Temperature Responsive Membranes for Separation and Water Detoxification

Membrane based separation process has been widely used in water detoxification, water purification and waste water treatment. Stimuli-responsive polymers have been gained much attention due to their unique and excellent physical and chemical responses to changes in physiological conditions and have applied in different areas: such as, drug delivery, bioseparation and tissue engineering, etc. Various types of responsive membranes for regulated permeation have been devised, such as pH, temperature and light, etc. The porous membranes with responsive polymer chain have advantages over hydrogel membrane for mechanical strength and quick response to external signal. In the case of temperature responsive hydrogels, the N-isopropylacrylamide (NIPAAm) is widely studied. It exhibits a lower critical solution temperature (LCST) behavior around 32^oC. The NIPAAm chains hydrate to form expanded structure when the solution temperature is below LCST and dehydrate to form a collapsed structure when heated to above the LCST. In our work, temperature responsive membrane has been designed and synthesized, in which pores open or close in response to temperature around LCST. Hydrophylized polyvinylidene fluoride (PVDF) membrane was used as support due to its chemical resistance properties and good thermal stability. In a narrow temperature range, hydration-dehydration changes lead to the membrane conformation change, resulting in the stimuli-responsive permeability of gating membrane. The thermo-dependent hydrophilic /hydrophobic transition of the membrane around response temperature was investigated. The effect of temperature on solute permeability was also determined. In addition, we also extended our work into catalytic area with immobilized nanoparticles in membrane platform for water detoxification.

       This research was supported by NIEHS-SRP and by DOE-KRCEE.