Study of the Second Order Transitions and Acid-Base Properties of Polymers Adsorbed on Oxides by Using Inverse Gas Chromatography at Infinite Dilution

In Part I, we gave the details concerning inverse gas chromatography (IGC) at infinite dilution and the methods and models that will be used to characterize solid substrates. This technique proved to be an excellent technique to determine not only the glass transitions, but also beta-transition and liquid-liquid transitions of polymers adsorbed on solid substrates. In this second part, we used the IGC technique to determine the second order transitions of the systems' polymethyl methacrylate (PMMA)/SiO(2) and PMMA/Al(2)O(3), at various covered surface fractions and for various tacticities of the polymer. The maxima of the dispersive component of the surface energy gamma(s)(d) of our two systems, obtained by IGC at infinite dilution, indicated clearly the presence of transition temperatures (glass or local transitions). In general, we observed with PMMA three principal maxima that reflect the changes in motions leading to reorganization and rearrangement of the various groups or chain segments of the polymer. The change in the retention mechanism of the probes at the transition temperatures is attributed to an increased molecular mobility of the polymer segments, allowing for the penetration of the probes into the polymer layer. The study of the chemical physical properties of PMMA/SiO(2) and PMMA/Al(2)O(3) revealed an important difference in the acidic and basic behavior, in Lewis terms, of oxide covered by various concentrations of PMMA. This study also highlighted an important effect of the tacticity of the polymer on the acidic basic character of PMMA adsorbed on oxides. Copyright 2001 Academic Press.     

Comparison of Dorris-Gray and Schultz methods for the calculation of surface dispersive free energy by inverse gas chromatography

Inverse gas chromatography (IGC) is an important technique for the characterization of surface properties of solid materials. A standard method of surface characterization is that the surface dispersive free energy of the solid stationary phase is firstly determined by using a series of linear alkane liquids as molecular probes, and then the acid-base parameters are calculated from the dispersive parameters. However, for the calculation of surface dispersive free energy, generally, two different methods are used, which are Dorris-Gray method and Schultz method. In this paper, the results calculated from Dorris-Gray method and Schultz method are compared through calculating their ratio with their basic equations and parameters. It can be concluded that the dispersive parameters calculated with Dorris-Gray method will always be larger than the data calculated with Schultz method. When the measuring temperature increases, the ratio increases large. Compared with the parameters in solvents handbook, it seems that the traditional surface free energy parameters of n-alkanes listed in the papers using Schultz method are not enough accurate, which can be proved with a published IGC experimental result.     

Inverse gas chromatographic method for measuring the dispersive surface energy distribution for particulates

Inverse gas chromatography (IGC) is a widely used method for determining the dispersive component of the surface energy (gamma s (d)) of particulate and fibrous solids. Such measurements are normally conducted at very low solute concentrations (infinite dilution), and they result in a single numerical value of gamma s (d) for homogeneous materials which exhibit Henry's Law adsorption behavior. However, many real solid surfaces are heterogeneous and this may be demonstrated by the nonlinear isotherms obtained at low solute surface coverages resulting in reported gamma s (d) values which are not unique. This paper presents a new method for determining of gamma s (d) distributions as a function of the solute surface coverage using adsorption isosteres for an homologous series of hydrocarbon adsorbates. gamma s (d) distributions reported here were successfully determined using two different solid materials (glass beads and alumina particles) up to typical surface coverages of approximately 10% and clearly show significant variations in gamma s (d) with solute surface coverage. The effects of sample aging and pretreatment also exhibited clear differences in the gamma s (d) distributions obtained. gamma s (d) was determined using both the Dorris-Gray and Schultz methods, with the Dorris-Gray method exhibiting a much lower experimental error. It was established that the errors associated with this statistical measurement of surface energy were strongly dependent on the quality of the experimental data sets obtained. R (2) for the linearity of fit of the retention data to the Dorris-Gray gamma s (d) analysis was found to be a valid criterion for predicting the robustness of gamma s (d) distributions obtained. Detailed discussions of other critical experimental and analysis factors relevant to this methodology, as well as the reproducibility of gamma s (d) profiles are also presented. This paper establishes that IGC can be used for determining the gamma s (d) distributions of particulate solids and is demonstrated that this method is very useful way for studying the surface energy heterogeneity of complex particulate solids.     

