Shear degradation, thermodynamically induced

Ballauff M, Wolf BA (1988) Thermodynamically induced shear degradation. Adv Polym Sci... 

Themodynamically induced shear degradation also has been investigated using solutions of anionically polymerized poly(n-alkyl methacrylate)s in poor solvents Three different lengths of the alkyl substituents (methyl PMMA n-butyl PBMA -decyl PDMA) were used in the course of the study. As an example for the thermodynamic characterization of these systems, Fig. 6 shows the cloud point curves of PDMA dissolved in -butanol... 

To discuss the thermodynamically induced shear degradation in further detail, we first turn to the chemistry of mechanical chain scission. The next step is the comparison of the experimental results with different breakage models according to the method developed in Sect. 3. Then, the dependence of chain scission on various parameters as the applied shear rate, concentration, and temperature will be discussed in detail. 

BallauffM. and Wolf, B. A. Thermodynamically Induced Shear Degradation. Vol. 84, pp. 1-31. 

Below a critical concentration, c, in a thermodynamically good solvent, r 0 can be standardised against the overlap parameter c [r)]. However, for c>c, and in the case of a 0-solvent for parameter c-[r ]>0.7, r 0 is a function of the Bueche parameter, cMw The critical concentration c is found to be Mw and solvent independent, as predicted by Graessley. In the case of semi-dilute polymer solutions the relaxation time and slope in the linear region of the flow are found to be strongly influenced by the nature of polymer-solvent interactions. Taking this into account, it is possible to predict the shear viscosity and the critical shear rate at which shear-induced degradation occurs as a function of Mw c and the solvent power. 

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