Molecular Weight Dependence of Zero-Shear Viscosity of Block Copolymers in the Disordered State

2004 ◽  
Vol 37 (1) ◽  
pp. 215-225 ◽  
Author(s):  
Soobum Choi ◽  
Chang Dae Han
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Shear Viscosity ◽  
Zero Shear Viscosity ◽  
Molecular Weight Dependence

scholarly journals Viscoelastic Properties of Unentangled Multicyclic Polystyrenes

Polymers ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 973 ◽  
Author(s):  
Zhi-Chao Yan ◽  
Md. Hossain ◽  
Michael Monteiro ◽  
Dimitris Vlassopoulos
Keyword(s):  
Molecular Weight ◽  
Shear Viscosity ◽  
Viscoelastic Properties ◽  
Dilution Effect ◽  
The Other ◽  
Low Molecular Weight ◽  
Zero Shear Viscosity ◽  
Rouse Model ◽  
Loop Size ◽  
Linear Chains

We report on the viscoelastic properties of linear, monocyclic, and multicyclic polystyrenes with the same low molecular weight. All polymers investigated were found to exhibit unentangled dynamics. For monocyclic polymers without inner loops, a cyclic-Rouse model complemented by the contribution of unlinked chains (whose fraction was determined experimentally) captured the observed rheological response. On the other hand, multicyclic polymers with inner loops were shown to follow a hierarchical cyclic-Rouse relaxation with the outer loops relaxing first, followed by the inner loop relaxation. The influence of unlinked linear chains was less significant in multicyclic polymers with inner loops. The isofrictional zero-shear viscosity decreased with increasing number of constrained segments on the coupling sites, which was attributed to the decreasing loop size and the dilution effect due to the hierarchical relaxation.

Prediction of Polymer Molecular Weight Distribution from Rheology: Polydimethylsiloxane Blends

2005 ◽  
Vol 480-481 ◽  
pp. 281-286 ◽  
Author(s):  
J. Llorens ◽  
E. Rudé ◽  
R.M. Marcos
Keyword(s):  
Molecular Weight ◽  
Shear Viscosity ◽  
Relaxation Spectrum ◽  
Average Molecular Weight ◽  
Entropy Method ◽  
Dynamic Moduli ◽  
Zero Shear Viscosity ◽  
Weight Average Molecular Weight ◽  
Plateau Modulus ◽  
A Chain

We apply a model that connects rheological properties of linear polymer blends with their molecular weight distributions (MWDs). The model is based on the assumption that the relaxation time, ti, of a chain depends on an average molecular weight, M, which determines the effect of the environment where the molecule reptates, and its own molecular weight according to ti = (kE / 0 N G )·M 3.4 - b·Mi b where kE is the constant of proportionality between zero shear viscosity, ho, and weight average molecular weight, Mw, in unimodal polydisperse systems and 0 N G is the plateau modulus. We deduce that the MWD is related to the relaxation spectrum as H(t) = ( 0 N G /b)·M·W(M). Therefore, the MWD is obtained from the relaxation spectrum, which is deduced from the dynamic moduli, G’(w) and G’’(w), constrained by the plateau modulus, the zero shear viscosity and the steady state compliance, 0 e J . The maximum entropy method has been used to solve the integral equation that provides the relaxation spectra from experimental dynamic moduli. The model has been tested in polydimethylsiloxane blends with weight average molecular weight ranging from 94 to 630 kDa and polydispersity from 1.5 to 3.3. Good agreement is found between experimental and calculated MWDs.

New Absolute Molecular Weight Method—Linear High Polymers

1959 ◽  
Vol 32 (1) ◽  
pp. 97-98
Author(s):  
F. Bueche ◽  
S. W. Harding
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Shear Viscosity ◽  
Rate Dependence ◽  
Zero Shear Viscosity ◽  
Molecular Weights ◽  
Weight Method ◽  
Shear Rate Dependence ◽  
High Polymers

Abstract It has been shown that the shear-rate dependence of the viscosity of concentrated polymer solutions can be explained in terms of known parameters of the solution. If the concentration, temperature, zero shear viscosity, and molecular weight of the polymer are known, the decrease in viscosity with increasing shear rate can be predicted. Conversely, if one measures the shear-rate dependence of the viscosity, the molecular weight may be computed. We believe this provides a convenient method for the absolute determination of molecular weights of linear, coiling, high polymers.

Dependence of zero-shear viscosity and steady-state compliance on molecular weight between entanglements for ethylene–cycloolefin copolymers

Polymer ◽  
2006 ◽  
Vol 47 (13) ◽  
pp. 4811-4815 ◽  
Author(s):  
Toshikazu Takigawa ◽  
Hidenori Kadoya ◽  
Takashi Miki ◽  
Takashi Yamamoto ◽  
Toshiro Masuda
Keyword(s):  
Molecular Weight ◽  
Steady State ◽  
Shear Viscosity ◽  
Zero Shear Viscosity ◽  
State Compliance
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