190 ISSN 0361-5219, Solid Fuel Chemistry, 2019, Vol. 53, No. 3, pp. 190–196. © Allerton Press, Inc., 2019. Russian Text © The Author(s), 2019, published in Khimiya Tverdogo Topliva, 2019, No. 3, pp. 66–72. Structure Simulation and Calculation of the Energy of Interaction of the Fragments of Cellulose Macromolecules A. M. Gyul’maliev a, *, R. Z. Safieva b,c, **, V. A. Vinokurov b, ***, and O. P. Parenago a, **** a Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia b Gubkin State University of Oil and Gas, Moscow, 119991 Russia c Nonprofit Partnership Technopark of Gubkin University, Moscow, 119296 Russia *e-mail: Gyulmaliev@ips.ac.ru **e-mail: safieva@mail.ru ***e-mail: vinoc_ac@mail.ru ****e-mail: parenago.o@ips.ac.ru Received October 24, 2018; revised November 19, 2018; accepted February 6, 2019 Abstract—Quantum chemistry methods were used to calculate the energy parameters of an elementary unit and a cellulose macromolecule dimer (cellobiose), and structure simulation was performed and the energy of interaction between the fragments of native cellulose macromolecules was calculated. It was established that the trans conformation of cellobiose is more stable than the cis conformation by 6.7 kcal/mol. Differences in the calculated and real (according to literature data) IR spectra of cellulose were related to the presence of intramolecular and intermolecular hydrogen bonds in the native structure. It was shown that the interaction of individual fragments of cellulose macromolecules from eight monomer units is due to the manifestation of intramolecular hydrogen bonds. It was found that the energies of intermolecular interactions ∆Е essentially depend on the terminal groups X in the cellulose macromolecule fragments, and they are –26, 49, and ‒32 kcal/mol for X = –H, –COOH, and –COH, respectively. The structure of the interacting fragments of cel- lulose macromolecules can be regulated by replacing the hydrogen atoms of hydroxyl or terminal groups of the macromolecules with functional groups that do not form intramolecular hydrogen bonds and impede self-orga- nization into fibrillar structures. It was shown that compounds with a high electron affinity or a negative energy of the lower vacant molecular orbital are the best reagents for complexation reactions with cellulose. Keywords: quantum chemistry methods, cellulose macromolecule, biopolymer, elementary unit, cellobiose, IR spectrum, hydrogen bonds, energy parameters DOI: 10.3103/S0361521919030030 The advantages of cellulose as a potential compo- nent of composite materials are biodegradability and valuable structural and mechanical properties. Recently, special attention has been paid to nano- fibrillar cellulose [1–3] because of its increased strength, which is due to the intra- and intermolecular hydrogen bonds of cellulose macromolecules. In this case, to ensure the effective interaction of fibrillar nanocellulose macromolecules with the matrix of a dispersion medium, problems should be solved to ensure the successive replacement of the aqueous phase of the initial nanocellulose hydrogels by an oleophilic phase. This can be achieved by selecting appropriate solvents and by chemically modifying the nanocellulose in order to ensure its hydrophobization. These problems are general in nature, and they are sig- nificant in the manufacture of nanocomposite poly- meric materials based on nanocellulose for use in vari- ous branches of industry (construction, oil, structural, aviation and automotive, medical, etc.). Nanocellu- lose can be a component of biodegradable lubricant compositions as an organic thickener. It is well known [4, 5] that biodegradable greases can be prepared based on nanocellulose and vegetable oils, which are of exceptional importance for applications at low tem- peratures. Experimental data on the structure and properties of cellulose and its derivatives have been published in the current scientific literature, the inter- pretation of which should be carried out on the basis of fundamental concepts of the structure and properties of substances with the use of modern quantum chem- istry methods. Native cellulose is a semirigid hydrophilic amor- phous–crystalline polymer, which has a complex supramolecular structure with an elementary fibril as the simplest element. In turn, the fibril is an associate