Local segmental dynamics polyisoprene

Adolf DB, Ediger MD, Kitano T, Ito K (1992) Viscosity dependence of the local segmental dynamics of anthracene-labeled polyisoprene in dilute-solution. Macromolecules 25... 

Glowinkowski S, Gisser DJ, Ediger MD (1990) C-13 nuclear-magnetic-resonance measurements of local segmental dynamics of polyisoprene in dilute-solution— nonlinear viscosity dependence. Macromolecules 23(14) 3520-3530. doi 10.1021/ma00216a021... 

While all relaxation times depend on temperature and pressure, only the global motions (viscosity, terminal relaxation time, steady state recoverable compliance) are functions of Mw (and to a lesser extent MWD). An example of the various dynamics of 1,4-polyisoprene are illustrated in Fig. 10. At frequencies beyond the local segmental relaxation, or at temperatures below Tg, secondary relaxation processes can be observed, especially in dielectric spectra. In polymers, many of these secondary processes involve motion of pendant groups. However, the slowest secondary relaxation, referred to as the Johari-Goldstein process, involves all atoms in the repeat unit (or the entire molecule for low M materials). This Johari-Goldstein relaxation serves as the precursor to the prominent glass transition. 

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