Development of “Liquid-like” Copolymer Nanocoatings for Reactive Oil-Repellent Surface Peng Liu,† Hengdi Zhang,† Wenqing He,† Hualin Li,† Jieke Jiang,† Meijin Liu,† Hongyan Sun,‡ Mingliang He,† Jiaxi Cui,§ Lei Jiang,∥ and Xi Yao*,† †
Department of Biomedical Sciences and ‡Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong § INM−Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany ∥ Key Laboratory of Bio-inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, Beihang University, Beijing 100191, People’s Republic of China S Supporting Information *
ABSTRACT: Here, we describe a simple method to prepare oil-repellent surfaces with inherent reactivity. Liquid-like copolymers with pendant reactive groups are covalently immobilized onto substrates via a sequential layer-by-layer method. The stable and transparent nanocoatings showed oil repellency to a broad range of organic liquids even in the presence of reactive sites. Functional molecules could be covalently immobilized onto the oil-repellent surfaces. Moreover, the liquid repellency can be maintained or finely tailored after post-chemical modification via synergically tailoring the film thickness, selection of capping molecules, and labeling degree of the capping molecules. Oil-repellent surfaces that are capable of post-functionalization would have technical implications in surface coatings, membrane separation, and biomedical and analytical technologies. KEYWORDS: oil repellency, interface, liquid-like surfaces, nanocoatings, polymer brush, surface chemistry
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liquid-repellent surface, homogeneous surface chemistry is usually required by the porous or textured substrates for lubricant immobilization because the change of surface chemistry may cause irreversible replacement of the overcoated lubricant.16,17 Actually, it has been rarely achieved on the development of oil-repellent surfaces from molecules with polar and reactive moieties. Therefore, it remains a challenge to design a strategy on the reactive oil-repellent surfaces with the capability of post-chemical modification. Directly grafting or tethering a layer of liquid-like, lowsurface-energy oligomer or polymer on a flat substrate represents another way to improve sliding behavior of oils and thus to obtain oil repellency.18−22 A key characteristic of the “liquid-like” coating is the high mobility of the tethered polymers, which transfers the solid−liquid interface to the liquid−liquid one with reduced hysteresis such that the impinging liquids can dewet and slip readily.18,20 For example,
iquid-repellent surfaces that repel low-surface-energy liquids have broad applications1,2 in self-cleaning,3,4 antifouling,5−7 anti-smudge,8,9 anti-icing,10,11 and oil− water separation.12 One challenge in designing liquid-repellent materials for their applications lies in developing methods that allow appropriate combination of multifunctionality in the material for further integration into sophisticated devices and processes. Post-modification methods are therefore very important to improve or modify physicochemical properties of liquid-repellent materials after fabrication. However, most asprepared liquid-repellent coatings are nonreactive and thus incapable of post-chemical modification or functionalization because the priorities of the coating molecules are offered to those low-surface-energy molecules with chemical inertness or resistance to further functionalization, for example, fluorinated alkanes. Reactive moieties have been integrated into superhydrophobic coatings to obtain both water repellency and chemical reactivity for post-functionalization.13,14 However, such design strategy is not applicable to the superoleophobic surfaces which are more sensitive to the change of surface chemistry and molecular polarity.12,15 Meanwhile, for the liquid-infused slippery surfaces, which are another type of © 2017 American Chemical Society
Received: January 4, 2017 Accepted: February 13, 2017 Published: February 13, 2017 2248
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Figure 1. (a) Schematic diagram showing the structures of the reactive oil-repellent surface used in this study. (b) Scheme of fabricating the reactive oil-repellent surface.
Figure 2. AFM images and cross-section analysis of the silicon wafer coated with two-cycle copolymer layers (a) and 10-cycle copolymer layers (b) after scratching with a scalpel (scale bar = 2 μm). (c) Ellipsometric thicknesses of PDMS film as a function of the number of layer cycles. (d) Variation of CAH of 10 μL n-hexadecane on reactive oil-repellent surfaces with different layer cycles and PDMS molecular weight.
