Ultrasonic irradiation to modify the functionalized bionanocomposite in sulfonated polybenzimidazole membrane for...

In this article the new proton exchange membranes were prepared from sulfonated polybenzimidazole (s-PBI) and various amounts of sulfonated titania/cellulose nanohybrids (titania/cellulose-SO₃H) via ultrasonic waves. The ultrasonic irradiation effectively changes the rheology and the glass transition temperature and the crystallinity of the composite polymer. Ultrasonic irradiation has a very strong mixing and dispersion effect, much stronger than conventional stirring, which can improve the dispersion of titania/cellulose-SO₃H nanoparticles in the polymer matrix. The strong -SO₃H/-SO₃H interaction between s-PBI chains and titania/cellulose-SO₃H hybrids leads to ionic cross-linking in the membrane structure, which increases both the thermal stability and methanol resistance of the membranes. After acid doping with phosphoric acid, s-PBI/titania/cellulose-SO₃H nanocomposite membranes exhibit depressions on methanol permeability and enhancements on proton conductivity comparing to the pristine s-PBI membrane. The chemical structure of the functionlized titania was characterized with FTIR, and energy-dispersive X-ray. Imidazole and sulfonated groups on the surface of modified nanoparticles forming linkages with s-PBI chains, improved the compatibility between s-PBI and nanoparticles, and enhanced the mechanical strength of the prepared nanocomposite membranes. From SEM and TEM analysis could explain the homogeneous dispersion of titania/cellulose-SO₃H in nanocomposite membranes. Moreover, the membranes exhibited excellent antibacterial activities against S. aureus and E. coli. A.