CELLULOSE CHEMISTRY AND TECHNOLOGY Cellulose Chem. Technol., 45 (1-2), 13-21 (2011) AMORPHOUS CELLULOSE – STRUCTURE AND CHARACTERIZATION DIANA CIOLACU, FLORIN CIOLACU * and VALENTIN I. POPA * “Petru Poni” Institute of Macromolecular Chemistry Iasi, Romania *“Gheorghe Asachi” Technical University Iasi, Romania Received July 26, 2010 Amorphous cellulose was obtained from different types of celluloses (microcrystalline cellulose, dissolving pulp and cotton cellulose), by regeneration with ethanol from their solutions in an SO 2 -diethylamine- dimethylsulfoxide (SO 2 -DEA-DMSO) solvent system. Different techniques, X-ray diffraction (XRD), FTIR spectroscopy and differential scanning calorimetry (DSC) were used to estimate the crystallinity degree. The values obtained for amorphous celluloses were compared with those of the initial samples and correlated with their supramolecular structures. Viscosity measurements have shown that little or no depolymerization occurs during dissolution. Keywords: cellulose I, dissolution, regeneration, amorphous cellulose, XRD, FTIR, DSC INTRODUCTION As generally known, cellulose is a very important and fascinating biopolymer and an almost inexhaustible and renewable raw material. The trend towards this kind of resources and the tailoring of innovative products for science, medicine and technology has led to a global renaissance of interdisciplinary cellulose research and to the extended use of this abundant organic polymer over the last decade. 1 In any chemical reaction, the accessibility of cellulose molecules to the reagent is highly important in the process and efficiency of modification. The premise for obtaining any derivative regards the contact of the reactants with each other. In the case of cellulose, this process is more difficult, due to its biphasic structure. Most cellulosic materials consist of crystalline and amorphous domains, in varying proportions, depending on both source and history. The physical properties of cellulose, as well as their chemical behavior and reactivity, are strongly influenced by the arrangement of the cellulose molecules with respect to each other and to the fiber axis, as well. Most of the reactants penetrate only the amorphous regions and it is only in these regions with a low level of order and on the surface of the crystallites that the reactions can take place, leaving the intracrystalline regions unaffected. Starting from this, the behavior of both regions has been extensively studied to elucidate the micro and macro responses of the cellulose material to thermal, hydrothermal and chemical treatments. 2-5 Interactions between solid cellulosic materials with water, enzymes or other reactive or adsorptive substances occur first in the noncrystalline domains and/or on the surface of cellulose crystallites. Thus, the secondary and tertiary structures of the noncrystalline domains in cellulose, their properties and their distribution states should be significant for understanding the behavior of cellulosic materials under various conditions. The distribution of noncrystalline domains in cellulose is related to DP leveling-off, which has always been observed in the acid hydrolysis of cellulose samples of higher plants, but has never been detected as periodic units by microscopic observations. The noncrystalline domains include liquid crystalline and nematic ordered cellulose and do not necessarily indicate amorphous cellulose. Amorphous cellulose samples have been often used for model experiments to understand the behavior of the noncrystalline domains in cellulose under various conditions.