Application of inverse gas chromatography in the characterization of raw material used in manufacturing of abrasive materials

The raw material—aloxite used during the manufacturing of grinding tools was characterized by means of inverse gas chromatography (IGC). The surface properties of the different types of aloxite were determined including: (i) the specific surface area; (ii) the dispersive component of surface free energy as well as the sensitivity of this parameter on the environment humidity; and (iii) acidity and basicity of the examined surfaces. The results of our experiments proved the usefulness of IGC in the characterization of this kind of materials.     

Estimation of the lateral to basal surface ratio of talc by inverse gas chromatography

Inverse Gas Chromatography at Infinite Dilution, i.e. IGC‐ID, allows following the evolution of surface properties of talc impregnated with increasing concentrations of polyethyleneglycol of molecular weight 20,000. Coupling Inverse chromatography in infinite dilution conditions measurements with controlled surface modification, we have developed a new method to estimate the lateral to basal surface ratio of talc crystals.     

New approach to characterise physicochemical properties of solid substrates by inverse gas chromatography at infinite dilution. I. Some new methods to determine the surface areas of some molecules adsorbed on solid surfaces

This study was divided into three different parts that tried to give a new contribution to determine and quantify more precisely the superficial properties of solid substrates (polymers and/or oxides) obtained by inverse gas chromatography (IGC) at infinite dilution. It criticised certain of the classical methods and relationships used to determine some physico-chemical properties of a solid and gave new methods and equations that can be more precise and more realistic. Part I developed some new methods to determine the surface areas of some molecules adsorbed on solids. A theoretical calculation of surface areas of molecules adsorbed on solid substrates was proposed by using some theoretical models. Two new methods to determine the surface areas of polar molecules were developed. The first one consists of the determination of surface areas by coupling two classical methods, the dynamic contact angle and IGC techniques. The second new and general method, using the IGC technique, assumes that the specific interactions between a polar molecule and a solid proposed by Papirer and Schultz are the same. A new equation was obtained to determine the surface areas of polar molecules.     

INVESTIGATION OF THE INTERACTIONS BETWEEN WATER AND MODIFIED SILICA GEL BY IGC AND TPD

In this work, the thermodynamic parameters for the adsorption of water vapor on untreated silica gel and silica gel treated with hygroscopic salts and silane coupling agent were determined by Inverse Gas Chromatography (IGC) in the infinite dilution region. The desorption activation energies of the water vapor on virgin and modified silica gels were estimated by using the Temperature Programmed Desorption (TPD) technique. The interactions between the water and the virgin and modified silica gels were discussed. Results showed that the thermodynamic parameters and desorption activation energy of water vapour on the silica gels increase with decreasing pore size and increasing the surface hydrophilic properties. The desorption activation energy of virgin and modified silica gels was found to increase with increasing the thermodynamic parameters. The larger the adsorption parameters and the desorption activation energy were, the interactions between water and virgin and modified silica gels were.     

INVESTIGATION OF THE INTERACTIONS BETWEEN WATER AND MODIFIED SILICA GEL BY IGC AND TPD

1. INTRODUCTIONSilica gel is an amorphous inorganic polymer composed of siloxane (Si-O-Si) groups in the inner region and silanol (Si-OH) groups distributed on the surface [1]. Silanol groups can be easily functionalized by different chemical procedures. …     

Effect of emulsifiers on surface properties of sucrose by inverse gas chromatography

Inverse gas chromatography (IGC) was employed to characterize the changes in surface properties of sucrose particles coated with either lecithin or polyglycerol polyricinoleate. IGC was performed using polar and non-polar adsorbates at infinite dilution with the sucrose particles as the solid stationary phase. Coating the sugar surface with emulsifiers induced an increase in the lipophilicity of the sugar particles, i.e. a sharp decrease in the acidity of the surface. Yet the two emulsifiers induced a slightly different increase in the surface basicity. It was hypothesized that this observation was due to a difference in the molecular structure of the emulsifiers.     

