Structure–property relationships of carboxymethyl hydroxypropyl guar gum in water and a hyperentanglement parameter

• Comprehensive analysis of the viscosity of Guar derivative.
• Chain dimensions of CMHPG as function of molecular weight.
• Determination of the chain flexibility.
• Structure–property relationships to arrive at the parameter for the Carreau–Yasuda equation.
• Introduction of an hyperentanglement parameter as a measure for the contribution of superstructures in CMHPG to the viscosity.

The viscoelastic properties of carboxymethyl hydroxypropyl guar gum (CMHPG) in aqueous solution were determined as function of concentration and of molecular weight, using SEC/MALLS/dRI and viscometry. The chain is more rigid as in native guar as was deduced from the molecular parameter in dilute solution. Superstructures are formed in moderately concentrated solutions as is shown from the comparison of steady state shear and small amplitude oscillatory shear (SAOS) experiments. The shear rate dependent viscosity of CMHPG can satisfactorily be described by the Carreau–Yasuda model with the rheological parameters (η0, λ0, n, b) obtained from the evaluation of viscosity data. A quantitative hyperentanglement parameter is introduced to account for the differences in responses in shear and SAOS experiments.