Effect of H(2)O-CO(2) organization on ovalbumin adsorption at the supercritical CO(2)-water interface

We have studied the formation of water-CO(2) interfaces in the presence of different concentrations of ovalbumin (OVA) by tensiometry and by means of interfacial rheological measurements to obtain some information on the capacity of protein film to stabilize H(2)O in CO(2) emulsion. The formation of pure water-CO(2) interface can be described as a two-step phenomenon.(1) The CO(2) molecules adsorb onto the water surface and then a reorganization of the interface creates a H(2)O-CO(2) cluster network. This organization occurs at a temperature (40 degrees C) higher than the higher temperature limit (10 degrees C) allowing the formation of crystalline structure called CO(2) clathrate.(2) Our results show that ovalbumin adsorption from bulk concentrations higher than 0.0229 g/L inhibits the cluster formation for a CO(2) pressure less than 80 bar. However, for lower concentrations, the more the CO(2) pressure is close to 80 bar, the more OVA adsorption is reduced by the H(2)O-CO(2) cluster network. Moreover, from a pressure of 90 bar, the affinity of OVA for the interface increases and mixed films made of protein molecules and clusters are obtained for the OVA concentrations lower than 1 g/L.     

A simple method for oxygen-18 determination of milligram quantities of water using NaHCO3 reagent

This paper presents a modified H(2)O-CO(2) equilibration method for stable oxygen isotopic composition (delta(18)O) analysis of water. This method enables rapid and simple delta(18)O analysis of milligram quantities of water, by employing solid reagent NaHCO(3) as the CO(2) source, a small (0.6 mL) glass vial for the equilibration chamber, and an isotope-monitoring gas chromatography/mass spectrometry (irm-GC/MS) system for delta 18O(CO2) analysis. This method has several advantages, including simple handling for the H(2)O-CO(2) equilibration (without purging and/or evacuation treatments), rapid and easy delta(18)O analysis of equilibrated CO(2), and highly sensitive and highly precise delta(18)O analysis of H(2)O, using samples as small as 10 mg and with a precision of less than +/-0.12 per thousand. The time needed to attain oxygen isotopic equilibration between CO(2) and water is also comparable (17 h for 10 mg H(2)O and 10 h for 100 mg H(2)O) to other previous methods using CO(2) gas for the CO(2) source. The extent of delta(18)O variation of sample water from its initial delta(18)O value due to isotope exchange with added NaHCO(3) is also discussed. It is concluded that the correction needed is negligible (less than 0.1 per thousand ) as long as the oxygen atom ratio (O(NaHCO3)/O(H2O)) is less than 3.3 +/- 10(-3) and provided the delta18O(H2O) determination is made by comparing delta(18)O of CO(2) equilibrated with sample water and that equilibrated with standard water of a moderately close delta(18)O value, less than 30 per thousand difference.     

Dynamical and rheological properties of fluorinated surfactant films adsorbed at the pressurized CO2-H2O interface

The dynamics of adsorption, interfacial tension, and rheological properties of two phosphocholine-derived partially fluorinated surfactants FnHmPC, designed to compensate for the weak CO(2)-surfactant tail interactions, were determined at the pressurized CO(2)-H(2)O interface. The two surfactants differ only by the length of the hydrocarbon spacer (5 CH(2) in F8H5PC and 11 CH(2) in F8H11PC) located between the terminal perfluoroalkyl chain and the polar head. The length of this spacer was found to have a critical impact on the adsorption kinetics and elasticity of the interfacial surfactant film. F8H5PC is soluble in both water and CO(2) phases and presents several distinct successive interfacial behaviors when bulk water concentration (C(W)) increases and displays a nonclassical isotherm shape. The isotherms of F8H5PC are similar for the three CO(2) pressures investigated and comprise four regimes. In the first regime, at low C(W), the interfacial tension is controlled by the organization that occurs between H(2)O and CO(2). The second regime corresponds to the adsorption of the surfactant as a monolayer until the CO(2) phase is saturated with F8H5PC, resulting in a first inflection point. In this regime, F8H5PC molecules reach maximal compaction and display the highest apparent interfacial elasticity. In the third regime, a second inflection is observed that corresponds to the critical micelle concentration of the surfactant in water. At the highest concentrations (fourth regime), the interfacial films are purely viscous and highly flexible, suggesting the capacity for this surfactant to produce water-in-CO(2) microemulsion. In this regime, surfactant adsorption is very fast and equilibrium is reached in less than 100 s. The behavior of F8H11PC is drastically different: it forms micelles only in the water phase, resulting in a classical Gibbs interface. This surfactant decreases the interfacial tension down to 1 mN/m and forms a strongly elastic interface. As this surfactant forms a very cohesive interface, it should be suitable for formulating stable water-in-CO(2) emulsions. The finding that the length of the hydrocarbon spacer in partially fluorinated surfactants can drastically influence film properties at the CO(2)-H(2)O interface should help control the formation of microemulsions versus emulsions and help elaborate a rationale for the design of surfactants specifically adapted to pressurized CO(2).     

