title: Reentrant behavior of grafted poly(sodium styrenesulfonate) chains investigated with a quartz crystal microbalance.
abstract: Poly(sodium styrenesulfonate) (PSSNa) chains have been grafted onto a SiO(2)-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.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, China230026.
authors.forename: Yi
authors.initials: Y
authors.lastname: Hou
authors.forename: Guangming
authors.initials: G
authors.lastname: Liu
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu
authors.forename: Guangzhao
authors.initials: G
authors.lastname: Zhang