A Superamphiphobic Macroporous Silicone Monolith with Marshmallow‐like Flexibility

Abstract

A number of research groups have been studying the preparation of hydrophobic and oleophobic surfaces, both for pure scientific interest and industrial applications. These studies are drawing increasing attention because of the growing demands for applications such as anti-fingerprint touch panels on electronic devices and solar panels that can prevent output fall from dust and smears on the surface by the self-cleaning effect. [1] In nature, many examples of superhydrophobic surface exist with a water contact angle of more than 1508, such as eyes of mosquitos and lotus leaves, [1a, 2] and these are important for their survival. Their non-wetting surfaces possess a combination of nano-or microscaled roughness [3] and low surface energy, which are known for the key of creating artificial superhydrophobic surfaces. [1a] However, most of the superhydrophobic materials can easily be wetted by organic liquids because of the lower surface tension of the liquids. In recent years, techniques for creating oleophobic surfaces have been vigorously investigated. A promising way to obtain a surface with a contact angle of more than 1508 for organic liquids is to make rough microstructures covered with perfluoroalkyl groups, which are bound on some kinds of polyhedral oligomeric silsesquioxanes (POSS), [4] monomeric silanes, [5] and polymers. [6] However, the reported technologies to achieve superamphiphobicity are limited in the forms of films and fibers. As far as we know, there have been no reports on monolithic superamphiphobic materials that can be prepared in a wide range of thickness and in any shapes.We have been recently investigating marshmallow-like gels derived from tri-and difunctional alkoxysilanes as coprecursors through a facile one-pot sol-gel reaction. [7] These silicone-based macroporous materials have high porosity (> 90 %), flexibility both for compression and bending, and built-in superhydrophobicity. The marshmallow-like gels can be used like a sponge for quick removal of organic liquids/oils from oil-water mixtures for environmental purposes and for new solid-phase extraction media in analytical chemistry. By changing the combination of the alkoxysilanes, various kinds of marshmallow-like gels with different functional groups can be obtained. For example, in the case of methyltrimethoxysilane-dimethyldimethoxysilane copolymer system, the obtained gels are composed of the cross-linked polydimethylsiloxane (PDMS)-like molecular structure. They retain the flexible mechanical properties over a wide temperature range from À130 8C to 320 8C, as evidenced from thermal and mechanical analyses. Moreover, owing to their elasticity and bendability even at temperature of under À196 8C, we can successfully absorb and squeeze-out liquid nitrogen. In the case of (3-mercaptopropyl)trimethoxysilane-(3-mercaptopropyl)methyldimethoxysilane copolymer system, gold ions can be adsorbed on the pore surface by the mercapto groups.We employed a vinyltrimethoxysilane (VTMS)-vinylmethyldimethoxysilane (VMDMS) co-precursor sys...

Integrating Superwettability within Covalent Organic Frameworks for Functional Coating

“…Given the increasing demand of water-repellent materials, [51][52][53][54] here we report on an effective approach of using a facile pore-surface modification to impart the COFs with superhydrophobicity, as demonstrated by grafting fluorinated compounds onto a vinyl-functionalized COF via a thiol-ene click reaction. Through judicious choice of fluorinated compounds and careful optimization of the post-synthetic modification conditions, the resultant COF exhibits superhydrophobic behavior while retaining the porosity and crystallinity of the pristine COF.…”

“…To test the feasibility of pore channel engineering for controlling the wettability of COFs, we selected a COF bearing the vinyl functionality synthesized from the condensation between 1,3,5-tris(4-aminophenyl)-benzene and 2,5-divinylterephthalaldehyde, which was developed by our group, for proof of principle because of its excellent chemical stability, large pore size, and abundant high reactivity vinyl groups for potential chemical transformations ( Figure 1). 23 Given the low surface free energy of fluorinated compounds, 53 especially for the long chain ones, in conjugation with the facility and controllability of the thiol-ene click reaction, 52 1H,1H,2H,2H-perfluorodecanethiol was chosen to modify the pore surface of COF-V to manipulate the wettability. Because the enhancement of hydrophobicity, by increasing the grafting degree of fluorinated compounds, is at the expense of both porosity and crystallinity of the material, reaction conditions were screened to achieve the trade-off between hydrophobicity and the retention of intrinsic properties of the COF.…”

“…To examine the change of surface functionalities after chemical modification, we performed Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (TEM) energy dispersive X-ray spectroscopy (EDX) mapping, and solid-state NMR spectroscopy. The appearance of new peaks at 1,241 and 1,212 cm À1 , which were assigned to the C-F stretching vibration 53 together with the presence of the C-F (292.2 eV), as well as elements F (F1s at 689.6 eV) and S (S2p at 163.4 eV) signals in the FTIR ( Figure S5) and XPS spectra of COF-VF ( Figure S6), respectively, indicate the successful incorporation of perfluoroalkyl groups onto COF-V. The EDX mapping via TEM verifies the homogeneously distributed F, N, and S elements throughout COF-VF ( Figure S7).…”

Fish scale inspired design of underwater superoleophobic microcone arrays by sucrose solution assisted femtosecond laser irradiation for multifunctional liquid manipulation

“…[1,4] Inspired by fish scales, many kinds of underwater superoleophobic and low-adhesive interfaces have been fabricated with diverse technologies to boost their applications in self-cleaning coatings, fluidic devices, oil-water separation, bioadhesion, oil-droplet manipulation and so on. On the other hand, bottom-up methods [5,[9][10][11][12][13][14][15] including electro/spray/vapor/deposition, [9,10] hydrothermal method, [11] sol-gel process, [12] dip coating, [13] self-assembly, [14] and template method [15] are also used for fabricating underwater superoleophobic surfaces due to their cheapness. However, these methods have many drawbacks such as the fabricated surfaces are fragile, or the process needs a long molding cycle, even forms residual solution which will pollute the environment.…”

Macroporous Silicone Sheets Integrated with Meshes for Various Applications

“…We have fabricated a flexible macroporous silicone material, which we call "marshmallow-like gel" (MG), by copolymerizing tri-and di-functional alkoxides while controlling phase separation with a cationic surfactant. [15][16][17][18] This macroporous silicone material has various possible applications owing to its chemical resistance, cold resistance, biocompatibility, and surface reactivity, which are similar to PDMS. We have reported the use of MG as a water-oil separation medium like a sponge, a liquid nitrogen absorption/holding material for simple dry shipping, and as a simple mass production medium for giant vesicles (liposomes).…”