Regenerative nano-hybrid coating tailored for autonomous corrosion protection

Corrosion-Responsive Self-Healing Coatings

Organic coatings are one of the most popular and powerful strategies for protecting metals against corrosion. They can be applied in different ways, such as by dipping, spraying, electrophoresis, casting, painting, or flow coating. They offer great flexibility of material designs and cost effectiveness. Moreover, self-healing has evolved as a new research topic for protective organic coatings in the last two decades. Responsive materials play a crucial role in this new research field. However, for targeting the development of high-performance self-healing coatings for corrosion protection, it is not sufficient just to focus on smart responsive materials and suitable active agents for self-healing. A better understanding of how coatings can react on different stimuli induced by corrosion, how these stimuli can spread in the coating, and how the released agents can reach the corroding defect is also of high importance. Such knowledge would allow the design of coatings that are optimized for specific applications. Herein, the requirements and possibilities from the corrosion and synthesis perspectives for designing materials for preparing self-healing coatings for corrosion protection are discussed.

Surface Decoration of Cetyltrimethyl Ammonium Bromide on SiC Particles and Its Effects on the Co-Deposition Process

Cetyltrimethyl ammonium bromide (CTAB) is used to decorate the SiC particle surface. The mechanism of the decoration process has been studied by simulation and experimental approaches. Molecular dynamics (MD) simulation finds a bilayer adsorbed structure of CTAB on the SiC particles, which is then verified by Fourier-transform infrared and thermal gravimetric analysis measurements. The MD simulation also finds that the decorative effects of CTAB on the SiC particle surface are related to the surface charge condition of the SiC particles and the concentration of CTAB. The measured zeta potential of the SiC particles shows dependence on the pH condition and the concentration of CTAB. The decorated SiC particles are used to produce composition by the co-deposition technology. With the help of CTAB, SiC particles are successfully incorporated in the deposited layer, where the content of SiC particles is dependent on the concentration of CTAB and the pH of the bath.

Defect Filling Method of Sensor Encapsulation Based on Micro-Nano Composite Structure with Parylene Coating

The demand for waterproofing of polymer (parylene) coating encapsulation has increased in a wide variety of applications, especially in the waterproof protection of electronic devices. However, parylene coatings often produce pinholes and cracks, which will reduce the waterproof effect as a protective barrier. This characteristic has a more significant influence on sensors and actuators with movable parts. Thus, a defect filling method of micro-nano composite structure is proposed to improve the waterproof ability of parylene coatings. The defect filling method is composed of a nano layer of Al2O3 molecules and a micro layer of parylene polymer. Based on the diffusion mechanism of water molecules in the polymer membrane, defects on the surface of polymer encapsulation will be filled and decomposed into smaller areas by Al2O3 nanoparticles to delay or hinder the penetration of water molecules. Accordingly, the dense Al2O3 nanoparticles are utilized to fill and repair the surface of the organic polymer by low-rate atomic layer deposition. This paper takes the pressure sensor as an example to carry out the corresponding research. Experimental results show that the proposed method is very effective and the encapsulated sensors work properly in a saline solution after a period of time equivalent to 153.9 days in body temperature, maintaining their accuracy and precision of 2 mmHg. Moreover, the sensors could improve accuracy by about 43% after the proposed encapsulation. Therefore, the water molecule anti-permeability encapsulation would have broad application prospects in micro/nano-device protection.

Unraveling the Formation Mechanism of a Hybrid Zr-Based Chemical Conversion Coating with Organic and Copper Compounds for Corrosion Inhibition

