Sonication-enhanced in situ assembly of organic/inorganic hybrid membranes: Evolution of nanoparticle distribution and pervaporation performance

Organic/inorganic hybrid membranes for separation applications have been widely studied. However, achieving a uniform dispersion of inorganic fillers in the polymer matrix is a primary challenge in the advancement of mixed-matrix membranes (MMMs). In the present study, a method for in situ assembly enhanced by sonication was developed to prepare hydrophobic polydimethylsiloxane (PDMS)/nanoparticle hybrid membranes. Results from scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectrometry, and atomic force microscopy (AFM) suggest that through ultrasonic cavitation during assembly of the hybrid membrane, this method could effectively avoid nanoscale agglomeration and in turn uniformly disperse inorganic particles within the polymer matrix. This method thus enabled the preparation of an organophilic membrane with higher hydrophobicity and higher performance. For example, the contact angle (CA) of SiO2/PDMS hybrid membrane increased from 135.5° to 146.3°, and the separation factor for the pervaporation of 5% ethanol/water mixture increased from 7.3 to 12.5. Furthermore, the method was used to prepare a zeolite imidazolate framework-8 (ZIF-8)-filled PDMS membrane. The ZIF-8/PDMS hybrid membrane showed high performance in the pervaporation of alcohol/water mixtures. These results further suggest that in situ assembly via sonication is a promising approach to improve the dispersion of inorganic fillers and thus the membrane performance.