Wetting phenomena at the CO2/water/glass interface

A novel high-pressure apparatus and technique were developed to measure CO2/water/solid contact angles (theta) in situ for pressures up to 204 bar. For two glass substrates with different hydrophilicities, theta increased significantly with CO2 pressure. As the pressure was increased, an increase in the cohesive energy density of CO2 caused the substrate/CO2 and water/CO2 interfacial tensions (gamma) to decrease, whereas the water/substrate gamma value increased. theta for the more hydrophobic substrate was predicted accurately from the experimental water/CO2 gamma value and an interfacial model that included only long-range forces. However, for the more hydrophilic substrate, short-range specific interactions due to capping of the silanol groups by physisorbed CO2 resulted in an unusually large increase in the water/substrate gamma value, which led to a much larger increase in theta than predicted by the model. A novel type of theta hysteresis was discovered in which larger theta values were observed during depressurization than during pressurization, even down to ambient pressure. Effective receding angles were observed upon pressurization, and effective advancing angles were observed upon depressurization on the basis of movement of the three-phase contact line. The greater degree of hysteresis for the more hydrophilic silica can be attributed in part to the capping of silanol groups with CO2. The large effects of CO2 on the various interfacial energies play a key role in the enhanced ability of CO2, relative to many organic solvents, to dry silica surfaces as reported previously on the basis of FTIR spectroscopy (Tripp, C. P.; Combes, J. R. Langmuir 1998, 14, 7348-7352).     

A new gas chromatographic methodology for the estimation of the composition of binary gas mixtures

The relatively new technique of reversed-flow gas chromatography (RFGC) is used to determine the diffusion coefficients of pure gases into gas mixtures (D(mix)(exp)). The pure gases are CO and CO(2), and the mixtures consist of H(2) and He in various volume percentage compositions. A linear regression analysis of D(mix)(exp) of CO and CO(2) in various mixtures of H(2) and He against the percentage composition (X(H2) or X(He)) of the mixtures at different temperatures results in an empirical equation relating D(mix)(exp) to the corresponding theoretical values of the diffusion coefficients of CO and CO(2) in the pure gases H(2) and He, as they are calculated from the Fuller-Schettler-Giddings equation. The empirical equation shows that the diffusion coefficient of an analyte gas in a gas mixture is the partial sum of its diffusion coefficients in the component gases, therefore making possible the determination of the mole fractions of the components of the mixture. The found percentage volume compositions are very close to those determined independently by routine gas chromatography, indicating that the proposed RFGC methodology could be successfully applied to the accurate determination of the volume composition of binary gas mixtures.     

Mechanical properties of protein adsorption layers at the air/water and oil/water interface: A comparison in light of the thermodynamical stability of proteins

Over the last decades numerous studies on the interfacial rheological response of protein adsorption layers have been published. The comparison of these studies and the retrieval of a common parameter to compare protein interfacial activity are hampered by the fact that different boundary conditions (e.g. physico-chemical, instrumental, interfacial) were used. In the present work we review previous studies and attempt a unifying approach for the comparison between bulk protein properties and their adsorption films. Among many common food grade proteins we chose bovine serum albumin, β-lactoglobulin and lysozyme for their difference in thermodynamic stability and studied their adsorption at the air/water and limonene/water interface. In order to achieve this we have i) systematically analyzed protein adsorption kinetics in terms of surface pressure rise using a drop profile analysis tensiometer and ii) we addressed the interfacial layer properties under shear stress using an interfacial shear rheometer under the same experimental conditions. We could show that thermodynamically less stable proteins adsorb generally faster and yield films with higher shear rheological properties at air/water interface. The same proteins showed an analog behavior when adsorbing at the limonene/water interface but at slower rates.     