Environmentally friendly chromate-free, zirconium (Zr)-based conversion coating is a promising green technology for corrosion protection. Additives in the surface treatment provide critical functionalities and performance improvements; however, mechanistic understanding as to how the additives influence the coatings remains unclear. In this study, a new organic-inorganic hybrid Zr-based conversion coating combines copper (Cu) compounds and polyamidoamine (PAMAM), taking advantage of the complementary nature of organic and inorganic additives. A multimodal approach combining electron and X-ray characterization is applied to study the interaction of Cu²⁺ and PAMAM and the resulting impacts on coating formation. Adding PAMAM changed the surface morphology, thickness, distribution of Cu in the clusters, and void formation of the coatings. High PAMAM (100-200 ppm) leads to little conversion coating formation, and low PAMAM (0-25 ppm) shows voids formation under the coatings. Moreover, PAMAM incorporates in the coating in the form of a PAMAM-Cu complex with a higher concentration toward the surface, providing an organic layer at the surface of the coating. X-ray absorption near-edge structure (XANES) spectroscopy shows the difference between the conventional and the hybrid coating treatments in an alkaline solution to simulate the E-coat process, suggesting the contribution of PAMAM in the enhanced chemical stability in an alkaline environment. Therefore, an intermediate range of addition of PAMAM (50 ppm) is optimal to (1) avoid excessive voids formation, (2) promote some Cu cluster formation and thus enhance the Zr-based coating formation, and (3) incorporate organic components into the coating to improve the adhesion of the subsequent coatings. Overall, this work furthers our knowledge on the formation mechanism of an effective and environmentally friendly hybrid conversion coating for corrosion inhibition, demonstrating a critical processing-structure-property relationship. This study will benefit future development of green and effective surface treatment technology.

Neuron-Inspired Self-Healing Composites via Dynamic Construction of Polypyrrole-Decorated Carbon Nanotubes for Smart Physiochemical Sensing

Mimicking human skin's functions to develop intelligent materials have inspired extensive exploration in the design and synthesis of a novel device. However, how to simulate neuron function and integrate highly sensitive, positive perceptions and self-healing into one single material remains a challenge. Here, we prepared a recycled polyurethane (PU) with high tensile strength values (11.37 ± 0.03 MPa), high maximum elongation (1130 ± 11.59%), and high self-healing property (100% for 6 h at 25 °C) and a smart PU composite of polypyrrole-decorated carbon nanotubes with higher sensitivity. The smart composite can not only actively identify physical change such as strain, moisture, and temperature but also proactively detect various chemical environment changes such as acid, alkali, oxidant, and reductant (T: 25-90 °C, ΔR/R₀ values were 0.1-1.6; strain: 10-150%, ΔR/R₀ values were 2.5-27; 0.01-0.1 mol L^-1 oxidant solutions, ΔR/R₀ values were 0.66-0.75; 0.01-0.1 mol L^-1 reductant solutions, ΔR/R₀ values were 0.51-0.65; 0.1-0.5 mol L^-1 acid solutions, ΔR/R₀ values were 0.54-0.58; and 0.1-0.5 mol L^-1 alkali solutions, ΔR/R₀ values were 0.42-0.46). More importantly, the signal values of the smart composite can quickly return to the initial values after eliminating physical and chemical stimuli. The abovementioned features of the smart composite, the high physicochemical response, and significant restorability make it potentially possible to apply it in intelligent chemical manufacturing.

Tattooing Plastics with Reversible and Irreversible Encryption

Self-healing materials are explored for restoring mechanical, electrical, and chemical properties. Inspired by the process of tattooing on human skin, a method for engraving non-permanent or permanent messages on plastics is developed. A self-healing polymer containing dynamic disulfide bonds is employed as substrate for encryption of written messages. The polymer is engraved with a dye solution which is subsequently covered by the polymer matrix upon activation with temperature increase. The dye is then located at the subsurface of the substrate so that the information cannot be removed easily by wear or extraction with solvents. Therefore, self-healing polymers can be applied as sustainable substrates for reversibly and irreversibly engraving information.

Spraying Preparation of Eco-Friendly Superhydrophobic Coatings with Ultralow Water Adhesion for Effective Anticorrosion and Antipollution

