Hydrophobic Materials Research Articles

Deep Margin Elevations, clinical considerations

Subgingival restorations are problematic due to reduced visibility at the preparation margins, humidity (saliva, crevicular fluid and/or blood), problems with taking impressions (digital or analogue) and problems with the application of a rubber dam. Solutions, such as the use of a surgical microscope, retraction cord and Teflon tape, are available. Since modern dentistry largely relies upon adhesive techniques with hydrophobic materials, these require a clean and dry working area. One solution is to place the preparation margin supragingivally. This can be done in three ways: a local build-up using a direct composite restoration, a surgical clinical crown lengthening or an extrusion (orthodontic or surgical). Since in practice only a small part is usually located subgingivally, placing a direct composite restoration is often sufficient. The term Deep Margin Elevation is generally used in the international English-language literature for this approach. If the area located subgingivally is larger, then techniques like crown lengthening and extrusion might be better.

One-step preparation of a biphasic monolithic separation media for enriching and purifying lupeol in medicine plants

In this study, a monolith consisted of two materials with different separation modes were prepared by a one-step method at both ends of a column. Acrylic acid and 2-hydroxyethyl methacrylate (HEMA) were used as monomers for hydrophilic and hydrophobic parts, respectively. The total pore volumes and porosities of hydrophilic and hydrophobic materials were 3.1098 mL/g and 75.2535 %, 4.4380 mL/g and 72.5317 %, respectively. The prepared monolithic columns had excellent mechanical strength and good permeability, and can bear high flow rates up to 5 mL/min. The biphasic monolith functioned in two retention modes: hydrophilic interaction chromatography (HILIC) and hydrophobic interaction chromatography (HIC), and the dual-mode were realized by switching the ratio of acetonitrile in the mobile phase. The biphasic monolithic column was used as solid phase extraction (SPE) adsorbent for on-line enrichment and purification of lupeol in Chinese herbal medicines (CHM), which showed good adsorption performance and excellent reproducibility. The spiked recoveries were from 88.52 % to 93.68 % under the optimal experimental conditions; the repeatability could reach 100 times. The method showed good linearity in the range of 0.13 ∼ 2.00 × 103 μg /mL with a correlation coefficient of r = 0.9991; the limit of detection (LOD) was 0.023 μg/mL and the limit of quantification (LOQ) was 0.076 μg/mL; the intra-day and inter-day precisions were both less than 1.05 %.

Superhydrophobic Graphene-based Materials

Abstract: International attention has been directed toward superhydrophobic nanocomposite coatings for a great variety of industrial applications. Nowadays, graphene-based self-cleaning coatings represent the most important examination arenas. This study reviews the superhydrophobicity fundamentals, graphene-based nanocomposite fabrication and applications for self-cleaning surfaces. These efforts have stimulated the modeling of recently structured surfaces via a micro-nano binary system. The controlled preparation of nanoscale orientation, configuration, arrangement, and direction along the architectural composite building blocks would result in air-entrapping capacity along the surface grooves. Polymer/graphene nanocomposites with novel and intriguing designs have offered efficient self-cleaning surfaces. These nano-surfaces have a rough structure, low surface free energy, and are hydrophobic materials. To improve the self-cleaning ability, several graphene/ inorganic nanofiller hybrids are dispersed in polymeric resins. The review covered the creation of graphene compounds, interactions with polymers, and uses of the resulting nanocomposites. It highlights the efficacy of controlling the nanostructured design mechanisms for self-cleaning applications. The applications of superhydrophobic materials developed using graphene-related nanocomposites for self-cleaning marine antifouling surfaces are the focus of this study. Stability, as well as long-standing durability, represents vital advantages for developing eco-friendly superhydrophobic alternatives. This review concludes with a discussion of the field's current and future advancements. It is expected to serve as a cutting-edge research hub for the creation of a durable and sustainable self-cleaning coating.

Microalgae cell adhesions on hydrophobic membrane substrates using quartz crystal microbalance with dissipation.

