Research ArticleENGINEERING

Supramolecular silicone coating capable of strong substrate bonding, readily damage healing, and easy oil sliding

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Science Advances  01 Nov 2019:
Vol. 5, no. 11, eaaw5643
DOI: 10.1126/sciadv.aaw5643
  • Fig. 1 Schematic illustration of the preparation of the healable DOSS coatings.

    (A) Chemical structure of three-arm siloxane oligomer and preparation of the DOSS coating with small oil slide angles. The coatings are prepared by melting siloxane oligomer grind and then casting them onto the substrate. (B) Structure of the DOSS coating on a substrate. The PDMS domains enriched in the surface of the DOSS coating offer the properties of oil sliding and dewetting; the multiple hydrogen bonds in the interior of the DOSS coating make it healable. The strong interaction between the DOSS coating and the substrate through hydrogen bonding enables the coating to firmly adhere to various substrates.

  • Fig. 2 Molecular configuration and adhesion force analyses of DOSS coatings.

    (A) ATR-IR spectra showing the comparison intensities of featured groups in the surface layer (green line), interior section (blue line), and bottom layer (black line) of the DOSS coating adhered on a substrate. The two colored boxes indicate peaks of methyl group (light yellow) and methylene group (light blue), respectively. Dashed lines indicate peaks regarding UPy motifs in aggregated state (blue) and dissociated state (black), respectively. (B to D) AFM adhesion force images (9 μm × 9 μm) of the surface layer, interior section, and bottom layer of the DOSS coating. (E to G) Distributions of adhesion forces measured between the bare AFM tip and the surface layer, interior section, and bottom layer of the DOSS coating. The adhesion force increases sequentially from the surface layer (B and E), to the interior section (C and F), and to the bottom layer (D and G) of the DOSS coating.

  • Fig. 3 Comparison of shear strengths between DOSS coatings and reported adhesive materials/commercial glues.

    (A) The shear strength between the DOSS coating and various substrates (blue columns) and, as a comparison, the results of reported adhesive materials/commercial glues (black columns) are listed (32, 33, 4152). The shear strength reported in this work is competitive with the results of reported adhesive materials/commercial glues. (B) Schematic illustration of the strong interaction between the coating and the adhered substrate through hydrogen bonding. PTFE, polytetrafluoroethylene.

  • Fig. 4 Wettability of the DOSS coatings.

    (A) The siloxane oligomer material–based coatings with small oil slide angles can be applied to various substrates such as glass, Al, and Cu sheets, and 10-μl n-hexadecane drops can be repelled by all these coated surfaces. Credit: Meijin Liu, City University of Hong Kong. (B and C) CAH of various liquids on glass slides coated with siloxane oligomer materials. Nonpolar liquids can be repelled by the DOSS coating with a low CAH, while a couple of polar liquids can be repelled by the DOSS coating with a higher CAH. (D) Schematic illustrations of the interactions between the drops of nonpolar liquid or polar liquid and the DOSS coating, respectively. The interaction between the drop of nonpolar liquid and the DOSS coating is weak, as UPy motifs on the surface layer are shielded by the siloxane motifs, while the drop of polar liquid will strongly interact with the surface layer of the coating, particularly the dissociated UPy motifs, leading to higher CAHs.

  • Fig. 5 Morphological and oil-repellent evaluation of self-healing coatings on glass slides.

    (A) A 10-μl n-hexadecane drop slides away on the pristine DOSS coating. (B) The DOSS coating is crosscut by a blade, and the 10-μl n-hexadecane drop is blocked at the damage region. (C) The damaged DOSS coating is treated by blowing nitrogen gas for 20 s and is subsequently healed by heating at 90°C for 15 min. A 10-μl n-hexadecane drop is repelled again on the healed surfaces, implying the recovery of oil repellency. (D) Repeating test on oil repellency of the coating after being damaged/healed for multiple cycles by using n-hexadecane as a probing liquid. (E) Optical microscopy image of a damaged film. (F) Optical microscopy image of the film after healing at 90°C for 15 min. Scale bars, 5 mm (A to C) and 20 μm (E and F).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/11/eaaw5643/DC1

    Fig. S1. Mechanical properties of siloxane oligomer materials with different MWs.

    Fig. S2. Structures of siloxane oligomer materials with different MWs.

    Fig. S3. Full ATR-IR spectra of different parts in DOSS coatings.

    Fig. S4. Surface chemistry of the surface layer of DOSS coatings.

    Fig. S5. Surface chemistry of the interior section of DOSS coatings.

    Fig. S6. Surface chemistry of the bottom layer of DOSS coatings.

    Fig. S7. Morphologies of different parts in DOSS coatings.

    Fig. S8. Application of siloxane oligomer materials as adhesive materials.

    Fig. S9. Oil repellency and contact angle/CAH values of DOSS coatings with different MWs.

    Fig. S10. Surface chemistry of the surface layer of DOSS coatings with MW of ~3000.

    Fig. S11. Surface chemistry of the surface layer of DOSS coatings with MW of ~5000.

    Fig. S12. Morphologies of the surface layers in DOSS coatings with different MWs.

    Fig. S13. Stability of DOSS coatings.

    Fig. S14. Self-healing properties of the DOSS coatings (~870-MW siloxane oligomers) in different healing conditions.

    Table S1. Mechanical properties of DOSS coatings with different MWs.

    Table S2. Assignment of the feature ATR–Fourier transform infrared bands of the spectra of the surface layer, interior section, and bottom layer of DOSS coatings corresponding to Fig. 2A and fig. S3.

    Table S3. Assignment of the relative atom content of the surface layer, interior section, and bottom layer of DOSS coating (MW, 870) from the corresponding XPS spectra.

    Table S4. Assignment of the relative atom content of the surface layers of DOSS coatings with different MWs from the corresponding XPS spectra.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Mechanical properties of siloxane oligomer materials with different MWs.
    • Fig. S2. Structures of siloxane oligomer materials with different MWs.
    • Fig. S3. Full ATR-IR spectra of different parts in DOSS coatings.
    • Fig. S4. Surface chemistry of the surface layer of DOSS coatings.
    • Fig. S5. Surface chemistry of the interior section of DOSS coatings.
    • Fig. S6. Surface chemistry of the bottom layer of DOSS coatings.
    • Fig. S7. Morphologies of different parts in DOSS coatings.
    • Fig. S8. Application of siloxane oligomer materials as adhesive materials.
    • Fig. S9. Oil repellency and contact angle/CAH values of DOSS coatings with different MWs.
    • Fig. S10. Surface chemistry of the surface layer of DOSS coatings with MW of ~3000.
    • Fig. S11. Surface chemistry of the surface layer of DOSS coatings with MW of ~5000.
    • Fig. S12. Morphologies of the surface layers in DOSS coatings with different MWs.
    • Fig. S13. Stability of DOSS coatings.
    • Fig. S14. Self-healing properties of the DOSS coatings (~870-MW siloxane oligomers) in different healing conditions.
    • Table S1. Mechanical properties of DOSS coatings with different MWs.
    • Table S2. Assignment of the feature ATR–Fourier transform infrared bands of the spectra of the surface layer, interior section, and bottom layer of DOSS coatings corresponding to Fig. 2A and fig. S3.
    • Table S3. Assignment of the relative atom content of the surface layer, interior section, and bottom layer of DOSS coating (MW, 870) from the corresponding XPS spectra.
    • Table S4. Assignment of the relative atom content of the surface layers of DOSS coatings with different MWs from the corresponding XPS spectra.

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