinetics. We find that adsorption process is thermally activated, with activation energy comparable to that of local non-cooperative processes. On the other hand, the final adsorbed amount depends on the interface interaction only (i.e. it is temperature independent in experiments). We identify a universal linear relation between the growth rates at short and long adsorption times, suggesting that the monomer pinning mechanism is independent of surface coverage, while the progressive limitation of free sites significantly limits the adsorption rate.