Robust and Self-Healable Bulk-Superhydrophobic Polymeric Coating

Abstract

Recovery of the compromised antifouling property because of perturbation in the essential chemistry on top of the hierarchical topography of a superhydrophobic coating is commonly achieved through some stimuli (temperature, humidity, pH, etc.)-driven reassociation of the low surface energy molecules. However, self-healing of superhydrophobicity in physically damaged materials having inappropriate topography is difficult to achieveand extremely important for the practical utility of this bioinspired property. Recently, very few materials have been introducedthat are capable of recovering the hierarchical featuresbut only after the application of appropriate external stimuli. Further, the optimization of appropriate stimuli is likely to be a challenging problem in practical scenarios. Here, we have strategically exploited a simple and robust 1,4-conjugate addition reaction between aliphatic primary amine and aliphatic acrylate groups for appropriate and covalent integration of a modified-graphene oxide nanosheetwhich is well recognized for its exceptional mechanical properties. The synthesized material exhibited a remarkable ability to protect the antifouling property from various harsh physical insults, including physical erosion of the top surface of the polymeric coating and various physical manipulations etc. However, after application of pressure on the same polymeric coating, the bioinspired, nonadhesive (contact angle hysteresis <5°) superhydrophobicity was compromised, and the physically damaged polymeric coating became highly adhesive (contact angle hysteresis ∼50°) and superhydrophobic. But, after releasing the pressure, the native nonadhesive (contact angle hysteresis <5°) extreme wettability was self-restored in the polymeric coating through recovery of the essential hierarchical topographywithout requiring any external stimulus. This unique material, having impeccable durability and absolute self-healing capability, was further explored in (i) developing rewritable aqueous patterns on the extremely water-repellent surface and (ii) selective impregnation of water-soluble agents on the surface of polymeric coatingwithout any permanent change in the extreme water repellency property. The unique self-healing process eventually provided a superhydrophobic printthat was made out of hydrophilic small molecules. This printing was performed directly from an aqueous medium, which is extremely hard to achieve using the conventional superhydrophobic materials. Such multifunctional interfaces could be an important avenue for various smart applications, including delivery of hydrophilic small molecules, catalysis, self-assembly of colloids, reusable chemical sensing, etc.

Recent Achievements of Self-Healing Graphene/Polymer Composites

“…Fabrication of self-healing anticorrosive coatings has attracted attentions as it has the ability to extend the service life and prevent the substrate from corrosive attack. The self-healing coating on the surface of the material can repair the damaged surface automatically to protect the material [ 35 , 36 , 38 , 75 , 105 , 106 , 107 , 108 , 109 , 110 ]. For example, Lu and coworker reported a novel nanocomposite coating that consisted of lignin-modified graphene and waterborne PU [ 38 ].…”

Industrial applications of superhydrophobic coatings: Challenges and prospects

“…An artificial self-healing surface can regenerate its surface morphology either as a result of the external wear or with the help of another physical affect or from a chemical reaction in the surface layer. For this purpose, the imitation of the living systems by using suitable materials was suggested which can expose fresh layers on the top surface of a SH coating to heal the damages when mechanical wear or some kind of chemical erosion was applied [20,[83][84][85].…”

“…to restore the initial SH properties. Self-organization of hydrophobic colloidal particles at interfaces to impart roughness after mechanical wear was another option [82][83][84][85][86][87][88]. A silane compound was employed to make a self-healing coating, which was absorbed in the bulk coating and diffused onto the surface when any mechanical damage happens.…”

Preparation of Superhydrophobic Fabrics via Chemical Self‐Healing Strategy and Their High Oil/Water Separation Performance and Enhanced Durability

“…Beaded water droplets easily rolls off such surfaces even at a small surface tilt (≤10°). Superhydrophobicity is widely utilized in development of smart materials for various applications such as oil/water separation, synthesis of smart textile, drug delivery, chemical sensors, and water harvesting . Oil/water separation applications are especially attractive because of the need to solve continuous oil pollution problem .…”