Lewis Acid Base Parameters Research Articles

Exploring the Application of Advanced Chromatographic Methods to Characterize the Surface Physicochemical Properties and Transition Phenomena of Polystyrene-b-poly(4-vinylpyridine)

The linear diblock copolymer polystyrene-b-poly(4-vinylpyridine) (PS-P4VP) is an important copolymer recently used in many applications such as optoelectronics, sensors, catalysis, membranes, energy conversion, energy storage devices, photolithography, and biomedical applications. (1) Background: The surface thermodynamic properties of PS-P4VP copolymers are of great importance in many chemical and industrial processes. (2) Methods: The inverse gas chromatography (IGC) at infinite dilution was used for the experimental determination of the retention volumes of organic solvents adsorbed on copolymer surfaces as a function of temperature. This led to the variations in the free energy of interaction necessary to the evaluation of the London dispersive and polar acid–base surface energies, the polar enthalpy and entropy, the Lewis acid–base constants, and the transition temperatures of the PS-P4VP copolymer. (3) Results: The application of the thermal Hamieh model led to an accurate determination of the London dispersive surface energy of the copolymer that showed non-linear variations versus the temperature, highlighting the presence of two transition temperatures. It was observed that the Lewis acid–base parameters of the copolymer strongly depend on the temperature, and the Lewis base constant of the solid surface was shown to be higher than its acid constant. (4) Conclusions: An important effect of the temperature on the surface thermodynamic properties of PS-P4VP was proven and new surface correlations were determined.

Temperature Dependence of the Polar and Lewis Acid-Base Properties of Poly Methyl Methacrylate Adsorbed on Silica via Inverse Gas Chromatography.

The adsorption of polymers on solid surfaces is common in many industrial applications, such as coatings, paints, catalysis, colloids, and adhesion processes. The properties of absorbed polymers commonly vary with temperature. In this paper, inverse gas chromatography at infinite dilution was used to determine the physicochemical characterization of PMMA adsorbed on silica. A new method based on the London dispersion equation was applied with a new parameter associating the deformation polarizability with the harmonic mean of the ionization energies of the solvent. More accurate values of the dispersive and polar interaction energies of the various organic solvents adsorbed on PMMA in bulk phase and PMMA/silica at different recovery fractions were obtained, as well as the Lewis acid-base parameters and the transition temperatures of the different composites. It was found that the temperature and the recovery fraction have important effects on the various physicochemical and thermodynamic properties. The variations in all the interaction parameters showed the presence of three transition temperatures for the different PMMA composites adsorbed on silica with various coverage rates, with a shift in these temperatures for a recovery fraction of 31%. An important variation in the polar enthalpy and entropy of adsorption, the Lewis acid-base parameters and the intermolecular separation distance was highlighted as a function of the temperature and the recovery fraction of PMMA on silica.

Effect of amino functional groups on the surface properties and Lewis's acid base parameters of UiO-66(NH2) by inverse gas chromatography

Amino-functionalized metal organic frameworks (MOFs) have attracted much attention for various applications such as carbon dioxide capture, water remediation and catalysis. The focus of this study is to determine the surface and Lewis's acid-base properties of UiO-66(NH2) crystals by the inverse gas chromatography (IGC) technique at infinite dilution. The latter was applied to evaluate the dispersive component of the surface energy γsd(T) by using thermal model and several molecular models. The obtained results proved that γsd(T) decreases when the temperature increases. The best results were achieved by using the thermal model that takes into account the effect of the temperature on the surface areas of the organic molecules. We also observed a decrease of the Gibbs surface free energy of adsorption by increasing the temperature of the different organic solvents. The polar interactions of UiO-66(NH2) were obtained by using the methods of Saint-Flour Papirer, Donnet et al., Brendlé-Papirer and the different molecular models. The Lewis's acid base constants KA and KD were further calculated by determining the different variables of adsorption of the probes on the solid surface and the obtained values were 1.07 and 0.45 for KA and KD respectively, with an acid-base ratio (KA/KD) of 2.38. These values showed the high acidic surface of the solid substrate; whereas, the values of the entropic acid base parameters, ωA, ωD and ωA/ωD respectively equal to 1.0×10−3, 3.8×10−4 and 2.73, also highlighted the important acidity of UiO-66-(NH2) surface. These important findings suggest that the surface defects (missing linkers and/or clusters) in UiO-66(NH2) are the main determining factor of the acid-base properties of UiO-66 based structures.