Microalgal cell adhesion and biofilm formation are affected by interactions between microalgae strains and membrane materials. Variations of surface properties of microalgae and membrane materials are expected to affect cell-membranes and cell-cell interactions and thus initial microalgal cell adhesion and biofilm formation rates. Hence, it should be possible to identify the dominant mechanisms controlling microalgal cell adhesion and biofilm formation. The effects of surface properties of three different microalgal strains and three different types of membrane materials on microalgal cell adhesion and biofilm formation were systematically investigated in real time by monitoring changes in the oscillation frequency and dissipation of the quartz crystal resonator (QCM-D). The results revealed that in general a higher surface free energy, more negative zeta potential, and higher surface roughness of membrane materials positively correlated with a larger quantity of microalgae cell deposition, while a more hydrophilic microalgae with a larger negative zeta potential preferred to attach to a more hydrophobic membrane material. The adhered microalgal layers exhibited viscoelastic properties. The relative importance of these mechanisms in controlling microalgae cell attachment and biofilm formation might vary, depending on the properties of specific microalgae species and hydrophobic membrane materials used.

Influence of glycerol, eggshells, and genipin on hydrophobicity and rigidity of antioxidant locust bean milling dust-derived bioplastics

Locust bean milling dust (LBMD) is an agrifood byproduct rich in proteins and polysaccharides able to form hydrophilic, flexible, and antioxidant bioplastics. Aiming a broad application for LBMD-based bioplastics, in this work, it was hypothesized that glycerol, milled eggshells, or genipin amount fine-tuning can originate rigid and hydrophobic antioxidant LBMD-based materials. With 20 g/100 g glycerol, the films became more 10-fold stiff (Young's modulus of 253 MPa), 1.7-fold hydrophobic (water contact angle of 109°), and 22-fold resistant to water vapor (5 pg/Pa.s.m) than pristine films (Young's modulus of 26 MPa, water contact angle of 64°, and water vapor permeability of 109 pg/Pa.s.m), keeping their yellowish color and transparency. Apart from stiffness that did not change, this profile was also evidenced when 1 g/100 g milled eggshells were incorporated, increasing hydrophobicity 1.5 times and decreasing water vapor permeability 1.6 times. The use of 0.03 g/100 g genipin conferred a blue color to LBMD-based bioplastics and more 5-fold rigidity, 1.7-fold hydrophobicity, and 2.2-fold water vapor barrier. Therefore, rigid, water tolerant, and antioxidant LBMD-based bioplastics can be developed by tailoring glycerol, milled eggshells, or genipin amount, with 20 g/100 g glycerol or 0.03 g/100 g genipin as best conditions to improve these features.

Effect of Hydrophilic and Hydrophobic Composite Microporous Layer Coated Gas Diffusion Layers on PEFC Performance

Addressing the voltage loss problem at high current densities is crucial to expand PEFCs output power. One approach to improve water management and extend the cell operating range is modifying the microporous layer (MPL) coated on the gas diffusion layer (GDL). This study developed a novel MPL coated GDL preparation method featuring randomly allocated hydrophobic and hydrophilic pores within the same layer, which was proven by the water permeability test. This design allows excess water at the interface between the catalyst layer (CL) and MPL to be expelled through the hydrophilic pores while maintaining gas transport via the hydrophobic pores to reduce the mass transport resistance. Various hydrophobic and hydrophilic materials were tested, and the different compositions were evaluated to determine the appropriate combination. The results demonstrated that the composite MPL further reduced total oxygen transport resistance compared to the conventional hydrophobic MPL.

Natural Rubber Latex-Modified Concrete with PET and Crumb Rubber Aggregate Replacements for Sustainable Rigid Pavements

There are ongoing research challenges for the addition of the blend of PET and crumb rubber in polymer-modified concretes, which aims to leverage the benefits of both materials. In this study, various percentage combinations of waste aggregates, such as PET and crumb rubber, were used to replace coarse and fine aggregates in natural rubber latex (NRL)-modified concrete. Engineering properties such as compressive and flexural strengths, modulus of elasticity, and toughness obtained from compressive- and flexural stress-strain curves were investigated. Scanning electron microscopy (SEM) analysis was performed to examine the microstructural properties and study the strength development of the studied concretes. The results revealed that the compressive and flexural strengths of NRL-modified concretes with PET and crumb rubber aggregate replacements decreased with increasing replacement ratios. SEM analysis indicated that PET and crumb rubber (hydrophobic and non-polar materials) can affect the microstructure of the studied concrete by creating a weak interface between the aggregate and cement pastes, leading to reduced strength development. With the addition of the NRL additive, the film formation was found to act as a bridge and improve the bond strength of aggregates and hydration products in NRL-modified concrete. Furthermore, the integration of PET and crumb rubber aggregate can enhance the ability of the concrete to absorb energy and improve ductility. It was found that 10% of PET and crumb rubber aggregate replacement can be used for NRL-modified concrete as a rigid pavement, as its mechanical strengths satisfy the requirements set by the Department of Highways (DOH) in Thailand. This research helps repurpose waste materials and reduce the environmental footprint of concrete production.

