Regulating the Flow-Driven Translocation of Macromolecules through Nanochannels by Interfacial Physical Adsorption

Abstract

By using a model system composed of an anodic aluminum oxide nanopore (AAO), poly(benzyl acrylate) (PBAN) adsorbent, and polystyrene (PSN) probe, where N represents the degree of polymerization, this work has explored how the physical adsorption of PBA onto the surface of the AAO nanopore (rp ≈ 10 nm) influences the flow-driven translocation of PS in toluene. In the low flow rate range (Q = 0.02 mL/h), the translocation of PS chains is purely diffusive, and the partially reversible adsorption behavior of PBAN is observed only when N < ∼360, showing a strong chain length dependence. In the partially reversible regime, the interfacial thickness (δ) of the adsorption layer is estimated to be from ∼1.5 to ∼2.9 nm depending on the chain length. In the mixed solutions, when N increases from 0 to 75 and 150 for PBAN, the cut-off size (COS) of the membrane for broadly distributed PSB-285K (Mw/Mn ≈ 2.48) is estimated to decrease from ∼10.0 to ∼8.0 and ∼6.0 nm, respectively; in addition, the introduction of PBA360 can promote the separation of narrowly distributed PS655 and PS1200 by regulating re, whereas in the high flow rate range (Q > 0.02 mL/h), the translocation for PS long chains is based on the mechanism of molecular deformation, and the flow rate-dependent translocation shows a strong dependence on the chain length of PBAN. Namely, in mixed solutions, when N increases from 150 to 360, the critical flow rate (Qc) is found to slightly increase from ∼0.30 to ∼0.45 mL/h for PS1500 translocation; in addition, the cut-off performance of PSB-285K displays dependence both on flow rate and PBAN chain length. Our result has demonstrated a novel strategy to regulate the cut-off performance during the translocation of (bio)macromolecules through nanopores via partially reversible interfacial physical adsorption.