CORRELATIONS OF CHEMICAL-STRUCTURE, ATOMIC-FORCE MICROSCOPY (AFM) MORPHOLOGY, AND REVERSE-OSMOSIS (RO) CHARACTERISTICS IN AROMATIC POLYESTER HIGH-FLUX RO MEMBRANES

A homologous series of thin-film composite membranes was prepared by i nterfacial polymerization of various bisphenols possessing structural variations and trimesoyl chloride (TMC). Correlations between the inhe rent chemical nature of bisphenols with methyl or halogen substitution s on the biphenyl rings, reverse osmosis (RO) characteristics, and sur face features characterized by atomic force microscopy (AFM) were stud ied. The methyl substitutions in bisphenol phenyl rings resulted in me mbranes with higher RO water flux but lower RO rejection, tending to g ive membrane surface morphology of irregular ambiguous nodule structur e with reduced size and a smoother surface. The halogen substitutions were found to play an important role in enhancing the RO rejection of the resulting membranes; the rough surface appearance of uniform disti nct nodule structure may also have contributed to obtaining higher rej ections.