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1.
Summary Several poly(3,3,3-methyltrifluoropropyl siloxane) stationary phases with a low percentage of trifluoropropyl have been recharacterised
by means of activity coefficients at temperatures in the range 60–140°C. The temperature effect of activity coefficients was
studied. Thermodynamic magnitudes: excess Gibbs energy, excess enthalpy and excess entropy for 44 solutes on these polymers
were calculated, and their relationships with solutes’ molecular connectivity indexes were tested. Solute-polymer interactions
were calculated at 120°C according to the solvation parameter model, and several correlations for selected solutes and polymers
were investigated, mainly the effect of solutes’ structure on the non-polar interactions and the effect of the solute dipole
moment on the polar interactions. In addition, the influence of polymer polarity on the different polar and non-polar interactions
was investigated. 相似文献
2.
Inverse gas chromatographic technique (IGC) was attempted as a new approach to follow the chemical changes that occur during lubricating base oil oxidation. Three groups of the oxidized base oils were prepared at different oxygen flow rates, periods and temperatures according to IP48 method. The corrected retention volumes (VR) were calculated for a series of selected test solutes possessing different functional groups on the oxidized base oils used as stationary phases. Kovats retention index (I), Flory-Huggins interaction parameter (κ∞1,2), and partial molar free energy of solution (ΔG∞L), were calculated for the given test solutes from their VR. The relationships between the I values and the oxidation variables were plotted and discussed. The obtained results were confirmed by potentiometric titration. The study reveals that the magnitudes of variation of I, κ∞1,2 or ΔG∞L retention parameters depend on the oxidation degree of the base oil. Large differences between the I values permit discrimination between the different oxidation steps. 相似文献
3.
In this work dynamic rheological and peel strength measurements on laminates of polyamide and several modified polyolefins
were made to evaluate the interfacial compatibilization phenomena. The polyolefins used were a low-density polyethylene, without
any treatment and γ-ray irradiated in air, and two copolymers, an ethylene– tert-butyl acrylate–acrylic acid terpolymer and a partially neutralized ethylene–methacrylic acid copolymer containing sodium
cations. Multilayer structures containing different amounts of both interfacial surface and volume fraction were studied.
Relationships between viscoelastic functions and composition were used to analyze the effect of bulk and surface modification
in the polyolefins at the interface with the polyamide. The results show that dynamic rheological measurements of stratified
polymers can be used as a tool to investigate interfacial activity in multiphase systems.
Received: 2 January 1998/Accepted: 21 March 1998 相似文献
4.
The enthalpies of solution of α- and β-cyclodextrins is aqueous peptide solutions were determined experimentally at 298.15
K. The obtained results were used to calculate pair cross interaction parameters between solutes. The results are discussed
in terms of the likelysolute–solute interactions. For systems α-cyclodextrin+peptide and β-cyclodextrin+peptide the diametrically
opposite character of interaction defined by structure and solvation of the molecules is observed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
The Hansen solubility parameter (HSP) seems to be a useful tool for the thermodynamic characterization of different materials. Unfortunately, estimation of the HSP values can cause some problems. In this work different procedures by using inverse gas chromatography have been presented for calculation of pharmaceutical excipients' solubility parameter. The new procedure proposed, based on the Lindvig et al. methodology, where experimental data of Flory-Huggins interaction parameter are used, can be a reasonable alternative for the estimation of HSP values. The advantage of this method is that the values of Flory-Huggins interaction parameter chi for all test solutes are used for further calculation, thus diverse interactions between test solute and material are taken into consideration. 相似文献
6.
The chromatographic performance of a Hypercarb ™ column was studied using some five-membered heterocyclic compounds. Significant retention of these molecules was observed
with water/acetonitrile eluents. The influence of the organic modifier on retention was studied and interpreted on the basis
of intermolecular interactions. The order of retention of solutes on Hypercarb ™ does follow their polarity order. Dispersion interactions undoubtedly have an influence, but do not determine the elution
order of solutes. From the results obtained, it appears that the retention of the investigated substances is defined by interaction
of polarized or polarizable functional groups in the samples with the graphite surface of the Hypercarb ™. 相似文献
7.
