Average limiting viscosity number

Table I. Average Limiting Viscosity Number and Weight-average, Molecular Weight for the Poly(l-amidoethylene) Sample...

The precipitated polyoxymethylene is filtered off, washed with ether and dried in vacuum at room temperature it melts between 176 and 178 °C.The limiting viscosity number is determined on a 1% solution in DMF at 140 °C (Tisp/c 0.08 l/g,corresponding to an average molecular weight of 80,000).The thermal stability can be tested before and after blocking the hydroxy end groups (see Examples 5-7 and 5-13). 

The limiting viscosity numbers are calculated with the equation of Mark and Houwink (K = 0.27 see 5ect.2.3.3.3.1) and from them the average molecular weights from these one can estimate the number of cleavages of the original chain and hence the frequency of 1,2-diol groupings. 

The second average is viscosity average molecular weight, M . This expression is obtained by using the exponent from the limiting viscosity number-molar mass relationship, a, as a power for the molecular weight of each molecule in the distribution. The formula for this average is... 

Weight-average molecular weight (measured by sedimentation equilibrium) Limiting viscosity number (ml/gram) (intrinsic viscosity) 22 189,800 2,100... 

Fig. 29. Double logarithmic plot of limiting viscosity number fr ] versus the number-average molecular weight M for cellulose triacetate solutions92, a) dichloromethane (DCM) O Kamide et al. 92> Dymarchuk et al.94, A Shakhparonov et al.95 b) trichloromethane (TCM) O Kamide et al. 82) A Staudinger and Eicher 96) Sharpies and Major 97) Howard and Parikh 98) Nair et atl. 93 ...

The term in brackets on the left-hand side of Eq. (3-37) is called the intrinsic viscosity or limiting viscosity number. It reflects the contribution of the polymeric solute to the difference between the viscosity of the mixture and that of the solvent. The effects of solvent viscosity and polymer concentration have been removed, as outlined earlier. It now remains to be seen how the term on the right-hand side of Eq. (3-37) can be related to an average molecular weight of a real polymer molecule. To do this we first have to express the volume V of the equivalent hydro-dynamic sphere as a function of the molecular weight A/ of a monodisperse solute. Later we substitute an average molecular weight of a polydisperse polymer for M in the monodisperse case. 

The viscosity of a dilute polymer solution depends on the nature of polymer and solvent, the concentration of the polymer, its average molecular mass and molecular mass distribution, the temperature, and the shear rate. The most important characteristic quantity in a very dilute solution, at vanishing shear rate, is the limiting viscosity number, which is defined as [1]... 

Also known as limiting viscosity number. See also dilute-solution viscosity, Huggins equation, and viscosity-average molecular weight. 

The limiting viscosity number, n,p/C, of the sol was related to weight-average molecular weight, of the aggregating polymer, by the relation... 

Figure 5.13 Log-log plots of limiting viscosity number [T ] for atactic polystyrene solutions against the weight-average molecular weight Q), