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    Reentrant behavior of grafted poly(sodium styrenesulfonate) chains investigated with a quartz crystal microbalance

    Year: 2011

    Journal: Phys. Chem. Chem. Phys., 2011, 13, 2880-2886, 20120104

    Authors: Hou Y 1, Liu G 1, Wu Y 1, Zhang G * 1 2

    Last authors: Guangzhao Zhang

    Organizations: 1 Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, China 230026. E-mail: gzzhang@ustc.edu.cn 2 Faculty of Materials Science and Engineering, South China University of Technology, Guangzhou, P. R. China 510640

    Country: China

    Poly(sodium styrenesulfonate) (PSSNa) chains have been grafted onto a SiO2-coated resonator surface. The conformational changes of grafted chains have been investigated using a quartz crystal microbalance with dissipation (QCM-D) in the presence of monovalent or multivalent salts as a function of ionic strength. In the case of monovalent counterions, the changes in frequency (Δf) and dissipation (ΔD) indicate that the highly extended PSSNa chains first shrink into a loose and inhomogeneous layer as the ionic strength increases. As the ionic strength increases further, the chains will collapse and form a denser and more homogeneous layer. In the case of divalent or trivalent counterions, the grafted PSSNa chains also collapse into a dense layer as the ionic strength increases. However, when the ionic strength is above a critical value, the chains would re-expand so that the layer becomes partially extended due to the charge inversion. Additionally, the effect of ion-specificity on the conformational changes of the chains has also been examined.