The effects of alkaline hydrolysis on the chemical structure of polyacrylonitrile (PAN) hollow fiber ultrafiltration (UF) membrane were studied using solid-state C-13 NMR spectroscopy. The PAN membrane was hydrolyzed in an NaOH solution of pH 13, which is generally used in water industry for anti-fouling treatments of UF membranes but is much weaker than the alkaline concentrations (0.5-2.5 N) used so far in conventional C-13 NMR studies. All of the carbon sites of the PAN were characterized by the solid-state H-1-C-13 CPMAS and HETCOR NMR spectra. Upon the alkaline treatments, the chemical conversion from the cyano functional groups of the PAN to the carboxylates was observed. The analysis of the C-13 CPMAS NMR spectra obtained as a function of the treatment time for 4-96 h showed that the chemical modification occurred very rapidly in the early stage (<= 6 h) of the reaction but then proceeded slowly up to 96 h. The relative amount of the hydrolyzed acrylonitrile units after 96 h of the reaction at room temperature was estimated to be only 3.8%. We suggested that the alkaline hydrolysis of the PAN membrane proceeds at two distinct rates, a rapid conversion of the cyano groups on or near the membrane surface and a slow conversion of the bulk. (C) 2011 Elsevier B.V. All rights reserved.