(251u) Magnetic Responsive Polymeric Colloids for Advanced Separations

Surfactants are widely used in industrial separation processes ranging from ore purification to environmental remediation. Separation systems involving surfactants could be made more efficient and / or cost effective with magnetic surfactants. Zubarev’s theory states that a magnetic field can cause significant changes in the size and shape of magnetic polymer coils. In order to test this theory, we synthesized novel magneto-responsive polymer-based surfactants by first synthesizing and adding magnetic functionality to pH-responsive polymeric colloids. We utilized reversible addition-fragmentation chain transfer (RAFT) polymerization to synthesize a family of pH-responsive cationic ammonium homo- and block copolymers. RAFT provides a facile method for synthesizing advanced polymer architectures from a variety of functional monomers while maintaining precise control over the macromolecular design (molecular weight, copolymer composition, functionality). We examined the pH-response of a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) (pKa ~ 7.3) series using dynamic light scattering to determine the hydrodynamic diameter of the polymers in solution at two pH values. At a solution pH of 4.0, the tertiary amine moieties along the polymer backbone were ionized enough for the polymers to be molecularly dissolved. At a pH of 10.4, however, the tertiary amine functionality is essentially 100% deprotonated. The corresponding decrease in hydrophilicity induced self-assembly into micelles with a diameter of roughly 60 nm. The pH-responsive, cationic polymers were rendered magneto-responsive via an ion exchange paramagnetic ions such as FeCl₄^- or CoCl₄^2-. Ongoing efforts focus on the effect of magnetic fields on the solubilization capacity of the polymeric micelles and the ability of utilizing the magneto-responsive polymeric micelles to affect low energy extraction and concentration of organics solutes.