Synthesis of hyper-branched quaternary ammonium salt and its application into montmorillonite

Abstract

Hyper-branched quaternary ammonium salts (HQAS) were synthesized by condensation polymerization between quaternary ammonium salt (QAS) and the monomer we prepared. The chemical structure, molecular weight, and thermal properties of these salts were determined by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), ultraviolet spectra (UV), nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA). The onset and center temperatures of decomposition (T-5% and Tmax) were improved from 113°C and 270°C, to 191°C and 275°C, respectively.Sodium-montmorillonite (Na+-MMT) was modified with these two types of intercalation agents, QAS and HQAS, via ion-exchange reactions. The interlayer space, interlamellar structure, thermal stability, and surface morphology of these organic montmorillonites (OMMTs) were investigated by FTIR, TGA, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The HQAS modified montmorillonites had expanded interlayer space and possessed good thermal stabilities due to steric hindering and thermal stability of the hyper-branched polymers. The basal spacing of QAS modified samples was 1.6-4.9nm, indicating a monolayer, bilayer, and pseudo-trilayer arrangement of quaternary ammonium ions in the interlayer space. The HQAS modified samples had basal spacing ranging from 1.9 to 2.5nm, and the intensive degree was much decreased. These experimental results and phenomena indicated bilayer and pseudo-trilayer arrangements of hyper-branched molecular chains, together with some exfoliated silicate layers.