Surfactant-mixing effects on the interfacial tension and the microemulsion formation in water/supercritical CO2 system

The effects of surfactant mixing on interfacial tension and on microemulsion formation were examined for systems of air/water and water/supercritical CO2 (scCO2) interfaces and for water/scCO2 microemulsions. A fluorinated surfactant, sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2), was mixed with the three hydrocarbon surfactants, Pluronic L31, Tergitol TMN-6, and decyltrimethylammonium chloride (DeTAC), at equimolar ratio. For all the cases, the interfacial tension was significantly lowered by the mixing. The positive synergistic effect suggests that the mixed surfactants tend to pack more closely on the interface than the pure constituents. It was found, however, that the microemulsion formation in scCO2 was never facilitated by the mixing, except for the case of TMN-6. This is probably due to the segregation of the surfactants into hydrocarbon-rich and fluorocarbon-rich phases on the microemulsion surface.     

TBP在水相中活度系数的探讨

本文对TBP-C6H6、TBP-CCl4、TBP-CHCl3及TBP-C6H5Cl四体系作了蒸汽压法测量.对TBP-C6H5Cl体系作了^3^2P标记法测量,其它三体系^3^2P标记法数据取自文献.分析了二种测量的结果.所得的稀释剂的活度系数应该基本一致.     

High internal phase CO2-in-water emulsions stabilized with a branched nonionic hydrocarbon surfactant

A nonionic-methylated branched hydrocarbon surfactant, octa(ethylene glycol) 2,6,8-trimethyl-4-nonyl ether (5b-C12E8) emulsifies up to 90% CO2 in water with polyhedral cells smaller than 10 microm, as characterized by optical microscopy. The stability of these concentrated CO2/water (C/W) emulsions increases with pressure and in some cases exceeds 24 h. An increase in pressure weakens the attractive van der Waals interactions between the CO2 cells across water and raises the disjoining pressure. It also enhances the solution of the surfactant tail and drives the surfactant from water towards the water-CO2 interface, as characterized by the change in emulsion phase behavior and the decrease in interfacial tension (gamma) to 2.1 mN/m. As the surfactant adsorption increases, the greater tendency for ion adsorption is likely to increase the electrostatic repulsion in the thin lamellae and raise the disjoining pressure. As pressure increases, the increase in disjoining pressure and decrease in the capillary pressure (due to the decrease in gamma) each favor greater stability of the lamellae against rupture. The electrical conductivity is predicted successfully as a function of Bruggeman's model for concentrated emulsions. Significant differences in the stability are observed for concentrated C/W emulsions at elevated pressure versus air/W or C/W foams at atmospheric pressure.     

Investigation of short-time particle dynamics near an interface in the presence of nonadsorbed macro-ions

The optical technique of total internal reflection microscopy was used to study the normal Brownian motion of a single colloidal particle near an interface. The measurements were made using a recently developed technique in which the diffusion coefficient was determined by the variance of the short-time (Deltat --> 0) motion of the particle. Experiments were performed in solutions containing either silica nanospheres or clay platelets (Laponite RD) to investigate the effect of nonadsorbed material on the dynamics of near-contact particle motion. The change in the diffusion coefficient with separation distance between the particle and plate in solutions containing nonadsorbed macro-ions was well-described by the theory developed for simple fluids. These results suggest that, in dilute solutions of nonadsorbed material in which the bulk rheological properties remain similar to those of the pure fluid, the mobility and diffusion coefficient correction factors developed for simple fluids remain valid.     

Interfacial properties of branch-tailed fluorinated surfactants yielding a water/supercritical CO2 microemulsion

