Polar Component Of Surface Energy Research Articles

Synergistic polarization engineering of dielectric towards low-voltage high-mobility solution-processed ultraflexible organic transistors

The emerging wearable skin-like electronics require the ultra-flexible organic transistor to operate at low voltage for electrical safety and energy efficiency and simultaneously enable high field-effect mobility to ensure the carrier migration ability and the switching speed of circuits. However, the currently reported low-voltage organic transistors generally present low mobility, originating from the trade-off between molecular polarity and surface polarity of the dielectrics. In this work, the orientation polarization of the dielectric is enhanced by introducing a flexible quaternary ammonium side chain, and the surface polarity is weakened by the shielding effect of the nonpolar methyl groups on the polar nitrogen atom. The resulting antisolvent QPSU dielectric enables the high-dielectric constant up to 18.8 and the low surface polarity with the polar component of surface energy only at 2.09 mJ/m2. Such a synergistic polarization engineering between orientation polarization and surface polarity makes the solution-processed ultraflexible transistors present the ultralow operational voltage down to −3 V, the ultrahigh charge-carrier mobility up to 8.28 cm2 V−1 s−1 at 1 Hz, excellent cyclic operational stability and long-term air stability. These results combined with the ultrathin thickness of transistor as low as 135 nm, the ultralight mass of 0.5 g/m2, the conformal adherence capability on human skin and 1-μm blade edge, and the strong mechanical robustness with stable electrical properties for 30,000 bending cycles, open up an available strategy to successfully realize low-voltage high-mobility solution-processed organic transistor, and presents the potential application of QPSU dielectric for the next-generation wearable imperceptible skin-like electronics.

Molecular-scale topographic design of multicomponent self-assembled monolayers for environmentally adaptable, lyophobic coating

HypothesisThe water wettability of a hydrophilic surface is dictated by the hydration of the region less than 1 nm below the surface plane, yet it hitherto remains a topic rarely touched upon how a subtle change in surface structural features at molecular level affects the surface wettability and its response to the environmental nature. ExperimentsBinary self-assembled monolayers (SAMs) consisting of plain and functional thiols were constructed, where the surface fraction of the functional thiols was varied from 0.1 to 0.3, 0.6, 0.8 and 1.0 and the difference in CH2 unit number between two types of thiols – defined as height difference between surface polar (OH, NH2, COOH, or H2PO3) and non-polar (CH3) groups – from 0 to 1, 3, and 5. The surface wettability of as-prepared binary SAMs and their surface energy were assessed in both air/water/solid and oil/water/solid triphasic systems. FindingsWith the relative height of surface H2PO3 groups being deliberately set as 3 in particular, as-prepared binary SAMs gain unique environmentally adaptable surface lyophobicity, namely, they can be both oleophobic in water and hydrophobic in oil. Thanks to this new environmentally adaptable surface lyophobicity, such binary SAM coating enables copper meshes to realize selective and efficient oil/water separation without need of pre-wetting. Both the polar and dispersion interaction components of surface energy of the binary SAM coatings are found crucial to effective oil/water separation of the coated copper meshes; the former defines critical intrusion pressure and the latter must be larger than 22 nN/m.

Nanotexture and crystal phase regulation for synergistic enhancement in re-endothelialization on medical pure titanium surface

