Supporting Information Robust and Self-Healable Bulk-Superhydrophobic Polymeric Coating Avijit Das, Jumi Deka, Kalyan Raidongia, Uttam Manna* Experimental Section: Experimental section: Materials: Branched polyethyleneimine (BPEI, MW~25000), dipentaerythritol penta-/hexaacrylate (5Acl, Mw~ 524.21), decylamine and methylene blue were procured from Sigma Aldrich, Bangalore, India. Rhodamine 6G and fluorescein were obtained from Labo Chemie, Mumbai, India. Graphite powder was acquired from Asbury Carbon. Sodium hydroxide (NaOH), ethanol, methanol, sulphuric acid, hydrochloric acid, hydrogen peroxide, nitric acid, hydrazine hydrate, ammonium hydroxide were supplied by Merck Specialties Private Limited, India. Potassium Permanganate was purchased from Fisher scientific. Tetrahydrofuran (THF) was supplied by RANKEM, Maharashtra, India. Sandpaper (grit no. 400) was purchased from Million International, India. Glass slide (Boroleb, India), aluminum foil (Parekh Aluminex Ltd. India), Adhesive tape (Jonson tape Ltd. India) were obtained from local sources. General considerations: Dynamic light scattering (DLS) measurements were performed with Zetasizer Nano ZS90 (model no ZEN3690) instrument. All the FTIR spectra were recorded by PerkinElmer instrument. KRUSS Drop Shape Analyser-DSA25 instrument was used in measuring liquid wettability on the synthesized materials at 20 c temperature, where deionized (DI) water droplets (3 µl) were used for dynamic and static contact angle measurements. All non-conductive polymeric samples were first gold sputtered under vacuum to achieve a thin
layer of conductive gold coating on the polymeric samples, and finally used those samples for FESEM characterization using Carl Zeiss field emission scanning electron microscope (FESEM). Raman spectra were collected using Laser Micro Raman System (Horiba Jobin Vyon, Model LabRam HR). All digital pictures were captured with canon power shot SX420 IS digital camera. Synthesis of Graphene Oxide (GO): A modified Hummers method was adopted here to prepare graphene oxide from graphite powder (J. Am. Chem. Soc., 1958, 80,1339). 1g of graphite powder was mixed with 50 ml of concentrated sulphuric acid, and ice bath (0 ) was used to maintain the low temperature of the mixture. Then, 6g potassium permanganate (oxidizing agent) was gradually poured in the acidic mixture of graphite, keeping the temperature of the system below 10 C. The mixture was removed from ice bath and transferred to a water bath. Then whole mixture was agitated using magnetic stirrer for two hours and temperature was slowly increased to 35 C. Next, the reaction mixture was again placed in an ice bath, and the whole reaction mixture was diluted with 100 ml of DI water. Finally, residual KMnO 4 and MnO 2, which were present in the reaction mixture was decomposed by adding 8ml of 30 % hydrogen peroxide. The synthesized material was thoroughly washed with HCl, and followed by acetone prior to use. Synthesis of amino graphene oxide (AGO): The synthesized GO was further modified to prepare amino-graphene oxide (AGO) sheets through synthesis of nitro graphene oxide. First, 50 mg of dried graphene oxide powder was mixed in 100 ml of 50 % nitric acid. Then, the solution was kept with continuous agitation for 12 hours at ambient condition. Later, the reaction mixture was washed with acetone, and was dried under vacuum. Next, this dry sample was re-dispersed in 1:1 ethanol-water mixture, and maintained the final concentration of the nitro graphene oxide at 0.1