Sustainability, eco-efficiency, and green chemistry guide the development of new materials in various fields. Herein, we designed and fabricated bio-based superhydrophobic coatings by means of a facile spraying synthesized method. The as-prepared superhydrophobic coatings exhibited high water repellency with higher water contact angle being up to 156.9 ± 2.7° and a lower sliding angle of only 4.3 ± 0.6°. Also, the water adhesion on the superhydrophobic coatings was as low as 11 μN, which was far less than that (346 μN) of the normal polyurethane surfaces. The superhydrophobic properties still retained high stability under the conditions of soaking in acid solution (pH = 1) and alkaline solution (pH = 13). Meanwhile, the as-prepared bio-based superhydrophobic coatings were verified for effective corrosion and pollution protection ability. The electrochemical measurements showed excellent corrosion resistance with a higher corrosion voltage of -204.7 mV and lower corrosion current of 1.494 × 10^-5 A/cm². The corrosion protection efficiency reached a value of 95.2%, and meantime, the superhydrophobic coatings displayed higher antipollution performance without any stains when they were removed from the polluted liquids. On this basis, the underlying physical-chemical mechanisms clearly revealed that the surface micro-nanostructures could capture the continuous and stable air layer to segregate the corrosion and pollution media.

Synthesis of nanosensors for autonomous warning of damage and self-repairing in polymeric coatings

Polymeric materials are susceptible to minor damage, which is undetectable. Without timely and effective repair treatment, the damage may deteriorate the integrity of the materials and ultimately result in material failure and catastrophe. Autonomous warning and simultaneous damage repair are of great practical significance yet difficult to realize. Herein, we introduce a smart coating with autonomous warning and repairing of damage by the simple incorporation of nanosensors embedded with phenanthroline as a corrosion indicator and inhibitor. The electrochemical corrosion resulting from coating damage can be rapidly indicated by a prominent orange-red color in just five minutes. In addition to the warning function, the smart coating exhibits efficient self-repairing in the defective region, as reflected from the disappearance of the electrochemical admittance peak. This simple and powerful strategy dependent on a single active component to achieve an autonomous warning and repairing effect is highly expected to provide a new avenue for enhancing the security and longevity of other polymeric materials.

Salt-Triggered Release of Hydrophobic Agents from Polyelectrolyte Capsules Generated via One-Step Interfacial Multilevel and Multicomponent Assembly

Controlled release of hydrophobic agents from salt-responsive capsules is hindered by the hydrophilic shell and interfacial tension between inner oil and surrounding water. Rupturing shells in salt solution is another effective way. However, the densely entangled polyelectrolytes (PEs) in shells determined that the rupture requires extremely high ion-strength. Herein, salt-responsive capsules with double-network shells including a continuous PE-nanocrystal network and interfacial ion pairs are proposed and revealed via a one-step interfacial multilevel and multicomponent assembly (IMMA) method. Rigid nanocrystals can weaken the entanglements of PE chains and reduce the critical salt-concentration. Interfacial ion pairs are responsible for maintaining the stability of the shells. Such double networks enable the disintegration of capsules in an applicable salt-concentration without damaging the stability of capsules. In addition, hydrophobic domains assemblied by surfactants and PE-nanocrystal network supply transport pathway for oil to across hydrophilic shells and subsequently produce inverse micelle to carry oil into water. The mechanism of formation and release of capsules is systematically investigated, which further demonstrates IMMA to be a typical method for creation of sophisticated structures in a brief way.

Self-Healable Superomniphobic Surfaces for Corrosion Protection

Corrosion-protective surfaces are of the utmost relevance to ensure long-term stability and reliability of metals and alloys by limiting their interactions with corrosive species, such as water and ions. However, their practical applications are often limited either by the inability to repel low surface tension liquids such as oils and alcohols or by poor mechanical durability. Here, a superomniphobic surface is reported that can display very high contact angles for both high and low surface tension liquids as well as for concentrated acids and bases. Such extreme repellency allowed for approximately 20% of the corrosion rate compared to the conventional superhydrophobic corrosion protective coatings. Furthermore, the superomniphobic surface can autonomously repair mechanical damage at an elevated temperature (60 °C) within a short period of time (60 s), and the surface can restore its intrinsic corrosion protection performance. Such superomniphobic surfaces thus offer a wide range of potential applications, including pipelines, with sustainable corrosion protection and rust inhibitors for steel in reinforced concrete.

