Antifogging and Frost-Resisting Polyelectrolyte Coatings Capable of

Article pubs.acs.org/cm

Antifogging and Frost-Resisting Polyelectrolyte Coatings Capable of Healing Scratches and Restoring Transparency Yan Wang, Tianqi Li, Siheng Li, and Junqi Sun* State Key Laboratory of Supramolecular Structure and Materials, International Joint Research Laboratory of Nano-Micro Architecture Chemistry (NMAC), College of Chemistry, Jilin University, Changchun 130012, People’s Republic of China S Supporting Information *

ABSTRACT: Polymeric antifogging/frost-resisting coatings are suitable for use on flexible substrates but are vulnerable to accidental scratches and cuts. To solve this problem, we present the fabrication of healable, highly transparent antifogging and frost-resisting polymeric coatings via the layer-by-layer assembly of poly(ethylenimine) (PEI) and a blend of hyaluronic acid and poly(acrylic acid) (HA-PAA). Due to their remarkable water-absorbing capability, the highly transparent and flexible (PEI/HA-PAA)*50 coatings show excellent antifogging and frost-resisting capabilities even under aggressive fogging and frosting conditions. Meanwhile, these coatings can conveniently and repeatedly heal scratches and cuts several tens of micrometers deep and wide in the same region upon exposure to water because of the dynamic nature of the PEI/ HA-PAA coatings. The healability of the (PEI/HA-PAA)*50 coatings provides a new way to design transparent antifogging/ frost-resisting polymeric coatings with high flexibility, enhanced reliability, and extended service life.

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lent13−16,21−28 and dynamic covalent bonds.17,29−33 Integrating healing properties into polymeric antifogging coatings will provide a practical way to fabricate antifogging coatings that are suitable for application on flexible polymer substrates without the aforementioned stability issue. An extrinsic self-healing method that uses the healing agents loaded in micrometer-sized capsules to heal damage is technically difficult in fabricating transparent self-healing coatings because the capsules strongly scatter visible light.34,35 Without the requirement of the encapsulated healing agent, the intrinsic self-healing method24,36,37 utilizes reversibility of noncovalent interactions and dynamic covalent bonds to heal damage and is highly suitable for the fabrication of self-healing transparent antifogging coatings. Compared with highly hydrophilic ultrathin polymeric films, polymeric films with high water-absorbing capacity are worthy of further study for the fabrication of self-healing/ healable antifogging coatings because both antifogging and selfhealing capabilities require thick polymer coatings. On one hand, increasing thickness of the water-absorbing polymer coatings will enhance their ability to handle an aggressive fogging challenge and even prevent frost formation;5,38,39 on the other hand, thick polymeric coatings can replenish sufficient materials at the damaged region to enable healing severe damage such as deep and wide cuts.14 In a typical example, Rubner, Cohen, and co-workers demonstrated that in spite of the zwitter-wettability, water-

INTRODUCTION Fog that results from nonuniformly condensed water droplets due to changes in temperature and humidity can cause light scattering on windshields, eyeglasses, swimming goggles, and other light-related objects.1−5 Superhydrophilic coatings with water contact angles smaller than 5° can prevent fog formation by rapidly spreading condensed water droplets into a thin water membrane that allows light to pass through without scattering.1,2 Nanoporous SiO2 and UV-activated TiO2 films are superhydrophilic and widely used for the fabrication of antifogging coatings.1,2,6,7 Although SiO2 and TiO2 antifogging coatings can be made highly transparent and scratch-resistant, the fragility of these coatings restricts their application on flexible polymer substrates because repeated bending/unbending treatments or abrupt temperature changes can lead to their exfoliation from the underlying substrates. In contrast to inorganic antifogging coatings, polymeric antifogging coatings are flexible and can endure repeated bending/unbending treatments without detachment from the underlying polymer substrates.8,9 However, the soft nature of polymeric antifogging coatings makes them susceptible to damage such as accidental scratch and cut, leading to the deterioration of the antifogging ability and transparency. Learning from the peculiar healing processes of living organisms, self-healing functions have been successfully imparted to artificial materials to achieve extended lifespans with reliable function and convenient maintenance.10−18 Upon damage, self-healing materials can restore their structural integrity and original functions by using the preloaded healing agents10−12,19,20 or through the reversibility of noncova© XXXX American Chemical Society

