Textured Organogel Films Showing Unusual Thermoresponsive Dewetting, Icephobic, and Optical Properties

Abstract

COMMUNICATION (1 of 7)liquids. [2] Thanks to both excellent mobility of the infusing liquids and deformability of the solid matrices, this strategy drastically improved overall performances of such coatings. Slippery liquid-infused porous surfaces, named SLIPS, [3] and related materials, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] are typical successful examples that exhibit external stimuli-responsive liquid/solid repellency, together with other physicochemical properties such as optical/self-healing properties, shape-memory effect, and so on. For example, Yao et al. reported smart coatings showing strain-responsive liquid repellency and optical transparency by infusing perfluorinated fluids into a polytetrafluoroethylene membrane. [4] Under mechanical deformation (stretching), originally transparent liquid-infused films became opaque because air pockets were formed both inside the membrane and on the surface, which enhanced light scattering and turbidity. Similar approaches were also reported by Liu et al. [10] and Roy et al. [13] However, such attempts relied on mechanical stimuli such as stretching and bending. Thus, they are not suitable for the majority of coating applications. To overcome this shortcoming, changes in the surrounding temperatures have also been used as an alternative external stimulus to control both optical and dewetting properties. [5,6] By utilizing the temperature-induced crystallization/decrystallization or solidification/ melting of polymer matrices or infusing liquids, respectively, optical transparency and slipperiness of the sample surfaces were successfully controlled. For example, organogels made of cross-linked polydimethylsiloxane (PDMS) infused with wax, alkanes, or paraffin were transparent and slippery above their melting points, while they became opaque and nonslippery below their melting points. [5,7,12,14] Although thermal change is a useful and universal external stimulus, optical properties of such organogels are difficult to precisely control, for example, when demonstrating a simple transition from transparency to opacity, or the reverse, [5][6][7]12,[14][15][16] because such systems generally rely on phase transitions of solid matrices and/or infusing liquids within entire samples. If such a phase transition could be strictly regulated only on the topmost region close to the sample surfaces, it would potentially lead to a promising and convenient method for preparing functional coatings possessing both Textured organogel films showing thermoresponsive (TR)-syneretic and optical behaviors are fabricated based on soft lithography, using micro/nanostructured master moulds, of polydimethylsiloxane infused with polymethylphenylsiloxane (PMPS) as a lubricating oil. The critical syneretic temperature (CST) of the organogels can be arbitrarily tuned in the range of −15-50 °C by varying the volume of PMPS. Below the CST, the oil is spontaneously released from the inside of the gel matrices to the topmost surface, and vice versa, and it gradually returns bac...

Dynamic Anti‐Icing Surfaces (DAIS)

“…Many anti-icing surfaces use dynamic substrates that respond to the ambient conditions of temperature, magnetic field, light, and so on. [36,44,[73][74][75][76][77][78][79][80][81] By integrating temperature sensitive com-ponents during fabrication, anti-icing substrates can respond to temperature change in the surrounding. [44,73] One of such substrates incorporated a binary liquid mixture (silicon oil and liquid paraffin) into a PDMS network, and the resulting reversibly thermosecreting organogel (RTS-organogel) demonstrated distinct The thermal responsive lubricant regenerable organogel, showing the droplets secretion at low temperature and reversible droplets absorption at high temperature.…”

“…[ 36 , 44 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 ] By integrating temperature sensitive components during fabrication, anti‐icing substrates can respond to temperature change in the surrounding. [ 44 , 73 ] One of such substrates incorporated a binary liquid mixture (silicon oil and liquid paraffin) into a PDMS network, and the resulting reversibly thermosecreting organogel (RTS‐organogel) demonstrated distinct morphologies at different temperature, as shown in Figure 4 a . [ 44 ] Specifically, the substrate was transparent at high temperature as the internal silicon oil and liquid paraffin were miscible.…”

External Stimuli Responsive Liquid‐Infused Surfaces Switching between Slippery and Nonslippery States: Fabrications and Applications

“…On this E‐LIS, sliding speeds of water droplets obviously increased when the temperature increased to higher than T m . Urata et al presented a micro/nanostructured PDMS displaying thermal responsive diffraction and antireflection optical properties . Polymethylphenylsiloxane was adopted as lubricant in this case.…”

“…Urata et al presented a micro/nanostructured PDMS displaying thermal responsive diffraction and antireflection optical properties. [73] Polymethylphenylsiloxane was adopted as lubricant in this case. The critical synergetic temperature (CST) could be tuned in a range from −15 to 50 °C based on different kinds of PDMS and lubricant.…”

Inherently UV Photodegradable Poly(methacrylate) Gels

“…[20] Moreover, the surface texture of organogels influences their wettability and optical properties. [21] However, fabrication of structured organogels is not trivial, since established methods for hydrogels cannot be employed readily. For example, the crosslinked polydimethylsiloxane (PDMS) molds utilized in soft-lithography swell in hydrophobic solvents and are thus prone to deformation.…”