mg/ml. Then, ammonium hydroxide (150 µl) and hydrazine hydrate (50 µl) were added to the mixture and reaction temperature was increased to 70 C for the reduction reaction. Coating on glass substrate: The colorless solution of 5Acl (132.5 mg/ml in methanol, 1mL) was first mixed with BPEI (50 mg/ml in methanol, 125 µl) in absence and presence of dispersion of amino graphene oxide (AGO), and depending on the amount of AGO in the BPEI/5Acl mixture, the polymeric coatings are denoted as AG 1 (2.17µg/mL), AG 2 (4.25µg/mL), AG 3 (8.16µg/mL), AG 4 (15.09µg/mL) and AG 5 (30.77µg/mL). The colorless mixture of BPEI/5Acl transformed to a turbid and milky solution in presence (8.16µg/mL) of AGO within 20 minutes, and this solution was spread uniformly over the clean glass slide with the help of a microscopic glass slide. After 30 minutes, a dry and stable coating (AG 3 ) was obtained on the glass substrate. Then, the coated glass slide was treated with decylamine solution (37.47mg/ml) in THF for overnight. After that, the coated slide was thoroughly washed with fresh THF solvent for multiple (five) times. Then, air-dried coating was further used in various demonstrations. Self-healing of Polymeric Coating: A pressure of 188 kpa was applied on the surface polymeric coating over an area of 0.5 cm 2 for 10 sec, and the polymeric coating (AG 5, thickness = 1 mm) was crushed with a depth of 600µm. The beaded water droplet on the crushed surface was found to be highly adhesive with contact angle hysteresis above 50. Both the physical integrity and embedded antifouling property (non-adhesive superhydrophobicity) were self-healed within 30 minutes, without any external intervention. Further, the same process was repeated to examine the self-healing ability of other polymer coatings (AG 3 and AG 4 ) that were with lesser amount of AGO. Selective Collection of Aqueous Phase: Similarly, polymeric coating was further crushed by application of pressure (188 kpa) with three circular objects. Then, the polymer coating with
three physically damaged spots was immersed in aqueous solution of rhodamine 6G dye for few seconds followed by drying it in air. Red colored aqueous solution was selectively immobilized on those three locations. After air-drying, both the physical deformation and antifouling property were self-healed in the polymeric coating. The blue-colored water droplets were beaded on the surface to examining the anti-fouling property after self-healing process. Paper Based Contact Printing of Water Soluble Agents: A dolphin-shaped filter paper was soaked with aqueous solution of rhodamine 6G, and then it was brought in contact with flattened and crushed surface for few seconds. Selective immobilization of aqueous phase was noticed on the polymeric coating after removal of the dolphin-shaped paper. The polymeric coating recovered its physical damage and the blue-colored aqueous droplets were again used to examine the antifouling property on the some specific locations (on the coating) where the water soluble rhodamine dye molecules were printed. For the proof of concept demonstration of printing multiple water soluble agent, a triangle shaped filter paper was first soaked with aqueous solution of methylene blue ( blue colored) dye, and immediately that paper was placed on the crushed polymeric coating (AG 5 ) and then it was allowed to air-dry. Next, the same polymeric coating was crushed again at same location through application of pressure, and another triangle shaped filter paper that soaked with aqueous solution of rhodamine was placed on it, to immobilize aqueous solution that was with another water soluble molecules (rhodamine), finally the material was allowed to dry. Thus, the complex superhydrophobic print composed of two water soluble agents was developed. In-Situ Printing of Hydrophilic Molecules: Here, aqueous solution of rhodamine was attached selectively on the polymeric coating during the location specific incurring of physical damage on the polymeric coating. A crude and lab made wooden stamp with the shape of IIT was first
inked with aqueous solution of rhodamine. Then this inked-stamp was brought in contact with the polymeric coating, and a manual pressure was applied on the coating for 10 sec and at the end the aqueous ink was transferred to the polymeric coating. Then the IIT printed nonadhesive superhydrophobic surface was used in demonstration of self-cleaning, where deposited dust and dirt on the tilted surface was self-cleaned during rolling of beaded water droplets on the surface. Figure S1. A-B) Digital image of BPEI/5Acl mixture in methanol in presence of GO (Vial-1) and AGO (Vial-3), and in absence of GO/AGO (Vial-2) at t=0 (A) and after t=20 minutes (B). C) The DLS study on the BPEI/5Acl mixture that were prepared in presence of GO (150.9 µg/ml,