Received: September 21, 2015 Revised: November 9, 2015

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DOI: 10.1021/acs.chemmater.5b03705 Chem. Mater. XXXX, XXX, XXX−XXX

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Chemistry of Materials

Figure 1. (a) Thickness of the (PEI/HA-PAA)*n coatings as a function of the number of coating deposition cycles. (b) AFM image of a (PEI/HAPAA)*50 coating. (c) UV−vis transmission spectrum of a (PEI/HA-PAA)*50 coating. UV−vis transmission spectra of a bare glass substrate and a glass substrate with both sides deposited with (PEI/HA-PAA)*50 coating are provided as references. (d) Digital images of a bare glass substrate (i) and a glass substrate with both sides covered with (PEI/HA-PAA)*50 coatings (ii).

absorbing polymeric films comprising of alternately deposited poly(vinyl alcohol) and poly(acrylic acid) (PAA) with a film surface covered with poly(ethylene glycol methyl ether) show excellent antifogging and frost-resisting capabilities.5 However, for most transparent films, image distortion and transmittance decreases caused by scratching limiting their applications. Here we demonstrate the first water-enabled healable antifogging and frost-resisting polyelectrolyte coatings fabricated by layer-bylayer (LbL) assembly of poly(ethylenimine) (PEI) and a blend of hyaluronic acid and poly(acrylic acid) (HA-PAA). The highly transparent PEI/HA-PAA coatings have excellent antifogging and frost-resisting capabilities and can heal cuts and scratches several tens of micrometers wide with exposure to water. The healability provides an effective way to extend lifespan and enhance reliability of the PEI/HA-PAA antifogging and frost-resisting coatings.

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PEI solution (2 mg/mL, pH 9.8) for 15 min to obtain a layer of PEI film followed by rinsing in four water baths for 1 min each to remove the physically adsorbed PEI. The substrate was then immersed into aqueous HA-PAA solution (HA, 1 mg/mL, PAA, 1 mg/mL, pH 3.8) for 15 min to obtain a layer of HA-PAA film followed by rinsing in four water baths for 1 min each. The deposition of PEI and HA-PAA was repeated until the desired number of deposition cycles was obtained. No drying steps were used in the coating deposition procedure until it was in the last layer. The (PEI/PAA)*n coatings were fabricated similar to the (PEI/HA-PAA)*n coatings by replacing aqueous HA-PAA solution with aqueous PAA solution. Film Characterization. The coating thickness was measured with a Dektak 150 surface stylus profilometer using a 5 μm stylus tip with 3 mg stylus force. The atomic force microscopy (AFM) images were taken on a commercial instrument (Veeco Company Nanoscope IV) in tapping mode under ambient environment. The UV−vis transmission spectra were recorded using a Shimadzu UV-2550 spectrophotometer. Temperature and relative humidity (RH) were carried out by using Humiport 20 sensors (Austria, E+E Elektronik Ges. m.b.H.). The scanning electron microscopy (SEM) images were obtained on a JEOL JSM 6700F field emission scanning electron microscope. Digital photographs were captured with a Canon SX40 HS camera. Optical micrographs were taken with an Olympus BX-51 optical microscope. The water contact angles of the coatings were measured using a Drop Shape Analysis System DSA-30 (Krüess, Germany) at ambient temperature. A water droplet of 4 μL was used as the indicator to characterize the wetting property of the coatings. Water contact angles on (PEI/HA-PAA)*n films were measured within 1 s of contact with water droplets. Mechanical properties of the coatings were measured with an Agilent Nano Indenter G200 with an XP-style actuator and continuous stiffness measurement (CSM) method. Young’s modulus and hardness were measured with a Berkovich diamond tip with a relative humidity (RH) of ∼20% at 30 °C. The storage modulus of the coatings in water was measured with a flat-ended cylindrical tip made of diamond by the “G-Series XP CSM

