Dispersive Surface Free Energy Research Articles

Dispersive surface free energy of adsorbents modified by supramolecular structures of heterocyclic compounds

In the present work, the dispersive surface free energy was calculated by Dorris-Gray method for 30 samples of adsorbents modified with chiral supramolecular structures of uracil, 6-methyluracil, 5-hydroxy-6-methyluracil, 5-fluorouracil, thymine, melamine, cyanuric and barbirutic acids, and perylene-3,4,9,10-tetracarboxylic dianhydride. It was shown that the homologous series of n-alkanes is better suited for measuring dispersive surface free energy than the homologous series of alcohols. It was established that the classical Dorris-Gray method does not allow obtaining well interpretable data for the objects studied. This is due to a noticeable effect that inductive interactions of a polar surface as an inductor with nonpolar alkane molecules have on the calculated values. We suggested to modify the Dorris-Gray method, making it possible to obtain data on the dispersive component of the free energy of adsorption. It was shown that the changes in dispersive surface free energy as a result of the modification correlate well with data on the structure and properties of supramolecular ensembles of the modifiers used. The results obtained can be used to predict the enantioselectivity of chiral adsorbents.

Hierarchical biocide-free silicone/graphene-silicon carbide nanocomposite coatings for marine antifouling and superhydrophobicity of ship hulls

A new series of fluorine-free, nonbiocidal, and hierarchical superhydrophobic silicone coatings filled with reduced graphene oxide (RGO)/β-SiC bamboo-like nanocomposites was successfully fabricated as durable ternary marine fouling release (FR) surfaces. RGO/β-SiC hybrid was used as coating nanofiller that would release fouling and confer surface robustness. It was facilely created using a straightforward one-phase ultrasonication technique. The dispersion of different concentrations of RGO sheets decorated with β-SiC bamboo-like fillers was determined to study the superhydrophobicity and antifouling behaviors of polysiloxane nanocomposites. RGO was prepared through a simple hydrothermal technique. Solution casting was used to distribute the RGO/β-SiC nanofillers throughout a silicone matrix. Atomic force microscopy, surface free energy, and water contact angle (WCA) were employed to examine the superhydrophobicity and micro/nanoroughness of the coatings. The mechanical, anticorrosive, and durability characteristics of the silicone-RGO/β-SiC-filled composites were also investigated. The antifouling effects of the coating systems were evaluated in the laboratory for 30 days with specific bacteria. The silicone-RGO/β-SiC (3 wt%) composite with the best dispersion, highest WCA (156°), and lowest surface free energy (12.7 mN/m) among the composites exhibited favorable FR characteristics. The well-dispersed PDMS-RGO/β-SiC (3 wt% nanofiller) composite presented the minimum degradation and cell viability percentages against Gram-positive and Gram-negative bacteria as well as diatoms. Therefore, this study produced a series of nonstick and fluorine-free ternary FR nanocomposites for maritime coatings with surface durability, superhydrophobicity, and fouling retardancy. This work highlights the design and preparation of multifunctional marine nanocoatings with excellent antifouling performance, easy applicability, and superhydrophobicity properties.

In Vitro and In Silico Studies of Functionalized Polyurethane Surfaces toward Understanding Biologically Relevant Interactions.

The solid-aqueous boundary formed upon biomaterial implantation provides a playground for most biochemical reactions and physiological processes involved in implant-host interactions. Therefore, for biomaterial development, optimization, and application, it is essential to understand the biomaterial-water interface in depth. In this study, oxygen plasma-functionalized polyurethane surfaces that can be successfully utilized in contact with the tissue of the respiratory system were prepared and investigated. Through experiments, the influence of plasma treatment on the physicochemical properties of polyurethane was investigated by atomic force microscopy, attenuated total reflection infrared spectroscopy, differential thermal analysis, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and contact angle measurements, supplemented with biological tests using the A549 cell line and two bacteria strains (Staphylococcus aureus and Pseudomonas aeruginosa). The molecular interpretation of the experimental findings was achieved by molecular dynamics simulations employing newly developed, fully atomistic models of unmodified and plasma-functionalized polyurethane materials to characterize the polyurethane-water interfaces at the nanoscale in detail. The experimentally obtained polar and dispersive surface free energies were consistent with the calculated free energies, verifying the adequacy of the developed models. A 20% substitution of the polymeric chain termini by their oxidized variants was observed in the experimentally obtained plasma-modified polyurethane surface, indicating the surface saturation with oxygen-containing functional groups.

