Regional Issue "Organic Chemistry in Argentina" ARKIVOC 2011 (vii) 416-425 Page 416 © ARKAT-USA, Inc. A physical organic chemistry approach to dissolution of cellulose: effects of cellulose mercerization on its properties and on the kinetics of its decrystallization Ludmila A. Ramos, a Daniella L. Morgado, a Fergus Gessner, a Elisabete Frollini, a and Omar A. El Seoud b * a Institute of Chemistry of São Carlos, University of São Paulo, P.O. Box 780, 13 560 970 São Carlos, SP, Brazil b Institute of Chemistry, University of São Paulo, P.O. Box 26.077, 05513-970 São Paulo, SP, Brazil E-mail: elseoud@iq.usp.br Dedicated to Professors Rita H. Rossi, Julio C. Podestá, Manuel González Sierra, and Oscar S. Giordano Abstract The effects of alkali treatment on the structural characteristics of cotton linters and sisal cellulose samples have been studied. Mercerization results in a decrease in the indices of crystallinity and the degrees of polymerization, and an increase in the α-cellulose contents of the samples. The relevance of the structural properties of cellulose to its dissolution is probed by studying the kinetics of cellulose decrystallization, prior to its solubilization in LiCl/N,N-dimethylacetamide (DMAc). Our data show that the decrystallization rate constants and activation parameters are only slightly dependent on the physico-chemical properties of the starting celluloses. This multi- step reaction is accompanied by a small enthalpy and large, negative, entropy of activation. These results are analyzed in terms of the interactions within the biopolymer chains during decrystallization, as well as those between the two ions of the electrolyte and both DMAc and cellulose. Keywords: Cotton linters, sisal, mercerization, cellulose dissolution, decrystallization, kinetics Introduction Most organic solvents, including strongly dipolar ones, e.g., DMSO cause swelling, but not dissolution of cellulose. The reason is that the biopolymer has a semi-crystalline structure, a consequence of the strong intra- and intermolecular hydrogen-bonding between the OH groups