EXPERIMENTAL SECTION

Materials. PEI (Mw ca. 25 000) and PAA (Mw ca. 100 000) were purchased from Sigma-Aldrich. HA (Mw ca. 100 000) was purchased from Shandong Freda Biotechnology Co., Ltd. Lucifer yellow cadaverine (LYC) was obtained from Invitrogen. All chemicals were used without further purification. Deionized water was used for all experiments. Fabrication of PEI/HA-PAA Coatings. Glass and silicon substrates were immersed in piranha solution (1:3 mixture of 30% H2O2 and 98% H2SO4) and heated until no bubbles were released. The poly(ethylene terephthalate) (PET) substrates were treated with oxygen plasma for 5 min to obtain oxygen-containing hydrophilic surfaces. The LbL assembly of (PEI/HA-PAA)*n coatings was conducted with a programmable dipping machine (Dipping Robot DR-3, Riegler & Kirstein GmbH, Germany). The newly cleaned substrate (glass, silicon, and PET) was first immersed into an aqueous B


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Figure 2. Antifogging and frost-resisting properties of (PEI/HA-PAA)*n coatings that were preconditioned at −20 °C for 1 h and then subjected to different environments. (a) Frost-resisting behaviors of a hydrophilic glass substrate (i) and a glass substrate deposited with (PEI/HA-PAA)*50 coatings (ii) at 25 °C and ∼65% RH. (b) Antifogging behavior of a PET substrate deposited with (PEI/HA-PAA)*50 coatings after 2000 cycles of bending/unbending. (c) Digital image of a PET substrate deposited with (PEI/HA-PAA)*50 coatings over boiling water (∼56 °C and ∼100% RH). A corresponding movie can be found in the Supporting Information. (d) Antifogging behaviors of glass substrates deposited with (PEI/HAPAA)*16 (i) and (PEI/HA-PAA)*18 (ii) coatings at ∼56 °C and ∼100% RH. The scale bar is 1 cm. flat punch complex modulus” method. Detailed measurements were made according to our previous publication.36,37

AFM indicates that the (PEI/HA-PAA)*50 coating has a smooth surface with a root-mean-square (RMS) roughness of ∼4.0 nm within a measured area of 40 × 40 μm (Figure 1b). HA and PAA conjugated with LYC (denoted as HA@LYC and PAA@LYC) were used to fabricate (PEI/HA@LYC-PAA)*50 and (PEI/HA-PAA@LYC)*50 coatings. The mass ratio of HA and PAA in (PEI/HA-PAA)*50 coatings were determined to be 1.3:1 by measuring the absorbance of LYC in (PEI/HA@ LYC-PAA)*50 and (PEI/HA-PAA@LYC)*50 coatings (Supporting Information, Figure S1). Because the smooth surface can significantly suppress light scattering, the (PEI/HAPAA)*50 coating without the underlying glass substrate is highly transparent in the visible region, with a transmittance of ∼98% at 550 nm (Figure 1c). Potted plants behind the bare glass and (PEI/HA-PAA)*50-coating-covered glass can clearly be seen with no visual difference between their photographs (Figure 1d). A glass substrate with both sides covered with the (PEI/HAPAA)*50 coatings was conditioned at a −20 °C refrigerator for 1 h and then exposed to an ambient environment at room temperature with a RH of ∼65% to investigate its antifogging and frost-resisting ability. A bare hydrophilic glass substrate served as the control. As indicated in Figure 2a(i), the bare glass substrate frosts immediately after being taking out from the refrigerator. The leaves behind the frosted glass substrate

