PH responsiveness of two-layer nano-composite membrane with ultrathin cylindrical nanopores PS-b-P4VP film

Abstract

In the present manuscript, we have demonstrated a new two-layer nano-composite membrane consisting pH-responsive nanoporous layer and a microporous membrane supporting layer. The nanoporous layer was a ca.30 nm thick film with cylindrical pores of diameter 30–50 nm, prepared by the polystyrene-block-poly(4-vinyl pyridine) copolymer (PS-b-P4VP) film. After spin-coating on silicon, this film was immersed into ethanol to generate pores. The nanoporous film was floated by buffered HF then combined with a microporous membrane to enhance mechanical strength. SFM, SEM and contact angle (CA) measurements were used to reveal structure of the block copolymer (BCP) film on silicon as well as the nano-composite membrane. Current–voltage measurements with different pH aqueous solution showed that transmembrane ionic current of this nano-composite membrane presented dramatically diversity at different pH. Confirmed by contact angle measurements, the wettability of the nanochannel is the key factor in this system. This work presents the first report on two layers nano-composite pH-responsive membrane with cylindrical porous ultrathin layer prepared by PS-b-P4VP surface reconstruction without any additional sacrificial components. This novel membrane can be widely used in medical examination, environmental monitoring and diaphragm cells.