We have examined the interfacial properties of several fluorinated surfactants in a water/CO2 mixture with a pendant drop tensiometer and revealed the relationships between the interfacial properties, the surfactant structure, and the microemulsifying power. We employed the following Aerosol-OT analogue surfactants that have two fluorinated tails: bis(1H,1H,5H-octafluoropentyl)-2-sulfosuccinate (di-HCF4), sodium bis(1H,1H,9H-hexadecafluorononyl)-2-sulfosuccinate (di-HCF8), sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2), and sodium bis((1H,1H,2H,2H-heptadecafluorodecyl)-oxyethylene)-2-sulfosuccinate (8FS(EO)4). To discuss the effect of the fluorocarbon/hydrocarbon ratio in single surfactant molecules, water/CO2 interfacial tension (IFT) of a hybrid surfactant with one fluorocarbon and one hydrocarbon tail, that of a surfactant with a single fluorinated tail, and that of a hydrocarbon surfactant, Aerosol-OT (AOT), were examined. The hybrid surfactant employed was sodium 1-oxo-1-[4-(tridecafluorohexyl)phenyl]-2-hexanesulfonate (FC6-HC4), and the single-tailed surfactant was perfluoropolyether ammonium carboxylate (PFPECOONH4, CF3CF2(CF2OCF(CF3))4COONH4). All of the fluorinated AOT analogue surfactants exhibited an excellent level of activity at the water/CO2 interface compared with other fluorinated surfactants and AOT. With a larger hydrocarbon chain number in the CO2-philic tails (i.e., from 0 to 2), the IFT of the AOT analogue surfactants was increased. The area occupied by one surfactant molecule at the water/CO2 interface, A, and the critical microemulsion concentration, cmicroc, were determined and used to examine the water-to-surfactant molar ratio within a reversed micelle, W0c, of the surfactants. The surfactants that form W/scCO2 microemulsions with a large W0c were found to lower the interfacial tension efficiently irrespective of increases in temperature. To achieve the most desirable W0C, the surfactant needs not only a high CO2-philicity of the tails but also a high Krafft point, properties which induce a low hydrophilic/CO2-philic balance.     

Uptake of CO2, SO2, HNO3 and HCl on calcite (CaCO3) at 300 K: mechanism and the role of adsorbed water

All experimental observations of the uptake of the four title compounds on calcite are consistent with the presence of a reactive bifunctional surface intermediate Ca(OH)(HCO3) that has been proposed in the literature. The uptake of CO2 and SO2 occurs on specific adsorption sites of crystalline CaCO3(s) rather than by dissolution in adsorbed water, H2O(ads). SO2 primarily interacts with the bicarbonate moiety whereas CO2, HNO3 and HCl all react first with the hydroxyl group of the surface intermediate. Subsequently, the latter two react with the bicarbonate group to presumably form Ca(NO3)2 and CaCl2.2H2O. The effective equilibrium constant of the interaction of CO2 with calcite in the presence of H2O(ads) is kappa = deltaCO2/(H2O(ads)[CO2]) = 1.62 x 10(3) bar(-1), where CO2 is the quantity of CO2 adsorbed on CaCO3. The reaction mechanism involves a weakly bound precursor species that is reversibly adsorbed and undergoes rate-controlling concurrent reactions with both functionalities of the surface intermediate. The initial uptake coefficients gamma0 on calcite powder depend on the abundance of H2O(ads) under the present experimental conditions and are on the order of 10(-4) for CO2 and 0.1 for SO2, HNO3 and HCl, with gamma(ss) being significantly smaller than gamma0 for HNO3 and HCl, thus indicating partial saturation of the uptake. At 33% relative humidity and 300 K there are 3.5 layers of H2O adsorbed on calcite that reduce to a fraction of a monolayer of weakly and strongly bound water upon pumping and/or heating.     

Surface adsorption behaviour of milk whey protein and pectin mixtures under conditions of air-water interface saturation

Milk whey proteins (MWP) and pectins (Ps) are biopolymer ingredients commonly used in the manufacture of colloidal food products. Therefore, knowledge of the interfacial characteristics of these biopolymers and their mixtures is very important for the design of food dispersion formulations (foams and/or emulsions). In this paper, we examine the adsorption and surface dilatational behaviour of MWP/Ps systems under conditions in which biopolymers can saturate the air-water interface on their own. Experiments were performed at constant temperature (20 °C), pH 7 and ionic strength 0.05 M. Two MWP samples, β-lactoglobulin (β-LG) and whey protein concentrate (WPC), and two Ps samples, low-methoxyl pectin (LMP) and high-methoxyl pectin (HMP) were evaluated. The contribution of biopolymers (MWP and Ps) to the interfacial properties of mixed systems was evaluated on the basis of their individual surface molecular characteristics. Biopolymer bulk concentration capable of saturating the air-water interface was estimated from surface pressure isotherms. Under conditions of interfacial saturation, dynamic adsorption behaviour (surface pressure and dilatational rheological characteristics) of MWP/Ps systems was discussed from a kinetic point of view, in terms of molecular diffusion, penetration and configurational rearrangement at the air-water interface. The main adsorption mechanism in MWP/LMP mixtures might be the MWP interfacial segregation due to the thermodynamic incompatibility between MWP and LMP (synergistic mechanism); while the interfacial adsorption in MWP/HMP mixtures could be characterized by a competitive mechanism between MWP and HMP at the air-water interface (antagonistic mechanism). The magnitude of these phenomena could be closely related to differences in molecular composition and/or aggregation state of MWP (β-LG and WPC).     