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RESULTS AND DISCUSSION The LbL assembly is a substrate-independent technique for composite film fabrication by alternate deposition of complementary species through noncovalent interactions as the driving force.40−44 The LbL assembly of PEI and HA-PAA blend produces rapidly deposited (PEI/HA-PAA)*n (where n refers to the number of coating deposition cycles) coatings based on the electrostatic and hydrogen bonding interactions between them (Figure 1a). Previously, we used LbL-assembled PEI/HAPAA coatings for the fabrication of healable conductive silver nanowire films.45 The parameters of the LbL assembly of the (PEI/HA-PAA)*n coatings were optimized to achieve high transparency in the visible region. The (PEI/HA-PAA)*n coatings undergo an exponential deposition in the initial 10 deposition cycles, and thereafter there is a rapid linear deposition with increasing number of coating deposition cycles. The rapid deposition of the (PEI/HA-PAA)*n coatings originates from the interdiffusion of PEI, HA, and PAA polyelectrolytes during the film deposition process. The polyelectrolyte interdiffusion leads to more polyelectrolyte deposition in the current layer than in the former layer.14,36,37,46 The (PEI/HA-PAA)*50 film has a thickness of 29 ± 0.23 μm. C


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Figure 3. (a) UV−vis transmission spectra of (PEI/HA-PAA)*18 and (PEI/PAA)*20 coatings without underlying substrates. (b) AFM image of a (PEI/PAA)*20 coating. (c) The frost-resisting behaviors of the (PEI/HA-PAA)*18 (i) and (PEI/PAA)*20 (ii) coatings at 25 °C and ∼65% RH. The coatings were first conditioned at −20 °C for 1 h.

conditioned at −20 °C and then transferred to room temperature with a RH less than ∼65%. However, the (PEI/ HA-PAA)*16 and (bPEI/HA-PAA)*18 coatings show completely different antifogging ability when they are first conditioned at −20 °C for 1 h and then immediately placed over boiling water (∼56 °C, ∼100% RH). As shown in Figure 2d, the (PEI/HA-PAA)*16 coating fogs while the (PEI/HAPAA)*18 coating effectively inhibits fog formation. The (PEI/ HA-PAA)*16 and (PEI/HA-PAA)*18 coatings have a water contact angle of 34° and 33° (Supporting Information, Figure S3), respectively. The fact that the (PEI/HA-PAA)*16 and (PEI/HA-PAA)*18 coatings have very similar wettability but largely different antifogging behaviors indicates that the hydrophilicity of these coatings is insufficiently high to rapidly spread water droplets into a uniform water membrane to prevent fog formation. The only difference between the (PEI/ HA-PAA)*16 and the (PEI/HA-PAA)*18 coating is that the thicker (PEI/HA-PAA)*18 coating has a higher capability to absorb water than the (PEI/HA-PAA)*16 coating. Therefore, the antifogging and frost-resisting ability of the (PEI/HAPAA)*18 coatings is ascribed to the remarkable capability of the (PEI/HA-PAA)*18 coatings to absorb and disperse water molecules. Upon water condensation on the (PEI/HAPAA)*18 coating, water molecules are immediately and rapidly absorbed into the coating in which the absorbed water molecules exist in a molecularly dispersed, nonfreezing state because of their hydrogen bonding interactions with PEI/HAPAA coating. The well dispersed water molecules within the PEI/HA-PAA coatings account for their antifogging and frostresistant performance. To demonstrate the importance of HA in fabricating highly transparent antifogging and frost-resisting coatings, LbLassembled (PEI/PAA)*20 coatings were fabricated in the same way for (PEI/HA-PAA)*n coatings by replacing HA-PAA