The miscibility and intermolecular interactions between polystyrene (PS) and poly(ethylene-co-propylene) (EPC), as well as between PS and long-chain poly(alkyl methacrylates) (PAMA), namely, poly(dodecyl methacrylate) (PDDMA) and poly(octadecyl methacrylate) (PODMA), in dilute xylene solutions at 30 °C were studied. Investigated polymers are widely used as rheology modifiers, i.e. viscosity index improvers and pour point depressants for lubricating mineral oils. The specific and reduced viscosities of two- and three-component polymer solutions as well as intrinsic viscosities and Huggins’ parameter values were determined as functions of the polymer mixture composition and overall polymer concentration. The reduced viscosity was found to be linearly dependent on the overall polymer concentration. The observed viscosities of polymer mixtures were intermediate to those of the mixture constituents; the values decrease in the order: EPC > PS > PAMA. The specific viscosities of all the polymer mixtures obtained as the experimental results and calculated applying the Catsiff-Hewett and Krigbaum-Wall theoretical equations were considered. Since all the polymer/polymer pairs showed the negative viscometric interaction parameter values (Δ b12 < 0), the PS/EPC and EPC/PAMA mixtures were found to be immiscible. The observed repulsive molecular interactions originate from the differences in polymer composition and molar masses. This conclusion was supported by calculations employing the group contribution approach of Coleman, Graf and Painter. The calculated values of interaction parameters for (co)polymer blends, Λ12, were 5.47, 6.42 and 13.1 J cm −3 for PS/PDDMA, PS/PODMA and PS/EPC, respectively. 相似文献
8.
Compositions of polymers (polyethylene and polyuretane) and fillers (initial silica and silicas modified with: N-2-aminoethyl-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxy-silane, 3-merkaptopropyltrimethoxysilane, octyltriethoxysilane) were examined by inverse gas chromatography at 383 K. Small amounts of the following test solutes were injected to achieve the infinite dilution conditions: pentane, hexane, heptane, octane, nonane, dichloromethane, chloroform, carbon tetrachloride and 1,2-dichloroethane.The retention times for these test solutes were determined and Flory-Huggins parameters were calculated. Flory-Huggins parameters characterize interactions between components: - between composition and the test solute and χ′23 - between polymer and filler in the composition.Values of both physicochemical parameters characterizing the examined materials were arranged in a matrix form: in the rows the compositions were enumerated at different temperatures whereas the columns contained the test solutes. After standardization the input matrix was subjected to principal component analysis. Three principal components explain more than 93% of the total variance in the data. Almost all test solutes carry very similar information. Therefore, it is justified to eliminate most of them from the series of test solutes. 相似文献
9.
The NMR spectra of four solutes, used as probes of liquid crystal orientational order, were analyzed. For each solute, samples were prepared at different solute concentrations, and the concentration dependence was used to extrapolate zero-concentration properties. The mean-field (Maier-Saupe) model when applied to solutes neglects solute-solute interactions and assumes all solutes in a mixed-solute sample see the same average environment. The first assumption is only valid as one approaches zero concentration, while experiments are typically carried out at concentrations between 0 and 10 mol %. The solute concentration dependence has in the past been "scaled out" using an internal solute reference as an orientational standard. We measured the concentration dependence of the orientational order parameter and calculate the corresponding interaction energies based on a mean-field interaction potential for a solute. We find agreement at the 3% level between experiments for different solutes while using (i) the zero-concentration values as solute-dependent orientational references and (ii) scaling to either order parameters or interaction energies; these two scalings gave equivalent but not identical results. We find, too, that errors inherent in the experiment and the calculations will limit attempts to refine the theory to push the comparisons beyond the 2% level. 相似文献
10.
Summary The Flory-Huggins interaction parameter,κ
1,2,
∞
, was determined for a number of fractions separated from vacuum distillation residues of natural oils. Examined fractions
were used as liquid stationary phases in inverse gas chromatography. The chemical character of the fractions was discussed
in terms of the interaction parameter. 相似文献
11.
Summary The Flory-Huggins interaction parameter, κ
1,2
∞
, was determined for a number of fractions separated from vacuum distillation residues of natural oils. Examined fractions
were used as liquid stationary phases in inverse gas chromatography. The chemical character of the fractions was discussed
in terms of the interaction parameter. 相似文献
12.
The Flory-Huggins interaction parameter (χ∞1,2) and solubility parameter (δ2) and its hydrogen bonding sensing component (δh) were determined using inverse gas chromatography (IGC). These parameters were successfully used in the probes of chemical changes that occur during the oxidation of naphthenic and paraffinic base oils in a GC column. Changes in χ∞1,2 values reflect the different types of intermolecular interactions (dispersive, polar, hydrogen bonding) of the given lubricating base oil during oxidation. The obtained results showed that δh component of solubility parameter is the most important parameter for probing the oxidative-chemical changes during the oxidation of given lubricating oils. 相似文献
13.