Inverse gas chromatography as a tool for screening materials: The relation between Lewis acid–base constants and triboelectric charge density of polymers

Since Saint-Flour and Papirer first introduced Gutmann's acceptor number and donor number parameters into the inverse gas chromatography (IGC) field in 1982, IGC has become an important technology for the measurement of surface Lewis acid–base properties of solid materials. However, introducing new roles of Lewis acid–base parameters, especially using them to predict material properties rather than just explain material properties, is an important aspect in developing IGC technology. In this paper, we first introduce the Schultz and Abraham methods for measurement of acid–base properties and discuss the traditional role of acid–base parameters. Then, we present a relation between the ratio of acid–base constants, Ka/Kb, and triboelectric charge density of some polymers to prove the possible new application field of IGC.

Surface properties of ionic liquids: A study of different calculation methods in inverse gas chromatography

The surface properties of 1-alkyl-3-vinylimidazolium hexafluorophosphate ([CnVIM][PF6], n = 2,4,6,8) ionic liquids and 1-allyl-3-vinylimidazolium ([AVIM]+), ionic-based liquids with different anions (Cl−, Br−, [BF4]−, [Tf2N]−) were investigated at temperatures between 303.15 and 343.15 K on the basis of inverse gas chromatography (IGC). The Schultz method and Dorris-Gray methods were used to estimate the dispersive free energy based on the net retention volumes of homogeneous n-alkanes, and it was found that the discrepancy between the two methods increases with increasing temperature, with the Dorris-Gray method providing slightly higher values than the Schultz method at the same test temperature. The Lewis acid-base parameters, KA and KB, were likewise assessed by the method proposed by Schultz, Flour and Papirer, Brookman and Sawyer, respectively. Although the difference between the values of acid-base parameters were observed, the ratios of KB/KA obtained by three methods presented the same tendency and implied that the surface of all the tested ionic liquids exhibited the Lewis amphoteric and stronger basic character. In addition, the values of the enthalpies of adsorption between the probes and ionic liquids were also determined.

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.

Characterization of an Algerian diatomite by inverse gas chromatography: Specific and non-specific contribution and Lewis acid–base parameters

The fundamental understanding of the behavior of a solid is intimately related to the understanding of the interactions on the surface of the latter, a major challenge in particular if the material is natural and ecological. The infinite dilution-inverse gas chromatography was used to evaluate the surface thermodynamic properties of several phases (grafted and/or coated) diatomite. A series of non- or polar-solute probes were injected at temperatures of 45 °C and 90 °C. The dispersive surface free energies values of the supports decrease with increasing temperature and their active surface is amphoteric with predominantly acidic character.

Effects of organic matter coatings on the mobility of goethite colloids in model sand and undisturbed soil

SummaryThe mobility of goethite (OMCG) colloids coated with organic matter was studied in goethite‐coated quartz sand and in undisturbed subsoil rich in natural coatings of iron oxide. Classic Derjaguin–Landau–Verwey–Overbeek (DLVO) interactions and DLVO extended by Lewis acid–base parameters (XDLVO) were estimated between colloids and goethite‐coated sand from zeta potentials and sessile drop contact angles. The OMCG colloids were retained completely in goethite‐coated sand, whereas preconditioning of the solid matrix with dissolved organic matter (DOM) enabled subsequent colloid transport. Zeta potential values showed that goethite‐coated sand was modified strongly by DOM preconditioning. The DLVO and XDLVO interactions were estimated for the pairs of OMCG colloids and for (i) quartz, (ii) goethite and (iii) organic matter‐coated goethite. Both DLVO approaches were able to predict general trends of colloid breakthrough. An exception was the XDLVO interaction for combination (iii), which showed short‐distance (<1.3 nm) repulsive interactions that were inconsistent with breakthrough behaviour. Analogous to OMCG colloid transport in the sand, DOM preconditioning was also the prerequisite for OMCG colloid transport in undisturbed subsoil. Total colloid breakthrough in the soil was less than in the sand, probably because of straining in pore throats and retention at air–water interfaces. We concluded that the DLVO and XDLVO approaches were in general capable of predicting trends of OMCG colloid mobility in goethite‐coated sand. We concluded further that the basic principles of OMCG colloid transport were transferrable from the simplified model system to the more complex natural system despite considerable differences in surface properties, pore structure and water content.Highlights How will organic matter (OM) coatings on the solid matrix affect mobility of iron oxide colloids? Effect of OM on mobility was assessed in simple model soil systems and in undisturbed soil. OM coatings modify properties of the solid matrix surface and are a prerequisite for colloid transport. Balances between OM transport, coating formation and decomposition control colloid mobility.

