Waterborne and water-reduced coatings are increasing in relevance in many sectors as an alternative to solventborne coatings. In this work, the internal structure of waterborne polymers as a function of colloid particle size is unveiled and directly related to macroscopic water absorption. To this aim, a set of acrylic waterborne films was prepared from dispersions of different colloidal particle sizes (100, 150, and 200 nm) with the same surfactant coverage. Macroscopic water absorption and water affinity were studied by Dynamic vapor sorption (DVS) and immersion tests. Small-Angle Neutron Scattering (SANS) was used to study deuterated water diffusion with time. This revealed the presence of remnant hydrophilic colloid-colloid interphases in all films, independently of the forming colloidal size and annealing conditions. Moreover, fitting of SANS data revealed that water transport in these films happens through surfactant-rich colloid-colloid interphases or through 10 nm-wide hydrophilic paths rich in surfactant aggregates (in the range of 4 nm) when these are present. The presence of the hydrophilic paths explains the higher water uptake measured in waterborne films made from 100 nm colloids, a process so far not previously reported. This study highlights how water diffusion in waterborne films may be engineered through fine control of particle size and film formation conditions.

Vitrimers are a class of polymer networks that hold promise as recyclable thermosets with self-healing capabilities, enabled by dynamic molecular-level rearrangements. However, achieving the desired network rearrangements usually demands thermal treatments at elevated temperatures substantially above the glass transition temperature Tg while maintaining these harsh conditions for prolonged dwell times. Therefore, the present paper examines the effects of thermo-oxidative degradation on the dynamicity of a disulfide-based epoxy vitrimer. First, comparison with a non-disulfide-containing reference indicates that disulfide bond degradation is the predominant early-stage degradation mechanism. The thermo-oxidative degradation process was described using model-free kinetics fitted to thermogravimetric data, which was subsequently used to selectively control the degradation state of the vitrimer samples as a function of temperature and exposure time. FTIR identified the presence of a highly oxidized carbonyl surface layer, while DMTA confirmed a drop in the primary Tg[jls-end-space/]. Stress-relaxation testing indicates a temporary, favorable effect of decreased crosslink density: increased bond exchange rates, which in turn facilitate shorter dwell times for healing and shape reconfiguration. This manifests as shifts in the initiation of macroscopic flow, reducing the (re)processing temperature regime. In the long run, cleavage of the dynamic S-S crosslinks becomes predominant, adversely compromising the dynamic properties of these systems, as evidenced by incomplete relaxation and reduced macroscopic flow capabilities. These insights into the distinct effects of thermo-oxidative aging provide a critical foundation for evaluating the long-term viability after high-temperature exposure in an oxygen environment and have important implications for designing appropriate (re)processing regimes for disulfide-based epoxy vitrimers.

The successful use of ice-binding proteins (IBPs) to develop anti-icing surfaces requires a comprehensive understanding of their working mechanism when introduced in environments distinct from the protein's natural setting. This study systematically addresses this aspect by investigating how IBPs control ice accretion when grafted onto an aluminum alloy using polyethylene glycol (PEG) linkers of various lengths and on the polymer backbone of a PEG hydrogel matrix. Freezing experiments monitored through thermal imaging reveal that the degrees of freedom of the proteins significantly influence their functionality. Specifically, we demonstrate that when the degrees of freedom of anti-freeze proteins (AFPs) are restricted by their functionalization on surfaces using short linkers or when they are present in restricted volumes in polymers, they behave as ice-nucleating proteins (INPs) promoting ice accretion. In conditions where their degrees of freedom are enhanced (long linkers, water-rich environment), AFPs effectively inhibit ice nucleation and propagation. The work underlines the relevance of protein mobility as a so far unforeseen key design factor needed to fully benefit from the potential use of natural or synthetic AFPs grafted on surfaces for cryopreservation of biological samples and the design of next-generation low-icing surfaces and coatings.

Recent works have shown the potential of diatomaceous earth (DE) as an efficient and environmentally friendly storage system for active chemicals such as corrosion inhibitors in coatings. The storage of organic inhibitors is nevertheless challenging. To address this challenge, in this work, we study the effect of surface modification of DE particles on the loading and release of organic corrosion inhibitors in solution and from coatings. To this aim, three trichlorosilanes with varying alkyl chain lengths (C4, C8, C18) were used to modify the surface of sp. Aulacoseira-type diatomite (DE). 2,5-Dimercapto-1,3,4-thiadiazolate di-potassium salts (KDMTD) were selected as a model corrosion inhibitor for its high solubility and effectiveness in protecting Cu-rich aerospace alloys, such as AA2024-T3. UV-Vis spectroscopy revealed a relationship between chain length and inhibitor loading and release, with mid-length silane (C8) adsorbing 3.5 times more inhibitor with no negative effect on release kinetics. When incorporated into epoxy-amine coatings, C8 surface modification significantly improved DE particle dispersion and protection of the inhibitor from the polymer matrix, preventing unwanted side reactions. This increased the availability of active organic inhibitors for protection at damaged sites. In-situ reflected microscopy during immersion and postmortem analysis of damaged coatings demonstrated high levels of corrosion protection and the formation of stable protective layers at damaged sites. The research opens the path to more efficient use of functional DE particles in coatings.