Optimizing the Neural Network Architecture for Automation of the Tailored UV Post-Treatment of Photopolymer Printing Plates

In this work, three types of photopolymer printing plates for packaging printing were subjected to varied UV (ultraviolet radiation) post-treatments, and their surface free energy (SFE) components were calculated. SFE of the photopolymer printing plate is crucial in the process of transferring the ink from the printing plate to the substrate. Calculated polar and dispersive SFE components were used to build and optimize artificial neural networks for the prediction of the surface properties of different photopolymer materials after the performed UVA and UVC post-treatments. In this way, the production of printing plates with tailored SFE components could be automated and optimized. Consequently, products with improved qualitative properties could be printed. Results of the research have shown that the choice of the neural network’s activation function is most significant for the minimization of the mean squared error (MSE), while the number of neurons and hidden layers in neural networks has less influence on MSE. The optimized neural networks applied for common photopolymer materials in this work have the potential to be applied for the automation of the printing plates’ post-treatment process and the production of printing plates with surface properties tailored to specific printing systems.

Thermal modeling for anionic surfactant using Inverse gas chromatography and image processing techniques

Anionic surfactants are one of the necessary ingredients demanded in extensive bio-and pharmaceutical industry. Their concern on human health and environmental safety get increase and is originated from its surface thermodynamic properties. Surface thermodynamic properties have severely an effect on thermodynamic and kinetic parameters in the chemical reaction. However, there is a kind of serious differences between theoretical calculation and experimental result because of lacks of understanding on complex surface thermodynamic properties. Inverse gas chromatography (IGC) is an analytic chemistry tool providing information on physicochemical and thermodynamic parameters. Herein, a thermal modeling of surface thermodynamic properties is suggested. Net retention volume, VN, of n-alkanes and polar probes upon sodium lauryl sulfate surface properties as an anionic surfactant are analyzed at diverse temperatures range from 363.15 to 433.15 K using IGC. VN of n-alkane values are employed to assess the London dispersive surface free energy, γSL by comprehensive thermodynamic models and results into the Guttmann Lewis acid-base parameters and acid-base constants. The results reveal that an excellent linear correlation coefficient value closer to 1. The current work demonstrates how to approach surface thermodynamic characteristics of anionic surfactant and suggests a new thermal model as an advanced model. Additionally, scanning electron microscopy image analysis regarding the surface morphology has been carried out using image processing techniques. Current comprehensive approach enables to analyze and apply for an effective understanding on surfactant molecules.

Determination of Hydrophobic Dispersive Surface Free Energy of Activated Carbon Fibers Measured by Inverse Gas Chromatographic Technique

Activated carbon fibers (ACFs) as one of the most important porous carbon materials are widely used in many applications that involve rapid adsorption and low-pressure loss, including air purification, water treatment, and electrochemical applications. For designing such fibers for the adsorption bed in gas and aqueous phases, in-depth comprehension of the surface components is crucial. However, achieving reliable values remains a major challenge due to the high adsorption affinity of ACFs. To overcome this problem, we propose a novel approach to determine London dispersive components (γSL) of the surface free energy of ACFs by inverse gas chromatography (IGC) technique at an infinite dilution. Our data reveal the γSL values at 298 K for bare carbon fibers (CFs) and the ACFs to be 97 and 260-285 mJ·m-2, respectively, which lie in the regime of secondary bonding of physical adsorption. Our analysis indicates that these are impacted by micropores and defects on the carbon surfaces. Comparing the γSL obtained by the traditional Gray's method, our method is concluded as the most accurate and reliable value for the hydrophobic dispersive surface component of porous carbonaceous materials. As such, it could serve as a valuable tool in designing interface engineering in adsorption-related applications.