Development of Cyclic Tetrasiloxane Polymer as a High-Performance Dielectric and Hydrophobic Layer for Electrowetting Displays.

Cyclic tetrasiloxane polymer (CTP) has recently garnered interest as a hydrophobic material with unique properties. This study aims to enhance the dielectric constant of CTP films by introducing excess Si-H groups and to explore the impact of synthesis and processing conditions on the resulting properties. The film demonstrates high hydrophobicity, with contact angles of 107° in air and 165° in n-decane, along with a notable dielectric constant of 5.1°. Furthermore, the CTP film displays reversible electrowetting behavior with low contact angle hysteresis (2°) and possesses good transparency (∼99%) and thermal stability. As such, the CTP film has significant potential as a material for the electric wetting of hydrophobic dielectric layers and may serve as a promising alternative in electrowetting applications.

FXII contact activation products have an inhibitory effect on αFXIIa.

It is accepted that the contact activation complex of the intrinsic pathway of blood coagulation cascade produces active enzymes that lead to plasma coagulation following biomaterial contact. In this study, FXII was activated through contact with hydrophilic glass beads and hydrophobic octadecyltrichlorosilane-modified glass beads from neat buffer solutions. These FXII contact activation products generated from material interaction were found to suppress the procoagulant activity of exogenous αFXIIa, and this inhibition was dependent on surface wettability and the concentration of exogenous αFXIIa. Higher relative inhibition rates were generally observed at low concentrations of αFXIIa (1-2 μg/mL) while both hydrophobic and hydrophilic materials showed similar inhibition levels (~39%) at high concentrations of αFXIIa (20 μg/mL). The presence of prekallikrein in the activation system increased the amount of FXIIa produced during FXII contact activation, and also suppressed the apparent levels of inhibitors on hydrophilic surfaces, while having no effect on apparent levels of inhibitors on hydrophobic surface. The combination of FXII contact activation products and activator surfaces was found to dramatically increase inhibition of αFXIIa activity compared to the activation products alone, regardless of activator surface wettability and the presence of prekallikrein. This finding of inhibitors in the suite of proteins generated by contact activation provides additional knowledge into the complex series of interactions that occur when plasma comes into contact with material surfaces.

A facile and scalable approach to tear-and-use polyethylene (PE) tape with adjustable hydrophobicity for water transferring

Despite the refined microstructures for liquid manipulation materials is hard to be readily and massively fabricate, the damage and abrasion during storage and transportation is still a main factor limiting its service life. Herein, a facile, scalable, and eco-friendly approach to superhydrophobic polyethylene (PE) tape via constructing polypropylene (PP)-PE-PP sandwiched structures with multi-melt multi-injection molding was reported. The PE tape can be long-term protected by PP layer before use. By peeling the protective PP layers from the PE tape, the hydrophobicity can be instantly endowed to the peeled PE surface, which should give credit is the failure of the interphase layer between PE and PP, followed by in-situ formation of multi-tier microstructures of the peeled PE surface during the peeling process. The hydrophobic performance can be regulated up to 154.0 ± 8.99° by optimizing PE chain structure. Moreover, by simply tunning the peeling temperature from −198 °C to 110 °C, the PE tunable water contact angle (WCA) ranges from 133.6 ± 4.39° to utmost 156.3 ± 3.57°, owing to the transformation of hierarchical multi-tier surface topography around the transition temperature (EP). Ultimately, the as-prepared hydrophobic PE tapes were successfully utilized for loss-free manipulation and transferring of the water droplet, which provides a significant prospect of eco-friendly and continuous production for durable hydrophobic materials.