Polyelectrolytes with ionic domains screened by bulky hydrophobic segments form processable, hydrophobic complexes called “compleximers”. Ionic liquids, which are chemically similar, further plasticize compleximers, yet the mechanisms behind their plasticization effects and distribution within the complexes remain unclear. This study examines the relaxation dynamics of plasticized compleximers across multiple length scales using rheology, fluorescence recovery after photobleaching (FRAP), and broadband dielectric spectroscopy (BDS). The incorporation of ionic liquids into compleximers reduces their glass transition temperature (T_g), accelerates diffusive processes, increases segmental motion, and leads to a small decrease in activation energy associated with these relaxation processes. However, the activation energies vary substantially between techniques, probing different physical processes: approximately 200 kJ/mol in rheology, 50 kJ/mol in FRAP, and 90 kJ/mol in BDS. These variations suggest that collective dynamics strongly influence the compleximer rheology, making the mobilization (and activation) of polymer chains distinct from the local movement of ionic segments.

The stability of inhibiting layers on AA2024-T3 intermetallic particles (IMPs) during re-immersion in saline following an initial immersion in a Ce(III)-containing electrolyte was investigated using in situ reflected light microscopy. Re-immersion behaviour varied due to differences in IMP composition, spatial distribution, and Ce(III) precipitation. IMPs were grouped into four categories based on whether their activity was high or low during both the immersion and re-immersion stages. Majority of the high activity particles during re-immersion had low activity during immersion. Longer immersion times (up to 72 h) and a brief delay in inhibitor supply (30 s) reduced re-immersion activity by increasing Ce(III) coverage. These findings suggest that corrosion protection systems promoting greater Ce(III) precipitation may enhance re-immersion stability.

This study demonstrates that galvanically coupling AA2024-T3 and AA7075-T6 affects localized corrosion even with the alloys’ comparable electrochemical behaviour. In situ reflected light microscopy tracked corrosion initiation and trench propagation, while zero resistance ammeter measurements quantified galvanic current density and potential. This combined approach allowed direct correlation between electrochemical signals and optically detectable surface phenomena. Galvanic coupling increased cathodic activity at AA2024-T3 intermetallic particles (IMPs) and caused the surrounding matrix to dissolve more extensively beyond the trench that formed around the particles. Local activity analysis revealed initial IMP dealloying was unaffected by galvanic coupling. However, lateral growth of trenches in both alloys was accelerated under coupling compared with electrically-isolated conditions. Correlation of optical activity with electrochemical measurements showed that trends and fluctuations in galvanic current and potential reflect different stages of local corrosion, facilitating the morphological and physicochemical interpretation of the electrochemical data.

Impacting supercooled water droplets commonly cause in-flight ice accumulation on aircraft surfaces. Ice accretion can lead to dangerous situations such as disturbance of airflow around the aircraft wings, breakdown of vital antennae, or even malfunction of the engines. The adverse effects of aircraft icing could be avoided by designing passive anti-icing surfaces that either delay ice nucleation after droplet impact and/or reduce ice adhesion to promote its shedding. Among potential passive anti-icing strategies, smooth surfaces with patterned hydrophilic and hydrophobic regions have shown good potential to control local frost formation. In this study, we investigate how hydrophilic 150 µm wide stripes influence the impact and freezing of supercooled water droplets on two polymeric substrates (Polyvinylchloride and Polypropylene). In addition to varying the wettability difference between the stripes and the substrate, the distance between the stripes (1.25—10 mm) and the impact velocity of the water droplet (4.1—6.5 m/s) were varied. High-speed video analysis of the impacting droplets shows that the presence of the hydrophilic patterns can lower ice nucleation rates and direct the shape of the droplet spreading after impact. However, a low wettability difference between the substrate and the patterns can lead to the opposite scenario with higher nucleation rates.