Surface thermodynamics of Efavirenz and a blend of Efavirenz with cellulose acetate propionate by inverse gas chromatography

The purpose of this paper is to study the effect of an excipient on the surface energetics of Efavirenz (EFV) drug. The net retention volumes, VN, for n-alkanes and polar solutes on the two columns, namely, EFV drug and a blend of EFV with cellulose acetate propionate have been measured by inverse gas chromatography. The dispersive surface free energy, , Lewis acid parameter, Ka, and Lewis base parameter, Kb, have been determined using VN values. The values are decreased linearly with increase of temperature for pure EFV as well as for the blend. Furthermore, the values of EFV are higher than in the blend, for example, values at T = 318.15 K for EFV, and for the blend are 28.09 ± 6.02 mJ/m2 and 28.30 ± 2.31 mJ/m2, respectively. The specific component of surface free energy has been obtained by the Schultz method as well as by the Dong et al. method. The values have been used to calculate Lewis acid-base parameters for the EFV as well as the blend. The Ka values for the EFV and the blend are almost similar, where as the Kb values are higher in EFV than in the blend. Similar trend in Ka and Kb has been observed in both methods studied. Copyright © 2015 John Wiley & Sons, Ltd.

Characterization of surface properties of 1-allyl-3-methylimidazolium chloride ionic liquid by inverse gas chromatography

The determination of the dispersive component of surface free energies (gamma(s)d) at different temperatures and Lewis acid-base parameters of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM]Cl) were investigated by means of inverse gas chromatography (IGC). Four n-alkanes, including n-hexane (C6), n-heptane (C7), n-octane (C8) and n-nonane (C9), were chosen as the apolar probes to characterize the dispersive component of the surface free energies at 343.15, 353.15, 363.15 and 373.15 K, respectively; and dichloromethane (DCM), trichloromethane (TCM), tetrahydrofuran (THF), ethyl acetate (EtAc), acetone (Acet) as the polar probes to estimate the Lewis acid-base parameters to judge the interactions between [AMIM] Cl and the solvents. The IGC characterizations encompassed the adsorption thermodynamic parameters to acid-base surface interactions, including the standard enthalpy (deltaHa(s)) and the free energy change of adsorption (deltaGa(s)) at different temperatures. The results showed that the Lewis acid parameter Ka of [AMIM] Cl was 0.34, and the base parameter Kb was 1.68, which indicated it was Lewis amphoteric with predominantly basic character. Furthermore, the free energy of adsorption deltaGa(s) was also figured out. It was found that the gamma(s)d of the [AMIM] Cl were 52.26, 50.82, 46.08 and 42.05 mJ/m2 at 343.15, 353.15, 363.15 and 373.15 K, respectively. The results are of great importance to the study of the surface properties and the application of ionic liquid.

Surface characterization of cellulose acetate propionate by inverse gas chromatography

The purpose of this paper is to study the surface energetics of the polymer excipient cellulose acetate propionate (CAP) in the solid form. The net retention volumes, V N, for n-alkanes and polar solutes have been measured in the temperature range 353.15–403.15 K by inverse gas chromatography. The dispersive surface free energy, \( \gamma_{\text{S}}^{\text{d}} \), and Lewis acid–base parameters \( K_{\text{a}} \) and \( K_{\text{b}} \), have been determined using V N values. The \( \gamma_{\text{S}}^{\text{d}} \) values are decreased linearly with increase of temperature. The \( \gamma_{\text{S}}^{\text{d}} \) value at 353.15 K is 24.50 ± 1.54 mJ/m2, and the temperature gradient was found to be −0.287 mJ/m2/K1. The \( K_{\text{a}} \) and \( K_{\text{b}} \) values are 0.410 ± 0.021 and 1.708 ± 0.388, respectively, which suggest that the CAP solid surface contain relatively more basic sites. The K a and K b values of CAP are compared with the similar values obtained on the cellulose acetate butyrate solid surface.

