(404c) Polymeric Membranes Manufactured from Solutions in Ionic Liquid
The manufacture of asymmetric porous membranes by phase inversion and of multilayer composite membranes by dip coating is well established in the industry. These are versatile and simple processes, which lead to high performance membranes. Polymer dissolution is a mandatory step. We have been investigating ionic liquid as minor or major component in the casting solutions of polymers such as cellulose1, polyacrylamide, polytriazole and polystyrene-b-poly(4-vinyl pyridine)2 for the following reasons: (1) ionic liquids are among the few solvents dissolving cellulose and less aggressive than the other alternatives; (2) the membrane preparation by phase inversion in large scale involves in many cases partial solvent evaporation and the operator exposure to volatile components. Ionic liquids can substitute at least part of the volatile solvents, reducing problems related to the toxicity of organic solvent vapors; (3) ionic liquids can help to control the morphology, leading to structures different than those observed with other casting solutions; (4) in the case of block copolymers ionic liquids can induce or influence self-assembly and is a good additive to tailor morphology. Following the motivation supported by these aspects we have demonstrated the preparation of cellulose membranes with molecular weight cut-off in the range of 3 kg/mol and water permeance 14 L m-2 h-1 bar-1. These corresponds to the low range of ultrafiltration. The membranes are resistant to organic solvents. They can be used also as intermediate layer for the preparation of interfacial polymerized composite membranes. Polyacrylonitrile hollow fiber membranes with high porosity have been prepared from solutions containing ionic liquids. The membranes were tested for ultrafiltration and as supports for interfacial polymerization with final application in nanofltration and forward osmosis. Hydroxyl-functionalized polytriazoles have been synthesized in our lab for application in organophilic ultrafiltration3 and as support for interfacial polymerization4, using regular solvents like dimethyl formamide. More recently membranes have been also prepared using solutions in ionic liquid. Finally different ionic liquids have been used as additive for morphology control in the preparation of isoporous block copolymer membranes. References 1. S. Livazovic, Z. Li, A. R. Behzad, K.-V. Peinemann and S. P. Nunes, J. Membrane Sci., accepted. 2. P. Madhavan, R. Sougrat, A. R. Behzad, K.-V. Peinemann and S. P. Nunes, J. Membrane Sci., accepted. 3. S. Chisca, P. H. H. Duong, A.-H. Emwas, R. Sougrat, S. P. Nunes, Polymer Chemistry 2015, 6, 543-554. 4. P. H. H. Duong, S. Chisca, P. Y. Hong, S. P. Nunes, T.-S. Chung, ACS Applied Materials and Interfaces, accepted.