How Do Solvent–Polymer–SurfaceInteractionsAffect the Physisorption of Polymer Chains during Flow-Induced Translocationthrough Inorganic Oxide Nanochannels?

This work aims to explore how polymer–surface–solvent ternary interactions play a synergistical role in affecting the physisorption of PBA_N [poly(benzyl acrylate)] chains inside 20 and 100 nm Whatman anodic aluminum oxide nanochannels in flow field by considering the Flory interaction parameter (χ_F), adsorption parameter (χ_S), solution concentration (<i>C</i>), and degree of polymerization (<i>N</i>). By using a homemade triple-pump system for in situ monitoring the transmembrane pressure during the solvent switching process, we have found: (1) a combination of χ_F and χ_S significantly impacts the adsorption and reversibility of PBA_N chains in toluene, ethyl acetate, and tetrahydrofuran, and an extremely slow kinetics process is revealed in dimethylformamide; (2) the adsorption kinetic curves for different PBA_N chain lengths are all nicely described by the dual exponential fitting including the fast and slow modes, which can be attributed to the fast approaching of whole chain and the slow reorganization of local conformation, respectively, and the conformational reorganization is found to be the most significant in dimethylformamide; (3) a universal two-regime scaling dependence <i>A</i>_occupy<i>/A</i>_total ∼ <i>N</i>^γ is observed between the cross-sectional coverage factor (<i>A</i>_occupy<i>/A</i>_total) and <i>N</i>, with γ ∼ 0.50 in the weak confinement regime when <i>A</i>_occupy<i>/A</i>_total < 0.30 and γ ∼ 1.5 in the strong confinement when <i>A</i>_occupy<i>/A</i>_total > 0.30, independent of pore size, chain length, and solvent type, indicating the dominant effect of the crowding effect when <i>A</i>_occupy<i>/A</i>_total > 0.30; (4) the adsorption reversibility and desorption efficiency are found to increase with the solvent quality and polarity in 20 and 100 nm systems during the solvent switching process, which provides a method for the regulation of adsorption thickness; (5) an extremely weak dependence of <i>A</i>_occupy<i>/A</i>_total ∼ <i>C</i> is observed, which is consistent with Silberberg’s prediction. Our present result provides useful guidance for understanding and comparing the behavior of chain adsorption in the nonidealized and idealized membrane system.