Responsive Ultrafiltration Membranes Composed of N-Isopropylacrylamide (NIPAAM) and Cellulose Acetate

Title:

Responsive Ultrafiltration Membranes Composed of N-isopropylacrylamide (NIPAAM) and Cellulose Acetate 

Abstract:

The purpose of this study is to develop stimuli responsive membranes to control fouling using membrane casting dopes made of cellulose acetate with N-isopropylacrylamide (NIPAAM). NIPAAM is a stimuli-responsive polymer, which offers the potential to collapse or expand the membrane with changes in temperature.  The phase change of N-isopropylacrylamide arises because of a lower critical solution temperature (LCST) such that the polymer precipitates from solution as the temperature is increased. Below the LCST, NIPAAM is hydrophilic (expanded), while above the LCST it is hydrophobic (collapsed). Therefore, by alternating between hot and cold conditions it is hypothesized that accumulation of foulants decreases. In order to provide localized and intensified heating within the membrane matrix, superparamagnetic iron oxide (SPIO) nanoparticles are embedded in the NIPAAM hydrogel. One form of  iron oxide, magnetite (Fe₃O₄), sized at  15nm can heat water several degrees in a short duration of time. The heating is caused by Neel and Brownian relaxations.  Thus, temperature activation can be triggered through alternating electromagnetic heating of the embedded SPIO nanoparticles.