Damping Molecular structure, effects

Importantly, mechanical resonances near 5 MHz and 1 kHz indicate the presence of regularly repeating dynamic structures. Extension of such structures reasonably gives rise to an entropic elastic force upon extension by the damping of internal chain d)mamics represented by mechanical resonance. Molecular mechanics and dynamics calculations based on the molecular structure shown in Figure 3 will demonstrate just how effectively the structure can explain the experimental elasticity and relaxation data. 

It is difficult to specify accuracy in this experiment. One reason is that there may be sampling effects, i.e., wide variability in the samples used. Consequently, the sample should be homogeneous and representative. There is a strong dependence of the modulus and damping behavior on molecular and structural parameters. Entrapped air/gas may affect the results obtained using powder or pellet samples. 

As an example, it has been pointed out that the Hamaker and Lifshitz theories assume (exphcitly and implicitly, respectively) that intensive physical properties of the media involved such as density, and dielectric constant, remain unchanged throughout the phase—that is, right up to the interface between phases. We know, however, that at the atomic or molecular level solids and liquids (and gases under certain circumstances) exhibit short-range periodic fluctuations they are damped oscillating functions. Conceptually, if one visualizes a hquid in contact with a flat solid surface (Fig. 4.8a), one can see that the molecules (assumed to be approximately spherical, in this case) trapped between the surface and the bulk of the liquid will have less translational freedom relative to the bulk and therefore be more structured. That structure will (or may) result in changes in effective intensive properties near the surface. 

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