A hyphenated optical-electrochemical set-up was used to investigate the early-stage dissolution mechanism of NdFeB permanent magnets immersed in acetic, citric, and formic acids at concentrations of 0.01 and 0.1 M. This approach enabled a direct correlation between quantifiable surface changes and dissolution behaviour under open-circuit potential (OCP) conditions. Despite minimal OCP variation (180 mV) across all conditions and rapid stabilisation within approximately 300 s, significant optically-detectable surface changes continued throughout the measurement period (1 h). This emphasises that surface dissolution kinetics, rather than thermodynamics, predominantly control the early-stage dissolution of NdFeB. Kinetic parameters obtained by fitting mean activity-level curves with a sigmoidal model revealed that higher acid concentrations result in shorter induction periods and faster surface activation. In-situ optical analysis indicated a consistent dissolution mechanism characterised initially by localised activation, followed by the progressive expansion of active sites across the surface. Post-immersion analysis confirmed preferential dissolution of rare-earth-rich phases at grain boundaries and triple points, alongside intragranular dissolution observed in 0.01 M citric acid. Among the tested conditions, dilute citric acid (0.01 M) emerges as particularly suitable medium for practical control, as its relatively long induction period (∼1378 s) allows monitoring and controlling local dissolution before rapid surface activation begins. The combined optical-electrochemical approach also revealed that, while rare-earth-rich sites are preferentially activated, early signs of matrix activation are detectable, underscoring the value of in-situ optical analysis for advancing process control in NdFeB recycling.

Micropatterned surfaces with both hydrophilic and hydrophobic regions are relevant for a wide range of applications from fuel cells to water harvesting systems. The preferential nucleation of water on hydrophilic regions can also be used to control frost nucleation on chemically patterned surfaces. So far, this concept has been tested on brittle silicon surfaces with only a few different sizes and shapes of hydrophilic regions. In this work, the concept of controlled icing is investigated on five polymeric surfaces with different surface energies modified by micropatterning them with three types of hydrophilic polymer brushes. Frost formation and propagation on the resulting patterned surfaces with regions of varying wettability is monitored and quantified using high-resolution thermal imaging. The study proves that control over frost nucleation and propagation using regions of varying wettability can be achieved on commodity polymers. In addition to influencing the time and location of ice nucleation, the local patterning affects the freezing propagation mode and rate due to its impact on the continuity and thickness of molecular water layers (MWL). These results show that local control over the state of MWLs is key to controlling both ice nucleation and propagation of freezing events on surfaces.

Understanding how late an inhibitor can be released once corrosion initiated without compromising corrosion protection may help in developing more efficient anticorrosion coatings. We explored this idea through time-controlled Ce(NO₃)₃ availability to AA2024-T3 immersed in 0.05 M NaCl. Ce(NO₃)₃ was supplied at 0, 30, 60, and 180 s from the start of immersion to get a concentration of 0.001 M. Detailed visualization of surface changes at the intermetallic particle level was obtained using in-situ reflected microscopy. SEM-EDX and confocal laser microscopy confirmed the extent of intermetallic degradation and local inhibitor deposition corresponding to operando changes. When the inhibitor is supplied within 60 s of immersion, the surface changes slowdown earlier and are visually less extensive than in uninhibited systems. Furthermore, our results highlight the potential of reflected microscopy for local corrosion inhibition studies and underscore the importance of understanding the interaction between inhibitor release timing and corrosion protection.

In this work, we study the relationship between the molecular water layer (MWL) and frost freezing onset and propagation. The progression of frost has been reported to be governed by various localized icing phenomena, including interdroplet ice bridging, dry zones, and frost halos. Reports studying the state of water on surfaces have revealed the presence of a thin nanometer water layer on a range of surfaces. Regardless of further investigations that show environmental humidity, temperature, and surface energy to affect the thickness of the MWL on surfaces, the influence of the MWL on frost nucleation and propagation has not yet been previously addressed in the literature. To study the effect of the MWL on surface freezing events, a range of surface-functionalized glass substrates were prepared. In situ monitoring of freezing events with thermal imaging allowed studying the effect of surface chemistry and environmental relative humidity (RH) on the thickness and continuity of the MWL. We argue that the observed icing nucleation and propagation kinetics are directly related to the presence and continuity of the MWL, which can be manipulated by controlling the environmental humidity and surface chemistry.