Surface characterization of 2-hydroxypyrimidine sulphate by inverse gas chromatography

The net retention volumes, V N , of n-alkanes and polar probes on 2-hydroxypyrimidine sulphate (2-HPS) drug surface are determined at 323.15, 328.15 and 333.15 K using inverse gas chromatography. The dispersive surface free energy, \( \gamma_{S}^{d} \) of 2-HPS are evaluated by applying Schultz method as well as Dorris–Gray method and found that \( \gamma_{S}^{d} \) values are higher by 8 per cent in the latter method. The \( \gamma_{S}^{d} \) values are decreasing in both the methods with increase of temperature. The specific component of the free energy of adsorption, \( \Updelta G_{a}^{S} \), for polar probes are obtained by three methods proposed by Schultz et al., Saint Flour–Papirer and Sawyer–Brookman. The Lewis acid–base parameters, K a and K b , are calculated using \( \Updelta G_{a}^{S} \) values. The surface character value, S = (K b /K a ) according to the Schultz et al., is found to be 3.9 whereas the S value in the other two methods are found to be 6.2 and 5.6. The results demonstrate that the 2-HPS powder surface contain relatively more basic sites and can interact strongly in the acidic media.

Surface Characterization of Phenylpropanolamine Drug by Inverse Gas Chromatography

The surface thermodynamic properties can be used to understand the interactive potential of a drug surface with a solid or liquid excipient during its formulation and drug release process. The retention data were measured for n-alkanes and polar solutes at intervals of 5 K in the temperature range 318.15–333.15 K by Inverse Gas Chromatography (IGC) on the solid surface of phenylpropanolamine (PPA) drug. The retention data were used to evaluate the dispersive surface free energy, γSd, and Lewis acid-base parameters, Ka and Kb, for the PPA drug. The values, γSd, were decreasing linearly with increase of temperature and at 323.15 K the value was found to be 26.01±0.40 mJ/m2. The specific components of enthalpy of adsorption of polar solutes have been applied to evaluate Lewis acid-base parameters. The Ka and Kb values were found to be 0.451±0.033 and 0.824±0.622, respectively, which suggests that the PPA surface contains more basic sites and interact strongly in the acidic environment.

Lewis acid-base properties of cellulose acetate phthalate-polycaprolactonediol blend by inverse gas chromatography

The net retention volumes, VN, of n-alkanes and five polar probes are determined on cellulose acetate phthalate–polycaprolactonediol blend column by inverse gas chromatography in the temperature range 323.15–363.15 K. The dispersive surface energy, , of the blend has been calculated using the VN values of n-alkanes and the at 333.15 K is 12.6 mJ/m2. The values are decreasing linearly with increase of temperature. The VN values of the five polar solutes are used to calculate the specific component of the enthalpy of adsorption, . The Lewis acid–base parameters, Ka and Kb, are derived using values and are found to be 0.019 and 0.403, respectively. The Ka and Kb values indicate that the blend surface contain more basic sites and interact strongly with the acidic probes. The acid–base parameters have been used to analyze the preferential interaction of the solid surface with acidic and basic probes. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers

Surface Thermodynamic Properties of Amberlite XAD-4 by Inverse Gas Chromatography

The dispersive component of surface free energy,, of amberlite XAD-4 as a function of temperature has been determined using the net retention volumes, V N , of n-alkanes by inverse gas chromatography. The values decrease with increase of temperature. The V N values of acid-base probes have been used to calculate the specific components of free energy of adsorption,, and enthalpy of adsorption. . The Donnet method employing molar deformation polarization of solutes has been used in the evaluation of . The Lewis acid-base parameters are calculated using and are found to be 0.267 and 0.788 respectively, which indicate that the amberlite XAD-4 surface contains mostly basic sites.

Characterization of surface properties of polybutadiene rubber by inverse gas chromatography

Inverse gas chromatography was applied to the characterization of the surface properties of polybutadiene rubber (PBR). Four n-alkanes (C6, C7, C8 and C9-alkanes) were chosen as the apolar probes to characterize the dispersive component of surface free energy. Dichloromethane, trichloromethane, acetone, ethyl acetate, diethylether and tetrahydrofuran were chosen as the polar probes to detect the Lewis acid-base parameters. It was found that the dispersive components of surface free energy were 47.07, 46.46, 45.85, 45.60 and 45.09 mJ/m2 at 303, 313, 323, 333 and 343 K, respectively. The results showed that the surface free energy decreased linearly with the increase of temperature. The Lewise acidic number Ka of PBR was 0.34, and the basic number Kb was 1.77. The fact Kb/Ka >1 means that the surface of PBR was amphoteric with dominant basic character and the total ability of the surface to acid-base interactions was 2.11. The free energies of adsorption -deltaG(a)s and -deltaH(a)s by Lewis acid-base interaction were also figured out.