Re-endothelialization has been recognized as a promising strategy to address the tissue hyperplasia and subsequent restenosis which are major complications associated with vascular implant/interventional titanium devices. However, the uncontrollable over-proliferation of smooth muscle cells (SMCs) limits the clinical application of numerous modified strategies. Herein, a novel modified strategy involving with a two-step anodic oxidation and annealing treatment was proposed to achieve rapid re-endothelialization function regulated by regular honeycomb nanotexture and specific anatase phase on the titanium surface. Theoretical calculation revealed that the presence of nanotexture reduced the polar component of surface energy, while the generation of anatase significantly enhanced the polar component and total surface energy. Meanwhile, the modified surface with regular nanotexture and anatase phase produced positive effect on the expression of CD31, VE-Cadherin and down-regulated α-SMA proteins expression, indicating excellent capacity of pro-endothelial regeneration and inhibition of SMCs proliferation and migration. One-month in vivo implantation in rabbit carotid arteries further confirmed that modified tube implant surface effectively accelerated confluent endothelial monolayer formation and promoted native-like endothelium tissue regeneration. By contrast, original titanium tube implant induced a disorganized tissue proliferation in the lumen with a high risk of restenosis. Collectively, this study opens us an alternative route to achieve the function that selectively promotes endothelial cells (ECs) growth and suppresses SMCs on the medical titanium surface, which has a great potential in facilitating re-endothelialization on the surface of blood-contacting titanium implant.

Effect of biochar aging in agricultural soil on its wetting properties and surface structure

Biochar wettability and ability to accumulate moisture inside the porous space are crucial for improving soil fertility, regulating soil water balance, and regulating nutrients. However, a long-term interaction of biochar with agricultural soils may drastically alter the wetting properties and, eventually, influence water holding capacity and the structure of soils. In this work, the structure and wetting properties of biochar samples after 6-year long exposure to a sandy loam Spodosol with a crop rotation and mineral fertilizers application were studied. It was found that the elemental composition of the aged biochars was richer and more "soil-like", which is explained by the presence of the mineral crust on the biochar surface. The temporal evolution of biochar in the soil without any mineral fertilizer application resulted in significant improvement of its surface wettability due to the effects of various environmental factors. The lateral surface of biochar after 6-year interaction with the soil changes into a loose porous layer in a form of grooved base filled with adherent mineral soil and clay particles. Contrary, the application of the mineral fertilizer to the soil resulted in decreased wettability of the biochar lateral surfaces due to a decrease in the polar component of surface energy and the crusting of the surface with fine material, which blocks the pore space of the biochar. As a result, water capacity of the biochar from the treatment with the fertilizer decreased compared to the biochar samples collected from the soil without the fertilizer application. The radial biochar surfaces of both types of samples collected from the soil were open vessels filled with soil particles that slow down complete wetting and water absorption. The treatment of the biochar samples with surfactants drastically increased wettability of lateral surface and water absorption capacity of control samples as compared to the samples collected from the soil. The obtained results support the idea that the hydrophilisation of biochar caused by the adhesion of soil particles and treatment of its pore surface with surfactants, can improve the water-holding capacity of the sandy loam Spodosol in the plant-available range of soil water.Graphical

Polar and dispersive surface tension components of water-guanidinium chloride (Gdmcl) binary mixtures

Interfacial interaction of water with guanidinium chloride (GdmCl) is crucial to understanding protein solubility and denaturing mechanism. However, molecularly resolved parameters such as polar and dispersive surface energy components of water-GdmCl mixtures remain unknown. Here, we developed a method to determine water-GdmCl mixture surface tension and its components using four different substrates including polydimethylsiloxane (PDMS), silicone, polyethylene, and polystyrene. Results show all six combinations, PDMS-silicone, PDMS-polystyrene, PDMS-polyethylene, silicone-polyethylene, silicone-polystyrene, and polyethylene-polystyrene can estimate similar trend of total surface tension, polar and dispersive components with respect to salt concentration changes. Silicone-polyethylene pairs yield the most accurate surface tension compared to others because silicone and polyethylene have large distinctive surface energy differences. Results show that polar components increase from 51 mJ/m2 to 64 mJ/m2 when salt concentration increases; dispersive components decrease from 21 mJ/m2 to 15 mJ/m2 when salt concentration increases. Total surface tension increases from 72.8 mJ/m2 to 78.1 mJ/m2 when GdmCl increases from 0% to 40 wt%. The results of this study can elucidate molecular interaction between water and GdmCl.