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Figure 3. Reactive oil-repellent surfaces show oleophobicity to various liquids. (a,b) CAH of various liquids on silicon wafers coated with twocycle copolymer layers. (c,d) Images showing the wetting and sliding of 10 μL of acetone and n-hexadecane on noncoated and coated surfaces: the droplet would pin and spread on the untreated substrate (top) but slip readily on the copolymer-coated substrate. The droplet of acetone rapidly evaporated due to liquid spreading out on the uncoated surfaces. (e,f) Stability tests of the reactive oil-repellent surfaces. Variation of the contact angle of the n-hexadecane (θAdv (blue), θRec (red), and CAH (green)) on the reactive oil-repellent surfaces sustained in 100 °C in an oven (e) and exposed to UV light (f).
sequence to obtain polymer brushes (Figure 1b). Here, both the IPDI and H2N-PDMS-NH2 are raw materials widely used in industry, and the highly efficient reaction between amino and isocyanate groups at room temperature facilitates rapid and readily available modification of the targeting substrate with the copolymer brushes with tunable chain lengths.24 Through the sequential immobilization of copolymers, we expect to obtain surfaces with well-controlled oil repellency, reactivity, and capability for functionalization. The reactive oil-repellent surfaces were demonstrated on amino-functionalized flat substrates such as silicon wafers and glass slides (Figure S1). The change of surface chemistry was analyzed by fluorescent labeling, X-ray photoelectron spectroscopy (XPS), and contact angle measurement (Figures S2−S4). The coated surfaces are smooth with a low roughness (rq ≈ 0.81 nm, Figure S5). The thickness of the copolymer film was measured by ellipsometry and was confirmed by atomic force microscopy (AFM). Basically, the thickness of the polymer brush layers can be tuned from a few nanometers to tens of nanometers when multiple grafting cycles are applied (Figure 2a−c). Since the length of PDMS backbones would influence the surface energy of the grafted polymers,25 we studied the effect of both the proportion of PDMS units and the length of the grafted copolymers on the coating’s wettability. The proportion of PDMS units in the copolymer was controlled by coherently tuning the molecular weight of H2N-PDMS-NH2 while the length of the grafted copolymers was tuned by the number of grafting cycles. As indicated in Figure 2d and Figure
covalently grafted polydimethylsiloxane (PDMS) and perfluoropolyether (PFPE) brushes have been considered as “liquidlike” coatings to create oil-repellent surfaces because their polymer chains are in a highly mobile state at room temperature due to the extremely low glass transition temperature. Particularly, the surface-tethered PDMS polymers have been considered as an ideal candidate for surface coatings due to the relatively low cost, excellent optical and mechanical properties, and biocompatibility. The flexible PDMS chains exhibit a “liquid-like” behavior that allows oil drops to slide easily even though the probe liquids have surface energies lower than those of free PDMS oils.23 Since PDMS backbones have been frequently integrated into various copolymers for versatile applications and there are numerous commercially available PDMS oligomers with functional or reactive chemical groups, it is promising to tailor the grafting chemistry of PDMS copolymers to elucidate oil repellency with the capability of post-functionalization.
RESULTS AND DISCUSSION Herein, we report a strategy of preparing reactive oil-repellent surfaces via surface-tethered “liquid-like” PDMS-based copolymer thin films with pendant reactive moieties and demonstrate their easy-sliding behavior for common organic solvents and inherent chemical reactivity for immobilization of functional molecules (Figure 1a). Briefly, the substrates were treated with isophorone diisocyanate (IPDI) and aminopropyl-terminated polydimethylsiloxane (H2N-PDMS-NH2) in an alternating 2250
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Figure 4. Oil-sliding behavior on copolymer-coated surfaces with different molecular configurations. Top: Schematics showing the molecular configurations of four types of copolymer coatings. Bottom: Time-sequence images of 10 μL toluene drops sliding on corresponding copolymer coatings. (a) Two-cycle PDMS copolymer brushes. (b) Two-cycle cross-linked PDMS copolymer coating. (c) Two-cycle alkyl copolymer brushes. (d) Two-cycle alkyl copolymer brushes plus two additional cycles of PDMS copolymer brushes.
