Design of sulfate‐free hair care formulations using functionalised guar hydroxypropyltrimonium chloride: a green cosmetic approach

This work reports the synthesis and characterisation of a low‐viscosity, moderately positive zeta potential cationic guar gum (CGG) for use in mild personal care formulations. CGG was synthesised by optimising the etherification of natural GG using 3‐chloro‐2‐(hydroxypropyl)‐trimethyl ammonium chloride as the etherifying agent via one‐factor‐at‐a‐time under optimal reaction conditions. High degrees of substitution (DS = 0.64) were obtained under the optimised reaction conditions, which are higher than those reported in the literature. Structural confirmation of the synthesised CGG was provided via physicochemical characterisation, which included Fourier transform infrared, 1 H NMR, gel permeation chromatography, HPLC and zeta potential measurement. The significant reduction in the average molecular weight, from 1.54 × 10 6 to 3.44 × 10 4 Da, along with a substantial increase in the zeta potential from 0.380 to 13.4 mV, indicated an increased charge density and enhanced electrostatic interactions with negatively charged hair surfaces. Improved performance of the CGG was demonstrated when it was used as a surfactant additive to enhance the conditioning efficiency of the shampoo formulation, as evidenced by SEM, a reduced surface tension of 25.84 dyn cm –1 and an increased foam volume of 108.8 mL. Furthermore, the CGG, in conjunction with the preservative, demonstrated antimicrobial activity against Pseudomonas aeruginosa . These data collectively demonstrate the effective optimisation of a low‐viscosity, low‐molecular‐weight guar derivative that could be utilised in personal care formulations.