Oxidation of cellulose fibers mediated by nonpersistent nitroxyl radicals

Three different nonpersistent radicals bearing >NO • moiety have been used to oxidize the viscose fibers at room temperature and alkaline pH. The generation of the free radical species was achieved in situ , from their corresponding OH precursors: 1‐hydroxybenzotriazole, violuric acid, and N ‐hydroxy‐3,4,5,6‐tetraphenylphthalimide. Three different routes were used: (i) in the presence of metallic cocatalyst (lead tetraacetate), (ii) under metal‐free conditions (anthraquinone as organic cocatalyst), and (iii) a homolytically scission of OH bond through a 365‐nm UV irradiation. The oxidized fibers were subjected to attenuated total reflection FTIR characterization, potentiometric titration, wide angle X‐ray, energy dispersive X‐ray analyses, microscopic investigations, and solid‐state 13 C‐NMR. The patterns of CP/MAS 13 C‐NMR spectra revealed that the oxidation occurred at the C6 primary hydroxyl groups of cellulose. Notably, as a result of the introduction of hydrophilic carboxylate groups, the water retention values of the oxidized fibers increased by 35% as compared to the original nonoxidized sample.