Facile fabrication of polyelectrolyte complex/carbon nanotube nanocomposites with improved mechanical properties and ultra-high separation performance

Polyelectrolyte-polyelectrolyte complexes/multiwall carbon nanotubes (PECs/MWCNTs) nanocomposites have not been prepared until now because PECs are generally insoluble and infusible. In this work, solution-processable PEC/MWCNT nanocomposites and their membranes were prepared by in situ incorporation of MWCNTs into bulk PECs. The ionic complexation between poly(diallyldimethylammonium chloride) (PDDA) and sodium carboxymethyl cellulose (CMCNa) in the presence of MWCNTs was followed by zeta potential and optical transmittance measurements. Structures of PEC/MWCNT nanocomposites were characterized by FT-IR, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). It is found that MWCNTs are encapsulated by a layer of PEC and dispersed in a PEC matrix mainly on a single nanotube level. Mechanical properties of the nanocomposite membrane loaded with 7 wt% MWCNTs are greatly improved, showing 2.6 times higher tensile strength and 1.8 times higher modulus as compared with that of the pristine PEC. PEC/MWCNT nanocomposite membranes also display very high performance in pervaporation dehydration of isopropanol. This high pervaporation performance is reproducible with cycling feed temperatures and stable with increasing operation time up to 20 days.