Smart Coatings Research Articles

Smart Coatings Prepared via MAPLE Deposition of Polymer Nanocapsules for Light-Induced Release.

Herein, smart coatings based on photo-responsive polymer nanocapsules (NC) and deposited by laser evaporation are presented. These systems combine remotely controllable release and high encapsulation efficiency of nanoparticles with the easy handling and safety of macroscopic substrates. In particular, azobenzene-based NC loaded with active molecules (thyme oil and coumarin 6) were deposited through Matrix-Assisted Pulsed Laser Evaporation (MAPLE) on flat inorganic (KBr) and organic (polyethylene, PE) and 3D (acrylate-based micro-needle array) substrates. SEM analyses highlighted the versatility and performance of MAPLE in the fabrication of the designed smart coatings. DLS analyses, performed on both MAPLE- and drop casting-deposited NC, demonstrated the remarkable adhesion achieved with MAPLE. Finally, thyme oil and coumarin 6 release experiments further demonstrated that MAPLE is a promising technique for the realization of photo-responsive coatings on various substrates.

Preface

III Smart NanoMaterials: Advances, Innovation and Applications (SNAIA) Summit École Nationale Supérieure de Chimie de Paris, ParisTech, France8-11 December 2020A. Baldycheva1,2 and E. Berseneva1,2 1University of Exeter, Exeter, UK 2STEMM Global, London, UKSmart nanomaterials are the basis of diverse emerging applications, including wearable and printed electronics, flexible optoelectronics, CMOS photonics, quantum computing, smart coatings and thin films. This collection focuses on the most recent scientific and technological advances, innovations and new practical applications of novel smart nanomaterials presented at the 3rd Smart Nanomaterials Conference, SNAIA 2020. It covers topics ranging from advances in the most critical aspects in chemistry and material fabrication of nanomaterials, to the engineering of prototype devices and systems.List of Scientific Committee, Organising Committee, Editorial Board, Invited Speakers, Supporters and Partners and this titles are available in this pdf.

Synthesis of Monoclinic Vanadium Dioxide via One-Pot Hydrothermal Route

Pure monoclinic vanadium dioxide nanoparticles (VO2 NPs) with a controlled uniform size are considered essential for the preparation of thermochromic smart window coatings on desired substrates. Herein, we report a facile one-step hydrothermal synthesis of VO2(M) NPs without post-treatment of annealing, which may induce unwanted aggregation of NPs. In contrast with the annealed sample, the one-step processed VO2(M) NPs exhibit superior thermochromic performance with the solar modulation efficiency of 11.8% and luminous transmittance of 37.3%.

The synergic effect of microcapsules and titanium nanoparticles on the self-healing and self-lubricating epoxy coatings: A dual smart application

In the present study, the multi-functional smart epoxy coatings were fabricated by incorporating the 15 wt.% microcapsules containing the linseed oil and various percentage of nano-TiO2 (4, 8, 12 and 16 wt.%). The self-healing and self-lubricating abilities of these nanocomposite coatings were investigated by corrosion and wear tests. The obtained results showed that the smart coating containing the 16 wt.% nano-TiO2 had the best function in the corrosion media, due to healing a scratch in form of layer by layer. By using the microscopically analysis, it was found that the linseed oil acted as lubricant agent in the wear test. Adding 4 wt.% nano-TiO2 had the negative effect on the anti-wear properties, due to forming the nanocomposite debris. However, by increasing the percentage of nano-TiO2 up to 12 wt.%, the anti-wear properties had the enhancing trend. Improving the mechanical function of coatings, forming the nano-TiO2/linseed oil self-suspense and trapping the debris by capsule containers were the characterized mechanisms for improving the anti-wear properties. It was also realized that the formation of nano-TiO2/epoxy skin on the surface of microcapsules and agglomeration of nanoparticles had the negative effect on the wear properties of smart coatings.