Tailoring porous silica films through supercritical carbon dioxide processing of fluorinated surfactant templates

The tailoring of porous silica thin films synthesized using perfluoroalkylpyridinium chloride surfactants as templating agents is achieved as a function of carbon dioxide processing conditions and surfactant tail length and branching. Well-ordered films with 2D hexagonal close-packed pore structure are obtained from sol-gel synthesis using the following cationic fluorinated surfactants as templates: 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octyl)pyridinium chloride (HFOPC), 1-(3,3,4,4,5,5,6,6,7,8,8,8-dodecafluoro-7-trifluoromethyl -octyl)pyridinium chloride (HFDoMePC), and 1-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluoro-decyl)pyridinium chloride (HFDePC). Processing the sol-gel film with CO2 (69-172 bar, 25 and 45 degrees C) immediately after coating results in significant increases in pore diameter relative to the unprocessed thin films (increasing from 20% to 80% depending on surfactant template and processing conditions). Pore expansion increases with CO2 processing pressure, surfactant tail length, and surfactant branching. The varying degree of CO2 induced expansion is attributed to the solvation of the "CO2-philic" fluorinated tail and is interpreted from interfacial behavior of HFOPC, HFDoMePC, and HFDePC at the CO2-water interface.     

Analysis of the subcritical carbon dioxide-water interface

We follow the evolution of the H(2)O/CO(2) interface at 300 K from the low pressure limit to near-critical pressures in molecular dynamics simulations using the SPC water and EPM2 carbon dioxide models. The intrinsic structure of the interface is elucidated by accumulating density profiles relative to the fluctuating capillary wave surface. Our main finding is that a carbon dioxide film of increasing density and thickness grows in two stages at the interface while the structure of the water surface barely changes. At low density, the entire film density profile grows linearly with the bulk CO(2) density. This regime continues up to a bulk CO(2) density of roughly 0.00095 ?(-3). At pressures above this point, we observe a distinct second peak in the CO(2) density, along with a tail of excess density that decays exponentially with distance from the interface. The decay length of the exponential tail diverges with increasing CO(2) pressure according to an inverse power law decay. Over the entire range of pressures, the CO(2) film had no detectable effect on the orientational order of the water surface. As expected, when the film of excess CO(2) at the interface grows, we find that the surface tension drops with increasing pressure. This is in qualitative accord with existing measurements, although the rate at which the surface tension falls with increasing pressure according to the SPC and EPM2 models is too small, indicating that the surface excess of CO(2) is underestimated by these models.     

Nuclear reaction analysis: A study on the interface formation in polymer mixtures below the critical point

We describe a method for directly determining the composition profile of deuterated polymer chains in polymer mixtures. Our technique, nuclear reaction analysis, is based on the ²H(³He, ⁴He)¹H nuclear reaction. By detecting ⁴He in a forward geometry, we achieve a spatial resolution of 14 nm (FWHM). We use this technique to probe the broadening of the interface between two partially miscible polymers. We found that such a system attains a finite interfacial width in equilibrium. For short times, we monitor the dynamics of interface formation. We found that the interfacial width increases significantly slower than in the case of free diffusion.     