Super-Aerophilic Biomimetic Cactus for Underwater Dispersed Microbubble Capture, Self-Transport, Coalescence, and Energy Harvesting.

Human ocean activities are inseparable from the supply of energy. The energy contained in the gas-phase components dispersed in seawater is a potential universal energy source for eupelagic or deep-sea equipment. However, the low energy density of bubbles dispersed in water introduces severe challenges to the potential energy harvesting of gas-phase components. Here, a super-aerophilic biomimetic cactus is developed for underwater dispersive microbubble capture and energy harvesting. The bubbles captured by the super-aerophilic biomimetic cactus spines, driven by the surface tension and liquid pressure, undergo automatic transport, coalescence, accumulation, and concentrated release. The formerly unavailable low-density dispersive surface free energy of the bubbles is converted into high-density concentrated gas buoyancy potential energy, thereby providing an energy source for underwater in situ electricity generation. Experiments show a continuous process of microbubble capture by the biomimetic cactus and demonstrate a 22.76-times increase in output power and a 3.56-times enhancement in electrical energy production compared with a conventional bubble energy harvesting device. The output energy density is 3.64 times that of the existing bubble energy generator. This work provides a novel approach for dispersive gas-phase potential energy harvesting in seawater, opening up promising prospects for wide-area in situ energy supply in underwaterenvironments.

Characterisation of the Surface Free Energy of the Recycled Cellulose Layer that Comprises the Middle Component of Corrugated Paperboards

The objective of this study was to determine the polar and dispersive surface free-energy (SFE) components of the central layer of corrugated paperboards, which are made of recycled fibres. The polar and dispersive components of, and the total, SFE (also known as interfacial energy) were calculated from the contact angles of water and diiodomethane liquids on recycled cellulose sheets. The total SFE of the middle component layers of two different grammages which comprised recycled fibres ranged from 47.9 mN/m to 51.05 mN/m. The contribution of the polar component to the total surface free energy of the two types of sheets ranged from 8.6 mN/m to 12.6 mN/m. This polar contribution was significantly lower than that of water. The contact angle method proved to be a consistent way to estimate the surface properties of industrially made recycled paper products.

Surface thermodynamic properties by reverse phase chromatography and visual traits using computer vision techniques on Amberlite XAD‐7 acrylic‐ester‐resin

AbstractIn the current work, the surface thermodynamic properties of Amberlite XAD‐7 acrylic‐ester‐resin have been determined. The inverse gas chromatography (IGC) technique at infinite dilution was applied to estimate the London dispersive surface free energy was estimated by using the well‐known Fowkes equation, Dorris–Gray relation, Hamieh–Dorris–Gray model and six other molecular models based on the values of the surface areas of organic molecules and Hamieh model considering the thermal effect. The London dispersive surface free energy values are reduced by increasing temperature in all used methods and models. The Gibbs surface free energy of the adsorption values also decreased by increasing temperature in all 14 methods such as that of Swayer–Brookman, Saint–Flour Papirer, Donnet, Brendlé and Papirer, Chehimi et al, Hamieh methods (thermal method) and the methods of the enthalpy of vaporization as a function of the temperature and the standard enthalpy of formation and the six molecular models. The Lewis acidity parameter and Lewis basicity parameter, was calculated by the above stated 14 methods. The surface character “S” value was estimated to be greater than one in all the 14 methods. This indicate that the Amberlite XAD‐7 polymer material contains mostly basic sites than the acidic sites, and it can be strongly interactive with an acidic media. In addition, the visual traits such as pore size distribution, surface roughness and intricate surface morphology of the polymer resin in its original form have been explored using computer vision techniques.

