Crosslinked copolystyrenes based membranes bearing alkylcarboxylated and alkylsulfonated side chains for organic solvent nanofiltration

Abstract

Polymeric membranes are more practicable to the cost-effective and energy-efficient solvent recovery and molecular separation in solvent mixtures, but the construction of structure-defined chemically stable as well as high permeance polymer membranes for organic solvent nanofiltration (OSN) applications is an important challenge. Herein, we designed and constructed crosslinked block copolystyrene membranes containing flexible alkylcarboxylated and alkylsufonated side chains for high-separation performance in organic media. The flexible side chains anchored on the all-carbon network render the membranes with good dimensional flexibility due to the rational manipulation of the intermolecular and intramolecular bonding interactions within the crosslinked structured polymer chains. Depending on the crosslinking degree, the resultant membranes exhibited outstanding stability in polar protic solvents, mild polar aprotic solvents (THF, acetonitrile and acetone) and nonpolar solvents. Specifically, the CPS-24% membrane with a cutoff of 380 g mol−1 showed good ethanol permeance of 4.16 L m−2 h−1 bar−1 and a high-efficient molecular separation (>96%) of a broad range of small molecular weight solutes (organic dye molecules, organic building blocks and antibiotics). The membrane also achieved molecular level selectivity of two molecules with a mass difference down to 141 g mol−1, which is attractive for molecular separation in the chemical and pharmaceutical industry. This work provides a promising strategy to improve selective solvent permeation and separation of organic molecules in OSN membranes by introducing flexible hydrophilic/hydrophobic side chain domains into the main backbone of rigid polymer structures.