Solvent responsive healing of guar gum and guar gum–multiwalled carbon nanotube nanocomposite gels prepared in an ionic liquid

Abstract

Guar gum, a galactomannan extracted from the seed of the leguminous shrub Cyamopsis tetragonoloba was found to form a soft elastic gel in 1-butyl-3-methylimidazolium chloride (10% w/v). A nanocomposite gel of the gum with higher strength was prepared in the presence of multiwalled carbon nanotubes (MWCNT). The gels showed healing ability in the presence of three polar aprotic solvents namely acetone, dimethyl sulfoxide and dimethylformamide. However, they did not heal in the presence of acetonitrile. The interactions taking place between the ionic liquid, guar gum and MWCNT were studied by SEM, TEM, FT-IR, powder XRD and rheological property measurements. It was concluded that the electrostatic interactions and the van der Waals interactions among the ionic liquid molecules facilitated the formation of reversible noncovalent bonds and eventually activated the healing in the gel systems through appropriate polymer entanglements. Further, the interactions with the solvents induced favourable polymeric chain mobility required for the healing.