Switching (bio-) adhesion and friction in liquid by stimulus responsive polymer coatings

Controlling (bio-) adhesion and friction is essential in many bio-medical and industrial applications. Such control can be achieved using stimulus responsive polymers. Coatings composed of these polymers are able to adapt their physicochemical properties to changes in the surrounding environment, such as temperature, light, pH, electronic and magnetic fields. This responsive behavior can be employed in the development of advanced technologies as for example underwater adhesives, self-adhering wound dressings, soft robotics and targeted drug delivery. In this review, we present an overview of the current status of research on controlling adhesion and friction in liquid environments using surface-bound stimulus responsive polymers. We focus in particular on polymer brushes and the role of specific interactions between the surfaces in the contact. These interactions can give rise to complex relations between swelling of the polymer film and its tribomechanical properties. A careful characterization of the change in specific interactions upon varying the environment is, therefore, critical for the design of effective smart coatings. We will finish this review with an overview of the open questions in the field and a discussion of the potential impact that the polymer-based smart adhesives and lubricants can have on industry and society.

Transparent hydrophobic thermal insulation CsxWO3-ZnO-SiO2 coatings:Energy saving, anti-dust and anti-fogging performance

CsxWO3-ZnO-SiO2 smart coatings were proposed to achieve multiple functions, such as thermal insulation, anti-dust, anti-fogging and blocking harmful ultraviolet light, etc. The transparent hydrophobic hybrid resins were prepared from methyltriethoxysilane (MTES) and SiO2 sol, which was used as the substrate of the composite coating. The CsxWO3 is served as the near-infrared (NIR) absorber, and the ZnO is functioned as the ultraviolet (UV) blocking agent. Coatings with different ratios of CsxWO3 and ZnO were successfully prepared by co-blending with nano-SiO2 resin. The morphology, microstructure, surface composition, hydrophobicity, thermal stability, anti-dust and optical property of the composite coatings were investigated comprehensively. The transmittance of C10Z10 (CsxWO3 10%, ZnO 10%, nano-SiO2 resin 80%) coating at 370 nm is 2.3%, and the value of Solar Energy Transmittance Selectivity (SETS) is 0.665, which exhibits excellent NIR shielding ability. Compared with nano-SiO2 resin coating, the thermal insulation temperature difference can reach 7.0 °C. The C10Z10 coating showed good durability in the twenty times anti-dust repeated tests and the efficiency could maintain 70.3% after the repeating tests. The coating showed excellent sustainability after a 45-day outdoor exposure experiment and a 240 h of artificial accelerated aging experiment. Thus, the proposed CsxWO3-ZnO-SiO2 coatings are promising for outdoor smart windows.

Stimulus Responsive Zeolitic Imidazolate Framework to Achieve Corrosion Sensing and Active Protecting in Polymeric Coatings

Metal substrates beneath polymeric coatings are susceptible to localized corrosion, which could result in lifetime reduction and catastrophic failure without timely repair treatment. In situ detection of corrosion and repair coating defects are in high demand yet challenging to fulfill so far. Herein, we report a smart polymeric coating by integrating nanosensors into the coating matrix, which is capable of efficient corrosion sensing and active anticorrosion protecting. The nanosensors were constructed by zeolitic imidazolate framework encapsulated with the polyethylene glycol-tannic acid complex. The morphology, chemical constitution, and stimulus responsiveness of nanosensors were systematically analyzed. The generation of local corrosion beneath coating can be promptly sensed and reported by a conspicuous purple color derived from tannic-iron ion coordinates. Meanwhile, local electrochemical impedance spectroscopy results proved that the metal degradation process at the defected interface can be largely inhibited, exhibiting active anticorrosion property. Furthermore, the constructed smart coating possessed superior impermeability and long-term protective performance under simulated seawater and harsh salts spray conditions. This feasible and effective strategy based on simple nanosensors to engineer smart coatings paves a new way to develop high environmental adaptability protective materials with protecting, corrosion sensing, and self-healing functions.