are invisible as the frozen water droplets decrease the light transmission. In sharp contrast, the (PEI/HA-PAA)*50 coating, which has a water contact angle of ∼35°, is fog- and frost-free. The leaves behind the (PEI/HA-PAA)*50 coatings are still clearly visible (Figure 2a(ii)). This result confirms that the (PEI/HA-PAA)*50 coatings can effectively prevent frost and fog formation. When an extremely cold substrate is transferred into a humid environment at room temperature, frost forms on the substrate surface and then turns into fog as the substrate temperature increases. The hydrophilic glass was fully frosted in the initial 8 s, and then the frost turned into fog (Supporting Information, Figure S2). The (PEI/HA-PAA)*50 coatings can be readily deposited on flexible polymeric substrates. The (bPEI/HA-PAA)*50 coatings deposited on a PET sheet show no detachment or cracking after 2000 cycles of bending/unbending treatments, demonstrating high flexibility of the (PEI/HA-PAA)*50 coatings as well as good adhesion onto the PET substrate (Figure 2b). The (PEI/HA-PAA)*50 coatings deposited on a PET substrate were first conditioned at −20 °C for 1 h and then exposed to steam (∼56 °C and ∼100% RH) to examine their antifogging capability under a harsh and aggressive condition. Even in this highly humid environment, the (PEI/HA-PAA)*50 can still effectively inhibit fog formation. Moreover, exposure to such a high temperature does not detach the (PEI/HA-PAA)*50 coatings from the PET substrate (Figure 2c). The thickness-dependent antifogging and frost-resisting properties of the (PEI/HA-PAA)*n coatings are investigated to understand the antifogging and frost-resisting mechanism. The (PEI/HA-PAA)*16 and (PEI/HA-PAA)*18 coatings have a thickness of 8.3 ± 0.16 and 9.7 ± 0.12 μm, respectively. Both (PEI/HA-PAA)*16 and (bPEI/HA-PAA)*18 coatings can effectively inhibit fog and frost formation when they are first D


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Figure 4. (a) Digital images of a (PEI/HA-PAA)*50 coating on a glass substrate that heals scratches. (i) Scratched coating, (ii) scratched coating after exposure to ∼65% RH for 6 h. (b) AFM images of a scratched (PEI/HA-PAA)*50 coating before (i) and after (ii) being healed. (c, d) SEM images of a (PEI/HA-PAA)*50 coating with a cut ∼55 μm wide before (c) and after (d) being healed. (e) Width of deep cuts of (PEI/HA-PAA)*50 coatings as a function of the length of the required healing time. (f) Hardness of a (PEI/HA-PAA)*50 coating as a function of penetration depth at 30 °C and RH of ∼20%.

Accidental scratches on the (PEI/HA-PAA)*50 coatings can strongly scatter visible light and decrease their transparency. Thus, it is highly necessary to repair these scratches and maintain their original transparency. As shown in Figure 4a(i), the (PEI/HA-PAA)*50 coating becomes translucent after being repeatedly scratched with 2000-grit sandpaper. The transmittance of the scratched (PEI/HA-PAA)*50 coating at 550 nm decreased to ∼42% (see Supporting Information, Figure S4a). After exposing the scratched (PEI/HA-PAA)*50 coating to room temperature and ∼65% RH, the scratches gradually disappear with time. However, complete healing of the scratches and restoration of the original transparency takes about 6 h. The leaves behind the completely healed (PEI/HAPAA)*50 coating are clearly seen (Figure 4a(ii)).The AFM image shows that the scratched (PEI/HA-PAA)*50 coating is full of ∼0.9 to ∼4.9 μm grooves (Figure 4b(i)), which strongly scatter visible light. The healed (PEI/HA-PAA)*50 coating is smooth and has a RMS roughness of ∼7.0 nm within a measured area of 40 × 40 μm, which is close to the RMS roughness of the as-prepared (PEI/HA-PAA)*50 coating (Figure 4b(ii) and Figure S4). This indicates that the (PEI/ HA-PAA)*50 coatings can autonomically heal shallow

