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    Formation of Polyelectrolyte Multilayers by Flexible and Semiflexible Chains

    Year: 2012

    Journal: J. Phys. Chem. B, 2012, 116 (10), pp 3106–3114, 20120618

    Authors: Bo Wu†, Chunliang Li†, Haiyang Yang‡, Guangming Liu*†, and Guangzhao Zhang§

    Last authors: Guangzhao Zhang

    Organizations: † Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, P. R. China 230026 ‡ Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, P. R. China 230026 § Faculty of Materials Science and Engineering, South China University of Technology, Guangzhou, P. R. China 510640

    Country: China

    Poly(sodium 4-styrene sulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDDA) are flexible polyelectrolytes, whereas sulfated chitosan (SC) and cationic guar gum (CGG) are semiflexible polyelectrolytes. By use of a quartz crystal microbalance with dissipation (QCM-D), a zeta potential analyzer (ZPA), and atomic force microscopy (AFM), we have investigated the growth of PSS/PDDA, PSS/CGG, SC/PDDA, and SC/CGG multilayers as a function of NaCl concentration (CNaCl). For the same layer number, the changes of frequency (−Δf) and dissipation (ΔD) regarding PSS/PDDA multilayer increase with CNaCl, whereas −Δf and ΔD for SC/CGG multilayer increase at CNaCl < 0.1 M and decrease at CNaCl > 0.1 M as CNaCl increases. In the cases of PSS/CGG and SC/PDDA multilayer, for the same layer number, −Δf and ΔD increase with CNaCl in the range of CNaCl < 0.5 M, and they decrease with the increasing CNaCl in the case of SC/PDDA multilayer but slightly change for the PSS/CGG multilayer at CNaCl > 0.5 M. QCM-D studies indicate that the growth of multilayers as a function of salt concentration is determined by the delicate balance between the weakening of electrostatic repulsion between identically charged groups and the decrease of electrostatic attraction between neighboring layers. ZPA and AFM measurements demonstrate that the extent of surface charge overcompensation and the surface morphology of the multilayers are controlled by the chain conformation.