Research ArticleChemistry

Heterogeneous ice nucleation correlates with bulk-like interfacial water

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Science Advances  12 Apr 2019:
Vol. 5, no. 4, eaat9825
DOI: 10.1126/sciadv.aat9825
  • Fig. 1 PVA films with various hydroxyl densities.

    (A and B) Schematic illustration shows that the density of hydroxyl groups of the PVA film decreases and crosslinking between PVA chains occurs during the thermal annealing at 150°C. (C) XPS spectra of PVA films (recorded in ultrahigh vacuum) in the O1s region as a function of annealing time reveal a gradual reduction in the O1s signal. (D) The ratio of the C1s to the O1s of XPS signals of the PVA films as a function of annealing time shows the decrease of the density of hydroxyl groups as the annealing time increases from 1 to 120 min (the line is to guide the eye).

  • Fig. 2 Ice nucleation activity of PVA films with various hydroxyl densities.

    (A) In situ polarized optical microscopic observation of water droplet (2.0 μl) freezing on PVA surfaces annealed for 1 min (upper row) and 60 min (bottom row) at a cooling rate of 2.0°C/min. The letters “W” and “I” represent water and ice, respectively. Scale bar, 200 μm. (B) HIN temperature (TH) of more than 200 individual freezing events on PVA surfaces annealed for 1 and 60 min. Each data point corresponds to one individual measurement of TH. (C) TH of water droplets on different annealed PVA surfaces and influence of the cooling rate on TH (inset). Each data point of TH is the mean of more than 200 independent freezing events. (D) Freezing delay time (tD) of water droplets on PVA surfaces annealed for 1, 30, and 60 min under different supercoolings.

  • Fig. 3 Phase change behaviors of different sub-ensembles of interfacial water molecules.

    (A) DSC of freezing water molecules inside PVA films with different annealing times (thickness of film, ~500 μm). (B) The freezing temperature of bulk-like water with different annealing times was measured from the onset points of the DSC peaks. (C) DSC of melting of water molecules inside PVA films of various annealing times. (D) The relative fraction of the bulk-like water (fb) among freezable waters was calculated on the basis of the enthalpies released upon the melting of bound water and bulk-like water from DSC.

  • Fig. 4 The mobility of different sub-ensembles of interfacial water molecules.

    (A) T2 decay curves of water fitted by a biexponential function for the PVA films annealed for 1, 30, and 60 min at 20°C; the inset shows the decay curve of bulk water fitted by one exponential function at 20°C. (B) Dependence of T2,a and T2,b on the annealing times at 20°C. (C) Plots of T2,b against the temperature for the PVA films annealed for 1, 30, and 60 min. (D) Plots of lnτc,b against 1000/T for the PVA films annealed for 1, 30, and 60 min.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/4/eaat9825/DC1

    Fig. S1. C1s regions of XPS data for different polymeric monomer structures.

    Fig. S2. The C:O ratios detected by XPS on the surface and in the bulk of PVA film.

    Fig. S3. The contact angle of samples annealed for different times at room temperature.

    Fig. S4. The contact angle of samples annealed for different times at −20°C.

    Fig. S5. The surface morphology of PVA films detected by AFM.

    Fig. S6. The surface morphology of PVA films detected by AFM in aqueous solution.

    Fig. S7. The Brunauer-Emmett-Teller results of PVA film annealed for 1, 30, and 60 min.

    Fig. S8. Data of the changes of frequency (ΔF) and dissipation (ΔD) of PVA samples with annealing times detected by QCM-D.

    Fig. S9. The average surface roughness (Ra) of PVA films with different annealing times.

    Fig. S10. Thickness of PVA films with different annealing times.

    Fig. S11. The degree of crystallinity of PVA ultrathin films.

    Fig. S12. Freezing process of individual water droplet on PVA surfaces.

    Fig. S13. AFM images of samples annealed for 0, 1, and 5 min before and after droplet freezing experiments.

    Fig. S14. TH of water droplets on PVA samples with different cooling rate.

    Fig. S15. TH of water droplets on PVA samples with different thicknesses and molecular weights.

    Fig. S16. TH of water droplets on PVA samples with different degrees of hydrolysis.

    Fig. S17. TH of water droplets on PVA before and after peeling off the top surface.

    Fig. S18. The equilibrium water content of PVA with different thermal histories.

    Fig. S19. FTIR investigation of water molecules inside the PVA films.

    Fig. S20. DSC melting curve of pure water.

    Fig. S21. Fitting results with a biexponential function.

    Fig. S22. The plot of lnEt versus t based on the single exponential function.

    Table S1. Data from DSC.

    References (5255)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. C1s regions of XPS data for different polymeric monomer structures.
    • Fig. S2. The C:O ratios detected by XPS on the surface and in the bulk of PVA film.
    • Fig. S3. The contact angle of samples annealed for different times at room temperature.
    • Fig. S4. The contact angle of samples annealed for different times at −20°C.
    • Fig. S5. The surface morphology of PVA films detected by AFM.
    • Fig. S6. The surface morphology of PVA films detected by AFM in aqueous solution.
    • Fig. S7. The Brunauer-Emmett-Teller results of PVA film annealed for 1, 30, and 60 min.
    • Fig. S8. Data of the changes of frequency (ΔF) and dissipation (ΔD) of PVA samples with annealing times detected by QCM-D.
    • Fig. S9. The average surface roughness (Ra) of PVA films with different annealing times.
    • Fig. S10. Thickness of PVA films with different annealing times.
    • Fig. S11. The degree of crystallinity of PVA ultrathin films.
    • Fig. S12. Freezing process of individual water droplet on PVA surfaces.
    • Fig. S13. AFM images of samples annealed for 0, 1, and 5 min before and after droplet freezing experiments.
    • Fig. S14. TH of water droplets on PVA samples with different cooling rate.
    • Fig. S15. TH of water droplets on PVA samples with different thicknesses and molecular weights.
    • Fig. S16. TH of water droplets on PVA samples with different degrees of hydrolysis.
    • Fig. S17. TH of water droplets on PVA before and after peeling off the top surface.
    • Fig. S18. The equilibrium water content of PVA with different thermal histories.
    • Fig. S19. FTIR investigation of water molecules inside the PVA films.
    • Fig. S20. DSC melting curve of pure water.
    • Fig. S21. Fitting results with a biexponential function.
    • Fig. S22. The plot of lnEt versus t based on the single exponential function.
    • Table S1. Data from DSC.
    • References (5255)

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