An ITC Study on the Interaction Energy Between Galactomannan Biopolymers and Selected MO 2 Nanoparticles in Hydrogels

The interaction of guar gum, a galactomannan polysaccharide, and its derivative hydroxypropyl guar (HPG) with MO 2 nanoparticles whereby M exhibits a decreasing metallic character (Ti → Sn → Si) and MO 2 different sizes (6 – 15 nm) was studied by applying isothermal titration calorimetry (ITC) and rotational viscosimetry. It was found that the crosslinking ability of the oxide nanoparticles towards galactomannans is controlled by the electropositive character of M and the size of the nanoparticles which should be as small as possible (< 10 nm) to produce extremely viscous gels. The thermodynamic parameters ΔH, ΔS and ΔG for the association reaction obtained from ITC revealed that the interaction generally is entropy driven, slightly stronger for guar gum than for HPG and is decreasing from TiO 2 to SnO 2 to SiO 2 . The results explain the observations made in the viscosimetric measurements.