Research ArticleMATERIALS SCIENCE

Multivalent ions induce lateral structural inhomogeneities in polyelectrolyte brushes

See allHide authors and affiliations

Science Advances  08 Dec 2017:
Vol. 3, no. 12, eaao1497
DOI: 10.1126/sciadv.aao1497
  • Fig. 1 PSS brush layer structure with and without multivalent ions.

    AFM tapping mode height (top) and phase images (bottom). (A) No distinct features were seen in 6 mM NaNO3 in the absence of multivalent ions, but (B) lateral structures formed with the addition of 0.1 mM Y(NO3)3 (keeping the total ionic strength at 6 mM). (C) One millimolar Y(NO3)3. Scan size, 3 μm × 3 μm (scale bars, 500 nm).

  • Fig. 2 Collapsed brush layer recovering upon addition of monovalent ions.

    AFM height (top) and phase (bottom) images showing the effect on PSS brush layers of replacing (A) 0.01 mM Y(NO3)3 in water (no added NaNO3) with increasing concentrations of NaNO3: (B) 8 mM NaNO3 and (C) 10 mM NaNO3. Scan size, 3 μm × 3 μm (scale bars, 500 nm).

  • Fig. 3 MD simulation of brush with and without multivalent ions.

    Top-down view of polymer brush density profile for concentrations of 5 × 10−3 σ−3 monovalent salt with (A) no trivalent salt, (B) 1 × 10−4 σ−3 trivalent salt, (C) 1 × 10−3 σ−3 trivalent salt, and (D) 3 × 10−3 σ−3 trivalent salt. Color scale corresponds to relative brush densities (red/orange for high density, dark blue for low density), with relative densities scaled to the lowest value of the surface density in each image.

  • Fig. 4 SFA force distance curves during compression and separation of two identical PSS brush layers.

    (A) In mixed IPA/water solutions with IPA volume fractions of 0, 40, 60, 80, and 100%, respectively. (B) In 6 mM NaNO3, 1 mM Y(NO3)3, and pure IPA solutions. Solid data points represent forces upon compression, and open data points were measured upon separation of the brush layers.

  • Fig. 5 Collapsed PSS brush layer in poor solvent.

    Height (top) and phase (bottom) image of PSS brushes in 80% IPA solution. Scan size, 3 μm × 3 μm (scale bars, 500 nm).

  • Fig. 6 MD simulation of brushes with solvophilic or solvophobic backbone.

    Top-down view of periodic polymer brush density profile at a grafting separation of 5σ for (A and B) salt-free, lB = 12σ conditions with (A) good solvent (0.4 kBT) and (B) poor solvent (1.4 kBT) LJ interactions. (C and D) Trivalent salt (2 × 10−3 σ−3), lB = 3σ, with (C) good solvent (0.4 kBT) and (D) poor solvent (1.4 kBT) LJ interactions. Color scale corresponds to relative brush densities (red/orange for high density, dark blue for low density), with relative densities scaled to the lowest value of the surface density in each image.

  • Fig. 7 Interaction of multivalent ions with polyelectrolyte chains.

    (A) Molecular-level model. Distribution of topological distances (α) for bridging in polyelectrolyte brushes at trivalent ion concentrations of (B) 10−4 σ−3 and (C) 10−3 σ−3, corresponding to the conditions of Fig. 3 (B and C, respectively). Values of α ≥ 5 denote trivalent ions involved in interchain bridging.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/12/eaao1497/DC1

    AFM imaging in solution

    fig. S1. AFM images of PSS brush layers in the absence and presence of multivalent ions.

    fig. S2. Charge distribution and polymer density plots corresponding to the data presented in Fig. 3A.

    fig. S3. Charge distribution and polymer density plots corresponding to the data presented in Fig. 3B.

    fig. S4. Charge distribution and polymer density plots corresponding to the data presented in Fig. 3C.

    fig. S5. Charge distribution and polymer density plots corresponding to the data presented in Fig. 3D.

    fig. S6. Distribution of diffusion rates of trivalent ions in the collapsed brush systems.

    fig. S7. Distributions of polyelectrolytes and ions in a brush layer.

    fig. S8. Collapsed PSS brush layer in poor solvent.

    fig. S9. Charge distribution and polymer density plots corresponding to the data presented in Fig. 6A.

    fig. S10. Charge distribution and polymer density plots corresponding to the data presented in Fig. 6B.

    fig. S11. Charge distribution and polymer density plots corresponding to the data presented in Fig. 6C.

    fig. S12. Charge distribution and polymer density plots corresponding to the data presented in Fig. 6D.

    fig. S13. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 3A.

    fig. S14. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 3B.

    fig. S15. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 3C.

    fig. S16. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 3D.

    fig. S17. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 6A.

    fig. S18. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 6B.

    fig. S19. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 6C.

    fig. S20. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 6D.

    Representative large-scale atomic/molecular massively parallel simulator input (used to generate data in Fig. 6C).

  • Supplementary Materials

    This PDF file includes:

    • AFM imaging in solution
    • fig. S1. AFM images of PSS brush layers in the absence and presence of multivalent ions.
    • fig. S2. Charge distribution and polymer density plots corresponding to the data presented in Fig. 3A.
    • fig. S3. Charge distribution and polymer density plots corresponding to the data presented in Fig. 3B.
    • fig. S4. Charge distribution and polymer density plots corresponding to the data presented in Fig. 3C.
    • fig. S5. Charge distribution and polymer density plots corresponding to the data presented in Fig. 3D.
    • fig. S6. Distribution of diffusion rates of trivalent ions in the collapsed brush systems.
    • fig. S7. Distributions of polyelectrolytes and ions in a brush layer.
    • fig. S8. Collapsed PSS brush layer in poor solvent.
    • fig. S9. Charge distribution and polymer density plots corresponding to the data presented in Fig. 6A.
    • fig. S10. Charge distribution and polymer density plots corresponding to the data presented in Fig. 6B.
    • fig. S11. Charge distribution and polymer density plots corresponding to the data presented in Fig. 6C.
    • fig. S12. Charge distribution and polymer density plots corresponding to the data presented in Fig. 6D.
    • fig. S13. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 3A.
    • fig. S14. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 3B.
    • fig. S15. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 3C.
    • fig. S16. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 3D.
    • fig. S17. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 6A.
    • fig. S18. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 6B.
    • fig. S19. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 6C.
    • fig. S20. Polymer density plots for the polydisperse simulation using conditions corresponding to Fig. 6D.
    • Representative large-scale atomic/molecular massively parallel simulator input (used to generate data in Fig. 6C).

    Download PDF

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article