Loosely Adsorbed Chains Expedite the Desorption of Flattened Polystyrene Chains on Flat Silicon Surface

Herein, the desorption of the adsorbed chains (includingtwo regionsof flattened chains and loosely adsorbed chains) was examined by monitoringthe chain exchange kinetics between the adsorbed chains and the top-freechains in a bilayer system by using fluorine-labeled polystyrene (PS).The results indicated that the exchange behavior of PS-flattened chainswith the top-free chains is much slower than that of PS-loose chainsand has a strong molecular weight (MW) dependence. Interestingly,in the presence of loosely adsorbed chains, the desorption of flattenedchains was accelerated greatly and had weaker MW dependency. We attributethe MW-dependent desorption phenomena to the average number of contactsites between polymer adsorbed chains and the substrate, which rapidlyincreased with increasing MW. Likewise, the desorption of looselyadsorbed chains may provide extra conformational energy to acceleratethe desorption of flattened chains.