Thermodynamic expression of surface reconstruction impact on surface wettability

In this work we demonstrated noticeable change in the surface wettability in response to environmental changes for self-assembled monolayers (SAM) of functional alkanethiols as a result of the orientation of surface polar groups as well as the permeation of the environmental phase into the SAM surface region with the aid of sum frequency generation spectroscopy and quartz microcrystal balance. Yet the revealed surface reconstruction caused unexpectedly subtle change in SAM surface energy (within ± 8 %) due to checks and balances of the dispersive and polar components of surface energy. By introducing the work of wetting as the difference between the work of adhesion of a fluid on a solid and its surface tension, here we managed to consistently express surface reconstruction impact in SAM surface wettability as an exponential function of the relative change in work of wetting for the wetting fluid. Furthermore, we also succeeded in harnessing the relative change ratio of the work of wetting of water to that of oil to demarcate surface polar groups, which are > 1 for weakly polar groups (e.g., Br and pyrrole), <1 for small, highly polar groups (e.g., OH, NH2 and COOH), and environmentally sensitive for large, highly polar groups (e.g., H2PO3).

Ti-based surface alloy formed on AISI 316 L austenite steel surface using low-energy high-current electron beam

Titanium and Ti-based alloys possess good biocompatibility and excellent corrosion resistance. This paper is devoted to an effort to create Ti-based surface alloy on specimens made of the AISI 316 L austenite steel. The Ti-based surface alloy is created by the Ti film deposition using the magnetron sputtering method followed by the low-energy high-current electron beam irradiation of the Ti film–316 L steel substrate system surface. Transmission electron microscopy shows that the surface alloy consists of several sublayers having different structures and phase compositions. In particular, these are α-Ti; TiSi2; FeTi and Fe2Ti; Fe2SiTi; Fe2Ti3O9 phases and more complex Cr13Fe35Ni3Ti7, Cr12Fe32Mo7Ni7, Cr12Fe36Mo10, Mo5Cr6Fe18 phases nearby the substrate. Phase compositions of the surface alloy layers are determined by the change in the chemical composition of the titanium–steel system and the heat depth distribution. It is shown that the formation of the Ti-based surface alloy on the AISI 316 L austenite steel surface, provides the increase in the polar component of the free surface energy from 3.2% to 34.5%.

Characterization of polar surface groups on siliceous materials by inverse gas chromatography and the enthalpy-entropy compensation effect.

Surface-modified porous silica is a well-established composite material. To improve its embedding and application behavior, adsorption studies of various probe molecules have been performed using the technique of inverse gas chromatography (IGC). For this purpose, IGC experiments were carried out in the infinite dilution mode on macro-porous micro glass spheres before and after surface modification with (3-mercaptopropyl)trimethoxysilane. To provide information about the polar interactions between probe molecules and the silica surface, in particular, eleven polar molecules have been injected. In summary, the free surface energy for pristine silica ( = 229mJ/m2) and for (3-mercaptopropyl)trimethoxysilane-modified silica ( = 135mJ/m2) indicates a reduced wettability after surface modification. This is due to the reduction of the polar component of the free surface energy ( ) from 191mJ/m2 to 105mJ/m2. Simultaneously, with the reduction of surface silanol groups caused by surface modification of silica and, therefore, the decrease in polar interactions, a substantial loss of Lewis acidity was observed by various IGC approaches. Experiments with all silica materials have been conducted at temperatures in the range from 90°C to 120°C to determine the thermodynamic parameters, such as adsorption enthalpy ( ) and adsorption entropy ( ), using the Arrhenius regression procedure evaluating the IGC data. With the help of the enthalpy-entropy compensation, two types of adsorption complexes are assumed between polar probe molecules and the silica surface because of different isokinetic temperatures. Identical adsorption complexes with an isokinetic temperature of 370°C have been assigned to alkanes and weakly interacting polar probes such as benzene, toluene, dichloromethane, and chloroform. Polar probe molecules with typical functional groups such as OH, CO, and CN, having the ability to form hydrogen bonds to the silica surface, exhibit a lower isokinetic temperature of 60°C. Quantum chemical calculations of the probe molecules on a non-hydroxylated and hydroxylated silica cluster supported the formation of hydrogen bonds in the case of a strong polar adsorption complex with a bonding distance of 1.7nm-1.9nm to the silica surface.

