Functional adsorbent as endocrine disruptor using pH-responsive polymer grafted on porous ethylene vinyl acetate disk

• Poly(NaAMPS-co-NaMmD) was grafted on a porous ethylene vinyl acetate (PEVA) disk.
• Permeability through the disk depended on the pH of the BPA solution.
• The total adsorption amount of BPA increased with an increasing the MmD groups.
• The encapsulated BPA amount within the micelles depended on the BPA solution pH.
• An equivalent molar ratio of NaAMPS and NaMmD was effective for BPA encapsulation.

Random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate (NaAMPS) and sodium 12-methacrylamidododecanoate (NaMmD) with three different molar ratios were grafted onto the pore surface of a porous ethylene vinyl acetate (PEVA) disk by a plasma-initiated polymerization method. Bisphenol-A (BPA) solutions with various pH values were permeated through the polymergrafted PEVA disk, and the adsorption and desorption properties of BPA were examined. The permeability through the polymer-grafted PEVA disk depended on the conformation of the polymer molecules grafted on the disk, which in turn depended on the pH of the permeated solution. A peak was observed at the pH value between 9 and 10. The adsorption amount of BPA also significantly depended on the pH of the permeated BPA solution and two peaks were observed, at pH values of around 6 and 10, respectively. The pH around 10 was the almost the same pH as that required for the formation of the unimolecular micelles. The adsorption amount of BPA resulted from the encapsulation of BPA within the hydrophobic microdomains in the micelles and its adsorption on the pendant hydrophobic MmD groups outside of the micelles by hydrophobic interactions. The encapsulated amount of BPA at pH 10 was significantly large compared with that at pH 6. Furthermore, the total adsorption amount of BPA largely depended on the composition of the copolymer, i.e., the molar ratio of NaAMPS and NaMmD; the amount increased with increase in the amount of the hydrophobic component NaMmD. However, the encapsulated amount of BPA within the hydrophobic microdomains was markedly larger when the grafted polymer was prepared with an equivalent molar ratio of NaAMPS and NaMmD.

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