title: Cation-specific conformational behavior of polyelectrolyte brushes: from aqueous to nonaqueous solvent.
abstract: We have investigated changes in the cation-specific conformational behavior of poly(sodium styrenesulfonate) (PSS) brushes as the solvent changes from water to methanol using a quartz crystal microbalance with dissipation (QCM-D). A solvation to desolvation transition of the grafted chains accompanied by swelling to the collapse transition of the brushes is observed for Na(+). In the case of Cs(+), the brushes undergo solvation to desolvation to resolvation accompanied by swelling to collapse to reswelling transitions. The resolvation and reswelling transitions for Cs(+) are induced by the charge inversion of the brushes via van der Waals interactions between Cs(+) and the brushes. All of the transitions for monovalent cations become less obvious as the methanol content increases. For divalent Ca(2+) and trivalent La(3+), a solvation to desolvation to resolvation transition of the grafted chains accompanied by a swelling to collapse to reswelling transition of the brushes can be observed. The resolvation and reswelling of the brushes for the multivalent cations are induced by the charge inversion of the brushes via charge-image charge interactions. The extent of the transitions for the PSS brushes in the presence of multivalent cations is only slightly influenced by the methanol content.
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China , Hefei, PR China 230026.
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.forename: Yunchao
authors.initials: Y
authors.lastname: Long
authors.forename: Lvdan
authors.initials: L
authors.lastname: Liu
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Wang
authors.forename: Vincent S J
authors.initials: VS
authors.lastname: Craig
authors.forename: Guangzhao
authors.initials: G
authors.lastname: Zhang
authors.forename: Guangming
authors.initials: G
authors.lastname: Liu