Weak base polyfunctional fibrous anion exchangers, containing small amount of carboxylic acid groups were obtained on the base of industrial modacrylic fibers Kanecaron (40% acrylonitrile, 60% vinylchloride) (Kaneka Ltd., Japan) by their reacting with aqueous solutions of diethylenetriamine (DETA). The sample obtained at optimal condition (DETA concentration 70-80%, process time 2-7 h, temperature 95 degrees C) have anion exchange capacity 3-5 meq/g and water uptake 0.3-0.4 gH(2)O/g. Their chemical stability in different media has been studied. On the base of studies of their ion exchange capacity, elemental analysis, potentiometric titration and IR spectra the structure of these ion exchangers has been clarified. Predominant reaction of the modification is substitution of the Cl atoms by nitrogen in DETA molecules with formation of tertiary and secondary amino groups. All three atoms of nitrogen react and the ratio of incoming N atoms and outgoing Cl atoms is close to one. (C) 2011 Elsevier Ltd. All rights reserved.