Microwave-assisted green synthesis of guar gum esters with enhanced physicochemical properties

Abstract

Several methods have been developed for the modification of natural polymers. Most of the reported methods are expensive since the chemical reactions are carried out using chemical additives along with stabilizers. Microwave assisted synthetic strategies gained significant importance for materials synthesis due their eco-friendly nature. Guar gum is one of the important naturally occurring non-ionic polysaccharide, which has incredible industrial and commercial applications. A rapid method for protecting the hydroxyl group in sterically hindered gum was developed by microwave-assisted synthesis (MAS). An efficient synthesis of different novel guar gum derivatives such as (acetate, butyrate and propionate; GG1-GG3) was performed. A significant higher yield of ester was achieved for 15 min at 600 W using iodine as a reaction promoter. Gum ester formation was carried out at various concentrations and for different reaction intervals. The synthesized products were characterized using FTIR, NMR, and SEM techniques. The efficiency of adopted synthesis method was evaluated based on swelling ratio, gelation ability and solubility. The study indicates that the guar gum can be modified using acid anhydride under microwave irradiation with enhanced physic-chemical properties. Moreover, microwave modification is an eco-friendly approach.