Solid surface mapping by inverse gas chromatography

Inverse gas chromatography (IGC) at infinite dilution, is a technique for characterising solid surfaces. Current practice is the injection of n-alkane homologous series to obtain the free energy of adsorption of the CH2 group, from which the London component of the solid surface free energy, gamma(d)s, is calculated. A value around 40 mJ/m2 is obtained for poly(ethylene), and 30 mJ/m2 for a clean glass fibre, while the potential surface interactivity of a glass fibre is far greater than that of poly(ethylene). A specific component of the surface, in mJ/m2, should be calculated in order to obtain significant parameters. As applied up to date, when calculating the specific component of the surface energy, the fact that W(sp)a energy values are in a totally different scale than AN or DN values is a major drawback. Consequently, Ka and Kb values obtained are in arbitrary energy units, different from those of the London component measured by injecting the n-alkane series. This paper proposes a method to obtain Ka and Kb values of the surface in the same energetic scale than the London component. The method enables us to correct the traditional London component of a solid, obtaining a new value, where the amount of WaCH2 accounting for Debye interactions with polar sites, is excluded. As a result, an approach to surface mapping is performed in several different substrate materials. We show results obtained on different solid surfaces: poly(ethylene), clean glass fibre, glass beads, chemically modified glass beads and carbon fibre.     

Influence of relative humidity on the properties of examined materials by means of inverse gas chromatography

Inverse gas chromatography (IGC) at infinite dilution was applied to evaluate the surface properties of sorbents and the effect of different carrier gas humidity. They were stored in different environmental humidity – 29%, 40%, and 80%. The dispersive components of the surface free energy of the zeolites and perlite were determined by Schulz-Lavielle method, whereas their tendency to undergo specific interactions was estimated basing on the electron donor–acceptor approach presented by Flour and Papirer. Surface parameters were used to monitor the changes of the properties caused by the humidity of the storage environment as well as of RH of carrier gas. The increase of humidity of storage environment caused a decrease of sorbents surface activity and increase the ability to specific interaction.     

反相气相色谱法测定高密度聚乙烯溶解度参数

采用反相气相色谱(IGC)技术测定了高密度聚乙烯(HDPE)在303.15～343.15 K温度范围内的溶解度参数(δ2)及相关指标。以正己烷(n-C6)、正庚烷(n-C7)、正辛烷(n-C8)、正壬烷(n-C9)、三氯甲烷(CHCl3)及乙酸乙酯(EtAc)作为探针分子溶剂,经计算获得了探针溶剂的比保留体积(V0g)、摩尔吸收焓(ΔHS1)、无限稀释摩尔混合焓(ΔH∞l)、摩尔蒸发焓(ΔHv)、无限稀释活度系数(Ω∞1)以及探针溶剂与HDPE的Flory-Huggins相互作用参数(χ∞1,2)等指标。结果表明,上述6种探针溶剂在测定温度范围内均为HDPE的不良溶剂。此外,还推导出了HDPE在室温(298.15 K)下的溶解度参数δ2为19.00 (J/cm3)0.5。     

Effect of acid treatment on surface properties evolution of attapulgite clay: An application of inverse gas chromatography