Inverse gas chromatography (IGC) has been widely used to measure the Flory-Huggins interaction parameters, χ, between two polymers. For over two decades studies have shown the polymer-polymer interaction parameter to be probe dependent. This study found that the solubility parameters of miscible polymer blends measured by IGC were lower than the volume average values of the components. This led to the conclusion that when specific interactions occur between two polymers the probes have less probability to contact the functional groups of the polymers, leading to a lower apparent solubility parameter. Using the solubility parameter model this deviation was shown to cause the probe dependency. Two methods were proposed to test the miscibility. One was to examine the deviation of the specific retention volume from the weight average rule. The other was to plot ?2?3RT( χ23/ V2) vs. the solubility parameters of probes. For miscible blends a linear trend with negative slope was observed. The slope was proportional to the deviation of solubility parameter of the polymer mixtures from the volume average, which could be used as a measurement for miscibility. 相似文献
14.
The interactions between two polymers, poly(vinyl chloride) and solution chlorinated polyethylene, with a series of solvents have been studied using inverse gas chromatography. Values of the interaction parameters show the importance of specific interactions in these systems. From these values and studies of polymer mixtures, values of the polymer-polymer interaction parameter have been calculated. The values were small in agreement with values of the heat of demixing of the two polymers reported previously.Measurements using PTFE and kaolin as the substrate for these polymers show the importance of the substrate. Results suggest that the pore structure of PTFE leads to problems in obtaining reliable results.By making measurements for the mixed polymer system over a range of temperatures, it has been found possible to detect the temperature of phase separation. The phase diagram obtained agrees well with results reported previously. 相似文献
15.
As proteins and other biomolecules consisting of amino acid residues require external additives for their dissolution and
recrystallization, it is important to have information about how such additives interact with amino acids. Therefore we have
studied the interactions of simple model amino acids with the additives urea and guanidine hydrochloride in aqueous solutions
at 298.15 K, using vapor pressure osmometry. During the measurements, the concentration of urea was fixed as ∼2 mol⋅kg −1 and that of guanidine hydrochloride was fixed as ∼1 mol⋅kg −1 whereas the concentrations of amino acids were varied. The experimental water activity data were processed to get the individual
activity coefficients of all the three components in the ternary mixture. Further, the activity coefficients were used to
get the excess Gibbs energies of solutions and Gibbs energies for transfer of either amino acids from water to aqueous denaturant
solutions or denaturant from water to aqueous amino acid solutions. An application of the McMillan-Mayer theory of solutions
through virial expansion of transfer Gibbs energies was made to get pair and triplet interaction parameter whose sign and
magnitude yielded information about amino acid–denaturant interactions, relative to their interactions with water. The pair
interaction parameters have been further used to obtain salting constants and in turn the thermodynamic equilibrium constant
values for the amino acid–denaturant mixing process in aqueous solutions at 298.15 K. The results have been explained in terms
of hydrophobic hydration, hydrophobic interactions and amino acid–denaturant binding. 相似文献
16.
Different sample preparation methods on the basis of the oxidation of Irgafos 168 (a phosphite ester used as a secondary antioxidant
in polymers) to phosphate ion are presented for its determination in polymers. Different reagents such as perchloric acid
and sodium hydroxide or heat were used to convert analyte to phosphate ions. In final step, a standard method (vanadomolybdophosphoric
acid method) was used to determine the phosphate ions produced. The method is simple, reliable and relatively rapid. The repeatability
was evaluated using a 20 mg·L −1 solution of analyte and it is found that the relative standard deviation is less than 5% for all procedures. Accuracy of
the method was tested by applying the spectrophotometric method along with gas chromatography to three commercial polymers.
The results in all cases are in good agreement. In nine other polymers Irgafos 168 was not detected using both methods. The
procedure in case of real samples (polyolefins) is: dissolution/precipitation of polymer, filtration, evaporation, dissolving
residue in acetone and performing digestion procedures using HClO 4 or NaOH. In the case of the pyrolytic method, the polymer was burned in an electrical furnace at 500 °C and the residue was
dissolved in HCl. 相似文献
17.
