Polystyrene viscoelastic behavior

The strong effect of molecular chains on the viscoelastic behavior of polymeric solutions, even in the most dilute ones, is shown in Figure 8.24 (37). Here the recoverable compliance of a very dilute solution of polystyrene of weight-average molecular weight 860,000 in tri-m-tolyl phosphate is compared with that of the solvent. It is noteworthy that the value of the steady-state compliance for the solvent is 10 cm /dyn while that of the very dilute solution (Wpoi = 0.001) is nearly 10 cm /dyn. In other words, a very small fraction of the molecular chains are responsible for the fact that the steady-state compliance of the solution is more than 10 times that of the solvent. 

Holmes, L. A., Lamb, J., Matheson, A. J. Viscoelastic behavior of dilute polystyrene solutions in an extended frequency range. J. Phys. Chem. 70, 1685-1689 (1966). 

E. Riande, H. Markovitz, D.J. Plazek, and N. Raghupathi, "Viscoelastic Behavior of Polystyrene-Tricresyl Phosphate Solutions," J. Poly. Sci. Polym. Symp., (1975). 

The effect of droplet size and its distribution on the adsorbed layer thickness may be inferred from a comparison of the results obtained with the o/w emulsions with those recently obtained using polystyrene latex dispersions containing grafted PEO chains of (molecular weight 2000) (49). As discussed earlier, the viscoelastic behavior of the system (which reflects the steric interaction) is determined by the ratio of the adsorbed layer thickness to the particle radius (8/R). The larger this ratio, the lower the volume fraction at which the system changes from predominantly viscous to predominantly elastic response. With relatively polydisperse systems, ( )cr shifts to higher values when compared to monodisperse systems with the same mean size. 

D. L. Siegfried, J. A. Manson, and L. H. Sperling, Viscoelastic Behavior and Phase Domain Formation in Millar Interpenetrating Polymer Networks of Polystyrene, J. Polym. Sci. Polym. Phys. Ed. 16(40), 583 (1978). PS/PS homo-IPNs. Visoelastic and morphological behavior. 

J. L. Thiel and R. E. Cohen, Synthesis, Characterization, and Viscoelastic Behavior of Single-Phase Interpenetrating Styrene Networks, Polym. Eng. Sci. 19, 284 (1979). Polystyrene/polystyrene homo-IPNs. Swelling equation for single-phase IPNs. Equilibrium swelling studies as a function of crosslink level. 

The five regions of viscoelastic behavior for linear amorphous polymers (3,7-9) are shown in Figure 8.2. In region 1 the polymer is glassy and frequently brittle. Typical examples at room temperature include polystyrene (plastic) drinking cups and poly(methyl methacrylate) (Plexiglas sheets). 

It is found empirically that the concentration dependence of 7 can be expressed by proportionality of n r) oo/Vs) to c, and the proportionality constant can be shown to be the high-frequency intrinsic viscosity [rf ]oo- An example is shown in Fig. 9-27 for five linear polystyrenes with widely different molecular weights and three branched samples.The high-frequency intrinsic viscosity is independent of branching as would be expected for a quantity which reflects a very local motion within the molecule it is also independent of molecular weight for M > 19,800. At M = 19,800, it is almost equal to the ordinary (steady-flow) intrinsic viscosity. However, W]oo does depend on detailed chemical structure as shown in Fig. 9-28, where data for several polymers are similarly plotted. Thus the high-frequency behavior is in a sense just the opposite of the low-frequency viscoelastic behavior... 

As an example of assignments of mechanisms for a specific polymer, the temperature-frequency loci shown in Fig. 15-11 for polystyrene have been attributed to the following motions " a, segmental motions of the main chain governed by the monomeric friction coefficient (i.e., the transition zone of viscoelastic behavior) j(3, local mode torsional oscillations of the main chain y, rotation of the phenyl group around the bond joining it to the main chain 5 (observed in dielectric measurements only, and nearly absent in isotactic polymer), relaxations of resultant... 

Figure 15.7 Logarithm of the relaxation modulus versus temperature for amorphous polystyrene, showing the five different regions of viscoelastic behavior.

Bailly, C., Stephanne, V., Muchtar, Z., Schappacher, M. Deffieux, A. Linear viscoelastic behavior of densely graftedpoly(chloroethyl vinyl ether)-g-polystyrene combs in the melt./. Rheol (2003) 47, pp.821-825... 

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