Control of nanoporous polymer matrix by an ionic liquid and water pressure for applications to water-treatment and separator

• Preparation of porous cellulose acetate polymer matrix by utilizing ionic liquid and water-pressure.
• The pore-generation of average 10 nm in cellulose acetate.
• The control of pore size with water-pressure.

A novel, simple, low-cost, energy-efficient, and environment-friendly method for generating pores in a polymer matrix was developed using a combination of an ionic liquid and water pressure treatment. A porous cellulose acetate (CA) matrix was successfully prepared using the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4) and subsequent water pressure treatment. Pores were generated in the CA polymer matrix when the CA/ionic liquid composite was subjected to water pressure. The characteristics of the thus-generated porous polymer matrix were evaluated using porosimetry and scanning electron microscopy. The pore sizes were ranged from less than 10 nm to over 10 μm, with an average value of 10 nm. Fourier transform infrared spectra and thermogravimetric analysis showed that when the CA polymer was subjected to water pressure, most of the BMIM-BF4 incorporated in the polymer during its preparation was removed, thereby generating the observed pores. In addition, it was observed that the flux was varied with water pressure, indicating that the pore size was controllable.