Adsorption and desorption properties of expanded poly(tetrafluoroethylene) films grafted with DMAEMA and their regeneration

Abstract

An investigation was undertaken on the adsorption and desorption properties of the expanded poly (tetrafluoroethylene) (ePTFE) films grafted with 2-(dimethylamino)ethyl methacrylate (DMAEMA) to anionic dye anions with one to three sulfonic groups in response to temperature changes. The amount of adsorbed metanil yellow (MY) anions increased with the grafted amount and most of the dimethylamino groups appended to the grafted PDMAEMA chains worked as an adsorption site to MY anions for the DMAEMA-grafted ePTFE (ePTFE-g-PDMAEMA) films with the grafted amounts of higher than 1.1 mmol/g. When the dye-anion-adsorbed ePTFE-g-PDMAEMA films were alternately immersed in water at two different temperatures, dye anions were desorbed from the ePTFE-g-PDMAEMA films at higher temperatures without any chemical agents. The amount of desorbed dye anions increased with an increase in the temperature of water from 40 to 80°C. Desorption of dye anions is caused by either deprotonation of dimethylamino groups appended to the grafted PDMAEMA chains or thermosensitive contraction of the grafted PDMAEMA chains. These results indicate that the ePTFE-g-PDMAEMA films can be applied as a regenerative ion-exchange membrane for adsorption and desorption processes of anionic compounds in response to the temperature change. The thermally regenerative ion-exchange properties of the ePTFE-g-PDMAEMA films was superior to that of the PE-g-PDMAEMA films reported in our previous article in the fact that the total degree of desorption was higher for the ePTFE-g-PDMAEMA films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007