PDMS mixed‐matrix membranes with molecular fillers via reactive incorporation and their application for bio‐butanol recovery from aqueous solution

Mixed‐matrix membrane (MMM) consisting of fillers in polymeric matrix offers a promising approach to develop high‐performance membranes, while remain challenges in achieving ideal filler dispersion and interfacial morphology. Herein, we reported on a new kind of MMM with molecular‐level dispersion of filler via a proposed reactive incorporation approach. Specifically, polyhedral oligomeric silsesquioxanes (POSS) with vinyl groups was grafted with ethoxy groups to build covalent bond with hydroxyl‐terminated polydimethylsiloxane (PDMS) chains to fabricate PDMS MMMs uniformly dispersed with POSS molecules. The molecular dispersion of POSS in PDMS matrix was visualized by SEM, AFM, and TEM characterizations, as well as reflected by XRD analysis. The PDMS chain conformation affected by the reactive incorporation of POSS was investigated by analyzing the thermal and mechanical properties of the POSS/PDMS MMMs using DSC, TGA, and DMA measurements. Contact angle test was used to study the surface affinity and positron annihilation technique was employed to probe the free volumes, which are respectively associated with the sorption and diffusion behavior in the POSS/PDMS MMMs. The results demonstrated that molecular cages and crosslinking effect of POSS led to an increase of large free volumes while a decline of small free volumes. Therefore, the PDMS MMM with reactive incorporation of only 2 wt.% POSS simultaneously enhanced the butanol permeability (by 78%) and butanol/water selectivity (by 124%) for pristine PDMS membrane, transcending the performance limit of state‐of‐the‐arts organophilic membranes. The proposed reactive incorporation approach may provide a platform of developing highly efficient membranes for molecular separation.