Relaxation time, segmental

FIGURE 24.1 Local segmental relaxation times for pol3miethyltolylsiloxane (PMTS) measured dielectrically as a function of temperature at constant pressure (circles) and as a function of pressure at fixed temperature (triangles). (From Paluch, M., Pawlus, S., and Roland, C.M., Macromolecules, 35, 7338, 2002.)... 

FIGURE 24.2 Local segmental relaxation times for polymethyltolylsiloxane (PMTS) from Figure 24.1 replotted as a function of specific volume. 

FIGURE 24.4 Master curves of the local segmental relaxation times for 1,4-polyisoprene (-y = 3.0) 1,2-polybutadiene (7=1.9) polyvinylmethylether (7 = 2.55) polyvinylacetate (7 = 2.6) polypropylene glycol (7 = 2.5) polyoxybutylene (7 = 2.8) poly(phenyl glycidyl ether)-co-formaldehyde (7 = 3.5) polymethylphe-nylsiloxane (7 = 5.6) poly[(o-cresyl glycidyl ether)-co-formaldehyde] (7 = 3.3) and polymethyltolylsiloxane (PMTS) (7 = 5.0) [15 and references therein]. Each symbol for a given material represents a different condition of T and P. 

Dielectric spectroscopy was also used by the same group in order to study the local and global dynamics of the PI arm of the same miktoarm star samples [89]. Measurements were confined to the ordered state, where the dynamics of the PI chain tethered on PS cylinders were observed in different environments since in the SIB case the faster moving PB chains are tethered in the same point as the PI arm. The distribution of segmental relaxation times were broader for SI2 than SIB. The effect was less pronounced at higher temperatures. The PI normal mode time was found to be slower in SIB, when compared to SI2 although both arms had the same molecular weight. Additionally, the normal mode relaxation time distributions of the PI chains tethered to PS cylinders in the miktoarm samples were narrower than in P(S-h-I) systems of lamellar structure. 

Xoa primitive relaxation time of the Coupling Model Johari-Goldstein secondary relaxation time Xoj primitive relaxation time of the network junction Xaf segmental relaxation time of the fast component in binary poly-... 

FIGURE 5.22 The segmental relaxation times for PEO neat (bold solid line) and in blends with PMMA (dashed lines) containing 3% to 30% PEO (from top to bottom) from deuteron NMR measurements. Fits to the data by the VET law given by Lutz et al. (2003) are shown but not the data themselves. Also shown is the independent relaxation time for PEO (dotted Une, using n = 0.5), which lies close to the characteristic time, tc = 2 ps. The most probable relaxation times calculated for a number of temperatures by the CM equation for concentrations of PEO at 3% (diamonds, n = 0.76), 10% (triangles, n = 0.75), and 30% (squares, n = 0.715), respectively. 

In Figure 5.23 we reproduce for high molecular weight PMMA its dielectric segmental relaxation time (Bergman et al., 1998), the shift factor of the Rouse dynamics in the softening dispersion measured by Ngai and Plazek (1996)... 

FIGURE 6.7 Atactic polypropylene segmental relaxation times (solid symbols) from mechanical spectroscopy, dynamic light scattering, dielectric relaxation, and NMR, along with the global time-temperature shift factors (open symbols) from dynamic mechanical spectroscopy, creep compliance, and viscosity. Vertical shifts were applied to superpose the data (Roland et al., 2001). 

FIGURE 6.8 Local segmental relaxation times (circles) and terminal shift factors (squares) for polybutadienes. The fitted VFTH equations illustrate the marked differences in temperature-dependence of the local and global dynamics (Robertson and Rademacher, 2004). 

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