Fundamental studies of a new hybrid (inorganic-organic) positively charged membrane: membrane preparation and characterizations

Hybrid (inorganic-organic) positively charged membranes were prepared through sol-gel process of trimethoxysilyl functionalized polyethylene oxide (PEO)-400, i.e. PEO-[Si(OCH3)(3)](2) and quarteramination with C2H5Br thereafter. The PEO-[Si(OCH3)(3)](2) was obtained by endcapping PEO-400 with Tolylene 2,4-diisocyanate (TDI), followed by a reaction with N-[3-(trimethoxysilyl) propyl] ethylene diamine (A-1120). IR measurements confirmed the chemical structure of the step products. The morphologies of the hybrid membranes were observed by scanning electron microscopy. Conventional ion exchange capacity (IEC) measurements showed that anion exchange properties of the membranes per unit area of surface were in the range of (1.6-3.9) x 10(-2) meq./cm(2), while streaming potential tests indicated that charge transition point of the membranes moved to pH 12 or higher. The average pore diameter evaluated from pure water flux measurements ranged from hundreds of nanometers to several nanometers, depending on the coating times and the sol composition, especially the concentration of the precursor. Thus, a series of membranes can be obtained to comply with different pressure-driven processes. (C) 2003 Elsevier Science B.V. All rights reserved.