cm7b02880_si_002.avi (754.59 kB)
Robust and Self-Healable Bulk-Superhydrophobic Polymeric Coating
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posted on 2017-09-19, 00:00 authored by Avijit Das, Jumi Deka, Kalyan Raidongia, Uttam MannaRecovery
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 achieveand extremely important for the practical
utility of this bioinspired property. Recently, very few materials
have been introducedthat are capable of recovering the hierarchical
featuresbut 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
nanosheetwhich 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
topographywithout 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 coatingwithout
any permanent change in the extreme water repellency property. The
unique self-healing process eventually provided a superhydrophobic
printthat 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.