Osteogenic and pH stimuli-responsive self-healing coating on biomedical Mg-1Ca alloy

Various coatings have been used to slow down the corrosion rate of biomedical magnesium alloys. However, these coatings usually act only as passive barriers. It is much more desirable to endow such coatings with active, biocorrosion-responsive self-repairing capacity. In the present work, a self-healing coating system (denoted as "silk-PA") was constructed in the form of a sandwich architecture of fluoride precoating (bottom), silk-phytic acid (PA) coating (middle), and silk fibroin coating (top). Here, PA was loaded in the middle coating as a corrosion inhibitor by harnessing its strong chelating ability toward dissolving Mg²⁺ and Ca²⁺ ions. The self-healing property was evaluated by scratch and SVET tests, and the corrosion resistance was evaluated by in vitro immersion and electrochemical measurements. The results showed that the silk-PA manifested intriguing self-healing capacity with pH responsiveness, hence profiting the corrosion resistance of the Mg-1Ca alloy. The biocompatibility and osteogenic activity of the coating system were further evaluated using MC3T3-E1 cells, and it demonstrated favorable responses in multiple cellular behaviors, i.e., adherence, spreading, proliferation, and differentiation. These findings open new opportunities in the study of self-healing coatings for protection against corrosion in biomedical Mg alloys. STATEMENT OF SIGNIFICANCE: In the present study, a self-healing coating system with pH stimuli-responsiveness and osteogenic activity was fabricated on Mg-1Ca alloy by integrating a silk fibroin barrier coating, a silk fibrin/phytic acid composite coating, and a fluoride precoating. This coating system demonstrated interesting self-healing ability as compared to traditional surface modification layers. Furthermore, the self-healing ability enhanced the corrosion resistance of biomedical magnesium alloys, while effective compositions of the coating system endowed the substrate with osteogenic activity. This work provides some new insights into smart surface modification for biomedical Mg alloys.

Pretreatment with a β-Cyclodextrin-Corrosion Inhibitor Complex Stops an Initiated Corrosion Process on Zinc

Metal pretreatment is typically the first step in a reliable corrosion protection system. This work explores the incorporation of complexes between the cyclic oligosaccharide β-cyclodextrin (β-CD) and the molecular organic corrosion inhibitor 2-mercaptobenzothiazole (MBT) into an oxide-based pretreatment layer on metallic zinc. The layers were produced by a precorrosion step in the presence of β-CD. The resulting films have a morphology dominated by spherical particles. X-ray photoelectron spectroscopy investigations of the surfaces show the sulfur atoms of MBT to be partially oxidized but mostly intact. Samples pretreated with such a layer were subsequently coated with a model polymer coating, and the delamination of this model coating from an artificial defect was monitored by a scanning Kelvin probe (SKP). The SKP results show a slow down of delamination after several hours of the ongoing corrosion process for surfaces pretreated with the complexes. Finally, an increase in the electrode potential in the defect was observed, with a subsequent complete stop in delamination and repassivation of the defect after ≈10 h. This repassivation is attributed to the release of MBT after the initiation of the corrosion process. Most likely, the increase of pH, combined with the availability of aqueous solution, facilitates the MBT release after the initiation of a corrosion process. Consequently, complexes formed from β-CD and corrosion inhibitors can be effectively incorporated into inorganic pretreatments, and the inhibitor component can be released upon start of the corrosion process.

pH-Sensitive Polymer Conjugates for Anticorrosion and Corrosion Sensing

In 2015, the global cost of corrosion in the world was estimated to be around 2.5 trillion dollars and has been continuously increasing. The active protection by corrosion inhibitors is a well-known technique for protecting metals against corrosion. However, one major disadvantage is that corrosion inhibitors can be leached in the environment, even when corrosion does not occur. We design and synthesize smart polymer/corrosion inhibitor conjugates as a new generation of materials for corrosion protection. These materials release inhibitors upon acidification, which may occur either by acidic rain or as a consequence of the metal corrosion process itself. A polymerizable derivative of 8-hydroxyquinoline (8HQ), an effective corrosion inhibitor, is prepared so that it contains acid-labile β-thiopropionate linkages. The monomer is copolymerized with ethyl acrylate, and the obtained functional polymer is processed to form nanoparticles. Under acidic conditions, >95% 8HQ is released from the nanoparticles of the polymer conjugates after 14 days. However, the release was significantly slower under neutral conditions, reaching only 15% during the same period. Additionally, nonconjugated 8HQ can be physically entrapped in the nanoparticles of the polymer conjugates by encapsulation. The nonconjugated 8HQ is then released in less than 30 min so that the coexistence of both conjugated and nonconjugated 8HQ in the nanoparticles allows a release profile, which is a hybrid of sustained and burst releases. Furthermore, the nanoparticles are advantageously used as nanosensors. The 8HQ released from the nanoparticles displays enhanced fluorescence upon chelation with aluminum ions. Therefore, the nanoparticles can be used simultaneously for corrosion sensing and protection.