Epidermis microstructure inspired mica-based coatings for smart corrosion protection

Two-dimensional (2D) graphene-like nanomaterials have gained interest in anticorrosion coatings due to their enable to act as physical barriers to aggressive species, yet 2D coatings are not always effective or sustainable. Inspired by the epidermis microstructure, herein we designed a high-performance anticorrosion coating with rapid self-healing ability via integrating the excellent adhesion property of polydopamine (PDA) and superior barrier properties of natural mica nanosheets (MNSs) for the first time. Such the coating comprises a protective hard top layer with MNSs constituents (“sealing” agents) and a bottom hybrid soft polymer multilayer, forming a stratified epidermis microstructure, can realize a complete restoration of coating defects under water owing to their mutual benefit. These MNSs not only can enhance the barrier performance of the coating matrix to retard the diffusion of aggressive species and hamper polymer release into water, but also induce an anisotropic diffusion to promote the self-healing of the polymer chains. The microstructures of the bioinspired coatings were systemically investigated by scanning electron microscopy (SEM) and optical microscopy (OM) measurements. Electrochemical results confirmed the anticorrosion performance of the coatings were significantly improved. This work provides a new insight for the design and fabrication of 2D nanomaterials reinforced high-performance and smart anticorrosion coatings.

Development of durable and superhydrophobic nanodiamond coating on aluminum surfaces for improved hygiene of food contact surfaces

Foodborne illness outbreaks caused by bacterial pathogens may take place on a large scale and result in millions of hospitalizations and thousands of deaths every year throughout the world. One key strategy for dealing with this global issue is the design of smart surfaces and coatings which inhibit and reduce bacterial attachment. This can mitigate contamination and cross-contamination during farm-to-table food processing, promoting food safety, and hygiene. Herein, we reported a durable superhydrophobic coating on aluminum surfaces fabricated by sequential deposition of ultrahard nanodiamond, self-assembly of l-3,4-dihydroxyphenylalanine (l-dopamine), and chemical modification with an organoflurosilane. This coating achieved static, advancing, and receding water contact angles of 159.0 ± 2.5°,154.0 ± 2.4°; and 153.7 ± 1.7°, respectively, representing water super-repellency with a low overall root mean square (rms) roughness of 173.5 ± 69.6 nm. In comparison to the bare, unmodified aluminum, the coated aluminum surfaces prevented the attachment of 99.5% of applied Escherichia coli O157:H7 (E.coli O157:H7) and 99.0% of Staphylococcus aureus (S. aureus) cells. In addition, due to the presence of nanodiamond building blocks, the coated surfaces demonstrated a high mechanical resistance against scratching and endured at least 10,000 shearing/rubbing cycles with a nylon surface. Overall, we anticipate that implementation of this coating could improve safety and hygiene of food-contact surfaces that require harsher mechanical operational conditions.

Enhanced Corrosion Protection of A-36 Steel Using Epoxy-Reinforced CSA-Doped Polyaniline-SnO2 Nanocomposite Smart Coatings

Reinforced epoxy polymer nanocomposites have been employed as anti-corrosion coatings on various metallic substrates due to their beneficial characteristics and high electrochemical performances. In this work, we explore the anti-corrosion behavior of reinforced epoxy (EP) polymer nanocomposite consists of polyaniline (PANI)-tin oxide (SnO2) doped with camphor sulfonic acid (CSA). PANI-SnO2 nanocomposites doped with CSA were prepared by in situ chemical oxidative polymerization of aniline in the presence of SnO2 nanoparticles. The morphological and structural features of the prepared nanocomposites were investigated through scanning electron microcopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Further, the coatings of these PANI:SnO2 nanocomposites with epoxy were employed on A-36 steel (carbon steel) substrates to investigate their corrosion protection behavior. The effect of SnO2 presence in the composite towards enhancing the corrosion protection was discussed through the Tafel polarization, polarization resistance, and electrochemical impedance spectroscopy (EIS) as well as oxygen gas permeability studies. Successful formation of potential barriers and their corrosion inhibition abilities were discussed. The EP:PANI:SnO2 composite coatings demonstrate an excellent corrosion inhibition efficiency of 98% in comparison to neat epoxy (43%). The investigation on mechanical properties of these coatings indicates improved adhesion, Young’s modulus, and tensile strength due to the presence of SnO2 nanoparticles. Owing to their enhanced conductivity, superior electrochemical performance and excellent mechanical properties, these EP:PANI:SnO2 nanocomposite coatings could form smart anti-corrosion formulations in protecting A-36 steel against harsh environments.