Not Just Surface Energy: The Role of Bis(pentafluorophenoxy) Silicon Phthalocyanine Axial Functionalization and Molecular Orientation on Organic Thin-Film Transistor Performance.

Understanding the effect of surface chemistry on the dielectric-semiconductor interface, thin-film morphology, and molecular alignment enables the optimization of organic thin-film transistors (OTFTs). We explored the properties of thin films of bis(pentafluorophenoxy) silicon phthalocyanine (F10-SiPc) evaporated onto silicon dioxide (SiO2) surfaces modified by self-assembled monolayers (SAMs) of varying surface energies and by weak epitaxy growth (WEG). The total surface energy (γtot), dispersive component of the total surface energy (γd), and polar component of the total surface energy (γp) were calculated using the Owens-Wendt method and related to electron field-effect mobility of devices (μe), and it was determined that minimizing γp and matching γtot yielded films with the largest relative domain sizes and highest resulting μe. Subsequent analyses were completed using atomic force microscopy (AFM) and grazing-incidence wide-angle X-ray scattering (GIWAXS) to relate surface chemistry to thin-film morphology and molecular order at the surface and semiconductor-dielectric interface, respectively. Films evaporated on n-octyltrichlorosilane (OTS) yielded devices with the highest average μe of 7.2 × 10-2 cm2·V-1·s-1 that we attributed to it having both the largest domain length, which were extracted from power spectral density function (PSDF) analysis, and a subset of molecules with a pseudo edge-on orientation relative to the substrate. Films of F10-SiPc with the mean molecular orientation of the π-stacking direction being more edge-on relative to the substrate also generally resulted in OTFTs with a lower average VT. Unlike conventional MPcs, F10-SiPc films fabricated by WEG experienced no macrocycle in an edge-on configuration. These results demonstrate the critical role of the F10-SiPc axial groups on WEG, molecular orientation, and film morphology as a function of surface chemistry and the choice of SAMs.

Laser surface treatment to enhance the adhesive bonding between steel and CFRP: Effect of laser spot overlapping and pulse fluence

Adhesive bonding is widely applied in joining between steel and carbon fiber reinforced plastics (CFRP), while the surface characteristics of steel have a significant effect on the joint strength. To improve the adhesive bonding between DP590 steel and CFRP, surface modifications of steel by laser surface treatment with different overlap rate of laser spot and pulse fluence were applied and investigated. The evolution of surface morphology, contact angle, surface energy, and surface chemical composition of DP590 steel after laser treatment with different parameters were also studied. The results showed that surface roughness, surface energy and polar component of surface energy after treatments were closely related to the interfacial bonding strength between steel and adhesives. Specifically, higher pulse fluence can increase the surface roughness of the steel, which reduced the contact angle and improve the surface energy, thus not only leading to a better mechanical interlocking effect, but also improving the surface wettability of the adhesive to the steel surface. When there was 50 % overlapping of the laser spots, the surface wettability was further improved. In addition, the strengths of steel-CFRP joints obtained with both epoxy adhesive E-120HP and polyurethane adhesive PU6700 were significantly enhanced by laser surface treatment. Especially for the joints bonded with E-120HP, which is a high-strength and poor-toughness adhesive, the shear strength can be increased by 299 %, from 4.10 ± 0.17 MPa to 16.35 ± 0.89 MPa after laser treatment. More importantly, the adhesive failure along steel-adhesive interface was entirely avoided. This study provides both technical and theoretical guidance of laser surface treatment for fabricating high-performance metal-polymer hybrid structures by adhesive bonding.