Redox-Responsive Polymer with Self-Immolative Linkers for the Release of Payloads

Previous couplings of corrosion inhibitors to redox-responsive polymers via covalent bonding suffer from several drawbacks. It is presented here novel redox-responsive polymer-corrosion inhibitor conjugates that contain self-immolative linkers in their side chains. Very fast redox-induced release of tryptamine, a drug and a corrosion inhibitor, is observed after applying a reductive trigger.

Encapsulation and Release of Functional Nanodroplets Entrapped in Nanofibers

A method is presented for preserving the structural integrity of nanodroplets produced by emulsification. Droplets of different hydrophobic liquids such as essential oils or monomers are produced by the miniemulsion process. The miniemulsions are then electrospun to yield dextran nanofibers entrapping the hydrophobic nanodroplets. The nanodroplets are then successfully redispersed by dissolving the nanofibers in water. Furthermore, it is shown that nanofibers can be used to store a monomer and a catalyst as healing agents for ring-opening metathesis polymerization. After dissolution, the healing agents are released and a self-healing reaction takes place. Embedding, storage, and release of emulsion nanodroplets is a promising method that avoids potential destabilization of droplets by coalescence or Ostwald ripening.

Designing Smart Polymer Conjugates for Controlled Release of Payloads

Incorporating labile bonds inside polymer backbone and side chains yields interesting polymer materials that are responsive to change of environmental stimuli. Drugs can be conjugated to various polymers through different conjugation linkages and spacers. One of the key factors influencing the release profile of conjugated drugs is the hydrolytic stability of the conjugated linkage. Generally, the hydrolysis of acid-labile linkages, including acetal, imine, hydrazone, and to some extent β-thiopropionate, are relatively fast and the conjugated drug can be completely released in the range of several hours to a few days. The cleavage of ester linkages are usually slow, which is beneficial for continuous and prolonged release. Another key structural factor is the water solubility of polymer-drug conjugates. Generally, the release rate from highly water-soluble prodrugs is fast. In prodrugs with large hydrophobic segments, the hydrophobic drugs are usually located in the hydrophobic core of micelles and nanoparticles, which limits the access to the water, hence lowering significantly the hydrolysis rate. Finally, self-immolative polymers are also an intriguing new class of materials. New synthetic pathways are needed to overcome the fact that much of the small molecules produced upon degradation are not active molecules useful for biomedical applications.

Hemiaminal ether linkages provide a selective release of payloads from polymer conjugates

Hemiaminal linkages allow for a selective and pH-responsive release of triazoles from polymer conjugates.

Nanocontainer-Enhanced Self-Healing for Corrosion-Resistant Ni Coating on Mg Alloy

The ability to manipulate the functionalization of Ni coating is of great importance in improving the corrosion resistance of magnesium (Mg) alloy for many industrial applications. In the present work, MCM-41 type mesoporous silica nanocontainers (MSNs) loaded with corrosion inhibitor (NaF) were synthesized and employed as smart reinforcements to enhance the integrity and corrosion inhibition of the Ni coating. The incorporation of the F-loaded MSNs (F@MSNs) to enhance the corrosion resistant capacity of a metallic coating is reported for the first time. The mesoporous structures of the as-prepared MSNs and F@MSNs were confirmed by transmission electron microscopy (TEM), small angle X-rays scattering (SAXS), and N₂ adsorption-desorption isotherms. The X-ray photoelectron spectroscopy (XPS) data demonstrated the successful immobilization of fluoride ion on the MSNs and formation of a magnesium fluoride (MgF₂) protective film at the corrosion sites of the Mg alloy upon soaking in a F@MSNs-containing NaCl solution. The results from potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) for both bare Mg alloy and Ni coatings with and without F@MSNs have revealed a clear decrease in corrosion rate in a corrosive solution for a long-time immersion due to the introduction of F@MSNs. These findings open new opportunities in the exploration of self-healing metallic coatings for highly enhanced anticorrosion protection of Mg alloy.