Vial-1) and AGO (8.16µg/mL) and in absence of GO/AGO and kept the solution for 20 minutes with continuous agitation. Figure S2. A) Digital images of the set up for sand paper test, where abrasive sand paper (grit no. 400) was sandwiched between the polymeric coating and applied load (100 g) and rubbed on the polymeric coating for at least 10 times. B-E) Digital images (B, D) and contact angle images (C, E) of beaded water droplets (red color aids visual inspection) on both the polymeric coating (B-C) and abrasive sand paper (D-E) after performing the abrasive sand paper test. F) Digital images of the set up for adhesive tape test, where adhesive surface of the tape was brought in contact with polymeric coating and a pressure (with 500g load) was applied to achieve uniform
and improve contact between the adhesive surface and polymeric coating. G-J) Digital images (G, I) and contact angle images (H, J) of beaded water droplets on both the polymeric coating (G-H) and adhesive tape surface (I-J), after peeling off the adhesive tape from the polymeric coating, during this adhesive tape peeling process, polymeric coating was fractured, and top surface of the coating was transferred to adhesive tape (I). K) Digital images of the set up for sand drop test, where 150 g of sand grains was poured onto the polymeric coating (tilted at 45 ) from a height of 20 cm. L-M) Digital images (L) and contact angle images (M) of beaded water droplets on the polymeric coating after performing the sand drop test. Figure S3. A-F) Cross sectional (A-C, scale bar: 500µm) and top (D-F, scale bar: 5mm) views of polymeric coating before (A,D) and after (B, E) incurring the physical damage to the polymeric coating (AG 3 ), and after partial physical recovery of the coating (C, F) after 1 day. G-L) Advancing (G,H,I) and receding (J,K,L) contact angle images of beaded water droplet before ( G, J) and after (H,K) crushing the polymeric coating, and after incomplete physical recovery of the coating over 1 day (I,L). M) Plot comparing the rate of physical recovery of polymeric coatings (AG 3, AG 4, AG 5 ) with time, after crushing the polymeric coating with applied pressure (~190kPa).
Figure S4. A-F) Cross sectional (A-C, scale bar: 500µm) and top (D-F, scale bar: 5mm) views of polymeric coating (AG 5 ) before (A,D) and after (B, E) application of pressure (~190 kpa) to the polymeric coating (AG 3 ), and after complete self-healing of the coating (C, F, within 30 minutes). G-L) Advancing (G,H,I) and receding (J,K,L) contact angle images of beaded water droplet before ( G, J) and after (H,K) incurring the physical damage to the polymeric coating, and after complete self-healing of the polymeric coating (I,L).
Figure S5. Demonstration of the rolling of beaded water droplet (5µL) on the tilted (3 ) polymeric coating (AG 5 ) before (A-D) and after (E-H) applying pressure, and after self-healing process (I-L). The right side of red dotted line in Figure E-H is the location of physical damage.
Figure S6. FESEM images of polymeric coating (AG3, having less amount of AGO) in low (AB, scale: 10µm) and high (C-D, scale: 5µm) magnifications, before incurring the physical damage (A,C), and after performing the damage /self-healing cycles for 5 times.
Figure S7: A-B) Demonstration of breaking of beaded water droplet (θ Adv.~160 ; 1 µl) by adhesive interaction with the physically damaged polymeric coating (AG 5 ) during receding of water droplet. C-E) Digital Images of physically damaged (C, with three circular spots) polymeric coating after selective collection (D) of DI-water, and after self-healing (E, θ adv. 161.1 and θ hys. 3.3 ) of the physical damage. F-G) Demonstration of rewritable aqueous pattern using a lab-made stamp of X and IIT ; first aqueous pattern of X was developed (F), and after removal of aqueous solution, another aqueous pattern (G) of IIT was formed on same polymeric coating. H) Different water soluble dye (rhodamine 6G, fluorescein, methylene blue) molecules were directly transferred to the aqueous pattern of IIT.