Synthesis and characterization of poly (N-tert butylacrylamide) copolymers and application of them in the fabrication of Nano-porous membranes

Polymeric membranes have many industrial applications such as microfiltration, ultrafiltration, reverse osmosis and gas separation [1]. For microfiltration and ultrafiltration, the important point is just the porosity of membranes, but for applicability in gas separation, the membrane should show selectivity and permeability. There exist some ways for the preparation of porous structures such as sintering, stretching, track etching and phase separation techniques. Phase separation of polymer solutions can be induced in several ways: a) Thermally induced phase separation (TIPS), b) Air-casting of polymer solution, c) Precipitation from the vapor phase, d) Immersion precipitation [2].Poly(N-isopropylacrylamide) (PNIPAM) exhibits a well-defined lower critical solution temperature (LCST) in water (~33ºC) [3,4]. The LCST, and the accompanying changes in polymer conformation, result from a balance between hydrogen bonding [5] and hydrophobic effects [6] in aqueous solutions of PNIPAM. The formation of membrane from PNIPAM has been reported [7].Poly(N-tertbutylacrylamide) (PNTBAM) is insoluble in water, but by copolymerization with more hydrophilic comonomers such as AM, it is possible to make it water-soluble. The poly(N-tertbutylacrylamide-co-acrylamide) P(NTBAM-co-AM) shows thermosensitivity in water and the resultant transition temperature is very dependent on the copolymer composition. A comprehensive study on the phase transition behavior of P(NTBAM-co-AM) copolymers in water and in the mixture of water-methanol has been done by us (submitted article). In spite of showing the same properties as PNIPAM in water, the reentrant behavior of P(NTBAM-co-AM) was completely different from PNIPAM in the water-methanol mixture.In the present study, the fabrication of membrane by using phase separation technique is investigated.