Robust and Self-Healable Bulk-Superhydrophobic Polymeric Coating

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

Robust and Self-Healable Bulk-Superhydrophobic Polymeric Coating

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

‘Charge Reverse’ Halogen Bonding Contacts in Metal-Organic Multi-Component Compounds: Antiproliferative Evaluation and Theoretical Studies

Two new metal–organic multi-component compounds of Ni(II) and Co(II), viz. [Ni(3-CNpy)2(H2O)4]ADS·2.75H2O (1) and [Co(3-CNpy)2(H2O)4](4-ClbzSO3)2 (2) (3-CNpy = 3-cyanopyridine, ADS = anthraquinone-1,5-disulfonate, 4-ClbzSO3 = 4-chlorobenzenesulfonate), were synthesized and characterized using single crystal XRD, TGA, spectroscopic (IR, electronic) and elemental analyses. Both the compounds crystallize as multi-component compounds of Ni(II) and Co(II), with uncoordinated ADS and 4-ClbzSO3 moieties in the crystal lattice, respectively. Crystal structure analyses revealed the presence of antiparallel nitrile···nitrile and π-stacked assemblies involving alternate coordinated 3-CNpy and uncoordinated ADS and 4-ClbzSO3 moieties. Moreover, unconventional charge reverse Cl∙∙∙N halogen bonding contacts observed in compound 2 provide additional reinforcement to the crystal structure. Theoretical calculations confirm that the H-bonding interactions, along with anion–π(arene) and anion–π(CN) in 1 and π–π, antiparallel CN···CN and charge reverse Cl···N halogen bonds in 2, play crucial roles in the solid state stability of the compounds. In vitro anticancer activities observed through the trypan blue cell cytotoxicity assay reveal that the compounds induce significant concentration dependent cytotoxicity in Dalton’s lymphoma (DL) cancer cells, with nominal effects in normal healthy cells. Molecular docking studies reveal that the compounds can effectively bind with the active sites of anti-apoptotic proteins, which are actively involved in cancer progression

Strategic Formulation of Graphene Oxide Sheets for Flexible Monoliths and Robust Polymeric Coatings Embedded with Durable Bioinspired Wettability

Artificial bioinspired superhydrophobicity, which is generally developed through appropriate optimization of chemistry and hierarchical topography, is being recognized for its immense prospective applications related to environment and healthcare. Nevertheless, the weak interfacial interactions that are associated with the fabrication of such special interfaces often provide delicate biomimicked wettability, and the embedded antifouling property collapses on exposure to harsh and complex aqueous phases and also after regular physical deformations, including bending, creasing, etc. Eventually, such materials with potential antifouling property became less relevant for practical applications. Here, a facile, catalyst-free, and robust 1,4-conjugate addition reaction has been strategically exploited for appropriate covalent integration of modified graphene oxide to developing polymeric materials with (1) tunable mechanical properties and (2) durable antifouling property, which are capable of performing both in air and under oil. Furthermore, this approach provided a facile basis for (3) engineering a superhydrophobic monolith into arbitrary free-standing shapes and (4) decorating various flexible (metal, synthetic plastic, etc.) and rigid (glass, wood, etc.) substrates with thick and durable three-dimensional superhydrophobic coatings. The synthesized superhydrophobic monoliths and polymeric coatings with controlled mechanical properties are appropriate to withstand different physical insults, including twisting, creasing, and even physical erosion of the material, without compromising the embedded antiwetting property. The materials are also equally resistant to various harsh chemical environments, and the embedded antifouling property remained unperturbed even after continuous exposure to extremes of pH (pH 1 and pH 11), artificial sea water for a minimum of 30 days. These flexible and formable free-standing monoliths and stable polymeric coatings that are extremely water-repellent both in air and under oil, are of utmost importance owing to their suitability in practical circumstances and robust nature