Mario Pagliaro
Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Palermo, Italy

Exactly 20 years have gone since Isogai and Kato in Japan reported a surprising discovery (1): regenerated and mercerized celluloses, despite being insoluble in water, when treated with the Anelli-Montanari reactants under the conditions identified by de Nooy for water-soluble polysaccharides in 1995 (2), namely aqueous hypochlorite buffered at pH 10-11 and a catalytic amount of TEMPO (2,2,6,6,-tetramethylpipelidine-1-oxyl radical) and sodium bromide, undergoes oxidation of the primary alcohol moiety at C-6 of the anhydroglucose unit giving place to a new water-soluble biomaterial: cellouronic acid.

Another 8 years, and in collaboration with Vignon’s team in France and Nishiyama’s in Japan, Isogai reported the discovery (3) of a new biomaterial simply obtained via the TEMPO-mediated oxidation of never-dried cellulose followed by disintegration into individual microfibrils by a simple mechanical treatment using a Waring Blendor: cellulose nanofiber (CNF).

The biomaterial has novel and unique properties. Aqueous dispersions of these cellulose nanofibers afford transparent films with high optical transparency and low haze called ‘transparent nanopaper’ which ...