A bionanocomposite based on 1,4-diazabicyclo-[2.2.2]-octane cellulose nanofiber cross-linked-quaternary polysulfone as an anion conducting membrane

Abstract

Anion conducting composite membranes were synthesized by cross-linking hydroxide conducting 1,4-diazabicyclo-[2.2.2]-octane (DABCO)–cellulose nanofibers (isolated from Citrus tangerine) with DABCO–polysulfone using 1,4-dibromo butane. The content of quaternized cellulose was adjusted to control the ion exchange capacity (IEC) and the ionic conductivity. The structural and morphological characteristics of the membranes were determined by Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance spectroscopy (¹H-NMR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microphase structure of the membranes was studied by atomic force microscopy (AFM). The effects of the DABCO–cellulose on water uptake (WU), ion exchange capacity (IEC) and ionic conductivity were investigated. The cross-linking of the quaternized cellulose with the polymer main chains formed a bedform type structure, ensuing good chemical and excellent mechanical stability of the membranes in aqueous and alkaline media. The composite membranes showed conductivity in the range of ca. 39–74 mS cm⁻¹ at 25 °C and reached 128 mS cm⁻¹ at 80 °C, derived from the nanophase separation and densely distributed ionic channels. Such a strategy provides a valuable prospect to design high anion conducting membranes for fuel cell applications.