In this paper, the evolution of structural, textural and surface properties of attapulgite after treatment with increasing concentrations of hydrochloric acid (0.5, 1, 3 and 5 M) is reported. The solids obtained were characterized by SEM, XRD, FTIR and BET analysis. The surface properties were also evaluated using inverse gas chromatography at infinite dilution (IGC-ID) and finite concentration (IGC-FC). The IGC analysis permitted us to reach several parameters such as: specific surface area, BET constant with organic probes and the distribution functions of the adsorption energy sites on the solid surface. At dilute concentrations of acid, carbonates are eliminated and the specific surface area increases. However, the morphology and crystal structure of attapulgite are preserved. At higher concentrations of acid, dissolution of octahedral sheets and at the same time formation of an amorphous silica from the tetrahedral sheets occur. However, the fibrous morphology is still preserved. The calculation of distribution functions reveals a clear evolution in the heterogeneity of the surface during the acid treatment, the appearance of shoulders is attributed to the development of strong specific interactions between the injected polar probe and silanol groups on the surface of amorphous silica formed during the acid treatment.     

Inverse gas chromatography for natural fibre characterisation: dispersive and acid-base distribution profiles of the surface energy

Inverse Gas Chromatography (IGC) is a gas sorption technique to determine the surface energy of natural fibres. The surface energy is directly related to the thermodynamic work of adhesion and it reflects the fibre adsorption capacity and its wettability. However, natural fibres have a complex surface chemistry of numerous organic species and present physical asperities that render the surface energetically heterogeneous. Since IGC is typically performed at infinite dilution where only the higher energetic sites interact with the solvent, a single measure of surface energy is likely to be misleading as the surface energy changes with changing chemical composition. Here we present the dispersive and acid-base surface energy profiles of flax and kenaf fibres as well as continuous filament fibres produced by a dry jet, wet spinning process (cellulose B). We injected a series of n-alkanes at finite dilution to obtain the dispersive energy distribution profile at \(30\,^{\circ }\hbox {C}\) and 0% RH. The acid-base contributions were determined by injection of mono polar probes (dichloromethane, ethylacetate) at the same surface coverages and applying the Van Oss method. The cellulose B fibres were the most energetically homogeneous, while the bast fibres were shown to have a higher polar component and much broader surface energy distributions than the cellulose fibres.     

The surface properties of cellulose and lignocellulosic materials assessed by inverse gas chromatography: a review

The physicochemical surface properties of cellulose and lignocellulosic materials are of major importance in the context of the production of composites, in papermaking, and textile area. These properties can be evaluated by using inverse gas chromatography (IGC), a particularly suitable technique for the characterization of the surface properties of fibrous materials and powders. At infinite dilution conditions of appropriate gas probes, IGC may provide important parameters including the dispersive component of the surface energy of the material under analysis, thermodynamic data on the adsorption of specific probes, and Lewis acid–base interaction parameters between the matrix and the filler of composite materials. This paper critically reviews the most relevant results available in the literature concerning the characterization of cellulose and lignocellulosic materials using IGC. Emphasis will be put into the cellulose and nanocellulose surface properties, changes in the surface properties of cellulose and lignocellulosic materials after chemical and physical modifications, and in the compatibility of cellulose-based materials with polymeric matrices. The surface properties of non-woody fibers will also be considered. Before discussing the results available in the literature, the theoretical background and the main approaches used for the calculation of parameters accessed by IGC will be given. It is expected that this review can contribute to a better knowledge of the physicochemical surface properties of cellulosics.     

Characterization of ceria-zirconia mixed oxides as catalysts for the combustion of volatile organic compounds using inverse gas chromatography