Structural evolution of aqueous NaCl solutions dissolved in supercritical carbon dioxide under isobaric heating by mid and near infrared spectroscopy

The local order in aqueous NaCl solutions diluted in supercritical carbon dioxide at constant pressure as a function of NaCl concentration and temperature has been investigated using near and mid infrared absorption spectroscopy. The near IR results have allowed us to estimate the water concentration in CO(2) rich phase, whereas the state of water aggregation in CO(2) phase was investigated using mid IR spectroscopy. The analysis of the band shape variations of the OD stretching mode of HOD led us to conclude that below 100 degrees C, water molecules dissolved in CO(2) exist only under their monomeric form, whatever the salt concentration is, whereas hydrogen-bonded species, namely, dimers start to appear at higher temperatures. Larger aggregates have a negligible concentration in the range of temperature-pressure investigated. Using near and mid infrared data, we have calculated the concentrations of water species in the CO(2) phase. Upon heating, it was found that the concentration of dimers considerably increases at the expense of the monomers and only dimers are detected in carbon dioxide at highest temperatures. Changing the salt concentration affects significantly the concentration of monomers and decreases strongly the dimers population as the solution becomes progressively saturated in salt. In the saturated solution, at 340 degrees C, the dimer concentration is at least two times smaller than in the binary water-CO(2) mixture. These findings are in qualitative agreement with existing thermodynamics data showing that addition of NaCl to the binary H(2)O-CO(2) system shifts the range of partial miscibility of water and CO(2) towards higher pressure and temperature.     

The role of rheology of polymer solutions in predicting nanofiber formation by electrospinning

Electrospun polymer nanofibers are gaining increasing importance in tissue engineering, wound dressing and drug delivery. Here, we present a thorough rheological study of polymer solutions in the bulk and at the interface to find correlations between those properties and the electrospinnability of the solutions and the morphology of the resultant nanofibers. Our results indicate that blended solutions of chitosan or alginate with poly(ethylene oxide) (PEO) are appropriate for electrospinning when they form conductive, unstructured fluids displaying plasticity, rather than elasticity, in the bulk and at the interface. The interfacial rheological parameters are three orders of magnitude lower than those in the bulk. We demonstrate for the first time that interfacial, rather than bulk, rheological parameters show improved correlation and can be used to predict the success of the electrospinning process. Using the interfacial parameters of samples with homologous compositions, different groups of solutions can be identified that form smooth nanofibers. However, rheological parameters of the bulk and at the interface provide complimentary information. The bulk parameters are determined by polymer concentration and directly affect jet initiation, while the interfacial behaviour determines the continuation of the jet and fibre formation. We propose that interfacial parameters are indispensible tools for the design of electrospinning experiments.     

Anisotropic interfacial free energies of the hard-sphere crystal-melt interfaces

We present a reliable method to define the interfacial particles for determining the crystal-melt interface position, which is the key step for the crystal-melt interfacial free energy calculations using capillary wave approach. Using this method, we have calculated the free energies gamma of the fcc crystal-melt interfaces for the hard-sphere system as a function of crystal orientations by examining the height fluctuations of the interface using Monte Carlo simulations. We find that the average interfacial free energy gamma(0) = 0.62 +/- 0.02k(B)T/sigma(2) and the anisotropy of the interfacial free energies are weak, gamma(100) = 0.64 +/- 0.02, gamma(110) = 0.62 +/- 0.02, gamma(111) = 0.61 +/- 0.02k(B)T/sigma(2). The results are in good agreement with previous simulation results based on the calculations of the reversible work required to create the interfaces (Davidchack and Laird, Phys. Rev. Lett. 2000, 85, 4571). In addition, our results indicate gamma(100) > gamma(110) > gamma(111) for the hard-sphere system, similar to the results of the Lennard-Jones system.     

疏水改性聚丙烯酰胺对原油组分界面扩张流变性质的影响

利用悬挂滴方法研究了疏水改性聚丙烯酰胺(HMPAM)对胜利采油厂高温高盐油藏采出原油中酸性活性组分和沥青质界面膜扩张流变性质的影响,考察了不同活性组分浓度条件下的界面扩张流变行为.实验结果表明:1750mg·L-1HMPAM能够在界面上形成网络结构,界面扩张模量数值高达100mN·m-1左右;油相中的酸性组分随着老化时间增加吸附到界面上,与HMPAM分子的疏水改性部分形成聚集结构,一方面通过快速的扩散交换过程大大降低扩张模量,另一方面通过与疏水改性部分的相互作用加强HMPAM分子间的缔合强度,增强网络结构的弹性.沥青质分子尺寸相对较大,分子间存在氢键等较强的相互作用,造成沥青质界面聚集体和HMPAM形成的网络结构共同决定界面膜性质,混合膜的扩张模量较单独HMPAM体系仅略有降低.