Nitroxides in Cotton and Cellulose Physicochemistry and Technology. 42 Years of History

Abstract: Since pioneering works of Marupov and Likhtenshtein groups, nitroxides are widely used in solving a number of challenging problems of structure and functions of cotton fibres and cellulose. Methods of nitroxide spin labelling have been proved to be a powerful tool in this area. Covalent modification cotton fibres and cellulose by the labels and the use electron Spin Resonance (ESR) allow to establish the label location and motion the labelled samples which in turn is modulated ’by the polymers local molecular dynamics and its distribution. Data on dependencies of the fibres’ molecular dynamics on origin, temperature, water and other plasticizing agents, nutrition, period of maturing, virus infection and radiation of seeds have been presented. Combination of ESR experiments and Zhurkov technique have revealed a strong dependence of fibres’ resistance to stress (durability) on microscopic structural defects. In the fibres, the distribution of the molecular dynamics correlation time within 10-4 – 10-9 s temporal range was also established. Employing non-covalently bound nitroxides as spin probes provides a way for studies of effect of humidity on the supramolecular structure of cotton, local polarity and heterogeneous viscosity of two types of unprocessed cotton fibers, cellulose modification by nitroxide-mediated graft polymerization, composites of poly(lactic) acid reinforced with TEMPO-oxidized fibrillated cellulose, photo-lnduced macromolecular functionalization of cellulose via nitroxide spin trapping. The developed approach, the efficiency of which is demonstrated in this review, can be used in the investigation of molecular dynamics, microstructure polymers and other complex molecular objects.