Surface elasticity modules

The reorientation of molecules in the adsorption layer should have a strong effect on the surface elasticity modules (cf paragraph 4.5 of Chapter 4). The Gibbs elasticity modulus (, =-(dy/dlnT), =(dy/dln A)p can be calculated from the equation of state (2.84) together with the relationships (2.85)-(2.88). Therefore, this value should reflect the processes involved in the equilibrium transition between the adsorption states. ... 

In the first case, the interfacial adsorption layers are characterized by clearly expressed viscoelastic properties and plasticity reflected by the yield stress Fig. 5a presents the interfacial shear viscosity, t], yield stress xys and surface elastic modules Gj. One can see that the elastic modules and the viscosity for gelatin layers without a surfactant (Ciec = 0) are equal to 1.2 mN/m and 8.3 mN s/m, respectively. Upon addition of phosphoUpids at low lecithin-to-gelatin ratio these parameters do not change. However some threshold component ratio exists and the elastic modules and the yield stress sharply increase beyond this threshold. This is the evidence of the increase in the number of contacts between strucmre elements in a gel-like layer. 

Maivald, P, Butt, H.J., Gould, S.A., Prater, C.B., Drake, B., Gurley, J.A., Elings, VB. and Hansma, P.K.. Using force modulation to image surface elasticities with the atomic force microscope. Nanotechnology, 2, 103-106 (1991). 

According to the experimental data presented above, the dependence of the contact ratio a on the test conditions and material properties, such as viscosity, speed, surface roughness, pressure, and elastic module can be descried by an exponential function as ... 

Lucassen (1968) and Lucassen-Reynders (1969) worked out the theory for longitudinal surface waves, which appear at elasticity modules higher than 30 mN/m and behaves like a stretched membrane. The related dispersion equation has the form... 

PM-IRRAS exploits the different attenuation of s- and p-polarized light by adsorbed species at a reflective (electrode) surface to annul the unchanging contributions to the infrared signal at the detector from the solvent, window, and so on, and produces an absolute rather than difference spectrum at a particular potential. In this approach, a photo-elastic modulator is employed to modulate the polarization state of the incident infrared ray between s- and p-states. On the basis of Greenler s theory [81, 82], this polarization modulation gives rise to an AC signal at the detector, which is proportional (/p —7s)-the difference in intensity of the two polarizations. Since, in principle, /p is absorbed... 

The elastic and viscoelastic properties of blends of PP and ethylene-propylene (EP) were investigated with the force modulation technique by Nysten and co-workers (250,251). In addition to a mapping of the distribution of the rubbery nodules of EP at the surface, the subsurface distribution of these nodules could be estimated. While the FMM data yielded qualitative data, more recent indentation mapping based on f-d curves allowed Nysten and co-workers to obtain quantitative information of the surface elastic modulus (252). 

Abstract The effect of lecithin (natural surfactant) addition to gelatin on the surface rheological properties of the water/ heptane interfacial layer and emulsion films formed by these liquids was studied. It was found that the gelatin/ledthin mixtures form complexes in the aqueous phase. Self-assembly of these complexes leads to the formation of viscoelastic interfacial adsorption layers characterized by a yield stress and elastic modules that provide stability of the emulsion films and emulsion systems. The above mentioned parameters evolve in time, though the formation of equilibrium interfacial layers proceeds during several hours emulsion bilayer films require only several minutes. 

P. Maivald, H.T. Butt, S.A. Gould, C.B. Prater, B. Drake, J.A. Gurley, V.B. Elings, and P.K. Hansma, Using Force Modulation to Image Surface Elasticities with the Atomic Force Microscope, Nanotech nology 2, 103 106 (1991). 

Substitution of this expression into the previous equation reveals a direct analogy between the role played by the surface elasticity (i.e. Gibbs elasticity) and the bulk compressibility in modulating density fluctuations ... 

It was previously shown that atomic force microscopy, AFM, and force modulation microscopy, FMM, can bring novel informations concerning the elastic and the viscoelastic properties of PP/EP resins at the microscopic level. They enabled the mapping of EP rubbery nodules distribution and the explanation of the macroscopic behavior of these resins (e.g. differences in the impact resistance) (5). Moreover, recent works showed that the use of AFM techniques (force-curves and force-modulation measurement, FMM cartography) can be used to characterize the surface elastic properties of PP/EP blends (6). Especially, these studies demonstrated that I M can map the surface and the subsurface distribution of EP nodules. 

For kpfm the same ac voltage is applied to the cantilever which, however, is now strictly kept away from the sample surface in the true noncontact mode [30,31]. The oscillation amplitude is kept to below 10nmp p in order to improve the force resolution and avoiding elastic tip sample interaction due to tapping. The additional ac field exerted by the tip modulates the... 

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