the amino group in the copolymer may increase the affinity of water to the copolymer coating and thus increase the CAH. Second, the PDMS backbone is insoluble to water and would be in a condensed state when it contacts water, which would also suppress the water sliding property.20 Although the use of PDMS polymer for “liquid-like” coating has been long suggested,20 their mechanism remains elusive. Here, we designed a couple of copolymer coatings with different molecular configurations to elucidate the mechanism of the “liquid-like” coating. In addition to the PDMS copolymers prepared from bifunctionalized H2N-PDMS-NH2, a comb-like PDMS oligomer (PDMS-(NH2)x) with multiple side-chain amino groups and a bifunctionalized alkyldiamine26 (H2N-R-NH2) were used as monomers to prepare copolymer coatings through sequential grafting with IPDI. We envision that the cross-linked structure in IPDI/PDMS-(NH2)x can significantly suppress the mobility of the PDMS segments and thus hinder the “liquid-like” property of the copolymer coating, while the alkyl copolymer brushes IPDI/H2N-R-NH2 would not exhibit the “liquid-like” property as it is in the PDMS copolymers. Actually, all of the coated surfaces were hydrophobic with high water CAs (Figure S10), and they indeed showed distinct sliding properties to oils. As shown in Figure 4a, the IPDI/H2N-PDMS-NH2 coating shows excellent oil repellency with CAH ∼ 1°, on which a 10 μL toluene drop could slide off the tilted surface within seconds. On the crosslinked coating of IPDI/PDMS-(NH2)x, the toluene drop could slide but moved much slower at the same tilted angle, and the measured CAH increased to ∼4° (Figure 4b). On alkyl polymer brushes of IPDI/H2N-R-NH2, the toluene drop spreads and leaves a wetting footprint (Figure 4c). After two
S6, one layer of IPDI/H2N-PDMS-NH2 is sufficient to make the modified silicon substrates oil-repellentcontact angle hysteresis (CAH) to hexadecane is less than 5°when the H2N-PDMS-NH2 oligomer with molecular weights (MW) of either ∼3000 or ∼5000 is applied. When the short-chain H2NPDMS-NH2 oligomer (MW 850−900) is used, more grafting cycles are needed to obtain oil repellency. Overall, the copolymers showed low CAH to hexadecane when a longer PDMS chain or a higher overall portion of PDMS units was integrated into the copolymers. To be consistent, the H2NPDMS-NH2 oligomers with MW 3000 were used in all of the following studies, and all of the tested copolymer coatings were prepared by grafting two cycles of IPDI/H2N-PDMS-NH2 unless specifically mentioned. The low CAH and oil-repellent properties are applicable to a broad range of polar or nonpolar organic liquids such as ethanol, tetrahydrofuran (THF), hexane, and toluene (Figure 3a−d and Figure S7). The impinging organic liquids showed improved dewetting behavior where the drops slid readily without pinning (Figure 3c,d). Moreover, the covalently immobilized copolymer coatings showed excellent stability. The low CAH was maintained for 30 days upon continuous heat treatment and UV irradiation (365 nm, 5 mW/cm2) (Figure 3e,f and Figure S8). Interestingly, when the copolymer coatings exhibited low CAH to a few polar organic liquids, its CAH to water was relatively high (θAdv/θRec = 106°/65°, Figure S9). However, in a water evaporation test, a water droplet could evaporate smoothly without pinning, which indeed indicated the water repellency of the copolymer coatings (Figure S9). There might be two reasons for the high CAH to water. First, the strong hydrogen bonding between the water molecule and 2251
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Figure 5. Demonstration on the post-functionalization and the tunability of the reactive oil-repellent surface. (a) Schematics showing liquid repellency tuned by changing the labeling density of FITC on the IPDI/H2N-PDMS-NH2 copolymers. (b) By regulating the proportion of the PDMS backbone, the polarity of copolymer and surface energy can be tuned. (c) CAH of the substrates reacted in solutions of different FITC concentrations. Multiple organic liquids were selected as probes. (d) CAH of the FITC-labeled substrates (in 10−5 M solution) could be improved by grafting more cycles, which the longer PDMS could hinder the effect of FITC molecule in the copolymer. (e) Images showing the retention of microdroplets on a FITC-patterned surface (three-cycle copolymer coating) during the sliding of an ethanol droplet. (f) Formation of an array of dyed ethanol droplets on a patterned glass slide. (g) Sliding of a 10 μL pyrene-dyed dioxane droplet on the patterned surface with the same treatment in e and f. Fluorescent images showed that no apparent retention of the dyed droplet was observed at the patterned area which was of 10 × 10 FITC-labeled microdots (scale bar = 1 mm). The fluorescent images were compared at the FITC channel (left) and the pyrene channel (right). The dyed dioxane droplet was overexposed in each channel and presented in pseudo green and blue colors, respectively.