Comparative study of nitrogen doped multi walled carbon nanotubes grafted with carboxy methyl cellulose hybrid composite by inverse gas chromatography and its UV photo detectors application

In this present work, the synthesis of nitrogen doped multi walled carbon nanotubes (N-MWCNTs) grafted Sodium-carboxy methyl cellulose (Na-CMC) hybrid composite was carried out via thermal reduction process. The hybrid composites were thermodynamically characterized by inverse gas chromatography (IGC) and compared to Na-CMC particles. The results were obtained by using 14 different IGC methods and models. We proved that the free energy of adsorption of the different solvents on N-MWCNTs-Na-CMC surface was equal to the summation of both free enthalpies of the solvents separately adsorbed on N-MWCNT and on Na-CMC surfaces. The London dispersive surface free energy of different materials was calculated by using the various molecular models. The more precise results were obtained by Hamieh model based on the effect of the temperature on the surface area of organic molecules. It was proved that the dispersive component of the surface energy of N-MWCNTs-Na-CMC was equal to the geometric mean than that of N-MWCNTs and Na-CMC surfaces. Lewis Acid base properties of the various materials were determined by using the different models and methods. A stronger basic character was highlighted for the different solid surfaces with more accentuated acid base character for N-MWCNT solid. Furthermore, the potential usage of the hybrid nanocomposite was studied for the practical application of the self-powered UV photodetection. On the other hand, the N-MWCNTs-Na-CMC hybrid heterostructure N-MWCNTs-Na-CMC exhibited excellent photoresponse characteristics with a good stability and reproducibility under the UV illumination (λ=382 nm) at zero bias. The high photoresponse performances were mainly attributed to the improved conductivity and enhanced charge transfer resulting from the synergetic effect of N-MWCNTs-Na-CMC hybrid heterostructure. The detailed photoresponse properties of the N-MWCNTs-Na-CMC hybrid heterostructure was discussed in detail using energy band theory.

Investigation of the Surface Properties of Hexagonal Boron Nitride and Boron Phosphate by Inverse Gas Chromatography at Infinite Dilution.

The boron-based ceramics namely hexagonal boron nitride (h-BN) and boron phosphate (BPO4) were synthesized and characterized by Fourier transform infrared spectroscopy and X-ray diffraction analysis. The surface properties of h-BN and BPO4 were examined by inverse gas chromatography method. The dispersive surface energy and the acidic-basic character of h-BN, and BPO4 surfaces were estimated by the retention time with probes such as n-hexane, n-heptane, n-octane, n-nonane, n-decane, acetone, ethyl acetate, dichloromethane, chloroform and tetrahydrofuran at infinite dilution region. The dispersive surface free energies calculated using both Schultz and Dorris-Gray methods, decreased linearly with increasing temperature. The specific adsorption free energy and the specific adsorption enthalpy corresponding to acid-base surface interactions were determined. By correlating with the donor and acceptor numbers of the probes, the acidic and the basic parameters of the h-BN and BPO4 were calculated. The values obtained for and parameters indicated that h-BN has a basic character, whereas BPO4 has an acidic character.

Surface thermodynamic properties of sodium carboxymethyl cellulose by inverse gas chromatography

