Evolution of the storage modulus (엯) and the loss modulus during an isothermal crystallization experiment for the sample PEO 16F9. The crossover of the moduli and signifies the crystallization transition. From bottom to top, the data correspond to different frequencies (see text): 36, 72, 140, and . The temperature variation from with different cooling rates is also shown with a solid curve in the figure (see text for details).
Dynamic frequency sweeps of star PEO (a) and linear PEO (b) samples at . Filled symbols: storage modulus, . Empty symbols: loss modulus, . Lines with slopes 1 and 2 indicate the terminal scaling for and , respectively.
Zero-shear viscosity (normalized with the plateau modulus and the Rouse time for an entanglement) for linear and star PEOs at (symbols explained in the bottom right part), plotted against the number of entanglements per arm (a linear polymer is considered as having two arms). Literature data on 1,4-polybutadiene stars [Roovers (1985, 1991a); Toporowski and Roovers (1986); Pakula et al. (1998)] are also included for comparison (symbols in top left). Note that the data for the high-functionality PB stars ( and 128) correspond to the arm relaxation time, i.e., the earliest of the two terminal modes (the slower being the center-of-mass motion). The line through the data is the Milner-McLeish (1998) theory with a dilution exponent of .
Normalized recoverable compliance (with the plateau modulus) for linear and star PEOs as function of the number of entanglements per arm (a linear polymer is considered as having two arms). For comparison, data on PBd stars [Roovers (1985, 1991a); Toporowski and Roovers (1986); Pakula et al. (1998)] are also presented. The solid line is the MM theory. The dotted lines are drawn to guide the eye. Inset: The extracted slope of plotted against the star functionality.
Hoffman–Weeks plot for linear and star PEOs from isothermal DSC experiments. The solid line has a slope of 1; the dashed line shows the approximate for sample 32F12.
Isothermal DSC curves of star PEO samples at (symbols in the figure). Inset: Avrami plot: Respective evolution of the relative degree of crystallinity (same symbols as in main figure). Solid lines are the fits to the data.
(a) Half crystallization times for linear and star PEO samples. Empty symbols: DSC. Filled symbols: Rheology (the latter data are results of the parallel model). (b) Linear growth rates times zero-shear viscosities as functions of temperature (growth rates obtained from POM).
Molecular characteristics of the PEO samples used.
Ideal melting points determined from the Hoffman–Weeks plot (Fig. 5) and Avrami parameters for star PEO and linear PEO .
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