© 2017 Portuguese Society of Materials (SPM). Published by Elsevier España, S.L.U. All rights reserved. http://dx.doi.org/10.1016/j.ctmat.2016.05.007 Ciência & Tecnologia dos Materiais 29 (2017) 55–62 ScienceDirect Available online at www.sciencedirect.com http://ees.elsevier.com/ctmat Spectral analysis of the chemical structure of carboxymethylated cellulose produced by green synthesis from coir fibre E.U. Ikhuoria a,* , S.O. Omorogbe b,c , O.G. Agbonlahor a , N.O. Iyare a , S. Pillai b , A.I. Aigbodion c a Department of Chemistry, University of Benin, Benin-City. 300213, Nigeria b Materials Science and Technology Division, CSIR - National Institute for Interdisciplinary Science and Technology (NIIST), Thiruvananthapuram, Kerala - 695019, India c Rubber Research Institute of Nigeria. Benin City. 300272, Nigeria Abstract In this work, CMC was synthesized from cellulose obtained from coir fibres. The obtained CMC yield was about 64.0 %. The Degree of Substitution value obtained was 0.44. The spectral pattern and thermogravimetric analysis of the synthesized CMC and cellulose were evaluated using FT-IR, XRD, and TGA/DTG. Characterization of the cellulose and CMC revealed their high crystallinity with cellulose showing a lower crystallinity value due to its lignin content. The CMC also showed a higher degree of crystallinity (56.93%) and hydrogen bonding compared to some earlier literature reports for CMC. The DTG curve revealed that the CMC had a maximum rate of degradation at about 310 ºC. The FT-IR spectra of the obtained CMC showed a finger print region characteristic of CMC (1590 cm -1 ). This work shows that the spectral characteristic and crystallinity of CMC can be related to the synthetic method applied in obtaining the cellulose prior to CMC synthesis. © 2017 Portuguese Society of Materials (SPM). Published by Elsevier España, S.L.U.. All rights reserved. Keywords: carboxymethylcellulose; spectral pattern; coir fibres; cellulose; liquid phase oxidation; degree of substitution. 1. Introduction * Carboxymethyl cellulose (CMC) is a derivative of cellulose that seeks to functionalize cellulose so as to increase its application prospects [1-3]. Functionalization of cellulose by carboxymethylation has been exploited in applications such as drug delivery [4,5], polymer blending [6,7], tissue engineering [8,9], cation exchange resins [10], nanoparticles stabilization [11,12], mineral processing [13] among others [14-18]. To achieve these, etherification of the hydroxyl groups in the amorphous regions of cellulose with carboxymethyl groups was carried out. The etherification occurs mainly at the primary OH group on C(6) resulting in the reduction of the O6- -chain hydrogen bonding interaction [19]. Depending on its degree of * Corresponding author. E-mail address: esyikhuoria@yahoo.com (E.U. Ikhuoria) substitution (which corresponds to the average number of carboxymethyl groups per anhydroglucose unit), CMC shows variable solubility [2]. Previous studies on CMC was centered on the spectral elucidation, optimization of CMC yield under various reaction conditions, the improvement of its degree of substitution, as well as chemical modification of CMC structure [15,19-26]. Various structural elucidation tools have been used by researchers to evaluate the changes that occur during the carboxylmethylation of cellulose [2,19,27], these changes are dependent on several factors such as the method of isolating cellulose from the native fibre, degree of substitution and hence, purity [10,28]. Hydrogen bond energy (EH) is an index that has been used in the study of hydrogen bonding in cellulose samples. The EH offers a quantitative and simple method of comparing the degree of hydrogen bonding due to OH groups in a cellulosic sample. To the best of our knowledge, there has been no reports on the use of EH in the study and characterization of CMC. © 2017 Portuguese Society of Materials (SPM). Published by Elsevier España, S.L.U. All rights reserved.