blend with PAA. The (PEI/PAA)*20 coating has a thickness of 10.2 ± 0.67 μm, which is similar to the thickness of 9.7 ± 0.12 μm of the (PEI/HA-PAA)*18 coating. As shown in Figure 3a, the (PEI/HA-PAA)*18 coating has a higher transparency than the (PEI/PAA)*20 coating across the entire visible region. The high transparency originates from the smooth surface morphology. The RMS roughness of a (PEI/HA-PAA)*18 coating with an area of 40 × 40 μm was only 5.7 nm, while the RMS roughness of a (PEI/PAA)*18 coating was 63.2 nm (Figure 3b). The (PEI/HA-PAA)*18 and (PEI/PAA)*20 coatings were conditioned at −20 °C for 1 h and then placed in a 25 °C environment at ∼65% RH. The (PEI/HA-PAA)*18 coating prevents frost formation, but frost clearly forms on the (PEI/PAA)*20 coating (Figure 3c). HA is more flexible than PAA and has a higher capacity than PAA to absorb water. Therefore, the introduction of HA enables the fabrication of smooth films with enhanced water-adsorbing capacity. This capacity is critically important in the production of highly transparent antifogging and frost-resisting coatings. Although (PEI/HA)*n coatings are also transparent and capable of antifogging and frost-resisting, their mechanical stability is inferior to (PEI/HA-PAA)*n coatings. E


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water molecules enable healing of cuts and scratches on the transparent antifogging and frost-resisting (PEI/HA-PAA)*50 coatings.

scratches under fogging conditions. The scratch healing on the (PEI/HA-PAA)*50 coatings made by sandpaper can be accelerated by immersing the scratched coatings in water. After 20 min of water immersion, the scratched (PEI/HAPAA)*50 coating can heal the scratches and restore its original transparency. As a kind of intrinsic healable material, the (PEI/ HA-PAA)*50 coating can heal scratches made by sandpaper multiple times in a given location. The transmittance at 550 nm and RMS roughness (see Supporting Information, Figure S5) of the scratched (PEI/HA-PAA)*50 coatings restore to their original values after five scratching/healing cycles in the same damaged area. In practical usage, the antifogging and frost-resisting (PEI/ HA-PAA)*50 coatings are also subjected to severe damage such as deep and wide cuts. To investigate the capability of the (PEI/HA-PAA)*50 coatings to heal severe damage, an ∼55 μm wide cut was made with a blade which exposes the underlying substrate (Figure 4c). After immersing the cut (bPEI/HAPAA)*50 coating in water for 90 min, the cut was completely healed (Figure 4d). Figure 4e indicates the time-dependent healing behaviors of the (PEI/HA-PAA)*50 coatings with deep cuts of different widths, with a wider cut requiring a longer immersion time to heal. The (PEI/HA-PAA)*50 coating failed to heal a cut that is wider than 60 μm even after immersing the coating in water for 200 min. Repeated healing of deep cuts in the same area can also be achieved on (PEI/HA-PAA)*50 coatings. For instance, 30 μm wide cuts are hardly seen even after five cycles of cutting/healing on a (PEI/HA-PAA)*50 coating (Supporting Information, Figure S6). Moreover, the healed (PEI/HA-PAA)*50 coatings preserve their original antifogging and frost-resisting properties. The mechanical properties of the (PEI/HA-PAA)*50 coatings in dry conditions and in water were measured by nanoindentation to clarify their healing mechanism. Figure 4f indicates the dependence of the hardness of the (PEI/HAPAA)*50 coating as a function of indentation depth measured in air with ∼20% RH at 30 °C. The hardness in the plateau region (≥200 nm) is the “real” hardness because the influence produced by the coating surface is avoided; this hardness is measured to be 0.47 ± 0.07 GPa, which is similar to the hardness of a commercially available Samsung screen protector film (RG Brand Screen Guard for Samsung I569/S5660, ∼130 μm thick). However, this material cannot heal scratches and has a hardness of 0.41 ± 0.02 GPa.36 The Young’s modulus of the (PEI/HA-PAA)*50 coating in air with ∼20% RH at 30 °C is 9.9 ± 1.0 GPa; its storage modulus in water as measured by nanoindentation is 17.0 ± 2.3 MPa (measured at 1 Hz; Supporting Information, Figure S7). The large decrease in the modulus from 9.9 ± 1.0 GPa in dry conditions to 17.0 ± 2.3 MPa in water indicates that the (PEI/HA-PAA)*50 coating can absorb a substantial amount of water to swell the coating. The absorbed water molecules can interact with amine, carboxylic acid, and hydroxyl groups of PEI, HA, and PAA and lead to a partial break of the electrostatic and hydrogen bonding interactions. As a result, the (PEI/HA-PAA)*50 coating becomes soft and flowable after water absorption. This facilitates the migration of PEI, HA, and PAA polyelectrolytes to fill in the cuts or scratches. In the damaged region, the replenished PEI, HA, and PAA polyelectrolytes reform electrostatic and hydrogen bonding interactions and heal the damage. Therefore, the reversibility of the electrostatic and hydrogen bonding interactions and the facilitated migration of PEI, HA, and PAA polyelectrolytes under the assistance of

