Thermal molecular motion

On the large side, the concept of diffusion also can be applied to macroscopic transport. This process is called turbulent diffusion. Turbulent diffusion is not based on thermal molecular motions, but on the mostly irregular (random) pattern of currents in water and air. 

Continual variations in the number, size, and location of pores as a result of thermal molecular motions in the membrane material... 

Moreover, Nieber and Doltsinis [64] have studied the effect of thermal molecular motion on the fluorescence energy by averaging over 10 configurations sampled from a 300 K ROKS Sr CP-MD run. Due to the flatness of the ROKS. S, PES, the... 

Jobling treated viscosity as due to the interaction of thermal molecular motions and molecular attraction Parshad attributed it to molecular potential barriers Girard and Abadie related it to dielectric properties. Bosworth, assuming the transmission of phonons , analogous to Debye waves ( 6.K N), found ... 

Because of the flat concentration profiles, the solution precipitates at virtually the same time over the entire film cross section, and no macroscopic gradients of activity or concentration of the polymer are obtained over the film cross-section. On a microscopic scale, however, because of thermal molecular motions, there are areas of higher and lower polymer concentration, which act as nucleation centers for polymer precipitation. These microscopic areas of higher polymer concentration are randomly distributed throughout the cast polymer film. Therefore, a randomly distributed polymer structure is obtained.during precipitation. This structure is also shown in Figure 13 in the form of a scanning electron microscope picture of the cross section of a symmetric membrane obtained with a vapor phase precipitant. 

Thermal molecular motion is erratic, so that the total scattered field varies randomly at the detector. A recording of this field will look very much like a noise pattern. Hence it is no wonder that the theory of noise and fluctuations is relevant to the study of light-scattering spectroscopy. Before deriving the fundamental formulas... 

In this review, we show our own results of thermal molecular motion of PS at the free surface by mainly scanning force microscopy and at the substrate interface by space-resolved fluorescence spectroscopy. To do so, we also adopt coarse-grained molecular dynamics simulation to strengthen experimental results. Finally, we... 

In this section, thermal molecular motion at the interface with solid substrates is discussed. It is needless to say that the issue is of pivotal importance for inherent scientific interest because motion at the interface seems to be totally different from that at the polymer surface. Also, the interface between polymers and inorganic materials is crucial in designing and constructing highly functionalized nanocomposites [43-45], which are now used for biomaterials [46, 47], sensors [48,49], power sources [50,51], etc., in addition to their popular and traditional use as structural materials [43-45, 52, 53]. 

Thermal molecular motion of PS at surfaces and interfaces in films was presented in this review. We clearly show that chain mobility at the surface region is more mobile than in the interior bulk phase and that chain mobility at the interfacial region is less than in the interior phase. This means that there is a mobility gradient in polymer films along the direction normal to the surface. This gradient can be experimentally detected if the ratio of the surface and interfacial areas to the total volume increases, namely in ultrathin films. 

PVC) and DOAB or SDHP in which the weight fraction of artificial amphiphiles was 15%. PVC did not exhibit any thermal transition or the prominent mechanical absorption due to thermal molecular motion in the temperature range studied here (285 330 K). The composite membrane exhibited the endothermic peaks at T due to melting of dialkyl chains of DOAB and SDHP. Polarized optical microscopic observation suggests that the crystallites of artificial amphiphiles are dispersed fairly homogeneously in the composite membrane. 

The Arrhenius plots of the diffusive permeability coefficient, P of water for the pol)nner/artificial amphiphile composite membranes reveal a distinct jump in the vicinity of the phase transition temperature of artificial amphiphiles. This striking increase of P may be caused by activation of thermal molecular motion which is closely related to the crystal-mesomorphic phase transition behavior. 

Brownian Motion Result of thermal molecular motion in a liquid environment. 

The present study suggests that the difference in cohesive energy between the hydrophobic groups in monolayer components was an important factor for determination of the mixing behavior. The mixing behavior may depend on various factors, such as the intermolecular interaction, particularly an electrostatic one, and the thermal molecular motion. A further systematic investigation is required to understand the aggregation mechanism in a multi-component monolayer. 

Fluctuations are spontaneous and random deviations of thermodynamic properties from their average equilibrium values. These deviations are caused by thermal molecular motion. Macroscopic thermodynamics ignores fluctuations because they do not affect thermodynamic properties in the thermodynamic limit and they are usually insignificant in finite macroscopic systems. However, the situation changes when the system becomes very small or when it is near the limit of thermodynamic stability. In these two cases, fluctuations may become very large and may play a significant role in determining thermodynamic properties. 

A general approach for introducing fluctuations into thermodynamics is given by statistical mechanics. Let us consider an arbitrary, small portion of an isolated fluid. This small portion, referred to as the system , has a fixed volume V and is in equilibrium with the surrounding fluid at temperature T and chemical potential p. The thermal molecular motion of the fluid particles causes fluctuations of the thermodynamic properties of the system. These fluctuations exist in violation of the Second Law since they decrease the total entropy St of the fluid. Hence, the probability density of a fluctuation is... 

Elastic and dielcclric relaxatioas are oommonly observed for most polymers. The onset of thermal molecular motions infiueoces the elastic and dielectric properties. Pi-ezoelectridty is a cross effect of the elastic and dielectric effects. Since the plezoclec-tridty expresses the internal strain of the polymer, the piezoelectric relaxation reflects the change of the internal strain. This is the most interesting characteristic ai the piezoelectric relaxation. 

Temperature is perhaps the most important experimental parameter in soft matter science because the structures of soft materials are so sensitive to energy changes on the order of kgT. (4.14 x 10 J or 0.026 eV at 300 K). Because soft materials can be so sensitive to small temperature changes, random thermal molecular motions help to define their behavior. Since the concepts of thermal equilibrium, phase behavior, and statistical physics are so central to both a basic and a more advanced understanding of this field, we must begin there. 

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