Summary Acidic and neutral compounds have been separated by strong anion-exchange capillary electrochromatography (SAXCEC) dynamically
modified by addition of sodium dodecylsulfate (SDS). It was found that separation of neutral solutes by SAXCEC without addition
of SDS is difficult because of the weak interaction of the solutes with the hydrophilic packing surface. The hydrophobicity
of the packing surface increases on addition of SDS to the mobile phase, however, and the capacity of separating neutral solutes
increases. Acidic solutes are retained, mainly because of the ion-exchange properties of this system. The influence of mobile
phase composition, e.g. SDS concentration, ionic strength, and organic modifier fraction, on the retention of acidic and neutral
solutes was investigated. Three acids and five neutral solutes were separated in only 5 min under optimized conditions, because
the direction of the strong electroosmotic flow (EOF) was the same as that of electrophoretic migration of the acids under
the conditions used. The repeatability of this system in terms of migration time relative standard deviation ( RSD) is good—less than 0.48% for 10 consecutive runs of all the solutes tested. Column efficiencies for acids were > 125000 plates
m −1; those for neutral solutes varied from 25000 to 100000 plates m −1. 相似文献
18.
Inverse gas chromatography (IGC) was used to analyze the secondary transition temperatures and the miscibility of binary mixtures of poly (ether imide) (Ultem™) and a copolyester of bisphenol-A with terephthalic and isophthalic acids (50/50) (Ardel™) in three compositions (25/50, 50/50 and 75/25). Retention diagrams of the mixtures of Ultem™ and Ardel™ for n-nonane, n-decane, n-butyl acetate and isoamyl acetate were obtained at temperatures between 60 and 285 °C. Second-order transition temperatures of the mixtures were determined according to the slope change in retention diagrams of the solvents. The glass transition temperatures of the mixtures suggested the miscibility of the polymers. Polymer–polymer interaction parameters of binary mixtures of the polymers were determined at temperatures between 260 and 285 °C by Flory–Huggins theory. The polymer–polymer interaction parameters were dependent on the solvent used. The small values of polymer–polymer interaction parameters close to zero suggest some weak interactions between the polymers in the mixture. It was concluded that it was possible to obtain more meaningful information related to the interactions of polymers in a mixture from IGC measurements, if binary polymer–solvent interaction parameters of the used solvent probes were around 0.5. 相似文献
19.
Crystallization, melting and structure of three different commercial types of isotactic polypropylene (iPP) grafted by maleic
anhydride (PP-g-MAH) with different maleic anhydride content (AC) and their β-nucleated versions were studied by X-ray diffractometry
(WAXS), differential scanning calorimetry (DSC), polarised light microscopy (PLM) and scanning electron microscopy (SEM).
The presence of maleic anhydride units disturbs the chain regularity, hereby decreases the crystallization tendency of iPP
in general and the β-crystallisation ability in particular. β-modification of iPP (β-iPP) forms only in β-nucleated PP-g-MAH
polymers studied if the anhydride content is not larger than 0.5 mass%. The influence of AC of PP-g-MAH on the feature the
spherulitic structure is demonstrated by PLM and SEM micrographs. The β-nucleated iPP/PP-g-MAH blends containing 10 mass%
PP-g-MAH crystallise predominantly in β-form independently of AC of the latter. The β-nuceated blends of iPP and PP-g-MAH
with lowest AC crystallise in β-form in whole concentration range. The interaction parameter between iPP and PP-g-MAH polymers
calculated by Nishi-Wang equation indicate limited interaction between the components. 相似文献
20.
Infinite-dilution gas–liquid chromatographic activity coefficients at 393.15 K (with their thermal and athermal components) and derived excess partial molar Gibbs energies, enthalpies, and entropies have been determined for each of 33 solutes of different polarity on four stationary phases with cyano groups, using retention data taken from the literature. The strongest interactions predicted by the solvation model are the dipolarity/polarizability, the acidic solute–basic stationary phase interaction, and nonpolar cavity formation and dispersion. These interactions were compared with those evaluated from the solute activity coefficients; the effect of the solute connectivity index and dipole moment on nonpolar and polar interactions, respectively, is discussed. The dependence of the thermal activity coefficient on nonpolar interactions, and the influence of stationary phase polarity on the four solute–stationary phase interactions, were evaluated. The nonpolar interaction increases with increasing connectivity and with increasing athermal activity coefficient. The dipolarity/polarizability interaction increases with increasing solute dipole moment. Finally, polar interactions increase with increasing stationary phase polarity whereas the nonpolar interaction is independent of stationary phase polarity. 相似文献
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