Design and Fabrication of a Novel Stimulus-Feedback Anticorrosion Coating Featured by Rapid Self-Healing Functionality for the Protection of Magnesium Alloy

Corrosion potential stimulus-responsive smart nanocontainers (CP-SNCs) are designed and synthesized based on the installation of the supramolecular assemblies (bipyridinium ⊂ water-soluble pillar[5]arenes) onto the exterior surface of magnetic nanovehicles (Fe₃O₄@mSiO₂), linked by disulfide linkers. The supramolecular assemblies with high binding affinity as gatekeepers effectively block the encapsulated organic corrosion inhibitor, 8-hydroxyquinoline (8-HQ), within the mesopores of Fe₃O₄@mSiO₂. When the corrosion potential of the magnesium alloy (-1.5 V vs SHE) is exerted, 8-HQ is released instantly because of the cleavage of disulfide linkers and the removal of the supramolecular assemblies. CP-SNCs were incorporated into the hybrid organic-inorganic sol-gel coating to construct a corrosion potential stimulus-feedback anticorrosion coating (CP-SFAC) that was then deposited on the magnesium alloy, AZ31B. With the aid of a magnetic field, CP-SNCs were gathered in the proximity of the surface of AZ31B. CP-SFAC showed a satisfactory anticorrosion performance, more importantly, through the evaluation of microzone electrochemical techniques. CP-SFAC presented the rapid self-healing functionality when the localized corrosion occurred. Shortening the distance between CP-SNCs and the surface of AZ31B enhances the availability of the incorporated CP-SNCs and makes most of the CP-SNCs to timely respond to the corrosion potential stimulus and facilitates the formation of a compact molecular protective film before the corrosion products pile up. The characteristics of fast response time and quick self-healing rate meet the requirements of the magnesium alloy for self-healing in local regions.

Cooperative self-healing performance of shape memory polyurethane and Alodine-containing microcapsules

In this study, a method to prepare self-healing coatings by incorporating Alodine-containing microcapsules as fillers in Shape Memory Polyurethane (SMPU) was presented.

Effect of nanosilica content on the corrosion inhibition of composite coatings of a filled epoxy resin grafted with a hydrophobic fluoroalkylsilane: a dual critical concentrations interpretation

Hydrophobic epoxy-resin composite coatings uniquely display double corrosion-inhibition extrema at nanosilica dual critical concentrations of 0–0.5 and ∼3 wt%.

A Novel Eco-Friendly Scale and Corrosion Inhibitor Modified by β-Cyclodextrin

A polymer, β-MEA, was synthesised from β-cyclodextrin (β-CD), 3-chloro-2-methylpropene (MAC), epoxysuccinic acid (ESA), and 2-acrylamido-2-methyl propane sulfonic acid (AMPS) with a (NH4)2S2O8-NaHSO3 redox initiator system by aqueous solution radical polymerisation. β-MEA was characterised by means of IR spectroscopy, time-of-flight mass spectrometry, gel permeation chromatography, and thermogravimetric analysis. Its structure, molecular weight, thermal stability, scale and corrosion inhibition performance and mechanism were investigated. The results verified that β-MEA achieves a better scale inhibition efficiency for BaSO4 compared with poly(aspartic acid) (PASP) (100 % cf. 94.9 % at a concentration of 20 mg L−1) and a better corrosion inhibition efficiency of N80 carbon steel in saline water compared with PESA (91.2 % cf. 79.7 % at a concentration of 1 g L−1). The BaSO4 was characterised by scanning electron microscopy (SEM) and X-ray diffraction to investigate the crystal morphology of the scale. Primary research on the mechanism for corrosion inhibition was carried by SEM-chemical analysis.

