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Mechanisms of irreversible adsorption: Nonequilibrium vs finite size effects

par Huang, Weide
Président du jury Tlidi, Mustapha
Promoteur Napolitano, Simone
Publication Non publié, 2019-10-10

Thèse de doctorat

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Résumé :

The complex processes leading to irreversible attachment of chains onto solid substrates are governed by two mechanisms: molecular rearrangement and potential-driven adsorption. In my Thesis, I 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. I 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). My work identifies 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.The interaction between two immiscible materials is related to the number of contacts per unit area formed by the two materials. For practical reasons, this information is often parametrized by the interfacial free energy, which is commonly derived via rather cumbersome approaches, where properties of the interface are described by combining surface parameters of the single materials. These combining rules, however, neglect any effect that geometry might have on the strength of the interfacial interaction. In this Thesis, I demonstrate that the number of contacts at the interface between a thin polymer coating and its supporting substrate is altered upon confinement at the nanoscale level. Explicitly considering the effect of nanoconfinement on the interfacial potential allows a quantitative prediction of how sample geometry affects the number of contacts formed at the interface between two materials.