Self-healing guar gum and guar gum-multiwalled carbon nanotubes nanocomposite gels prepared in an ionic liquid

• Published in: Carbohydrate polymers 2013-10, Vol.98 (1), p.1025-1030
• Main Authors: Sharma, Mukesh, Mondal, Dibyendu, Mukesh, Chandrakant, Prasad, Kamalesh
• Format: Article
• Language: English
• Subjects: ambient temperature; Applied sciences; Bio-adhesive; Bio-inspired; Carbon nanotube; carbon nanotubes; Composites; Cyamopsis tetragonoloba; Exact sciences and technology; Forms of application and semi-finished materials; Fourier transform infrared spectroscopy; Galactans - chemistry; galactomannans; Gels; guar gum; Imidazoles - chemistry; Ion-gel; Ionic liquid; ionic liquids; Ionic Liquids - chemistry; Mannans - chemistry; nanocomposites; Nanocomposites - chemistry; Nanotubes, Carbon - chemistry; Plant Gums - chemistry; Polymer industry, paints, wood; rheometry; scanning electron microscopy; Self-healing; shrubs; storage modulus; Technology of polymers; transmission electron microscopy; van der Waals forces; viscoelasticity; X-ray diffraction
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2013.06.074

•Guar gum, a natural polysaccharide in an ionic liquid formed a viscoelastic gel.•The above gel became tougher in presence of MWCNT.•Above gels got self-healed upon complete bisection.•The self-healing process could be repeated several times.•These viscoelastic gel systems showed thixotropic nature and formation of reversible non covalent bond is responsible for self-healing. Guar gum is a galactomannan extracted from the seed of the leguminous shrub Cyamopsis tetragonoloba. It was found to form a soft viscoelastic gel in 1-butyl-3-methylimidazolium chloride, an ionic liquid at an optimized concentration of 10%w/v. A nanocomposite gel of the gum with enhanced strength could be prepared with 0.2%w/v of multiwalled carbon nanotubes (MWCNTs) in the ionic liquid. When the gels thus prepared were subjected to surface fractures or bisected completely, they found to self-heal at room temperature without any external interventions. The self-healing process could be repeated several times. These viscoelastic gel systems showed thixotropic nature and recovery of the storage modulus with time for several cycles was observed upon rheological investigations. The interaction took place between ionic liquid, guar gum and MWCNT was studied by SEM, TEM, FT-IR, powder XRD and rheometry. The results suggested that, upon standing at room temperature development of electrostatic interactions and the van der Waals interactions among the ionic liquid molecules facilitated the formation of reversible noncovalent bonds and eventually activated the self-healing in the gel systems through appropriate chain entanglements.