Ultrathin pH‐Sensitive Nanoporous Membranes for Superfast Size‐Selective Separation

Abstract

Stimuli-responsive nanoporous membranes have attracted increasing interest in various fields due to their abrupt changes of permeation/separation in response to the external environment. Here we report ultrathin pH-sensitive nanoporous membranes that are easily fabricated by the self-assembly of poly(acrylic acid) (PAA) in a metal hydroxide nanostrand solution. PAA-adsorbed nanostrands (2.5-5.0 nm) and PAA-Cu(II) nanogels (2.0-2.5 nm) grow competitively during self-assembly. The PAA-adsorbed nanostrands are deposited on a porous support to fabricate ultrathin PAA membranes. The membranes display ultrafast water permeation and good rejection as well as significant pH-sensitivity. The 28 nm-thick membrane has a water flux decrease from 3740 to 1350 L m(-1) h(-1) bar(-1) (pH 2.0 to 7.0) with a sharp decrease at pH 5.0. This newly developed pH-sensitive nanoporous membranes may find a wide range of applications such as controlled release and size- and charge-selective separation.

A Versatile Approach Towards the Fast Fabrication of Highly-Permeable Polymer Mesoporous Membranes

“…Negatively charged polymer chains easily self‐assemble on their surface via electrostatic interaction. By employed this merit, we have prepared ultrathin pH‐sensitive mesoporous membranes by self‐assembly of poly(acrylic acid) on the Cu(OH) 2 nanowires in aqueous solution . The resultant 28 nm‐thick membrane displays ultrafast water permeation and a 10−12 nm cut‐off as well as significant pH‐sensitivity.…”