Chitosan-based smart hybrid materials: a physico-chemical perspective.

Chitosan is one of the most studied cationic polysaccharides. Due to its unique characteristics of being water soluble, biocompatible, biodegradable, and non-toxic, this macromolecule is highly attractive for a broad range of applications. In addition, its complex behavior and the number of ways it interacts with different components in a system result in an astonishing variety of chitosan-based materials. Herein, we present recent advances in the field of chitosan-based materials from a physico-chemical perspective, with focus on aqueous mixtures with oppositely charged colloids, chitosan-based thin films, and nanocomposite systems. In this review, we focus our attention on the physico-chemical properties of chitosan-based materials, including solubility, mechanical resistance, barrier properties, and thermal behaviour, and provide a link to the chemical peculiarities of chitosan, such as its intrinsic low solubility, high rigidity, large charge separation, and strong tendency to form intra- and inter-molecular hydrogen bonds.

Teddy, The Little Refugee Mouse by Dorothy Burroughes, and: The Magic Herb by Dorothy Burroughes

Reviewed by: Teddy, The Little Refugee Mouse by Dorothy Burroughes, and: The Magic Herb by Dorothy Burroughes Jan Susina (bio) Teddy, The Little Refugee Mouse. By Dorothy Burroughes, edited by Jack Zipes. Little Mole and Honey Bear, 2021. The Magic Herb. By Dorothy Burroughes, edited by Jack Zipes. Little Mole and Honey Bear, 2021. The most recent reprints in Jack Zipes's Fabulous Excavated Tales series are two books written and illustrated by Dorothy Burroughes. Popular during the 1930s and 1940s, Burroughes is a British children's author who is rarely mentioned in the histories of children's literature but is still held in high regard as a print maker and poster artist. Trained at the Slade School of Fine Art, Burroughes's first major success as a commercial artist was designing posters in 1920 for the London Underground that encouraged visitors to the London Zoo in Regent's Park. Drawn in the style of Japanese woodcuts, her image of Langur monkeys became popular with the public. Her second zoo poster, known as "the monkey poster," became the most requested poster in the history of the London Underground and is reprinted in both volumes along with her striking print of "The Black Panther." In the 1930s and 1940s, Burroughes was considered one of the leading British animal artists, along with Harry Rountree and Cecil Aldin. Many of her twenty children's books, like her better-known posters and prints, focus on animals and animal rights. Burroughes established her reputation as an animal artist with her prints and posters often featuring animals that she sketched at the Regent's Park Zoo and was awarded a Zoological Society Fellowship for her animal artwork. Yet she expressed mixed feelings about zoos and restricting animals in cages. In addition to illustrating informational books on animals such as Queer Beasts at the Zoo (1927) and Queer Birds at the Zoo (1927), Burroughes also wrote children's stories featuring anthropomorphized creatures that address social issues and emphasize the need to treat animals with respect and kindness. While Burroughes uses watercolor illustrations interspersed with linocuts in her children's books, her stories are longer and more complicated than those by Beatrix Potter and are intended for older readers. Her chummy and social world of animals more closely resembles that of Kenneth Grahame in [End Page 445] The Wind in the Willows, without the humorous escapades of Mr. Toad that A.A. Milne admired. The Magic Herb shows a bit of Lewis Carroll influence. Three badgers go on a quest for the Magic Herb to aid their seriously ill baby brother. To obtain the mysterious plant, they must journey to the Magic Isle where the white plant is guarded by the Dodo and the Unicorn. Burroughes draws the Dodo so he resembles John Tenniel's illustration of the Dodo in Alice's Adventures in Wonderland. The Dodo, who initially appears rather fierce, is just "a little embittered by being misunderstood" (19). He is moved by the unselfish nature of the badgers' quest. As the Unicorn explains to the badgers, he and the Dodo are tasked with the responsibility of preventing the life-restoring plant from falling into the wrong hands, such as "pompous scientists and people who-want-towrite-to-the-papers" about discovery of this rare species. The selfless nature of the badgers' quest is reminiscence of Gluck's journey in John Ruskin's The King of the Golden River. The badgers succeed on their impossible journey, liberate the Dodo and the Unicorn from their long-term duties as protectors of the Magic Herb, and restore their younger brother to health, all a result of their selflessness. Teddy, The Little Refugee Mouse is an updated version of Aesop's "Country Mouse and City Mouse." Teddy is an elegant mouse who wears a smart gray coat with clean white collars. He accompanies his human family when they vacate London for the country for the duration of the War. Burroughes uses animal figures to comfort younger readers who were moved from the cities to escape Nazi bombing during World War II. Teddy is befriended by the Brown Mouse family who introduce him to the rural world of cows, pigs...

