Separation of bisphenol-A by unimolecular micelles formed by pH-responsive polymer grafted onto polypropylene nonwoven fabrics

• Poly(NaAMPS-co-NaMmD) formed a unimolecular micelle at pH around 9.
• The copolymer-grafted polypropylene nonwoven fabric (PPNWF) was prepared.
• The adsorption/desorption of BPA by pH swing with polymer-grafted PPNWF was achieved.
• The encapsulated BPA amount within micelles increased by changing the pH gradually.

A novel pH-responsive random copolymer, prepared from equimolar concentrations of sodium 2-(acrylamido)-2-methylpropanesulfonate (NaAMPS) and sodium 12-methacrylamidododecanoate (NaMmD), formed a pH-responsive unimolecular micelle. The copolymer was grafted onto a polypropylene nonwoven fabric (PPNWF) by a plasma-initiated polymerization method. The formation of a unimolecular micelle of poly(NaAMPS-co-NaMmD) was observed to occur at a pH of around 9. Then, using the polymer-grafted PPNWF as a separation medium, the adsorption behaviors of bisphenol-A (BPA), which is a representative hydrophobic endocrine disruptor, were examined. The adsorption amount of BPA on the polymer-grafted PPNWF reached a maximum value at a pH of around 9, and it decreased significantly as the pH increased further. The reversible adsorption and desorption of BPA by the pH swing was achieved. Furthermore, it was found that the adsorption of BPA onto the polymer-grafted PPNWF occurred via encapsulation within the hydrophobic microdomains and adsorption on the pendent hydrophobic groups outside of the micelles by the hydrophobic interaction. The amount of BPA encapsulated within the hydrophobic microdomains in the micelles increased by changing the pH gradually.

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