Polyisoprene dielectric loss

Interesting entanglement relaxation behavior is observed in zones III and IV. As an example of this behavior. Figure 3.5 shows the G and G" data for binary blends of monodisperse linear ds-polyisoprene (PI) samples with Ml = 2.1 X 1(P (PI21) and M2 = 3.1 x 1(P (PI308) reported by Watanabe et al. (2004a). The data for the dielectric loss e" are also shown (bottom panel). Those M, are well above Me,buik (= 5.0 x 10 for bulk PI), and the components are mutually entangled in the blends. 

Test of time-temperature superposability for dielectric loss data of a miscible blend of cis-polyisoprene (PI12 Mp, = 1.2 x 1(H) and poly(vinyl ethylene) (PVE60 Mpyp = 6 x 1(H) with the PI content rup, = 75 wt%. (Data taken, with permission, from Hirose, Y, O. Urakawa, and K. Adachl. 2003. Dielectric study on the heterogeneous dynamics of miscible polyisoprene/ poly(vinyl ethylene) blends Estimation of the relevant length scales for the segmental relaxation dynamics. Macromolecules 36 3699-3708.)... 

Dielectric loss e" measured at 10°C for a PI12/PVE60 miscible blend with Mp = 1.2 x W, Mpvp = 6 X lO, and Wp, = 17 wt% (circles). Dotted and solid curves, respectively, indicate the results of fitting with Havriliak-Negami empirical equation without and with the mode broadening due to the concentration fluctuation. (Data taken, with permission, from Hirose, Y., O. Urakawa, and K. Adachi. 2004. Dynamics in disordered block copolymers and miscible blends composed of poly(vinyl ethylene) and polyisoprene. /. Polym. Sci. Part B Polym. Phys. 42 4084-4094.)... 

Storage and loss moduli, G and G" and the dielectric loss, e" of a high-M PI99/PtBS348 miscible blend (Mpi = 9.9 x 10, Mpi g = 3.5 x 10 , w i = 50 wt%) measured at temperatures as indicated. The e" data are multiplied by a factor of 10. (Data taken, with permission, from Watanabe, H., Q. Chen, Y. Kawasaki, Y. Matsumiya, T. Inoue, and O. Urakawa, 2011. Entanglement dynamics in miscible polyisoprene/poly(p-ferf-butylstyrene) blends. Macromolecules 44 1570-1584.)... 

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,...

There are other polymers which show in addition the chain disentangling associated, with the flow transition. An example is given by ds-polyisoprene (PIP). Figure 5.19 depicts the dielectric loss e" in a three-dimensional representation of the functional dependence on frequency and temperature. Two relaxation processes show up. The one with the higher frequency again represents the a-process, the other is called the normal mode , for reasons to be seen in a moment. 

Figure 7.10 Frequency dependence of the dielectric loss factor of 164 kDa cis-polyisoprene in (a) benzene at concentrations (O) 1-91 and (0) 31.3 wt%, and (b) dioxane at concentrations (O) 0.85 and (0) 26.1 wt%, from original measurements by Adachi and Kotaka(6).

Figure 7.11 Frequency dependence of the dielectric loss function of cis-polyisoprenes in toluene at concentrations near 50 wt%, namely (x) 5 kDa, 52 wt% ( ) 14 kDa, 49 wt% (0) 32 kDa, 52 wt% and (O) 53 kDa, 52 wt%, using original measurements by Adachi, et a/. (31). Lines represent stretched exponentials, power laws, and their sums as described in the text.

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...

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]...

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