SUPPORTING INFORMATION Fabricating nanometer-thick ...
SUPPORTING INFORMATION Fabricating nanometer-thick simultaneously oleophobic/hydrophilic polymer coatings via a photochemical approach Yongjin Wang, Michael Dugan, Brian Urbaniak and Lei Li* Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA *: Corresponding author. Email: [email protected]
Table S1. Contact angles on the Z-03/Silica Non-treated 10 min-UV treated Hexadecane 22.7 ± 0.8 66.3 ± 0.1 Dodecane 10.3 ± 1.1 59.2 ± 0.8 Hexane 0 48.9 ± 1.1 Water 38.6 ± 0.8 0
Figure S1 HCA change with time on Z-03/Silica wafer without UV treatment and with 10 minutes’ UV treatment
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Our CA, ellipsometry and XPS results suggested that UV irradiation created covalent bonding between Z-03 and the substrate and therefore results in a more ordered packing structure of polymer segments on the silica substrate, leading to smaller inter-chain distance within the polymer network. As a result, water molecules can penetrate the PFPE nanofilm quickly while hexadecane molecules penetrate it very slowly, i.e., the simultaneous oleophobic/hydrophilic is observed. If the hypothesis is true, it is expected that the HCA will decrease with time for the same drop of hexadecane deposited on the UV-treated Z-03/Silica sample while HCA will stay the same for the non-treated Z03/Silica samples. Indeed, as shown in Figure S1, HCA didn’t change with time up to 400 minutes for non-treated Z-03/Silica while HCA decreased from 68.2˚ to 34.8˚ during the same time period for UV-treated sample. Since hexadecane doesn’t evaporate during the experiment,
[3,4]
the decrease of HCA is attributed to the penetration of hexadecane
through UV-treated Z-03 nanofilms, as described in our hypothesis.
Fig. S2 Contact angles on 10 min UV-treated Z-03/Silica (different drops on the different locations w/ time) 2
As shown in Figure S2, WCA of UV-treated Z-03/silica increases gradually with the aging time in the ambient air. This is line with the previous reports on the effect of the airborne hydrocarbon contamination on the water wettability1,2. Meanwhile, HCA showed little change with the aging time. This can be contributed to the fact that hydrocarbon contaminants should be deposited on the regions with high surface energy, which are the silica not covered by the PFPEs while hexadecane cannot penetrate the PFPE layers due to its larger molecular size. As a result, hexadecane can only see the PFPEs on top; but not the hydrocarbon contaminants at the “bottom”. Another significant finding from Figure S2 is that, even after long-term aging, the UV-treated Z-03/silica is still simultaneously oleophobic/hydrophilic.
Fig. S3 AFM topography images of silica, Z-03/silica and 10-min UV Z-03/silica
As shown in Figure S3, the AFM topography images show that silica, Z-03/Silica and 10min UV-treated Z-03/silica samples are all very smooth and exhibit very similar topography features.
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References: (1) Vig, J. R. "UV/ozone cleaning of surfaces" Journal of Vacuum Science & Technology A 1985, 3, 1027-1034. (2) Li, Z.; Wang, Y.; Kozbial, A.; Shenoy, G.; Zhou, F.; McGinley, R.; Ireland, P.; Morganstein, B.; Kunkel, A.; Surwade, S. P. "Effect of airborne contaminants on the wettability of supported graphene and graphite" Nature materials 2013, 12, 925-931.
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Table S1. Contact angles on the Z-03/Silica Non-treated 10 min-UV treated Hexadecane 22.7 ± 0.8 66.3 ± 0.1 Dodecane 10.3 ± 1.1 59.2 ± 0.8 Hexane 0 48.9 ± 1.1 Water 38.6 ± 0.8 0
Figure S1 HCA change with time on Z-03/Silica wafer without UV treatment and with 10 minutes’ UV treatment
1
Our CA, ellipsometry and XPS results suggested that UV irradiation created covalent bonding between Z-03 and the substrate and therefore results in a more ordered packing structure of polymer segments on the silica substrate, leading to smaller inter-chain distance within the polymer network. As a result, water molecules can penetrate the PFPE nanofilm quickly while hexadecane molecules penetrate it very slowly, i.e., the simultaneous oleophobic/hydrophilic is observed. If the hypothesis is true, it is expected that the HCA will decrease with time for the same drop of hexadecane deposited on the UV-treated Z-03/Silica sample while HCA will stay the same for the non-treated Z03/Silica samples. Indeed, as shown in Figure S1, HCA didn’t change with time up to 400 minutes for non-treated Z-03/Silica while HCA decreased from 68.2˚ to 34.8˚ during the same time period for UV-treated sample. Since hexadecane doesn’t evaporate during the experiment,
[3,4]
the decrease of HCA is attributed to the penetration of hexadecane
through UV-treated Z-03 nanofilms, as described in our hypothesis.
Fig. S2 Contact angles on 10 min UV-treated Z-03/Silica (different drops on the different locations w/ time) 2
As shown in Figure S2, WCA of UV-treated Z-03/silica increases gradually with the aging time in the ambient air. This is line with the previous reports on the effect of the airborne hydrocarbon contamination on the water wettability1,2. Meanwhile, HCA showed little change with the aging time. This can be contributed to the fact that hydrocarbon contaminants should be deposited on the regions with high surface energy, which are the silica not covered by the PFPEs while hexadecane cannot penetrate the PFPE layers due to its larger molecular size. As a result, hexadecane can only see the PFPEs on top; but not the hydrocarbon contaminants at the “bottom”. Another significant finding from Figure S2 is that, even after long-term aging, the UV-treated Z-03/silica is still simultaneously oleophobic/hydrophilic.
Fig. S3 AFM topography images of silica, Z-03/silica and 10-min UV Z-03/silica
As shown in Figure S3, the AFM topography images show that silica, Z-03/Silica and 10min UV-treated Z-03/silica samples are all very smooth and exhibit very similar topography features.
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References: (1) Vig, J. R. "UV/ozone cleaning of surfaces" Journal of Vacuum Science & Technology A 1985, 3, 1027-1034. (2) Li, Z.; Wang, Y.; Kozbial, A.; Shenoy, G.; Zhou, F.; McGinley, R.; Ireland, P.; Morganstein, B.; Kunkel, A.; Surwade, S. P. "Effect of airborne contaminants on the wettability of supported graphene and graphite" Nature materials 2013, 12, 925-931.
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