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Abstract: In this paper, we demonstrated the successful fabrication of crosslinked porous films with varying monomer-crosslinker ratios, by photo-induced crosslinking during the breath figure formation. For all the samples fabricated, the pores at the peripheral regions appeared more uniform in size and showed higher degree of ordering, due to the interplay between the solvent evaporation and crosslinking reaction. The pore morphology remains similar despite varying film compositions, suggesting that the pore-fixing process is still dominated by the solvent evaporation similar to that of conventional breath figure process, and is less dependent on the crosslinking process. Detailed characterizations of the chemical and physical properties, including the glass transition temperature, thermal stability, and surface wettability of the porous films were carried out. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Thin film composite (TFC) reverse osmosis (RO) membranes enjoy widespread use in desalination, but their sensitivity to oxidizing agents such as chlorine remains a continuing challenge. In contrast to many reports on the chemical aspects associated with decreased membrane performance after chlorine exposure, studies on the fundamental physical properties of the polyamide barrier layer (PBL) of TFC membranes are scarce. This omission is mostly due to the lack of techniques capable of characterizing such interfacially polymerized PBLs, which are ultrathin and insoluble. The focus of this study is the development of an AFM-based nano-thermal analysis technique that provides the first-ever result for the direct measurement of the glass transition temperature (Tg ) of the PBL on several commercial TFC RO membranes. Moreover, the technique is utilized to study the changes in Tg of the PBL after exposure to chlorine solutions as a function of concentration and duration at constant pH. Results indicate significant and systematic reduction in Tg of the PBL with increasing chlorine concentration and exposure time. [Copyright &y& Elsevier]