The Simha-Frisch Parameter

One of the approaches uses the first term of the Huggins expression for concentration dependence of viscosity in polymer solutions  

In Simha s early model (Simha and Zakin 1962), transition from a dilute to a concentrated polymer solution was envisioned as being due to interpenetration of polymer chains that occurs when concentration lies somewhere in the region 1 [ryjc 10. This transition is evident from the change in the concentration dependence of viscosity in polymer solutions. The quantity [r ]c, the Simha-Frisch parameter (Frisch and Simha 1956), also sometimes called the Berry number (Gupta et al. 2005), is therefore a reasonable measure of chain overiap in solution. As Shenoy et al. (2005b), however, correctly point out, the dependency, being ultimately based on the equivalent hard sphere hydrodynamic model, is strictly applicable only at low polymer concentrations. 

It is convenient to also express c in terms of intrinsic viscosity rather than the chain dimension, using the relationship 

Therefore c will be essentially independent of molecular weight. 

As chain overlap and/or entanglements in solution appear to be critical to achieve bead-free nanofibers (McKee et al. 2004b, 2005 Shenoy et al. 2005b) 

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