Inverse gas chromatography (IGC) has been used in this work for characterizing the adsorption of different volatile organic compounds (VOCs) (1,2-dichloroethane (DCE), trichloroethylene (TCE), and n-hexane) over ceria-zirconia mixed oxides (Ce(x)Zr(1-x)O2, with x = 0, 0.15, 0.5, 0.68, 0.8 and 1). These materials have shown to be very active catalysts for the deep oxidation of the studied VOCs in previous papers. The enthalpies of adsorption (-deltaH(ads)), adsorption isotherms (corresponding to the Henry region), and dispersive (gamma(s)(D)) and specific (I(sp)) components of the surface energy for the adsorption of the investigated compounds are determined using IGC at infinite dilution. These chromatographic data and other surface parameters (surface area, oxygen storage capacity, surface acidity, and reducibility) are correlated with the activity and selectivity of these catalysts. As a result, for n-hexane, the catalytic activity is mainly correlated with the adsorption capacity of the solids, whereas the activity for chlorinated compounds oxidation (as well as the selectivity to oxidation products) depends on both oxygen storage capacity and specific interaction of the chlorinated compound with the surface.     

Evaluation of the dispersive component of the surface energy of active carbons as determined by inverse gas chromatography at zero surface coverage

The methods to obtain the dispersive component of the surface energy (gamma(s)(d)) of active carbons (AC) from inverse gas chromatography (IGC) measurements usually render values much higher than those obtained by other techniques. In this paper this is ascribed to two factors: (i) the high temperatures at that IGC measurements are carried out and (ii) the microporosity of the AC. It is shown that the temperature dependence of the area of the methylene group is an important factor in the high gamma(s)(d) values. Thus, corrections for this dependence should be considered in the calculations. In relation to microporosity, the cooperative effect of the pore walls is also an important factor to be considered in the evaluation of gamma(s)(d). The values gamma(s)(d) obtained after these corrections have their own physical meaning related to ideal flat carbon surfaces. Critical comments are made about some reported relationships between gamma(s)(d), obtained from IGC, and the BET surface area or pore volume of AC as determined from nitrogen adsorption at 77K. These are based on the very different experimental conditions at which nitrogen and IGC measurements are carried out.     

Study of the carbon fiber–poly(ether–ether–ketone) (PEEK) interfaces, 1: surface characterization of fibers and matrices,and interfacial adhesion energy

The aim of this general study is to determine the physicochemical characteristics and mechanical properties of carbon fiber–PEEK interfaces. In the first part, the dispersive component of the surface energy and the electron acceptor–donor (acid–base) characteristics of PEEK polymer and different types of untreated and surface-treated carbon fibers are determined by means of inverse gas–solid chromatography at infinite dilution. It appears, in particular, that the acid–base surface properties of PEEK and, consequently, the orientation of macromolecules near the surface, depend on the processing of this polymer. Moreover, according to previous work, an estimation of the adhesion energy, corresponding to physical interactions (London and acid–base interactions) at carbon fiber–PEEK interfaces is proposed. Whatever the surface characteristics of PEEK, the highest level of carbon fiber–PEEK adhesion is achieved in systems involving oxidized or sized carbon fibers.     

A study of the surface properties of cotton fibers by inverse gas chromatography

In the present study, the potential relationships between the microstructure and the surface properties of different cotton fibers are analyzed by inverse gas chromatography (IGC) at infinite dilution. By measuring the retention time of polar and nonpolar gaseous probes into a column containing the fibers, surface characteristics of these fibers, in particular the dispersive component of their surface energy and their surface morphological index, were determined. It is clearly shown that the presence of natural waxes on cotton fibers plays a major role on their thermodynamic surface properties, affecting the surface energy and the acid-base character as well as the morphological aspects of such fibers. Finally, it appeared that IGC is a well appropriate method for the evaluation of the surface characteristics of cotton fibers.     

Acid-base and surface energy characterization of grafted polyethylene using inverse gas chromatography

For a specific design of interfaces, i.e. in composites and blends, it is essential to know the surface thermodynamics of the components. Polyethylene grafted with maleic anhydride and maleic anhydride-styrene mixtures, respectively, was the component of interest of our investigations. Inverse gas chromatography (IGC) at infinite dilution was shown to be an appropriate method to evaluate the dispersive and acid-base surface characteristics although there is an influence of bulk absorption and morphology when performing IGC above the glass transition temperature of the polymer.