Hydrophobic Bombyx mori Silk Fibroin: Routes to Functionalization with Alkyl Chains

AbstractBombyx mori silk fibroin (SF) is a very versatile biopolymer due to its biocompatibility and exceptional mechanical properties which make possible its use as a functional material in several applications. SF can be modified with a large variety of chemical approaches which endow the material with tailored chemical–physical properties. Here, a systematic investigation of different routes is reported to graft long alkyl chains on SF based on both liquid‐ and solid‐phase, aiming to modulate its hydrophobic behavior. The liquid phase method involves direct activation of SF tyrosine residues via diazo coupling and cycloaddition reactions, generating hydrophobic materials insoluble in any common solvent. The solid phase approach consists of the chemical modification of drop‐casted SF films by esterification of hydroxyl groups of serine, threonine, and tyrosine SF residues with acyl chlorides of fatty acids. For the solid‐state functionalization, a new class of hydrophobic pendant groups is synthesized, based on triple esters of gallic acid anhydrides, that are reacted with the biopolymer to further enhance its resulting hydrophobic features.

Preparation and anti-triple-negative breast cancer cell effect of a nanoparticle for the codelivery of paclitaxel and gemcitabine

Amphiphilic polymers (HA-ANI) were prepared by grafting hyaluronic acid (HA) and 6-(2-nitroimidazole)hexylamine (ANI) and then self-assemble in water to form nanoparticles (NPs) that could be loaded with paclitaxel (PTX) and gemcitabine (GEM) by dialysis. Infrared spectroscopy and 1H-NMR indicated the successful synthesis of HA-ANI. Three different ratios of NPs were prepared by adjusting the ratios of hydrophilic and hydrophobic materials, and the particle size decreased as the ratio of hydrophilic materials increased. When HA:ANI = 2.0:1, the nanoparticles had the smallest size distribution, good stability and near spherical shape and had high drug loading and encapsulation rates. In vitro release experiments revealed that NADPH could accelerate the drug release from NPs. Cellular uptake rate reached 86.50% at 6 h. The toxic effect of dual drug-loaded nanoparticles (P/G NPs) on MDA-MB-231 cells at 48 h was stronger than that of the free drug. The AO/EB double-staining assay revealed that a large number of late apoptotic cells appeared in the P/G NPs group, and the degree of cell damage was significantly stronger than that of the free drug group. In the cell migration assay, the 24 h-cell migration rate of the P/G NPs group was 5.99%, which was much lower than that of the free group (13.87% and 17.00%). In conclusion, MDA-MB-231 cells could effectively take up P/G NPs, while the introduction of the nano-codelivery system could significantly enhance the toxicity of the drug to MDA-MB-231 cells as well as the migration inhibition effect.

A review on 3D printing of bioinspired hydrophobic materials: oil-water separation, water harvesting, and diverse applications

A review on 3D printing of bioinspired hydrophobic materials: oil-water separation, water harvesting, and diverse applications

Surface Pressure-Area Mechanics of Water-Spread Poly(ethylene glycol)-Based Block Copolymer Micelle Monolayers at the Air-Water Interface: Effect of Hydrophobic Block Chemistry.

Amphiphilic block copolymer micelles can mimic the ability of natural lung surfactant to reduce the air-water interfacial tension close to zero and prevent the Laplace pressure-induced alveolar collapse. In this work, we investigated the air-water interfacial behaviors of polymer micelles derived from eight different poly(ethylene glycol) (PEG)-based block copolymers having different hydrophobic block chemistries to elucidate the effect of the core block chemistry on the surface mechanics of the block copolymer micelles. Aqueous micelles of about 30 nm in hydrodynamic diameter were prepared from the PEG-based block copolymers via equilibration-nanoprecipitation (ENP) and spread on the water surface using water as the spreading medium. Surface pressure-area isotherm and quantitative Brewster angle microscopy (QBAM) measurements were performed to investigate how the micelle/monolayer structures change during lateral compression of the monolayer; widely varying structural behaviors were observed, including the wrinkling/collapse of micelle monolayers and deformation and/or the desorption of individual micelles. By bivariate correlation regression analysis of surface pressure-area isotherm data, it was found that the rigidity and hydrophobicity of the hydrophobic core domain, which are quantified by glass-transition temperature (Tg) and water contact angle (θ) measurements, respectively, are coupled factors that need to be taken into account concurrently in order to control the surface mechanical properties of polymer micelle monolayers; micelles having rigid and strongly hydrophobic cores exhibited high surface pressure and a high compressibility modulus under high compression. High surface pressure and a high compressibility modulus were also found to be correlated with the formation of wrinkles in the micelle monolayer (visualized by Brewster angle microscopy (BAM)). From this study, we conclude that polymer micelles based on hydrophobic block materials having higher Tg and θ are more suitable for surfactant replacement therapy applications that require the therapeutic surfactant to produce a high surface pressure and modulus at the alveolar air-water interface.

