Title
New route for carboxymethylation of cellulose: synthesis structural analysis and properties
Authors
SURENDRA S. BISHT K. K. PANDEY GYANESH JOSHI and SANJAY NAITHANI

Received March 16, 2016
Published Volume 51 Issue 7-8 July-August
Keywords cellulose triacetate, carboxymethyl cellulose, degree of substitution, viscosity

Abstract
An efficient and new route for the synthesis of carboxymethyl cellulose (CMC), a most widely used biopolymer for various applications, has been developed. Cellulose was converted into cellulose triacetate (CTA) intermediate, which was then converted to CMC by deprotection, followed by etherification using NaOH and ClCH2COONa in the tetrahydrofuran-water (THF-H2O) solvent system. Reaction parameters were optimized and a maximum degree of substitution (DS) of 1.02 was achieved at 50 °C within 1 h with 0.95 M and 1.1 M concentration of NaOH and ClCH2COONa, respectively. The rheological characterization of the 1-3% aqueous solution of optimized CMC product showed non-Newtonian pseudo-plastic behavior. The 2% aqueous solution of CMC had a maximum viscosity of 40 cP. The reaction products (CTA and CMC) were characterized by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. 1H and 13C chemical shift assignment of the anhydroglucose units (AGUs) that comprise sodium carboxymethyl cellulose with a degree of substitution of 1.02 was performed using 2D NMR spectra obtained from COSY and TOCSY experiments. In the 2D COSY and TOCSY spectra, there were four correlation networks for the H1 to H6 atoms of AGU; the four types of AGUs with H1 resonances appearing at 4.96, 4.94, 4.90 and 4.88 ppm, are referred to as residue A, B, C and D, respectively.