The capability to finely tailor or modify physicochemical properties of liquid-repellent coatings after fabrication would facilitate their technical applications. In our copolymer coatings, the pendant amino groups provide potential reactive sites for chemical modification and functionalization. Meanwhile, the oil repellency of post-functionalized surfaces could be improved or controlled by coherently tuning the copolymer chain and the
additional cycles of IPDI/H2N-PDMS-NH2 were grafted on the same alkyl polymer brushes, the “liquid-like” interface was restored (Figure 4d), and the CAH was reduced to ∼1° again. Our results highlighted that the free copolymer brushes with a PDMS backbone are favorable for an oil-repellent “liquid-like” surface. 2252
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Figure 6. (a) Optical transmittance of an untreated glass slide and a slide with two-cycle copolymer coating in the UV/vis range. (b) Images showing the mobility of a dyed chloroform droplet on treated and untreated regions of a glass display. (c) Ink-resistant test by an oil-based permanent ink marker on treated and untreated glass slides. (d) Schematics showing the reaction of oil-repellent surfaces with two different functional groups. (e,f) Corresponding fluorescence images of micropatterns on reactive oil-repellent surfaces (microdots, scale bar = 200 μm; microstripes, scale bar = 100 μm).
labeling of FITC molecules. For example, on the substrate with two-cycle copolymer grafting followed by FITC modification in 10−5 M solution, the probe liquids such as ethanol and THF that could slip readily on the unlabeled surface would spread and wet the FITC-labeled surface, indicating the loss of oil repellency. The CAH also increased for a few more solvents such as ethyl acetate, dioxane, and toluene. These results could be ascribed to the affinity of solvent molecules to the FITC moieties. The CAHs of testing liquids were reduced accordingly on the surfaces with lower FITC labeling densities obtained from lower FITC concentrations. Moreover, the FITC-labeled substrate still exhibited unchanged oil-repellent properties to a few solvents including chloroform, dichloromethane, and ethyl ether, all of which are good solvents to PDMS but poor solvents to FITC molecules.28 These solvents might induce an environment preferentially for the PDMS backbones and hinder the FITC moieties at the interface, resulting in enhanced “liquid-like” property of the copolymer coating and easy-sliding behavior for contacting liquids. As we addressed previously, the oil-repellent properties of the copolymer surface could be improved by increasing the grafting cycles of IPDI/H2N-PDMS-NH2 (Figure 5b). This feature might be applied to maintain oil repellency after the post-chemical modification. As shown in Figure 5d, ethanol showed reduced CAH on the surface with three-cycle grafting layers followed by FITC labeling in 10−5 M solution. All of the tested liquids showed improved dewetting and sliding behavior when the grafting cycle is more than 4, which means the surface oil repellency could be maintained after post-modification. Therefore, the liquid repellency might be finely tuned on our
capping molecules. We demonstrated the reactivity and the capability of post-modification on the as-prepared oil-repellent surfaces via the employment of a reactive fluorescent probe, fluorescein isothiocyanate (FITC). Here, FITC was chosen as the labeling molecule for several reasons. First, the isothiocyanate group can react with the pendant amino group under mild conditions. Second, the fluorescent signal of FITC can help illustrate the labeling of amino groups (reactive sites) on the copolymers. Third, compared to the amino group, FITC has a larger molecular structure with more polar moieties, which would change its affinity to organic solvents and thus effectively change the surface wettability after labeling.27 Therefore, the immobilization of FITC on the reactive copolymers could not only serve as evidence for the capability of chemical modification of the copolymers but also allow us to study the reliability of the oil repellency after the chemical modification (Figure 5a,b). Briefly, the silicon