Thermoresponsive Membranes from Electrospun Mats with\nSwitchable Wettability for Efficient Oil/Water Separations

Abstract

A simple\nand versatile method is described to obtain polycaprolactone\n(PCL) porous membranes, consisting of fibers prepared by electrospinning.\nThe surface of the fibers is modified by grafting poly­(<i>N</i>-isopropyl­acrylamide) (PNIPAM) brushes by surface-initiated\natom-transfer radical polymerization (SI-ATRP). PCL mixtures, featuring\nBr end-functionalized and nonfunctionalized polymer, are used to enable\nSI-ATRP. Wettability at variable temperatures is governed by the lower\ncritical solution temperature (LCST) of PNIPAM as contact angle and\nswelling ratio measurements demonstrate. Because of the PNIPAM LCST,\nthe membranes show a variation of pore size with temperature, which\nis accompanied by flux changes of water permeating the membranes.\nTemperature gated separation is demonstrated using oil/water emulsions\nat 1 bar pressure. Typical separation efficiencies are 92% and 25%\nat 25 and 50 °C, respectively. Employment of anionic and neutral\nsurfactants shows that the separation efficiency also depends on the\ninteraction between the membranes and the emulsions.