Regeneration of interfacial bonding force of waste carbon fibers by light: Process demonstration and atomic level analysis

Although interest in recycling carbon fibers is rapidly growing, practical applications of recycled carbon fibers (rCFs) are limited owing to their poor wettability and adhesion. Surface modification of CFs was achieved through intense pulsed light (IPL) irradiation, which functionalizes surface of rCFs. Surface energy, chemical composition, morphology, and interfacial shear strength (IFSS) of rCFs before and after IPL irradiation were investigated. The rCF IPL-irradiated at 1,200V improved both polar and dispersive components of surface energy, and the IFSS significantly increased by 2.93 times in relation to that of the pristine rCF and reached 95% of that of high-grade commercial CFs. We proposed a mechanism by which oxygen functional groups on the rCF surface enhance the molecular bonding force with HDPE, and the model was validated from molecular dynamics simulations. IPL irradiation is a rapid and effective surface treatment method that can be employed for the manufacture of rCF-reinforced composites.

Fluorination of flax fibers for improving the interfacial compatibility of eco-composites

Because of their specific properties, vegetal fibers are increasingly used as sustainable polymer reinforcements for eco-composites. Nevertheless, their polar character hinders them from being used more frequently at industrial scale due to their incompatibility with mostly dispersive polymers (the cheapest and most common ones). In this study, direct fluorination treatment was carried out to covalently graft fluorine atom at the outmost surface of flax fibers. Such a grafting has been proved by FT-IR, 19F NMR and XPS spectroscopies, and these characterizations allowed to understand chemical change due to the treatment. This chemical modification induced an augmentation of the dispersive character of flax fibers, by significantly lowering the polar component of surface energy without significant change of the dispersive component. Young's modulus was also maintained. Thereby, treated fibers become perfectly compatible with hydrophobic polymer, and an improvement in the mechanical performance of the resulting composite is expected according to the literature.

Surface Functionalized Polyaniline Nanofibers:Chitosan Nanocomposite for Promoting Neuronal-like Differentiation of Primary Adipose Derived Mesenchymal Stem Cells and Urease Activity.

Bioscaffolds having electrically conducting polymers (CPs) have become increasingly relevant in tissue engineering (TE) because of their ability to regulate conductivity and promote biological function. With this in mind, the current study shows a conducting polyaniline nanofibers (PNFs) dispersed chitosan (Ch) nanocomposites scaffold with a simple one-step surface functionalization approach using glutaraldehyde for potential neural regeneration applications. According to the findings, 4 wt % PNFs dispersion in Ch matrix is an optimal concentration for achieving desirable biological functions while maintaining required physicochemical properties as evidenced by SEM, XRD, current-voltage (I-V) measurement, mechanical strength test, and in vitro biodegradability test. Surface chemical compositional analysis using XPS and ATR FT-IR confirms the incorporation of aldehyde functionality after functionalization, which is corroborated by surface energy calculations following the Van Oss-Chaudhury-Good method. Surface functionalization induced enhancement in surface hydrophilicity in terms of the polar component of surface energy (γiAB) from 6.35 to 12.54 mN m-1 along with an increase in surface polarity from 13.61 to 22.54%. Functionalized PNF:Ch scaffolds demonstrated improvement in enzyme activity from 67 to 94% and better enzyme kinetics with a reduction of Michaelis constants (Km) from 21.55 to 13.81 mM, indicating favorable protein-biomaterial interactions and establishing them as biologically perceptible materials. Surface functionalization mediated improved cell-biomaterial interactions led to improved viability, adhesion, and spreading of primary adipose derived mesenchymal stem cells (ADMSCs) as well as improved immunocompatibility. Cytoskeletal architecture assessment under differentiating media containing 10 ng/mL of each basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) revealed significant actin remodeling with neurite-like projections on the functionalized scaffolds after 14 days. Immunocytochemistry results showed that more than 85% of cells expressed early neuron specific β III tubulin protein on the functionalized scaffolds, whereas glial fibrillary acidic protein (GFAP) expression was limited to approximately 40% of cells. The findings point to the functionalized nanocomposites' potential as a smart scaffold for electrically stimulated neural regeneration, as they are flexible enough to be designed into microchanneled or conduit-like structures that mimic the microstructures and mechanical properties of peripheral nerves.