substrates with two-cycle copolymer coatings were immersed in FITC solutions of various concentrations from 10−5 to 10−9 M for controlling the labeling density. More FITC molecules are immobilized on the copolymers with the increase of the solution concentration in the proposed concentration range (Figure S11). As a comparison, rhodamine 6G (R6G) was selected as a control that cannot react with the amino group on the copolymer, and no apparent fluorescence was observed after immersing the substrate in R6G solution with the same condition (10−5 M) (Figure S12). We subsequently studied the oil repellency of the copolymer surface after the postimmobilization of FITC molecules. As shown in Figure 5c, the CAH significantly changes on the surfaces with high density 2253
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nate (FITC), rhodamine 6G (R6G), 7-(diethylamino)coumarin-3carboxylic acid N-succinimidyl ester, sulforhodamine B acid chloride, 3-aminopropyltriethoxysilane (APTES), and poly[dimethylsiloxane-co(3-aminopropyl)methylsiloxane] (eq wt. 4400 amine) were purchased from Sigma-Aldrich. Dimer diamines (Priamine 1074) were purchased from CRODA Coatings & Polymers. Preparation of Initial Amino-Functionalized Surfaces. Substrates were cut into a 1.5 cm × 3 cm slide and cleaned by O2 plasma for 20 min followed by immersion in a piranha cleaning solution for 1 h at 90 °C and then rinsed in deionized water and dried with compressed air. The slides were placed in individual vials. A 1% (v/v) APTES solution of anhydrous toluene was added to each sealed vial.30 The coating process was held at a temperature of 70 °C for 1 h. The wafers were then rinsed individually with excess toluene and ethanol, followed by sonication in toluene and ethanol for 10 min. Preparation of a Reactive Oil-Repellent Surface. IPDI toluene solution (0.5 mg/mL) and H2N-PDMS-NH2 THF solutions (1 mg/ mL) were used for copolymer grafting. The amino-functionalized substrates were first dipped in IPDI solution for 30 min at room temperature, rinsed in anhydrous toluene, and washed rapidly. The silicon wafer terminated with an isocyanate group was then dipped in the H2N-PDMS-NH2 solution for another 30 min at room temperature, rinsed in excess pure THF and toluene, and then dried by compressed air. Next, the surface covalent isocyanate/amine layer was counted as one layer cycle. The preparation of cross-linked PDMS and alkyl copolymer-coated surfaces was similar to that described above. IPDI toluene solution (0.5 mg/mL) and poly[dimethylsiloxaneco-(3-aminopropyl)methylsiloxane] THF solutions (1 mg/mL) or dimer diamine THF solutions (1 mg/mL) were used for copolymer grafting. FITC Immobilization and Chemical Micropatterning on the Reactive Oil-Repellent Surface. The reactive oil-repellent surfaces were immersed in FITC acetone solutions for 10 min. FITC-patterned surfaces were carried out by dotting FITC solution (10−5 mol/L) onto the reactive oil-repellent surfaces (two-cycle copolymer layers) with Biodot spotter (AD3200, XYZ3210 Dispense Platform) via the contact model. Microdots were applied by directly dropping a 1 μL droplet of 7-(diethylamino)coumarin-3-carboxylic acid N-succinimidyl ester (10−6 mol/L, in chloroform with 1% TEA by volume) or sulforhodamine B acid chloride (10−6 mol/L, in chloroform with 1% TEA by volume) onto the reactive oil-repellent surface. Microcontact printing on the reactive oil-repellent surface was achieved via the PDMS stamp that was wetted with “ink” of 7-(diethylamino)coumarin-3-carboxylic acid N-succinimidyl ester (10−3 mol/L, in chloroform with 1% TEA by volume) or sulforhodamine B acid chloride (10−6 mol/L, in chloroform with 1% TEA by volume). After 10 min of contact, the stamps were removed from the surface. All of the modified substrates were washed with excess ethanol and THF, followed by sonication in ethanol, THF, or chloroform for 2 min. Characterization. Contact angle and contact angle hysteresis measurements were carried out with OCA20 equipment (Data Physics, Germany) under ambient conditions. To measure the contact angle hysteresis, the surface was tilted with respect to the horizontal plane until the liquid droplet started to slide along the