Surface characterization of urushiol-titanium chelate polymers by inverse gas chromatography

Urushiol-titanium chelate polymer (UTP), the reaction product of urushiol with titanium compound, is a special eco-friendly polymer with excellent performances, such as strong acids-resistance, strong alkalis-resistance, salt solution-resistance and several organic solvent-resistance. Inverse gas chromatography (IGC) was used to measure the dispersive component of surface free energy (gamma(s)d) and the Lewis acid-base parameters of UTP in this work. The gamma(s)d and the acid/base characters of UTP' surfaces were estimated by the retention time with different non-polar and polar probes at infinite dilution region. n-Pentane (C5), n-hexane (C6), n-heptane (C7), n-octane (C8) and n-nonane (C9) were chosen as the non-polar probes to characterize the gamma(s)d. Trichloromethane (CHCl3), tetrahydrofuran (THF) and acetone were chosen as polar probes to detect the Lewis acid-base parameters. The specific free energy (deltaG(a)AB) and the enthalpy (deltaH(a)AB) of adsorption corresponding to acid-base surface interactions were determined. By correlating deltaH(a)AB with the donor and acceptor numbers of the probes, the acidic (K(a)) and the basic (K(b)) parameters of the samples were calculated. The results showed that the dispersive components of the free energy of UTP were 37.68, 33.53, 35.92, 24.01 and 31.32 mJ/m2 at 70, 80, 90, 100 and 110 degrees C, respectively. The Lewis acidic number K(a) of UTP was 0.185 3, and the Lewis basic number K(b) was 0.966 2. The results were of great importance to the study of the surface properties and the applications for urushiol-metal chelate polymers.

Surface characterization of a series of cured polyurethane adhesives by inverse gas chromatography and adhesion strength testing of plywood

Inverse gas chromatography (IGC) was used to determine the surface properties of a series of polyurethane adhesives, A 1, A 2, A 3 and A 4 cured with water. The weight percentages of isocyanate group (NCO) in polyurethane adhesives were 5.3, 7.0, 13.0 and 19.6%, respectively. Four n-alkanes, C6, C7, C8 and C9 were chosen as non-polar probes to characterize the dispersive component of surface free energy, $$ \gamma_{s}^{d} . $$ Acetone, tetrahydrofuran and ethyl acetate were chosen as polar probes to detect the Lewis acid–base parameters, K a and K b. The trend of $$ \gamma_{s}^{d} $$ and K a and K b of the series of cured adhesives was also shown in this paper. The cured adhesives were all amphoteric, but predominantly Lewis basic. The adhesion strength of the poplar plywood bonded with polyurethane adhesives was tested. The results showed that the adhesion strength of plywood increased with increasing the NCO content of the adhesives and K b/K a of the cured adhesives.

Surface characterization of glass fiber by inverse gas chromatography

The surface properties of glass fiber were quantificationally analyzed by inverse gas chromatography (IGC). Five n-alkanes (C6, C7, C8, C9, and C10) were chosen as apolar probes to characterize the dispersive component of surface free energy. Trichloromethane (CHCl3), acetone, and tetrahydrofuran (THF) were chosen as polar probes to detect the Lewis acid-base parameters. It is found that the dispersive components of free energy are 32.3, 30.5, 27.5, and 26.9 mJ/m2 at 70, 80, 90, and 100 °C, respectively. The Lewis acidic number Ka of the glass fiber is 0.512 4, and the basic number Kb is 2.862. The results mean the glass fiber is a Lewis basic material.

A Preliminary Study of the Relationship between Lewis Acid–Base Parameters and Structure of Polymers

Acid–base theory is an important method to describe the interaction between materials. The inverse gas chromatography (IGC) technique can be used to measure the surface Lewis acid–base parameters of materials. Compared with the solubility parameter method, the merit of the IGC technique is that it can give the surface acid–base properties of many undissolvable materials, such as inorganic materials, metal‐oxides, and thermosetting polymers. In this paper, six polymers are chosen to discuss the rationality of their Lewis acid–base parameters from the molecular structure viewpoint. Compared with some small molecules, the values of these polymers are reasonable. However, endowing each group with a set of acid–base parameters is impossible at this stage because of the lack of sufficient data. Thus more characterization work is needed to develop the IGC method.