Control of the rheological properties of concentrated aqueous MXene sediment suspensions using polymeric additives

MXenes constitute a new class of two-dimensional materials and have received considerable attention in the past decade from researchers in a wide variety of fields. In this study, we showed that the rheological properties of the concentrated (50 wt%) colloidal suspensions of the MXene sediment can be easily controlled by various water-soluble polymers to facilitate their solution processing in practical applications. The viscosity of the initially gelled polymer-free suspension at low shear rates was reduced by several orders of magnitudes by adding nonionic, anionic, and cationic polymers that can adsorb on the particle surface. The cationic poly(diallyldimethylammonium chloride) (PDDA) afforded the highest reduction in viscosity, attributed to the decrease in the undesirable face-to-edge electrostatic attraction between the MXenes. The PDDA-doped concentrated suspensions exhibited remarkably low viscosities and elastic moduli and thus can be applied to spray coating process without clogging even at high particle loadings.