surface. Then advancing (θAdv) and receding (θRec) contact angles were measured by a single 10 μL droplet of liquid with tilt angles less than 10°.31−33 AFM data were collected on Bruker Dimension Icon. XPS was performed with a scanning auger XPS PHI5802. The fluorescence images were captured by a Nikon Eclipse Ni-E upright fluorescence microscope. Optical transparency was characterized using a UV−visible light spectrophotometer (Shimadzu 1700) with a wavelength ranging from 300 to 800 nm. The optical images were obtained on a tilted glass platform with a Nikon D5500. The brightness and contrast of optical images were enhanced for clarity. Measurements of PDMS film thickness were carried out with a J.A. Woollam α-SE laser spectroscopic ellipsometer at a 70° incident angle and a He−Ne laser light source (λ = 632.8 nm). Thickness was calculated using a Cauchy model. The thickness of the SiO2 of a piranha-cleaned silicon surface was measured and used as the baseline layer. The refractive index of all films was assumed to be constant at n = 1.46. Each
copolymer coatings. For example, a surface (three-cycle copolymer coating) with patterned wettability could be prepared, in which the patterned area could be wetted by one organic liquid but show repellency to another organic liquid. As shown in Figure 5e,f, microdroplets could be retained on the patterned area with FITC labeling when ethanol slides and is dewetted on the coated surface. Whereas in Figure 5f we showed that the pyrene-dyed dioxane drop would not remain in the area with the same treatment, there is no visible pinning or fluorescent signal of dioxane (blue) on the patterned area (green). This is because the FITC labeling has a stronger influence on the CAH of ethanol than on dioxane. Based on all of the evidence that we have, we anticipated that we could be able to finely control the sliding behavior of oils by coherently tuning the grafting copolymers, capping molecules, and labeling degree of the capping molecules. Such tunability is different from the current technologies of both superoleophobic surfaces and the liquid-infused slippery surfaces which have strict requirements on the surface chemistry and limited tunability of oil repellency. Our copolymers are also transparent, and they can be used as an anti-smudge coating on glass windows of cell phones and other displays (Figure 6a,b). As shown in Figure 6c, the coating of two-cycle copolymers can be sufficient to pass an inkresistant test. Written lines made by an oil-based permanent marker can be readily removed from the coated area by fresh tissue, whereas they will be left on the uncoated area as effectively “permanent”. In addition to FITC, surface labeling of two other dyes with different conjugating groups was also demonstrated (Figure 6d−f). Even more functional molecules can be applied on the copolymer coatings as capping molecules through versatile conjugating chemistry,29 which would largely broaden the tunability and application of our system.
CONCLUSIONS In summary, by sequentially grafting PDMS oligomer and IPDI molecules on the flat substrate, we have produced oil-repellent copolymer nanocoatings with pendent reactive moieties. The copolymer coatings showed tunable oil-repellent property and low CAH to a range of polar or nonpolar organic liquids. We revealed that the mobile “liquid-like” PDMS chains in the copolymer played a key role in the oil-repellent property. The terminal reactive moieties on the copolymers ensure intrinsic capability of post-chemical modification. In addition, we showed that the oil repellency of the copolymer coatings could be tuned or maintained after chemical modification via tuning the overall portion of the PDMS units in the copolymers as well as the chemistry of the capping molecules. The raw materials used in this work are all industrial level, and our system is compatible with large-scale manufacturing due to the simplicity of the coating design. Considering the convenient preparation method on the oil-repellent copolymers and the ease of chemical conjugation on the reactive moieties of the copolymer, our reactive oil-repellent surfaces hold great potential for a broad range of applications in material fabrication, chemical and environmental analysis, and biomedical diagnosis such as nanoparticle preparation, detection of trace amount of molecules and ions, and so on. METHODS Materials. Aminopropyl-terminated polydimethylsiloxane (H2NPDMS-NH2) was purchased from Gelest, Inc. Isophorone diisocyanate (IPDI), triethylamine (TEA), pyrene (98%), fluorescein isothiocya2254