The Adhesion Strength of Semi-Clathrate Hydrate to Different Solid Surfaces

The adhesion between a hydrate and a pipe wall is the main cause of hydrate deposition and blockage. In this study, the adhesion strength of semi-clathrate hydrate (tetrabutylammonium bromide hydrate) to four kinds of solid surfaces (E235B carbon steel, E355CC low alloy steel, SUS304 stainless steel, and polytetrafluoroethylene) was measured. This investigation reveals that the adhesion strength of the hydrate to a solid surface is negatively correlated with the wettability of the solid surface, which suggests that hydrophobic materials effectively reduced the hydrate adhesion to the pipe wall. The surface roughness showed different effects on the adhesion of the hydrate to hydrophilic or hydrophobic surfaces. To be specific, when the surface roughness increased from 3.2 µm to 12.5 µm, the hydrate adhesion strength to the hydrophilic surface of SUS304 increased by 123.6%, whereas the hydrate adhesion strength to the hydrophobic surface of polytetrafluoroethylene only increased by 21.5%. This study shows that low wettability and low surface roughness effectively reduce the critical rate required to remove hydrate deposition, which achieves the self-removal of hydrates. At the same time, it was found that the adhesion strength of the hydrate to surfaces increases with increasing subcooling. This investigation holds significant theoretical implications for designing self-cleaning surfaces for oil and gas pipes.

Development of a novel hierarchical porous and hydrophobic silica from montmorillonite for benzene adsorption

A hierarchical porous and hydrophobic adsorbent is the key to removing the volatile organic compounds through adsorption technology, especially under humidity conditions. In this work, we synthesized a hierarchical porous and hydrophobic montmorillonite-derived adsorbent by a facile strategy, i.e., a combination of ball milling, acid activation, and thermal treatment. Our results showed that ball milling could efficiently grind the montmorillonite sheets into small fragments, which caused the rapid dissolution of octahedral cations from the edges of these fragments during the subsequent acid activation process. The resulting porous silica showed more porosity (including micropores and mesopores) and a larger specific surface area (664 m2 g−1), compared with the product (345 m2 g−1) obtained by only acid washing without ball milling. The next thermal treatment readily removed the surface hydroxyl of porous silica, leading to the formation of the target product (HP-SiO2) with enhanced hydrophobicity and well-preserved pore structures. As an adsorbent for benzene molecules, HP-SiO2 exhibited a high dynamic benzene adsorption capacity (257.1 mg g−1) due to the large specific surface area and abundant micropores. Furthermore, HP-SiO2 maintained outstanding benzene adsorption performance under different humidity conditions (with a high adsorption capacity of 185.0 mg g−1 even under 40% relative humidity). Our work provided a low-cost and facile strategy for the synthesis of hierarchical porous and hydrophobic silica materials, and this adsorbent would serve as a promising adsorbent for the elimination of practical volatile organic compounds.

Effects and mechanisms of capric acid/silica capsule on water absorption reduction of cement paste

Inspired by the structure design on biomaterials for drug delivery, the encapsulation of hydrophobic capric acid (CA) core with a hydrophilic silica shell was proposed and demonstrated in a cement paste system for improving the resistance to water absorption. Firstly the fabrication of CA/silica capsule by interfacial polymerization reaction was reported. Subsequently, the effects of CA/silica capsule and mono-doped CA-hollow silica as hydrophobic admixtures on the compressive strength, water absorption, hydration process and pore structure of 28-day cement pastes were studied. Compared with the mono-doped one, the cement paste incorporated with the capsule exhibited an increased compressive strength and hydrophobicity with reduced water absorption. The increment in the compressive strength and the resistance to water absorption of capsule/cement paste was further ascribed to the improved dispersion and possible sustained release of CA/silica capsule in water, resulting in the improved hydration degree with refined pore structures and the hydrophobicity of the cement paste matrix. The study based on prepared capsule materials suggested a simple but effective approach to the fabrication of hydrophobic cement-based materials with reduced water absorption and extended service life.