Interfacial properties of liquid metal immersed in various liquids

HypothesisWhen gallium-based liquid metal (LM) droplets are injected through different solvent media, the oxygen solubility of the environment influences the droplet eccentricity. The formation of an oxide membrane in solvents can determine whether a bulk-scale droplet behaves in a liquidlike or solidlike manner. In the case of LM emulsions, the solvent’s oxygen solubility leads to varying degrees of organic solvent adsorption. The adsorption of solvent molecules changes the surface energy of the oxide layer. ExperimentsThe pinch-off frames of LM droplets immersed in liquids with differing oxygen solubility were captured using a high-speed camera. Through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), the surface composition of micro and nanoscale LM emulsions in different solvents was investigated. The van Oss-Good model was implemented to determine the polar and nonpolar surface energy components of LM layers with adsorbates. FindingsPear-shaped LM droplets displaying solidlike behavior are created when the mole fraction of dissolved oxygen in the ambient solution is above approximately 2.43×10-4. For LM emulsions sonicated in organic solvents, Carbon/Oxygen (C/O) and Carbon/Gallium (C/Ga) atomic percent ratios display an increasing trend with increasing oxygen solubility. The nonpolar component of surface energy shows a logarithmic relationship with the oxygen solubility of the solvent used to treat the LM layer. The polar component of surface energy is more susceptible to the chemical properties of the solvent.

Deciphering the Reduced Loss in High Fill Factor Inverted Perovskite Solar Cells with Methoxy-Substituted Poly(Triarylamine) as the Hole Selective Contact.

A dopant-free polymeric hole selective contact (HSC) layer is ubiquitous for stable perovskite solar cells (PSCs). However, the intrinsic nonwetting nature of the polymeric HSC impedes the uniform spreading of the perovskite precursor solution, generating a terrible buried interface. Here, we dexterously tackle this dilemma from the perspective of dispersive and polar component surface energies of the HSC layer. A novel triarylamine-based HSC material, poly[bis(4-phenyl)(2,4-dimethoxyphenyl)amine] (2MeO-PTAA), was designed by introducing the polar methoxy groups to the para and ortho positions of the dangling benzene. These nonsymmetrically substituted electron-donating methoxy groups enhanced the polar components of surface energy, allowing more tight interfacial contact between the HSC layer and perovskite and facilitating hole extraction. When utilized as the dopant-free HSC layer in inverted PSCs, the 2MeO-PTAA-based device with CH3NH3PbI3 as the absorber exhibited an encouraging power conversion efficiency of 20.23% and a high fill factor of 84.31% with negligible hysteresis. Finally, a revised detailed balance model was used to verify the drastically lessened surface defect-induced recombination loss and shunt resistance loss in 2MeO-PTAA-based devices. This work demonstrates a facile and efficient way to modulate the buried interface and shed light on the direction to further improve the photovoltaic performance of inverted PSCs with other types of perovskites.

Principal Component Analysis to Determine the Surface Properties That Influence the Self-Cleaning Action of Hydrophobic Plant Leaves.

It is well established that many leaf surfaces display self-cleaning properties. However, an understanding of how the surface properties interact is still not achieved. Consequently, 12 different leaf types were selected for analysis due to their water repellency and self-cleaning properties. The most hydrophobic surfaces demonstrated splitting of the νs CH2 and ν CH2 bands, ordered platelet-like structures, crystalline waxes, high-surface-roughness values, high-total-surface-free energy and apolar components of surface energy, and low polar and Lewis base components of surface energy. The surfaces that exhibited the least roughness and high polar and Lewis base components of surface energy had intracuticular waxes, yet they still demonstrated the self-cleaning action. Principal component analysis demonstrated that the most hydrophobic species shared common surface chemistry traits with low intra-class variability, while the less hydrophobic leaves had highly variable surface-chemistry characteristics. Despite this, we have shown through partial least squares regression that the leaf water contact angle (i.e., hydrophobicity) can be predicted using attenuated total reflectance Fourier transform infrared spectroscopy surface chemistry data with excellent ability. This is the first time that such a statistical analysis has been performed on a complex biological system. This model could be utilized to investigate and predict the water contact angles of a range of biological surfaces. An understanding of the interplay of properties is extremely important to produce optimized biomimetic surfaces.

