Fig. 12.12 Dielectric loss versus temperature at fixed frequency of 10 Hz for cw-l,4-polyisoprene. The molecular weights are as follows circles, |

Figure 6 Inversion of the dielectric loss data for the normal mode spectrum of the type-A polymer polyisoprene. In the inset, the dielectric loss data show the spectrum of normal modes and at higher frepuencies the segmental mode. The distribution of relaxation times shows peaks at times that are characteristic of the different normal modes. However, the obtained peak positions differ from the Rouse theory predictions (shown by vertical lines). |

Fig. 1.3 Relaxation map of polyisoprene results from dielectric spectroscopy (inverse of maximum loss frequency/w// symbols), rheological shift factors (solid line) [7], and neutron scattering pair correlation ((r(Q=1.44 A )) empty square) [8] and self correlation ((t(Q=0.88 A" )) empty circle) [9],methyl group rotation (empty triangle) [10]. The shadowed area indicates the time scales corresponding to the so-called fast dynamics [11] |

Figure 9.23 Normalized dielectric constant o - s ( ), where Sq is the zero-frequency dielectric constant, and dielectric loss constant ( ) at 40 °C for a 6-arm polyisoprene star with = 459,000. Symbols are data ofWatanabeef a/. [66], and the lines are predictions of the slip link model. The parameters of the model = 4650 and Tq=42 s,are used for all calculations with the |

There are other polymers that in addition show the chain disentangling associated with the flow transition. An example is given by cis-polyisoprene (PIP). Figure 6.20 depicts the dielectric loss e" in a three-dimensional representation of the functional dependence on frequency and temperature. Two [Pg.263]

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