Modulation of flexo-rigid balance in photoresponsive thymine grafted copolymers towards designing smart healable coating.

Efficacy and durability of the photovoltaic device mandates its protection against hot, humid weather condition, high energy of UV light and unwanted scratches. Such challenges can be mitigated by smart polymeric coating with inherent properties e.g. hydrophobicity to prevent moisture, optimal viscocity for better processibility and crack-healing. The hydrophobic polymers TP1–TP4 containing pendant photo-crosslinkable thymine moieties are designed that undergo [2 + 2] photocycloaddition upon UVB irradiation and can be dynamically reverted back upon irradiation with UVC light. A judicious control of solvent environment, chain length, functionality% and concentration of the polymers regulate the aspects of photodimerization thereby, rendering intra or inter-chain collapse to form diverse nanostructures. Photodimerization of the thymine moieties renders coil to globule transformation in dilute condition whereas irradiation performed at high macromolecular concentration regime exhibits higher order nanostructures. The photoresponsive chain collapse leads to the formation of rigid crosslinked domains within flexible polymer chains akin to the hard–soft phases of thermoplastic elastomers. Such rigidification of the crosslinked segments endows a tool to photomodulate the glass transition temperature (Tg) that can dynamically revert back upon decrosslinking. Further, the structural modulation of the polymers is explored towards autonomic and nonautonomic self-healing behaviour at ambient conditions. Moreover, the self-healing efficacy can be tuned with the film thickness and it remains unaltered upon using solar simulator or direct sunlight. Overall, such hydrophobic low Tg polymers display photo-regulated self-healing mechanism consisting of both autonomic and non-autonomic self-healing and may find applications in designing smart protective coatings for photovoltaic devices.

Self-healing polymers using electrosprayed microcapsules containing oil: Molecular dynamics simulation and experimental studies

In the present study, a group of microcapsule-based smart coatings has been investigated to decrease the corrosion rate in oil and gas transmission lines. The microcapsules are made of epoxy resin and self-healing materials such as oil, which acts as a repairing agent. In this study, the parameters affecting the coating performance such as agitation rate in the micro capsulation process, microcapsule size, and percentage of microcapsule used in the coating structure have been investigated and optimized. Also, other properties of the smart coating, such as the ability to protect against corrosion and adhesion of the coating to the substrate, are examined by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) analysis, and pull-off test. The use of microcapsules indicates that as the microcapsules become smaller, the corrosion resistance, as well as the adhesion of the coating to the substrate, is improved. Also, the use of microcapsules in the structure improves the protective capability significantly. The best percentage of microcapsules is the sample with 40 wt%, which increases the corrosion resistance of the coating, although the polymers increase the results of electrochemical and water absorption tests. The formation of microcracks is a serious problem in the use of polymers composites. The creation and spread of these microcracks cause the destruction of these materials and reduces the lifetime of the polymeric material. Above for the synthesis of microcapsules, the method of preparing self-healing polymers and adding them to the containing 40% of microcapsules may provide a suitable coating for carbon steels of oil and gas industries along with a suitable model of its molecular dynamics simulation (MDs).

A Self-Strengthening Epidermis-Like Smart Coating Enabled by Dynamic Iron Sequestration

Living organisms rely on materials sequestration from the environment to strengthen their bodies. Such constant activity provides necessary supplies for critical biological functions, which is diff...

