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.

Automated summary

In this study, the desorption of adsorbed chains in a bilayer system was investigated using fluorine-labeled polystyrene (PS). The results showed that the exchange of PS-flattened chains with top-free chains was slower compared to PS-loose chains, and it was highly dependent on molecular weight (MW). Interestingly, in the presence of loosely adsorbed chains, the desorption of flattened chains was greatly accelerated and had weaker MW dependence. The MW-dependent desorption was attributed to the average number of contact sites between polymer adsorbed chains and the substrate, which increased rapidly with increasing MW. Additionally, the desorption of loosely adsorbed chains provided extra conformational energy to accelerate the desorption of flattened chains.