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Devices Prevents Thrombosis and Biofouling. Nat. Biotechnol. 2014, 32, 1134−1140. (7) Manna, U.; Raman, N.; Welsh, M. A.; Zayas-Gonzalez, Y. M.; Blackwell, H. E.; Palecek, S. P.; Lynn, D. M. Slippery Liquid-Infused Porous Surfaces That Prevent Microbial Surface Fouling and Kill NonAdherent Pathogens in Surrounding Media: A Controlled Release Approach. Adv. Funct. Mater. 2016, 26, 3599−3611. (8) Rabnawaz, M.; Liu, G. Graft-Copolymer-Based Approach to Clear, Durable, and Anti-Smudge Polyurethane Coatings. Angew. Chem., Int. Ed. 2015, 54, 6516−6520. (9) Rabnawaz, M.; Liu, G.; Hu, H. Fluorine-Free Anti-Smudge Polyurethane Coatings. Angew. Chem., Int. Ed. 2015, 54, 12722− 12727. (10) Kim, P.; Wong, T. S.; Alvarenga, J.; Kreder, M. J.; AdornoMartinez, W. E.; Aizenberg, J. Liquid-Infused Nanostructured Surfaces with Extreme Anti-Ice and Anti-Frost Performance. ACS Nano 2012, 6, 6569−6577. (11) Yin, X. Y.; Zhang, Y.; Wang, D. A.; Liu, Z. L.; Liu, Y. P.; Pei, X. W.; Yu, B.; Zhou, F. Integration of Self-Lubrication and near-Infrared Photothermogenesis for Excellent Anti-Icing/Deicing Performance. Adv. Funct. Mater. 2015, 25, 4237−4245. (12) Wang, L.; Zhao, Y.; Tian, Y.; Jiang, L. A General Strategy for the Separation of Immiscible Organic Liquids by Manipulating the Surface Tensions of Nanofibrous Membranes. Angew. Chem., Int. Ed. 2015, 54, 14732−14737. (13) Manna, U.; Broderick, A. H.; Lynn, D. M. Chemical Patterning and Physical Refinement of Reactive Superhydrophobic Surfaces. Adv. Mater. 2012, 24, 4291−4295. (14) Li, J.; Li, L.; Du, X.; Feng, W.; Welle, A.; Trapp, O.; Grunze, M.; Hirtz, M.; Levkin, P. A. Reactive Superhydrophobic Surface and Its Photoinduced Disulfide-Ene and Thiol-Ene (Bio)Functionalization. Nano Lett. 2015, 15, 675−681. (15) Feng, W.; Li, L.; Du, X.; Welle, A.; Levkin, P. A. Single-Step Fabrication of High-Density Microdroplet Arrays of Low-SurfaceTension Liquids. Adv. Mater. 2016, 28, 3202−3208. (16) Wong, T. S.; Kang, S. H.; Tang, S. K.; Smythe, E. J.; Hatton, B. D.; Grinthal, A.; Aizenberg, J. Bioinspired Self-Repairing Slippery Surfaces with Pressure-Stable Omniphobicity. Nature 2011, 477, 443− 447. (17) Vogel, N.; Belisle, R. A.; Hatton, B.; Wong, T. S.; Aizenberg, J. Transparency and Damage Tolerance of Patternable Omniphobic Lubricated Surfaces Based on Inverse Colloidal Monolayers. Nat. Commun. 2013, 4, 2176. (18) Chen, W.; Fadeev, A. Y.; Hsieh, M. C.; Oner, D.; Youngblood, J.; McCarthy, T. J. Ultrahydrophobic and Ultralyophobic Surfaces: Some Comments and Examples. Langmuir 1999, 15, 3395−3399. (19) Rolland, J. P.; Van Dam, R. M.; Schorzman, D. A.; Quake, S. R.; DeSimone, J. M. Solvent-Resistant Photocurable Liquid Fluoropolymers for Microfluidic Device Fabrication. J. Am. Chem. Soc. 2004, 126, 2322−2323. (20) Cheng, D. F.; Urata, C.; Yagihashi, M.; Hozumi, A. A Statically Oleophilic but Dynamically Oleophobic Smooth Nonperfluorinated Surface. Angew. Chem., Int. Ed. 2012, 51, 2956−2959. (21) Cheng, D. F.; Masheder, B.; Urata, C.; Hozumi, A. Smooth Perfluorinated Surfaces with Different Chemical and Physical Natures: Their Unusual Dynamic Dewetting Behavior toward Polar and Nonpolar Liquids. Langmuir 2013, 29, 11322−11329. (22) Wang, L.; McCarthy, T. J. Covalently Attached Liquids: Instant Omniphobic Surfaces with Unprecedented Repellency. Angew. Chem., Int. Ed. 2016, 55, 244−248. (23) Urata, C.; Masheder, B.; Cheng, D. F.; Miranda, D. F.; Dunderdale, G. J.; Miyamae, T.; Hozumi, A. Why Can Organic Liquids Move Easily on Smooth Alkyl-Terminated Surfaces? Langmuir 2014, 30, 4049−4055. (24) Gody, G.; Roberts, D. A.; Maschmeyer, T.; Perrier, S. A New Methodology for Assessing Macromolecular Click Reactions and Its Application to Amine–Tertiary Isocyanate Coupling for Polymer Ligation. J. Am. Chem. Soc. 2016, 138, 4061−4068.
