Transition zone of polymer melts

The transition zone is the range of frequency (or time) over which the storage modulus (or stress relaxation modulus) changes from the glassy 

However, the crossover between these two limiting regimes is not well understood, so there is no quantitative description of viscoelasticity for the 

Our discussion above focuses on intramolecular effects, but leaves out any intermolecular effects. Current ideas about relaxation in glassforming liquids speculate that monomer motion is cooperative, involving multiple monomers collectively rearranging in a cooperative fashion. While there is some evidence for this cooperative motion, it is an area of active research that has not yet yielded a generally accepted model. Intermolecular constraints such as the requirement of cooperative 

At still higher frequencies than the highest frequency in Fig. 8.14, polymer liquids exhibit a solid response, with storage modulus G independent of frequency and equal to the glassy modulus Cg. A typical value of the glassy modulus is of order lO Pa (see Table 8.2). The glassy modulus 

This same glassy modulus describes the linear elastic response of the polymer at temperatures below its glass transition temperature Tg, [see Hooke s law, Eq. (7.98)]. The physical reason that the liquid s response becomes similar to that of the glass is that at such high frequencies (or short time scales) monomers (and even small parts of monomers) do not have time to move and relax stress. 

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Temperature dependence of dynamics 8.7.2 Transition zone of polymer melts... 

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