Unique relaxation process

Now we can visualise that each of these models represents a relaxation process in the system. However, it is likely that some spacings, or sizes, and interactions occur more often than others, so that each process is not unique. We could represent the m models by a series of unique models where each model occurs / , times. There would be n such models where n is less than m ... 

Tanaka et al. have studied the surface molecular motions of PS films coated on a solid substrate by lateral force microscopy and revealed that the Tg at the surface was much lower than the corresponding bulk one [148]. Possible reasons for this included an excess free volume induced by localized chain ends, a reduced cooperativity for of-relaxation process, a reduced entanglement, and a unique chain conformation at the surface. For comparison, they examined surface relaxation behavior of high-density PMMA brushes. 

However, since the energy separation between the two states is a critical factor, it does not follow necessarily that in any of the cases discussed the mechanism posed is the unique one, for there are certainly many competing paths of electronic relaxation. It is only when additional quantitative data become available that it may be possible to distinguish with any certainty between different relaxation processes. There is clearly a great need for thorough studies of this nature to be made. 

There are also two factors that have already been noted in the numerical analysis of the kinetic model of CO oxidation (1) fluctuations in the surface composition of the gas phase and temperature can lead to the fact that the "actual multiplicity of steady states will degenerate into an unique steady state with high parametric sensitivity [170] and (2) due to the limitations on the observation time (which in real experiments always exists) we can observe a "false hysteresis in the case when the steady state is unique. Apparently, "false hysteresis will take place in the region in which the relaxation processes are slow. 

The DS method occupies a special place among the numerous modern methods used for physical and chemical analysis of materials because it enables investigation of relaxation processes in an extremely wide range of characteristic times (105—10 13 s). Although the method does not possess the selectivity of NMR or ESR, it offers important and sometimes unique information about the dynamic and structural properties of substances. DS is especially sensitive to intermolecular interactions, and therefore cooperative processes may be monitored. It provides a link between the properties of the bulk and individual constituents of a complex material (see Fig. 1). 

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