Abstract
Controlling the physicochemical properties of solid surfaces is of utmost importance in many fields, from Life Sciences to Physics to Chemistry. Besides protection of the support material underneath, energy conversion, catalysis, and waterproofing properties are just a few examples. Creating rough surfaces on the micro and nanoscale and modifying the structures with different chemical compounds are considered promising methods to extend the applicability of the functional surfaces. Therefore, the interest in developing the new strategy that can fabricate morphological-tunable micro and nanostructures on solid surfaces, improving the efficiency and controllability of surface functionalization, and applying the functional surface coatings in different practical scenarios has been growing for many years. In the first and second parts of this work, systematic investigations of the effects of the synthesis conditions on the morphology and surface properties of the single-component (SC) silicone nanostructures have been conducted. Practical applications of silicone nanorods (SNRs) materials have been explored. Especially when different cellulosic papers are used as the substrate, SNRs coating endows them with a completely different nanoscale surface texture. While maintaining normal appearance, printability, and writeability, the decorated papers exhibit enhanced physicochemical durability and functionalities in waterproofing, self-cleaning, and anti-microbial. In the third part, to investigate the geometrical effects of the coating structures, a dynamic Droplet Assisted Growth and Shaping (d-DAGS) synthesis strategy is developed to synthesize the stiff bamboo-shaped SC-SNRs. Unless the other silicone- based micro and nanostructures, such as filaments and wires, the obtained bamboo-shaped SNRs present many advanced features, including in situ controllable morphology, tunable height, robust anti-wetting property, and enhanced mechanical stiffness and chemical durability. Tentative applications of the as prepared samples in promoting the buoyancy of the floating stuff, self-cleaning, and water harvesting have been successfully conducted, and exciting results have been obtained, for example, a maximum water collecting rate (WCR) of 32.3 ± 0.6 mg∙cm-2∙min-1 is achieved from the sample with 6-segments bamboo-shaped silicone coating, which is at an advanced level in related studies. In addition, the bottom-up growing mechanism is perfectly verified and explained by the d-DAGS mechanism. Further attempts to grow ultra-long rods with 12 and 18 segments (very high aspect ratio) expand the possibility of developing this method and replicating it on other materials. In the final part, based on the d-DAGS method, different precursors are introduced to synthesize the multi-component hybrid (MCH) silicone nanostructures. Small units (segments) with different chemical compositions are arranged in a controllable specific order to form a bamboo-shaped structure, i.e., MCH-SNRs. The co-existence of the inert and reactive components enables the as-prepared superhydrophobic products to be modified directly and selectively. Region-selective functionalization (RSF) has been successfully performed on the level of a single nanostructure, whose modifiable regions hinge upon the dynamic arrangement of the synthesis process. A vertical region-selective protection (RSP) mechanism is proposed to explain the different surface behaviors of the functionalized MCH-SNRs samples. Additionally, confocal microscopy has been the first-time used to visually reveal the water penetration level and directly exhibit the intermediate wetting state. In addition, a mushroom-like structure, namely, silicone micro-hoodoos (SMHs), has been synthesized when tri-chlorosilane and di-chlorosilane are mixed during the synthesis process. A possible new growing mechanism is proposed and discussed. The excellent anti-adhesive performance shown in the adhesive loop tack strength test of this unique structure strongly supports their potential applications in protecting the substrates underneath the functional coatings. In summary, the results presented in this work systematically demonstrate the one-step synthesis, in-situ shape control, region-selective functionalization, and practical applications of the homo- and heterogeneous silicone-based nanostructures. Further developing and applying the presented facile, efficient, and low-cost d-DAGS method on other materials will provide more opportunities to engineer the surfaces and interfaces with unique physicochemical properties, expand the applicability of the functional coatings, and explore the new world of material science and nanotechnology.
Chen, Kangwei