This study constitutes a new development of surface thermodynamic methods to determine the London dispersive surface free energy component γsd, the specific free energy of adsorption and the Lewis acid-base properties of polymers by using inverse gas chromatography (IGC) at infinite dilution. The net retention volumes Vn of n-alkanes and polar solvents adsorbed on a sodium carboxymethyl cellulose (Na-CMC) polymer surface were determined at four temperatures 313.15K, 323.15K, 333.15 and -343.15K by IGC technique The London dispersive surface free energy component of Na-CMC was determined by using Dorris-Gray and Dorris-Gray-Hamieh methods, Van der Waals, Redlich-Kwong, Kiselev, geometric, cylindrical, spherical and Hamieh models. The more accurate value of γsd of Na-CMC was obtained by Hamieh model taking into account the thermal effect on the surface areas of molecules: γsd(T)(mJ/m2)=−0.630T(K)+229.01 showing a maximal temperature TMax = 91°C that can be considered as a new characteristic of the Na-CMC polymer. Above TMax, there is no dispersive component of the surface energy of the polymer surface.The specific interactions of Na-CMC particles were determined by using the various molecular models, and the vapor pressure, the boiling point, the topological index and the deformation polarization IGC methods. The obtained results clearly showed a strong Lewis basicity of Na-CMC (about seven times more basic than acidic polymer surface). It was proved that the IGC methods and models do not give similar results. The thermal model gave the most accurate result of the Lewis acid-base properties of Na-CMC surface.

Adhesion-cohesion balance of prepreg tack in thermoset automated fiber placement. Part 1: Adhesion and surface wetting

The constitution of prepreg tack in automated fiber placement (AFP) is affected by a sensitive balance between adhesive interfacial bond strength and cohesive strength of the prepreg resin. In an effort to explore the role of interfacial liquid-solid interaction on the tack of commercial aerospace-grade epoxy prepreg, a surface wetting analysis was performed on AFP-related substrates. The standard test liquid combination water/diiodmethane and extracted neat epoxy resin were used for contact angle measurement employing the sessile drop method and the Owens-Wendt-Rabel-Kaelble (OWRK) model. Additional rheological and topographical analyses were carried out to account for viscous resin flow on surfaces of different roughness. The results from the material characterization are discussed against the background of tack measurement by probe tack testing utilizing a rheometer. Significant differences between the investigated surfaces in terms of both the maximum tack level and the onset temperatures of adhesion were found as a function of test parameters relevant for contact formation. General agreement with the experimental tack results was observed employing a topographically extended version of the Dahlquist criterion. For each substrate, a temperature-dependent critical storage modulus could be determined that conforms to the onset temperature of tackiness. Contact angle measurements revealed a correlation between the thermodynamic work of adhesion and maximum tack and, moreover, the tack onset in the adhesive regime when additionally incorporating surface topography. Matching ratios of polar and dispersive surface free energy and surface tension components were found to favor the molecular interaction at the interface between prepreg resin and substrate.

Evaluation of the surface properties of 4-(Decyloxy) benzoic acid liquid crystal and its use in structural isomer separation.

The selectivity of 4-(Decyloxy) benzoic acid (DBA) liquid crystal in surface adsorption region (303.2–328.2 K) and thermodynamic region (423.2 – 433.2 K) was investigated by inverse gas chromatography at infinite dilution (IGC-ID). The selectivity parameters of the structural isomer series named butyl acetate, butyl alcohol, and amyl alcohol series were calculated for the DBA using IGC-ID technique. Additionally, the surface properties including dispersive surface energy (gS D), free energy (DGA S), enthalpy (DHA S), and acidity-basicity constants were calculated with net retention volumes obtained from IGC-ID experiment results. When the DHA S and DGA S are constants, DBA surface was found to be an acidic character (KD/KA @ 0.89).

Investigation of the surface properties of dibutyl amine modified poly(styrene) based polymer by inverse gas chromatography method

