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Title: Structure of Polyelectrolyte Brushes in the Presence of Multivalent Counterions

Polyelectrolyte brushes are of great importance to a wide range of fields, ranging from colloidal stabilization to responsive and tunable materials to lubrication. Here, we synthesized high-density polystyrenesulfonate (PSS) brushes using surface initiated atom transfer radical polymerization and performed neutron reflectivity (NR) and surface force measurements using a surface forces apparatus (SFA) to investigate the effect of monovalent Na +, divalent Ca 2+, Mg 2+, and Ba 2+, and trivalent Y 3+ counterions on the structure of the PSS brushes. NR and SFA results demonstrate that in monovalent salt solution the behavior of the PSS brushes agrees with scaling theory well, exhibiting two distinct regimes: the osmotic and salted brush regimes. Introducing trivalent Y 3+ cations causes an abrupt shrinkage of the PSS brush due to the uptake of Y 3+ counterions. The uptake of Y 3+ counterions and shrinkage of the brush are reversible upon increasing the concentration of monovalent salt. Divalent cations, Mg 2+, Ca 2+, and Ba 2+, while all significantly affecting the structure of PSS brushes, show strong ion specific effects that are related to the specific interactions between the divalent cations and the sulfonate groups. Our results demonstrate that the presence of multivalent counterions, evenmore » at relatively low concentrations, can strongly affect the structure of polyelectrolyte brushes. Finally, the results also highlight the importance of ion specificity to the structure of polyelectrolyte brushes in solution.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1] ;  [1]
  1. Univ. of Chicago, IL (United States). Inst. for Molecular Engineering; Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
  2. Univ. of Chicago, IL (United States). Inst. for Molecular Engineering
  3. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research; Univ. of Akron, OH (United States). Dept. of Polymer Engineering
  4. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research
  5. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
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Grant/Contract Number:
Accepted Manuscript
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Additional Journal Information:
Journal Volume: 49; Journal Issue: 15; Journal ID: ISSN 0024-9297
American Chemical Society
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
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