Hollow polysiloxane nanostructures based on pressure-induced film expansion

Abstract

IntroductionSuperhydrophobic surfaces comprise a class of materials characterized by extreme water repellency, a low roll-off angle and self-cleaning ability.1-5 These ultimate properties are achieved by combining roughness with a low-energy surface.1-3,6-9 The composite CassieBaxter wetting state 10 is connected to superhydrophobicity through high contact angles and low roll-off angles. Industrial applications concerning superhydrophobicity are currently only slightly behind the academic state-of-the-art, which makes the field interesting from the point of view of basic research as well as applications, provided the structures are able to cope with both chemical and mechanical wear and tear. 11An interesting approach using 1D nanostructures, denoted as silicone nanofilaments (SNFs), has shown excellent properties as well as resilience toward chemical and also mechanical wear. 12,13 In addition, SNFs have been shown to retain the CassieBaxter wetting state even when subjected under pressure.9 In 2006-2007, three groups independently reported on the first successful synthesis of the 1D polysiloxane nanostructures [14][15][16] and later more studies emerged to deepen the understanding of the process parameters, 12,13,17-25 and recently, also larger tubular polysiloxane structures were introduced. 26A few growth models for the SNFs have been proposed until this day. [18][19][20]24,27,28 However, these models are challenged by our observation of hollow polysiloxane nanostructures. Gao and McCarthy 27 were the first to propose a growth mechanism for SNFs, which they synthesized in solution phase from a trimethylchlorosilane/tetrachlorosilane (TMCS/TCS) azeotrope. In their model, TCS molecules cross-linked and formed 3D structures, yet occasionally TMCS molecules terminated the growth. Finally, the lateral expansion was fully blocked and growth continued in one direction. Rollings and Veinot 18 systematically expanded their original study 16 using the atmospheric gas-phase process and introduced a growth model hypothesis. They reasoned

Superhydrophobic Coatings Prepared by the in Situ Growth of Silicone Nanofilaments on Alkali-Activated Geopolymers Surface

“…It is logical to conclude that the condensation between Si–OH/Al–OH existing on the surface of the geopolymer and PMHSO may always occur during the self-cross-linking of the PMHS to form silicone nanofilaments. This may be different from the previous view that the growth of the silicon nanofilaments is initiated by the tip. ,,,, The in situ growth of this silicon nanofilaments can be attributed to the root, which triggers the “mushroom like” strand to stretch upwards successively to form the final one-dimensional nanostructure.…”

“…From this, one-dimensional soft matter, silicone nanofilaments (SNFs), with unusual wetting behavior is derived. These were first synthesized through chemical vapor deposition and liquid deposition by Gao and McCarthy using methyltrichlorosilane and vapor-phase plasma-induced polymerization using vinyltrichlorosilane by Rollings et al Currently, these have been prepared on the surfaces of glass, ceramics, cotton fabric, silk, wood, nanofibrillated cellulose, etc. ,,− In addition to excellent hydrophobicity, they exhibit high transparency, environmental stability, good solvent resistance, and chemical resistance over a certain range. − Up to now, the preparation technology of silicone nanofilaments is still based on vapor-phase and liquid-phase depositions mainly, ,− and only a few changes or improvements on this basis have been found in the follow-up study. , There is no exception that the relationship between the formation of a filamentous structure and the film water layer enriched on the surface of the substrate was emphasized in these publications. Proper control of the humid environment and reasonable dosage of silane had always occupied the core of the research on these materials. ,,,,, Recently, a droplet-assisted growth and shaping mechanism has been proposed to explain the in situ formation of nano- and microstructures composed of polysiloxane and other materials such as germanium oxide.…”

“…38−40 Up to now, the preparation technology of silicone nanofilaments is still based on vapor-phase and liquid-phase depositions mainly, 34,41−45 and only a few changes or improvements on this basis have been found in the follow-up study. 46,47 There is no exception that the relationship between the formation of a filamentous structure and the film water layer enriched on the surface of the substrate was emphasized in these publications. Proper control of the humid environment and reasonable dosage of silane had always occupied the core of the research on these materials.…”

Mapping microscale wetting variations on biological and synthetic water-repellent surfaces

“…Surface was prepared as described in the literature 34 . Silicon (100) wafer was cleaned by ultrasonication in alkaline solvent (Deconex 11 Universal, VWR), rinsed thoroughly by Milli-Q water, and dried under nitrogen flow.…”

Surface Structuring and Water Interactions of Nanocellulose Filaments Modified with Organosilanes toward Wearable Materials

“… 21 Such features were reported earlier for other systems. 27 , 28 For instance, a study dealing with the superhydrophobization of textile materials with TC indicated the appearance of hairy features, therein described as nanofilaments. 27 Within a different scope, Korhonen et al 28 implemented a controlled system to grow hollow polysiloxane nanofilaments from silicon wafer surfaces using TC as the precursor and provided detailed insight into the growing mechanisms.…”