In the present study, poly(vinyl benzyl chloride) (PVBC) was prepared by the radical polymerization method. Then, PVBC was reacted with dibutyl amine to obtain tertiary amine-modified poly(styrene) based polymer (PVBC-Dibutyl amine) and the resulting polymer was characterized. Surface properties of the polymer were investigated by inverse gas chromatography method at infinite dilution region. For this purpose, the retention diagrams of carefully selected polar and non-polar solvents (probes) on PVBC-Dibutyl amine were obtained over a temperature range from 30 to 50 $$^\circ{\rm C}$$ . By using the diagrams, the dispersive component of the surface free energy of the polymer surface was calculated for the studied temperatures by two different methods. The specific enthalpy of adsorption and the specific component of the adsorption free energy of solvents on PVBC-Dibutyl amine which are adsorption thermodynamic parameters were determined for each solvent used. Using the adsorption data, Lewis acid and Lewis base parameters of PVBC-Dibutyl amine surface were calculated. The obtained parameters reflected that surface of PVBC-Dibutyl amine exhibited a basic behavior. Considering the values in the literature, the effect of dibutyl amine moieties in the structure of poly(styrene) based polymer PVBC-Dibutyl amine on the dispersive surface free energy and acid–base parameters of poly(styrene) was discussed.

Surface Thermo-Dynamic Characterization of Poly (Vinylidene Chloride-Co-Acrylonitrile) (P(VDC-co-AN)) Using Inverse-Gas Chromatography and Investigation of Visual Traits Using Computer Vision Image Processing Algorithms.

The Inverse Gas Chromatography (IGC) technique has been employed for the surface thermo-dynamic characterization of the polymer Poly(vinylidene chloride-co-acrylonitrile) (P(VDC-co-AN)) in its pure form. IGC attributes, such as London dispersive surface energy, Gibbs free energy, and Guttman Lewis acid-base parameters were analyzed for the polymer (P(VDC-co-AN)). The London dispersive surface free energy () was calculated using the Schultz and Dorris–Gray method. The maximum surface energy value of (P(VDC-co-AN )) is found to be 29.93 mJ·m and 24.15 mJ·m in both methods respectively. In our analysis, it is observed that the values decline linearly with an increase in temperature. The Guttman–Lewis acid-base parameter values were estimated to be 0.13 and 0.49. Additionally, the surface character S value and the correlation coefficient were estimated to be 3.77 and 0.98 respectively. After the thermo-dynamic surface characterization, the (P(VDC-co-AN)) polymer overall surface character is found to be basic. The substantial results revealed that the (P(VDC-co-AN)) polymer surface contains more basic sites than acidic sites and, hence, can closely associate in acidic media. Additionally, visual traits of the polymer (P(VDC-co-AN)) were investigated by employing Computer Vision and Image Processing (CVIP) techniques on Scanning Electron Microscopy (SEM) images captured at resolutions ×50, ×200 and ×500. Several visual traits, such as intricate patterns, surface morphology, texture/roughness, particle area distribution (), directionality (), mean average particle area () and mean average particle standard deviation (), were investigated on the polymer’s purest form. This collective study facilitates the researches to explore the pure form of the polymer Poly(vinylidene chloride-co-acrylonitrile) (P(VDC-co-AN )) in both chemical and visual perspective.

QCM-D Study of Time-Resolved Cell Adhesion and Detachment: Effect of Surface Free Energy on Eukaryotes and Prokaryotes.

Cell-material interactions are crucial for many biomedical applications, including medical implants, tissue engineering, and biosensors. For implants, while the adhesion of eukaryotic host cells is desirable, bacterial adhesion often leads to infections. Surface free energy (SFE) is an important parameter that controls short- and long-term eukaryotic and prokaryotic cell adhesion. Understanding its effect at a fundamental level is essential for designing materials that minimize bacterial adhesion. Most cell adhesion studies for implants have focused on correlating surface wettability with mammalian cell adhesion and are restricted to short-term time scales. In this work, we used quartz crystal microbalance with dissipation monitoring (QCM-D) and electrical impedance analysis to characterize the adhesion and detachment of S. cerevisiae and E. coli, serving as model eukaryotic and prokaryotic cells within extended time scales. Measurements were performed on surfaces displaying different surface energies (Au, SiO2, and silanized SiO2). Our results demonstrate that tuning the surface free energy of materials is a useful strategy for selectively promoting eukaryotic cell adhesion and preventing bacterial adhesion. Specifically, we show that under flow and steady-state conditions and within time scales up to ∼10 h, a high SFE, especially its polar component, enhances S. cerevisiae adhesion and hinders E. coli adhesion. In the long term, however, both cells tend to detach, but less detachment occurs on surfaces with a high dispersive SFE contribution. The conclusions on S. cerevisiae are also valid for a second eukaryotic cell type, being the human embryonic kidney (HEK) cells on which we performed the same analysis for comparison. Furthermore, each cell adhesion phase is associated with unique cytoskeletal viscoelastic states, which are cell-type-specific and surface free energy-dependent and provide insights into the underlying adhesion mechanisms.

