In this study we report changes in the glass transition temperature (T-g) of the polyamide barrier layer (PBL) of a commercial RO membrane as a function of chlorine treatment in which concentration and pH were systematically varied. The results indicate a monotonic decrease of T-g with increasing exposure time at a given chlorine concentration. Further, both the degree and the rate of T-g decrease vary significantly with both the chlorine concentration and pH value of the aqueous chlorine solution. Moreover, the decrease in PBL T-g correlates well with the reduction in the salt rejection of the membrane, but the magnitude of the correlation is specific to chlorine concentration and pH values. (C) 2012 Elsevier B. V. All rights reserved.