(Invited) Printing Optical Materials

Will future of smart lighting and window coatings enable energy-efficient cooling in smart buildings? Can printed color converters lead to next generation micro displays with high brightness, sharp image resolution, and ultra‐low power consumption? Recently, exciting new physics of nanoscale optical materials has inspired a series of key explorations to manipulate, store and control the flow of information and energy at unprecedented dimensions. In this talk we will report our recent efforts on controlling light harvesting and conversion process using scalable micro/nanofabrication. These emerging optical materials show promise to a range of important applications, from optical networks and chip-scale photonic sensors to lasers, LEDs, and solar technology.For example, pixelated color converters are envisioned to achieve full-color high-resolution display through down conversion of blue micro-LEDs. Quantum dots (QDs) are promising narrow-band converters of high quantum efficiency and brightness enabling saturated colors. However, challenges still remain to produce high resolution color-selective patterns compatible with the advanced blue micro-LEDs with pitch and pixel size approaching 1 µm. Here we demonstrate our preliminary study on scalable printing of high-resolution pixelated red and green color converters patterned through projection lithography. We will also discuss potential applications such as high-resolution wide-gamut microdisplay for mixed reality and high speed visible light communication.In this talk, We will also introduce versatile 3D shape transformations of nanoscale structures by deliberate engineering of the topography-guided stress of gold nanostructures. By using the topography-guided stress equilibrium, rich 3D shape transformation such as buckling, rotation, and twisting of nanostructures is precisely achieved, which can be predicted by our mechanical modeling. Benefiting from the nanoscale 3D twisting features, giant optical chirality is achieved in an intuitively designed 3D pinwheel-like structure, in strong contrast to the achiral 2D precursor without nano-kirigami. The demonstrated nano-kirigami, as well as the exotic 3D nanostructures, could be adopted in broad nanofabrication platforms and could open up new possibilities for the exploration of functional micro-/nanophotonic and mechanical devices.

Smart Coatings for Corrosion Protection: On the Need for New Coating Concepts

Ideally smart coatings for corrosion protection have to be able to protect the underlying metal from corrosion by providing excellent barrier properties, at the same time showing a fast and efficient self-healing in case a defect down to the metal is inflicted into them, while being as delamination resistant as possible.These seem to be basically incompatible properties, as either mobility of species is high or the coating is highly impermeable, i.e. it is difficult to envisage a coating that can be both at the same time. In fact, in recent works we have shown that for excellent self-healing performance especially the resistance against cathodic delamination of a coating should be significantly weakened [1, 2]. Using conductive polymer additions to non-conductive coatings, both high self-healing activity [1-3] as well as high resistance against cathodic delamination [4, 5] can be controlled in a wide range.Based on an in-depth understanding of the underlying mechanisms we are currently working on strategies for developing coatings that show excellent active as well as passive protection properties. Latest progress of the research on this topic well be presented and the implication will be discussed.[1] M. Uebel, L. Exbrayat, M. rabe, T.H. Tran, D. Crespy, M. Rohwerder, On the Role of Trigger Signal Spreading Velocity for Efficient Self-Healing Coatings for Corrosion Protection, Electrochem. Soc. 165 (2018) C1017-C1027[2] H. Tran , A. Vimalanandan , G.Genchev , J. Fickert , K. Landfester, D. Crespy , M.Rohwerder, Regenerative Nano-Hybrid Coating Tailored for Autonomous Corrosion Protection, Advanced Materials 27(25) (2015) 3825-3830[3] A. Vimalanandan, L.P. Lv, T.H. Tran, K. Landfester, D. Crespy, M. Rohwerder, Redox-Responsive Self-Healing for Corrosion Protection, Advanced Materials 25(48) (2013) 6980-6984[4] Anna Merz, Matthias Uebel, Michael Rohwerder, The Protection Zone: A Long-Range Corrosion Protection Mechanism around Conducting Polymer Particles in Composite Coatings: Part I. Polyaniline and Polypyrrole, Electrochem. Soc. 166 (2019) C304-C313[5] Anna Merz, Michael Rohwerder, The Protection Zone: A Long-Range Corrosion Protection Mechanism around Conducting Polymer Particles in Composite Coatings: Part II. PEDOT:PSS, Electrochem. Soc. 166 (2019) C314-C320

Preparation of Sub-50 nm Colloidal Monodispersed Hollow Siloxane-Based Nanoparticles with Controlled Shell Structures.