Long-term surface modification of PEEK polymer using plasma and PEG silane treatment

Despite the several advantages of the Polyetheretherketone (PEEK) polymer, its wide application is limited due to its hydrophobic nature and poor surface adhesion performance. The plasma treatment can effectively transform the hydrophobic surface to hydrophilic. However, their effects are for a short duration, and the modified surfaces gradually lose their wetting and surface adhesion properties. In this work, we have reported a combined effect of plasma and PEG Silane treatment for permanent hydrophilic modification and improved adhesion strength of PEEK surfaces. The time-dependent changes in the contact angles, XPS, and ATR-FTIR spectra results were carefully recorded to investigate the surface properties of the modified surfaces. It was observed that the functional groups and polar component of surface energy played a pivotal role in long-term modification of PEEK surfaces. The Plasma and PEG Silane treated PEEK surface retained a very low contact angle and high content of hydroxide, carboxylic acid, and peroxide groups as compared to the plasma-treated PEEK surfaces. The lap shear test confirms the long-term effects of Plasma and PEG Silane treatment on adhesion properties with high bonding strength after 48 days of sample storage, which was dropped for Plasma treated surface just after 7 days of storage.

Hydrophilization of the polyethyleneterephthalate ion track membrane surfaces

Results of polyethylenterephtalate ion track membranes hydrophilization by (Chytozan/Dextran)4 multilayers with using Layer-by-Layer method and by Nafion monolayer with using Langmuir – Blodgett and spin-coating methods are presented in articles. The structure, contact angles and polar component of specific surface energy of modified membranes has been researched.

Surface properties of cork in relation to reactive washing

Reactive washing consists of treating cork stoppers with hydrogen peroxide under strong alkaline conditions at elevated temperature. This causes changes in the surface of the stoppers, affecting their wettability. This study aimed to relate the reactive washing with changes in the surface properties of cork stoppers and their affinity for hydroalcoholic solutions with different concentrations of ethanol. The surface composition was evaluated by Fourier Transform Infrared-Attenuated Total Reflectance spectroscopy, confocal Raman spectroscopy and the free surface energy by contact angle measurements with liquid probes using Owens-Wendt-Rabel-Kaelble method. The surface morphology and topology was assessed by scanning electron microscopy and 3D optical profilometry, respectively. Different wettability of the top and lateral of the cork stoppers is due to the difference in the exposure of phellogen cell wall layers. After reactive washing, the partial degradation of suberin and the increased exposure of hydrophilic biopolymers lead to an increase in the polar component of the free surface energy, thus promoting wettability with aqueous solutions. The changes in the surface observed imply an enhancement in the wettability of cork stoppers towards hydroalcoholic solutions mimicking alcoholic beverages, as revealed by modeling studies employing a wetting envelope.

Synthesis of low surface energy thin films of nonhalogenated polyepichlorohydrin-triazoles with side alkyl chain

The dispersive and polar components of surface energy of a polymer thin film are hypothesized to be reduced by introduction of intramolecular interactions to pull side chains to the backbone and by establishment of hydrophobic interactions between extended alkyl chains to compact the molecular volume. A series of new polymer, polyepichlorohydrin (PECH)-triazole polymer with side chain with different number of methylene groups, were synthesized to prove this proposal. The newly synthesized polymer has high film-formation capacity and no halogens. The interactions between ether oxygen and imine nitrogen atoms depress the dipole effects and the hydrophobic interactions between extended methylene groups of the side chain on triazole compact the molecular volume, so the yielded surface energy has been effectively reduced to a level lower than PTFE. The synthesized polymer is a nonhalogenated low surface-energy material with potential applications.