Ultrathin amphiphilic membranes polymerized from hydrophobic terpenoids and hydrophilic polyamines for versatile organic solvent nanofiltration

Abstract

Ultrathin membranes with fast solvent transport are promising in organic solvent nanofiltration. However, achieving high permeance for both polar and non-polar solvents remain challenging. Here we report ultrathin amphiphilic membranes (UAPMs) polymerized from hydrophobic terpenoid molecules and hydrophilic polyamines that enable fast and versatile solvent transport. The terpenoid carboxylic acid (TCA) in the organic phase react with polyethyleneimine (PEI) in the aqueous phase at the liquid-liquid interface, during which the glutaraldehyde is added into the aqueous phase to enhance the crosslinking of polymeric network and thus forming UAPMs. Regulating the ratio of hydrophilic to hydrophobic components allow for the precise manipulation of the surface polarity of UAPMs, rendering affinity to both polar and non-polar organic solvents. The increased PEI/TCA ratio also provides more amine sites to bind with the carboxylic monomers and thus generating denser and thicker membranes. The optimized UAPM demonstrates high permeance values of 175.9 L m⁻² h⁻¹ bar⁻¹ for polar ethanol and 116.5 L m⁻² h⁻¹ bar⁻¹ for non-polar n-hexane, with a molecular weight cut-off of 591 Da, which achieves 96.4 % rejection of Reactive Red in ethanol and 94.8 % rejection of Chlorophyll in n-hexane. Our structural design of UAPMs may pave a new avenue for engineering high-performance molecular-separation membranes.