New approach to optimizing risk management of the sticking problem using scale-independent critical material attributes and the quantitative process parameter.

In pharmaceutical manufacturing of solid formulations, blending with a lubricant is a key process in preventing sticking during compression. Sticking not only results in tablets with a disfigured appearance but also brings about the interruption of continuous operations. The aim of our study was to identify blending scale-independent critical material attributes (CMAs) in relation to the sticking problem to appropriately define the end-point of the blending process with magnesium stearate as lubricant. Results showed that the dispersive surface free energy (SFE) and the specific free energy absorptions (ΔGsp) of ethanol decreased during blending with magnesium stearate. As the two parameters decreased, the sticking problem was improved. In conclusion, we propose that the dispersive SFE and ΔGsp of ethanol are scale-independent CMAs, and that the minimum blending time (BTmin), which can be calculated from the two CMAs, of the quantitative process parameter show the minimum blending time required to achieve higher risk assessment of the sticking problem.

Surface characterization and London dispersive surface free energy of functionalized single‐walled carbon nanotubes with a blend of polytetrafluoroethylene by inverse gas chromatography

The SWCNTs and SWCNT‐polytetrafluoroethylene (PTFE) blend were prepared by using simple reaction mixture in the presence of chromosorb (SiO2). Surface morphology of SWCNTs and (SWCNT‐PTFE) blend was characterized by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and surface BET analysis. In addition, the surface thermodynamic properties of n‐alkanes and polar probe net retention volumes are measured by inverse gas chromatography (IGC). The London dispersive surface free energy values were found to be decreased linearly with increase of temperature. The specific component of the surface free energy of adsorption for the polar probes was obtained using the Donnet‐Park method. The surface character “S” value (Kb/Ka) at SWCNTs was found to be 0.74, and SWCNT‐PTFE blend surface character value was found to be 0.86. This result demonstrates that the (SWCNT‐PTFE) blend surface contains relatively more acidic sites then that of SWCNT surface. Therefore, the IGC results provide useful complementary information on the (SWCNT‐PTFE) blend surface.

Determination of surface properties and Gutmann’s Lewis acidity–basicity parameters of thiourea and melamine polymerized graphitic carbon nitride sheets by inverse gas chromatography

Melamine and thiourea-derived graphitic carbon nitrides (M-GCN/T-GCN) were synthesized and characterized. The surface properties were investigated using inverse gas chromatography (IGC) and compared. Net retention volumes of M-GCN and T-GCN were measured with n-alkanes (C5–C10) and polar probes. The London dispersive surface free energies (γsd), calculated using Schultz and Dorris–Gray methods, decreased linearly with increasing temperature. The specific components of the enthalpy and entropy of adsorption for the polar probes were obtained using the Schultz, Dong, and Sawyer–Brookman methods. The Gutmann’s Lewis acid–base parameters, Ka and Kb, were determined using the surface free energy (ΔGaS) via these methods. The surface character ‘S’ values (Kb/Ka) of M-GCN and T-GCN using the respective methods are 4.04, 3.78, and 5.08 and 4.11, 5.27, and 2.86. Hence, the surfaces contain more basic than acidic sites and could interact strongly with acidic media. Thus, IGC elucidates the surface charges of the GCN matrix resulting from surface chemical modification.