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CONCLUSIONS In summary, we have demonstrated the fabrication of optically transparent healable coatings with antifogging and frostresisting capacities by LbL assembly of PEI and HA-PAA blends. The (PEI/HA-PAA)*50 coatings show excellent antifogging and frost-resisting behavior even under aggressive fogging and frosting conditions. The antifogging and frostresisting functions originate from the high capacity of the (PEI/ HA-PAA)*50 coatings to absorb water. Therefore, the (PEI/ HA-PAA)*50 coatings can uniformly disperse the absorbed water molecules through hydrogen bonding interactions with PEI, HA and PAA polyelectrolytes to prevent fog and frost formation. The reversibility of the electrostatic and hydrogen bonding interactions as well as the high mobility of PEI, HA and PAA polyelectrolytes upon exposure to water give the (PEI/HA-PAA)*50 coatings the ability to repeatedly heal damage such as scratches and cuts to restore their original transparency as well as antifogging and frost-resisting behavior. The integration of healability into highly transparent (PEI/HAPAA)*50 coatings provides an effective way to solve the stability issue that is otherwise difficult to deal with for polymeric antifogging/frost-resisting coatings. The substrateindependent deposition process and the high flexibility of the (PEI/HA-PAA)*50 coatings suggest many applications on various substrates including flexible polymer substrates with nonflat surfaces. This study offers a new route for the fabrication of flexible antifogging and frost-resisting coatings with an extended lifespan and reliability.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.chemmater.5b03705. Mass ratio of HA and PAA in (PEI/HA-PAA)*50 coatings; the frost-to-fog transition process of a hydrophilic glass substrate; water contact angles of (PEI/HAPAA)*16 and (PEI/HA-PAA)*18 coatings; the healing process of transparency of a (PEI/HA-PAA)*50 coating; multiple healing of transparency and structural integration of a (PEI/HA-PAA)*50 coating; and mechanical properties of the (PEI/HA-PAA)*50 coatings (PDF) A movie about the antifogging properties of a PET substrate coated with (PEI/HA-PAA)*50 coating (MPG)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Basic Research Program (2013CB834503) and the National Natural Science Foundation of China (NSFC Grants 21225419 and 21221063). F


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ABBREVIATIONS PEI, poly(ethylenimine); HA, hyaluronic acid; PAA, poly(acrylic acid); LbL, layer-by-layer; PET, poly(ethylene terephthalate); AFM, atomic force microscopy; RH, relative humidity; SEM, scanning electron microscopy; CSM, continuous stiffness measurement; RMS, root-mean-square

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Antifogging and Frost-Resisting Polyelectrolyte Coatings Capable of

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