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Galactomannans are functionalized biopolymers and possess diverse applications in various fields due to a wide range of inherent properties such as thickening, emulsifying, binding, gelling, film forming, and so on. In the present study, highly viscous solutions were obtained by the treatment of 1,2 galactomannan (Guar gum) with 2-(chloromethyl)oxirane leading to the formation of new 1,3-diethereal linkages of propanetriol (RO CH 2 CHOH CH 2 OR) between the galactomannans backbone. The reaction was studied by varying the amount of 2-(chloromethyl)oxirane in aqueous methanol (methanol: water; 80:20) under alkaline conditions. The 0.5% solution of modified cross-linked galactomannan (MGM) using the least amount of 2-(chloromethyl)oxirane (0.06 Â 10 À3 mol) formed a highly viscous (1031 cps) solution in comparison to native GM (440 cps). Intriguingly, the decreasing amount of 2-(chloromethyl)oxirane led to significant improvement in rheological properties whereas a gradual increase resulted in insoluble products. These observations have so far not been reported for galactomannans. The formation of new 1,3-diethereal linkages (RO CH 2 CHOH CH 2 OR) introduced between the galactomannan backbone was analyzed by NMR (1D and 2D) and FT-IR. Additionally, thermal analysis (TGA and DSC), swelling behavior, the effect of salt, acid, and alkali on MGM were studied. The modified products were resistant to acid, salt, and alkali and can be used for diverse end-use applications.

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