Carboxymethylation of cashew tree exudate polysaccharide

Cashew tree gum was carboxymethylated in aqueous alkaline medium using monochloroacetic acid (MCA) as etherifying agent. The effects of reaction parameters such as alkali concentration, MCA/cashew gum (CG) ratio and temperature on reaction yield and degree of substitution (DS) were investigated. Products were characterized by 13C nuclear magnetic resonance, infrared Fourier transform spectroscopy, gel permeation chromatography and flow capillary viscosity. Carboxymethyl gum samples with DSs between 0.10 and 2.21 were prepared. The reaction yield was in the range of 31–70%. The best MCA efficiency towards production of carboxymethylated macromolecules was obtained in 5.5 M sodium hydroxide concentration, 55 °C, 3 h reaction time and 1:1 MCA/CG molar ratio. Degradation of the chain length of the starting material during carboxymethylation occurred with intensity dependent on reaction conditions.