The most common way to protect metallic structures from corrosion is through the use of passive and active corrosion protection with coatings containing dispersed corrosion inhibitor particles. Current approaches use inorganic microparticles containing mostly toxic and/or critical elements (e.g. CrVI, Li-salts). Organic inhibitors have been identified as a potential replacement technology due to their high inhibiting efficiency in solution, high versatility and lower toxicity. Nevertheless, when brought into organic coatings these inhibitors lose their efficiency due to unwanted side reactions with the surrounding organic matrix (coating). In this work we propose a novel strategy to isolate the organic corrosion inhibitor microparticles from the surrounding matrix. The new approach is based on the gas-deposition of an oxide nanolayer on the microparticles using gas deposition in a fluidized bed reactor. As a result, the organic particles are better dispersed in the coating and do not react with the surrounding matrix. Upon coating damage the particles are exposed to water and release sufficiently high amounts of the organic corrosion inhibitor at the damaged location. The work introduces a technique that can be used in other applications with similar challenges and a new technology that enables for the first time to store large amounts of active organic corrosion inhibitors in reactive organic coatings for efficient protection of metallic infrastructure. This opens the path to the practical use of highly efficient organic inhibitors in coatings for corrosion protection.

Water-borne coatings often contain nanofillers to enhance their mechanical or optical properties. The aggregation of these fillers may, however, lead to undesired effects such as brittle and opaque coatings, reducing their performance and lifetime. By controlling the distribution and structural arrangement of the nanofillers in the coatings and inserting reversible chemical bonds, both the elasticity and strength of the coatings may be effectively improved, while healing properties, via the reversible chemistry, extend the coating’s lifetime. Aqueous dispersions of polymer-core/silica-corona supracolloidal particles were used to prepare water-borne coatings. Polymer and silica nanoparticles were prefunctionalized with thiol/disulfide groups during the supracolloid assembly. Disulfide bridges were further established between a cross-linker and the supracolloids during drying and coating formation. The supracolloidal nanocomposite coatings were submitted to intentional (physical) damages, i.e., blunt and sharp surface scratches or cut through into two pieces, and subsequently UV irradiated to induce the recovery of the damage(s). The viscoelasticity and healing properties of the coatings were examined by dynamic, static, and surface mechanical analyses. The nanocomposite coatings showed a great extent of interfacial restoration of cut damage and surface scratches. The healing properties are strongly related to the coating’s viscoelasticity and interfacial (re)activation of the disulfide bridges. Nanocomposite coatings with silica concentrations below their critical volume fraction show higher in situ healing efficiency, as compared to coatings with higher silica concentration. This work provides insights into the control of nanofillers distribution in water-borne coatings and strategies to increase the coating lifetime via mechanical damage recovery.

The interaction of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) with the AA2024-T3 local microstructure (S-phase, secondary phases and matrix) as function of the NaCl concentration is studied. The inhibiting power and the local interaction of DMTD with the metal were studied by in–situ opto-electrochemistry, XPS and Raman spectroscopy. The stability of the inhibiting layers was evaluated by re-exposing the samples to NaCl solutions without inhibitor. The amount of DMTD and its interaction state (chemisorption/physisorption) vary with the local microstructural composition and NaCl concentration. Higher stability of the inhibiting layers is obtained when these are formed in presence of small amounts of NaCl (0.025–0.25 M).

In this paper, graphene oxide (GO) modified microcapsules have been developed for use in self-healing Cardanol-based epoxy anti-corrosion coatings on steel substrates. The microcapsules had a polymethyl methacrylate (PMMA) shell, covered with aminated GO flakes and contained either of the two complementary healing agents mixed with nanosized GO flakes. One set of capsules contained epoxidized nanosized GO and Cardanol-based epoxy resin, while the other contained aminated nanosized GO and Cardanol-based amine curing agent. The microcapsules had a narrow size distribution with a peak value of 4 μm. The Cardanol-based coatings containing various fractions of up to 20 wt% microcapsules in their stoichiometric ratio showed excellent anti-corrosion and self-healing properties. FT-IR, XPS, AFM, and Raman spectroscopy were used to characterize the size and chemical composition of the GO. Optical microscopy and SEM were used for morphological characterization. Double cantilever test upon bulk samples showed an excellent load transfer across the fracture plane after only 1 day curing at room temperature. The anti-corrosion properties of the Cardanol-based coating containing the two-component microcapsules were tested using electrochemical impedance spectroscopy (EIS). It was found that, after 60-day immersion in 3.5 wt% NaCl solution, the low-frequency impedance modulus |Z|_0.01Hz of the Cardanol-based coating containing GO-modified microcapsules was three orders of magnitude higher than that of the systems with capsules without GO. After scratching the coating containing 20 wt% GO-modified microcapsules and exposing it to an aqueous 3.5 wt% NaCl solution, the |Z|_0.01Hz of the Cardanol-based coating returned over a period of 7 days to the original value.