Research ArticlePHYSICAL SCIENCES

Tuning ice nucleation with counterions on polyelectrolyte brush surfaces

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Science Advances  03 Jun 2016:
Vol. 2, no. 6, e1600345
DOI: 10.1126/sciadv.1600345
  • Fig. 1 Illustration of HIN on cationic and anionic PB surfaces with different counterions.

    Cationic poly[2-(methacryloyloxy)-ethyltrimethylammonium] (PMETA) and anionic poly(3-sulfopropyl methacrylate) (PSPMA) brushes are used to study the effect of diffused counterions on tuning HIN. The counterions on the PMETA and PSPMA brush surfaces can be successfully exchanged by immersing the brush surface into a solution containing expected counterions (fig. S1).

  • Fig. 2 TH on the PMETA brush surfaces.

    (A) Polarized optical microscopic images of water drops before (1) and after (3) freezing on PMETA-SO4 and PMETA-I brush surfaces (on the same wafer; in fig. S4). The PMETA-SO4 and PMETA-I brush surfaces exhibited distinct TH. Scale bar, 200 μm. (B) Reversible switch of the TH of water drops on the PMETA brush surfaces through the consecutive counterion exchange of I and SO42− (0.05 chain/nm2). (C and D) The influence of grafting density (C) and thickness (D) (fixed grafting density of 0.50 chain/nm2) on the TH of PMETA-SO4, PMETA-Cl, and PMETA-I brush surfaces. The measurements were carried out in a closed chamber with a relative humidity of 100%, and the samples were chilled from room temperature to −50.0°C with a cooling rate of 2.0°C/min. All experimental results on the TH were based on more than 200 freezing events for each PMETA-SO4, PMETA-Cl, and PMETA-I brush surfaces (in fig. S5).

  • Fig. 3 Distinct efficiency of anions and cations in tuning HIN follows the Hofmeister series.

    (A and B) TH (A) and tD (B) on the PMETA brush surfaces with different counteranions follow the Hofmeister series. The brush grafting density is 0.50 chain/nm2, and the thickness is 50 nm. (C and D) TH (C) and tD (D) of ice nucleation on PSPMA brushes with different countercations. The brush grafting density is 0.95 chain/nm2, and the thickness is 20 nm.

  • Fig. 4 The concentration of counteranions and the water structure and dynamics at the brush/water interfaces.

    (A) Concentration of diffused counteranions outside the PMETA brush. (B) Fraction of ice-like water molecules (tetrahedrality above 0.9). (C) Time correlation function of −OH orientation of water molecules at a distance within 8 Å from the brush/water interface. (D) Making rate constant and breaking rate constant (inset) of ice-like water molecules. (E) Kinetics of structural transformation between liquid-like and ice-like water molecules at the brush/water interface.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/6/e1600345/DC1

    fig. S1. XPS spectra of PEMTA brushes with different counterions (SO42−, Cl, and I) in the regions of S2p, Cl2p, and I3d.

    fig. S2. Homemade experimental apparatus used to detect the HIN on PB surfaces.

    fig. S3. Freezing process of individual water droplets on PMETA-I brushes (0.05 chain/nm2) during the temperature-jump experiment at a cooling rate of 2.0°C/min (detected by a high-speed camera).

    fig. S4. Preparation process of PMETA-SO4 and PMETA-I brush surfaces divided by a gap of Si on the same wafer.

    fig. S5. Distribution of TH on PMETA brush surfaces (grafting density of 0.5 chain/nm2 and thickness of 50 nm) with different counterions (SO42−, Cl, and I).

    fig. S6. HIN on cationic SAMs with different counteranions.

    fig. S7. Influence of cooling rate (from 1.0 to 10.0°C/min) on the ice nucleation temperature of PMETA-SO4, PMETA-Cl, and PMETA-I brush surfaces (grafting density of 0.5 chain/nm2 and thickness of 50 nm).