Hollow siloxane-based nanoparticles (HSNs) have attracted significant attention because of their promising unique properties for various applications. For advanced applications, especially in catalysis, drug delivery systems, and smart coatings, high dispersibility and monodispersity of HSNs with precisely controlled shell structures are important. In this study, we established a simple method for preparing colloidal HSNs with a uniform particle size below 50 nm by the reaction of colloidal silica nanoparticles with bridged organoalkoxysilane [1,2-bis(triethoxysilyl)ethylene: (EtO)3Si-C2H2-Si(OEt)3, BTEE] in the presence of a cationic surfactant. Upon the formation of organosiloxane shells by hydrolysis and polycondensation of BTEE, the core silica nanoparticles were spontaneously dissolved, and a part of the silicate species was incorporated into the organosiloxane shells. The size of the colloidal silica nanoparticles, the amount of BTEE added, and the pH of the reaction mixture greatly affected the formation of HSNs. Importantly, colloidal HSNs having micropores and mesopores in the shells were successfully prepared using silica nanoparticles (20, 30, and 40 nm in diameter) at pH values of 9 and 11, respectively. These HSNs are potentially important for applications in drug delivery systems and catalysis.

Dynamically morphing microchannels in liquid crystal elastomer coatings containing disclinations

Liquid crystal elastomers (LCEs) hold a major promise as a versatile material platform for smart soft coatings since their orientational order can be predesigned to program a desired dynamic profile. In this work, we introduce temperature-responsive dynamic coatings based on LCEs with arrays of singular defects-disclinations that run parallel to the surface. The disclinations form in response to antagonistic patterns of the molecular orientation at the top and bottom surfaces, imposed by the plasmonic mask photoalignment. Upon heating, an initially flat LCE coating develops linear microchannels located above each disclination. The stimulus that causes a non-flat profile of LCE coatings upon heating is the activation force induced by the gradients of molecular orientation around disclinations. To describe the formation of microchannels and their thermal response, we adopt a Frank–Oseen model of disclinations in a patterned director field and propose a linear elasticity theory to connect the complex spatially varying molecular orientation to the displacements of the LCE. The thermo-responsive surface profiles predicted by the theory and by the finite element modeling are in good agreement with the experimental data; in particular, higher gradients of molecular orientation produce a stronger modulation of the coating profile. The elastic theory and the finite element simulations allow us to estimate the material parameter that characterizes the elastomer coating's response to the thermal activation. The disclination-containing LCEs show potential as soft dynamic coatings with a predesigned responsive surface profile.

Microphase Arrangement of Smart Superhydrophilic Segmented Polyurethanes at Their Interface with Water.

Smart coatings have aroused a growing interest because of the performance of predefined surface functions upon reacting to external stimuli. Among them, responsive polymer coatings to water, which often benefit from the presence of a mobile hydrophilic material, are of great interest. Polyurethanes (PUs) are versatile materials with respect to the structure-property relationship. Therefore, the incorporation of hydrophilic segments in PUs is a rational way to produce water-sensitive smart coatings; however, having a considerable amount of hydrophilic material deteriorates the physical properties because of a large amount of water uptake. In this study, we have analyzed previously synthesized smart PUs, based on hydrophobic polycarbonate (PC) and hydrophilic polyethylene glycol (PEG) soft segments, in which only a limited amount of PEG is used. These coatings maintain, more or less, zero water contact angle, whereas the water uptake remains below 15 wt %. The combination of experimental analysis and coarse-grained molecular dynamics (CG MD) simulations reveals that PEG segments migrate to the coating/water interface and partially cover the surface, whereas the hydrophobic nature of the PC keeps the bulk of the coating intact when the coating is covered with water. Moreover, our CG MD simulations and experimental analysis suggest a reversible phase arrangement under wet/dry cycles on molecular and macroscopic scales.