Highly hydrophobic cotton fabric by in-situ co-deposition of lignin/metal particles for oil/water separation

Highly hydrophobic fabrics by chelating lignin (alkali lignin, sodium lignin sulfonate and formic acid lignin) with metal ions (Fe3+, Fe2+ and Cu2+) were prepared with the surface wettability from superhydrophilic to highly hydrophobic. The lignin/metal chelated particles are in-situ deposited onto the fabric surface using dip-coating. Different lignin/metal ion system influenced the construction of hierarchical surface roughness and energy of fabrics greatly. Specially, the formation of homogeneous spherical particles on surface contributed to the minimal contact area of water droplets and fabric, and thus avoiding their adherence. The surface morphology results showed that the active groups of lignin is closely related with the surface roughness. It was found that the alkali (AL)/FeⅢ@cotton fabric achieved a maximum water CA value of 149.9° and a low surface energy of 1.90 mN/m. Its oil-water separation efficiency was higher than 99.9% and the resultant AL/FeⅢ@cotton fabric owned an excellent stability and suitability under harsh conditions. Collectively, this work is greatly significant for achieving the high-value utilization of lignin in wastewater treatments.

Effect of capillary pressure on the CO2 flux in the pores of membrane contactor: Theory and simulation results

A simulation model was made to evaluate the effect of the capillary pressure on the CO2 capture by membrane absorption. More specifically, the model calculated the changes in the interfacial pressure and CO2 flux as the interface of gas and liquid moves through the pore opening to its exit. Two cases were considered; hydrophilic or hydrophobic membrane materials with a respective contact angle of less or more than 90°. It was revealed that CO2 flux is about 70% higher for the hydrophilic membrane of 10−6 m radius and 50 × 10−6 m length than the hydrophobic membrane of equal pore radius and pore length, when nearly equal to 1.72 × 105 Pa is applied either on the feed side (hydrophilic membrane) or on the permeate side (hydrophobic membrane) to keep the membrane pore dry without gas bubble formation. It should be noted that CO2 flux is higher when a hydrophilic membrane is used, which is against the common belief that a hydrophobic membrane is preferable for membrane absorption. Also, the duration for the interface to get to the pore exit was determined. The effect of capillary pressure increases as the membrane pores become smaller, which turns into an increase in CO2 flux when the porosity and the pore length are maintained constant. It was also revealed that the CO2 flux can be significantly increased when water absorbent is replaced by 1 M monoethanolamine solution due to increased CO2 solubility. Thus, this work is the first attempt to study the effect of capillary pressure on the flux of membrane contactors. It is recommended to collect more data on membrane contactors by the hydrophilic membrane. Electronic structure calculations were also performed to investigate the reaction mechanism between CO2 and MEA, with a focus on non-conventional interactions such as hydrogen bonding and van der Waals interactions. This is to know the details of the reaction occurring between CO2 and MEA.

Harnessing the power of floating photovoltaic: A global review

As the global demand for energy continues to increase, floating photovoltaic (FPV) power is gaining more attention as a promising clean energy source. This paper summarizes the unique advantages of FPV, such as its freedom from land restrictions, higher energy output, and potential integration with other forms of energy. However, FPV also faces challenges due to complex and harsh environmental conditions such as wind, waves, corrosion, and biological fouling. Therefore, the integrated mechanism design and the use of lightweight hydrophobic materials are crucial for ensuring the safety and stability of FPV systems under such conditions. This article also highlights certain key design points and optimization techniques that can improve the structural reliability of FPV systems. With continuous technological advancements and the accumulation of experience, the production efficiency of FPV has improved, leading to the expansion of FPV projects and a reduction in investment costs. As a result, the development of FPV has been accelerating globally, with numerous high-capacity projects being constructed. Building upon the previous literature reviews, this paper provides a concise review of the latest FPV case studies, innovative technologies, challenges in marine environments, economic costs, and market prospects from various perspectives. The primary objective is to encourage further research and application in the field of FPV.