    fig. S8. Distribution of TH on PSPMA brush surfaces (grafting density of 0.9 chain/nm2 and thickness of 20 nm) with different counterions (Li+ , Na+, and K+).

    fig. S9. HIN on anioinc SAMs with different countercations.

    fig. S10. Quartz crystal microbalance with dissipation monitoring results as a function of different counteranions in the PMETA brushes.

    fig. S11. Thickness of PMETA brushes with different counterions measured by spectroscopic ellipsometer under aqueous solution.

    fig. S12. Contact angle of PMETA brush surfaces with different counterions.

    fig. S13. Surface morphology and roughness of PMETA brush.

    fig. S14. MD simulation illustration of PB with counterions.

    fig. S15. Distribution of outmost QA+ headgroup of PMETA-F, PMETA-Cl, and PMETA-I at the brush/water interface.

    fig. S16. Concentration of the diffused counterions above the PMETA brush at 300 K.

    fig. S17. Strength of the electric field of PMETA-F, PMETA-Cl, and PMETA-I above the brush/water interface.

    fig. S18. Water density and ice-like water density of PMETA-F, PMETA-Cl, and PMETA-I brushes.

    table S1. The fraction of ice-like water molecules (tetrahedrality above 0.9), the ice-like water making rate constant k, and the concentration of ice-like water at the brush/water interface with the same concentration of counterion (0.25 M).

    Experiment details

    MD simulation details

    References (5258)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. XPS spectra of PEMTA brushes with different counterions (SO42−, Cl, and I) in the regions of S2p, Cl2p, and I3d.
    • fig. S2. Homemade experimental apparatus used to detect the HIN on PB surfaces.
    • fig. S3. Freezing process of individual water droplets on PMETA‐I brushes (0.05 chain/nm2) during the temperature-jump experiment at a cooling rate of 2.0°C/min (detected by a high-speed camera).
    • fig. S4. Preparation process of PMETA-SO4 and PMETA-I brush surfaces divided by a gap of Si on the same wafer.
    • fig. S5. Distribution of TH on PMETA brush surfaces (grafting density of 0.5 chain/nm2 and thickness of 50 nm) with different counterions (SO42−, Cl, and I).
    • fig. S6. HIN on cationic SAMs with different counteranions.
    • fig. S7. Influence of cooling rate (from 1.0 to 10.0°C/min) on the ice nucleation temperature of PMETA-SO4, PMETA-Cl, and PMETA-I brush surfaces (grafting density of 0.5 chain/nm2 and thickness of 50 nm).
    • fig. S8. Distribution of TH on PSPMA brush surfaces (grafting density of 0.9 chain/nm2 and thickness of 20 nm) with different counterions (Li+, Na+, and K+).
    • fig. S9. HIN on anioinc SAMs with different countercations.
    • fig. S10. Quartz crystal microbalance with dissipation monitoring results as a function of different counteranions in the PMETA brushes.
    • fig. S11. Thickness of PMETA brushes with different counterions measured by spectroscopic ellipsometer under aqueous solution.
    • fig. S12. Contact angle of PMETA brush surfaces with different counterions.
    • fig. S13. Surface morphology and roughness of PMETA brush.
    • fig. S14. MD simulation illustration of PB with counterions.
    • fig. S15. Distribution of outmost QA+ headgroup of PMETA-F, PMETA-Cl, and PMETA-I at the brush/water interface.
    • fig. S16. Concentration of the diffused counterions above the PMETA brush at 300 K.
    • fig. S17. Strength of the electric field of PMETA-F, PMETA-Cl, and PMETA-I above the brush/water interface.
    • fig. S18. Water density and ice-like water density of PMETA-F, PMETA-Cl, and PMETA-I brushes.
    • table S1. The fraction of ice-like water molecules (tetrahedrality above 0.9), the ice-like water making rate constant k, and the concentration of ice-like water at the brush/water interface with the same concentration of counterion (0.25 M).
    • Experiment details
    • MD simulation details
    • References (52–58)

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