Electro-casting aligned MWCNTs/polystyrene composite membranes for enhanced gas separation performance

Embedding particulate fillers in the matrix of membranes have proven effective in improving their gas separation performance. To further improve the membrane performance, this study explores the possibility of aligning the fillers in membranes with the assistance of an alternating electric field. Composite membranes with different contents of multi-walled carbon nanotubes (MWCNTs) dispersed in polystyrene (PS) have been prepared via electro-casting, in which an alternating electric field of 2000 V/cm is vertically exerted on the thin layer of pre-membrane solution until the solvent is evaporated completely. The electro-casting results in not only vertical alignment, but also more uniform dispersion of MWCNTs in the membranes. The electro-cast composite membranes exhibit higher oxygen and nitrogen permeability, but the increment of the former is higher than that of the latter, resulting in improved selectivities of the membranes