Facile Synthesis of Smart Nanocontainers as Key Components for Construction of Self-Healing Coating with Superhydrophobic Surfaces

SiO2-imidazoline nanocomposites (SiO2-IMI) owning high loading capacity of corrosion inhibitor, 1-hexadecyl-3-methylimidazolium bromide (HMID), and a special acid/alkali dual-stimuli-accelerated release property have been synthesized via a one-step modified Stöber method. SiO2-IMI were uniformly distributed into the hydrophobic SiO2 sol to construct "host"-"guest" feedback active coating with a superhydrophobic surface (SiO2-IMI@SHSC) on aluminium alloy, AA2024, by dip-coating technique. SiO2-IMI as "guest" components have good compatibility with "host" sol-gel coating, and more importantly, once localized corrosion occurs on the surface of AA2024, SiO2-IMI can simultaneously respond to the increase in environmental pH around corrosive micro-cathodic regions and decrease in pH near micro-anodic regions, promptly releasing HMID to form a compact molecular film on the damaged surface, inhibiting corrosion spread and executing a self-healing function. The scanning vibrating electrode technique (SVET) was applied to illustrate the suppression process of cathodic/anodic corrosion activities. Furthermore, benefiting from the superhydrophobic surface, SiO2-IMI@SHSC remained its protective ability after immersion in 0.5 M NaCl solution for 35 days, which is far superior to the conventional sol-gel coating with the same coating thickness. The facile fabrication method of SiO2-IMI simplifies the construction procedure of SiO2-IMI@SHSC, which have great potential to replace non-environmental chromate conversion coatings for practical use.

A Nanocapsule-Based Approach Toward Physical Thermolatent Catalysis

Performance under pressure is utilized as a key concept for colloidal control of reaction kinetics. Barrier nanocapsules containing a catalyst and a low-boiling-point release agent enable a highly desired, adjustable, and distinct non-Arrhenius behavior for thermoset curing.

Osmotic pressure-dependent release profiles of payloads from nanocontainers by co-encapsulation of simple salts

The encapsulation of payloads in micro- to nano-scale capsules allows protection of the payload from the surrounding environment and control of its release profile. Herein, we program the release of hydrophilic payloads from nanocontainers by co-encapsulating simple inorganic salts for adjusting the osmotic pressure. The latter either leads to a burst release at high concentrations of co-encapsulated salts or a sustained release at lower concentrations. Osmotic pressure causes swelling of the nanocapsule's shell and therefore sustained release profiles can be adjusted by crosslinking it. The approach presented allows for programing the release of payloads by co-encapsulating inexpensive salts inside nanocontainers without the help of stimuli-responsive materials.

Composite hydrogels of polyacrylamide and crosslinked pH-responsive micrometer-sized hollow particles

Whilst hydrogels and hollow particles both continue to attract much attention in the literature there are few examples of hydrogel composites containing hollow particles. Here, we study composite polyacrylamide (PAAm) hydrogels containing micrometer-sized pH-responsive shell-crosslinked hollow particles (abbreviated as HPXL) based on poly(methylmethacrylate-co-methacrylic acid) functionalised with glycidyl methacrylate (GMA). The HPXL particles were prepared using our scaleable emulsion template method and inclusion of GMA was found to promote spherical hollow particle formation. The pendant vinyl groups from GMA enabled shell-crosslinked hollow particles to be prepared prior to formation of the PAAm/HPXL composite gels. The morphologies of the particles and composite gels were studied by optical microscopy, confocal laser scanning microscopy and scanning electron microscopy. Dynamic rheology measurements for the composite gels showed that the modulus variation with HPXL concentration could be described by a percolation model with a HPXL percolation threshold concentration of 4.4 wt% and a scaling exponent of 2.6. The composite gels were pH-responsive and largely maintained their mechanical properties over the pH range 4.0 to 8.0. Because the composite gels had tuneable mechanical properties (with modulus values up to 530 kPa) and were pH-responsive they are potential candidates for future wound healing or membrane applications.

Control of the release of functional payloads from redox-responsive nanocapsules

Stimuli-responsive nanocontainers allow for storage and controlled release of functional payloads in response to external stimuli.

Dual-responsive multicompartment nanofibers for controlled release of payloads

Dual-responsive multicompartment nanofibers are designed by embedding redox-responsive nanocapsules in pH-responsive nanofibers by colloid-electrospinning and for enhanced control over the release of payloads.