Effects of polymer concentration on structure and properties of Zwitterionic nanocomposite gels

Abstract

Zwitterionic nanocomposite gels (Zw-NC gels) composed of a zwitterionic sulfobetaine copolymer and inorganic clay (hectorite) are synthesized through the in situ free-radical copolymerization of N,N-dimethyl(acrylamidopropyl) ammonium propanesulfonate (90 mol%) and N,N-dimethylacrylamide (10 mol%) with exfoliated clay platelets in an aqueous medium. The effects of polymer concentration (Cp) on the dynamic viscoelasticity, tensile mechanical properties, transparency, and the thermosensitivity with the upper critical solution temperature (UCST) of the Zw-NC gels are investigated in the range Cp = 26-260 g L-1 and are compared with those of chemically cross-linked zwitterionic gels. All the mechanical and thermosensitive properties strongly change depending on the type of network and Cp. The Cp-induced changes in the polymer-clay structure of the Zw-NC gel are discussed based on the mechanical, optical, and thermosensitive properties, and on transmission electron microscopy and X-ray diffraction measurements. Zwitterionic nanocomposite gels composed of zwitterionic sulfobetaine copolymer and exfoliated inorganic clay are prepared with various polymer concentrations (Cp). The dynamic viscoelastic and tensile mechanical properties, transparency, and the upper critical solution temperature strongly depend on the type of network and Cp. The Cp-induced changes in the polymer-clay structure are discussed based on these properties, as well as transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.