ASSOCIATED CONTENT S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsnano.7b00046. Fluorescence image of initial amino-functionalized surface, the coating efficiency rate for preparation of the reactive oil-repellent surface, XPS spectra of the reactive oil-repellent surface, contact angle variation of surface during the preparation, AFM images of the reactive oilrepellent surface, variation of advancing and receding contact angles on the reactive oil-repellent surfaces with different layer cycles and PDMS molecular weight, images for comparison of mobility of solvents, images of long-term repellency of coated surfaces, behaviors of water on reactive oil-repellent surfaces, CA and CAH of water and toluene on copolymer-coated surfaces with different molecular configurations, fluorescent intensity of the surfaces reacted with FITC solutions of different concentrations, fluorescence images of reactive oilrepellent surfaces after immersed in the solutions of R6G and FITC (PDF)
AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected]. ORCID
Lei Jiang: 0000-0003-4579-728X Xi Yao: 0000-0001-8986-3571 Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS This work was supported by the National Basic Research Development Program (Grant No. 2013CB911302), the National Natural Science Foundation of China (Grant No. 21501145), the General Research Fund (GRF) Hong Kong (Grant Nos. 21214215 and 11274616), and financial support from City University of Hong Kong (Grant Nos. 7200429 and 9610329). REFERENCES (1) Yao, X.; Song, Y.; Jiang, L. Applications of Bio-Inspired Special Wettable Surfaces. Adv. Mater. 2011, 23, 719−734. (2) Wang, S.; Liu, K.; Yao, X.; Jiang, L. Bioinspired Surfaces with Superwettability: New Insight on Theory, Design, and Applications. Chem. Rev. 2015, 115, 8230−8293. (3) Lu, Y.; Sathasivam, S.; Song, J. L.; Crick, C. R.; Carmalt, C. J.; Parkin, I. P. Robust Self-Cleaning Surfaces That Function When Exposed to Either Air or Oil. Science 2015, 347, 1132−1135. (4) Yao, X.; Wu, S.; Chen, L.; Ju, J.; Gu, Z.; Liu, M.; Wang, J.; Jiang, L. Self-Replenishable Anti-Waxing Organogel Materials. Angew. Chem., Int. Ed. 2015, 54, 8975−8979. (5) Epstein, A. K.; Wong, T. S.; Belisle, R. A.; Boggs, E. M.; Aizenberg, J. Liquid-Infused Structured Surfaces with Exceptional Anti-Biofouling Performance. Proc. Natl. Acad. Sci. U. S. A. 2012, 109, 13182−13187. (6) Leslie, D. C.; Waterhouse, A.; Berthet, J. B.; Valentin, T. M.; Watters, A. L.; Jain, A.; Kim, P.; Hatton, B. D.; Nedder, A.; Donovan, K.; et al. A Bioinspired Omniphobic Surface Coating on Medical 2255
DOI: 10.1021/acsnano.7b00046 ACS Nano 2017, 11, 2248−2256
Article
ACS Nano (25) Jalbert, C.; Koberstein, J. T.; Yilgor, I.; Gallagher, P.; Krukonis, V. Molecular Weight Dependence and End-Group Effects on the Surface Tension of Poly(Dimethylsiloxane). Macromolecules 1993, 26, 3069−3074. (26) Agnaou, R.; Capelot, M.; Tence-Girault, S.; Tournilhac, F.; Leibler, L. Supramolecular Thermoplastic with 0.5 Pa.S Melt Viscosity. J. Am. Chem. Soc. 2014, 136, 11268−11271. (27) Ulman, A. Formation and Structure of Self-Assembled Monolayers. Chem. Rev. 1996, 96, 1533−1554. (28) Lee, J. N.; Park, C.; Whitesides, G. M. Solvent Compatibility of Poly(Dimethylsiloxane)-Based Microfluidic Devices. Anal. Chem. 2003, 75, 6544−6554. (29) Biju, V. Chemical Modifications and Bioconjugate Reactions of Nanomaterials for Sensing, Imaging, Drug Delivery and Therapy. Chem. Soc. Rev. 2014, 43, 744−764. (30) Howarter, J. A.; Youngblood, J. P. Optimization of Silica Silanization by 3-Aminopropyltriethoxysilane. Langmuir 2006, 22, 11142−11147. (31) Fadeev, A. Y.; McCarthy, T. J. Trialkylsilane Monolayers Covalently Attached to Silicon Surfaces: Wettability Studies Indicating That Molecular Topography Contributes to Contact Angle Hysteresis. Langmuir 1999, 15, 3759−3766. (32) Extrand, C. W. Contact Angles and Hysteresis on Surfaces with Chemically Heterogeneous Islands. Langmuir 2003, 19, 3793−3796. (33) Cheng, D. F.; Urata, C.; Masheder, B.; Hozumi, A. A Physical Approach to Specifically Improve the Mobility of Alkane Liquid Drops. J. Am. Chem. Soc. 2012, 134, 10191−10199.
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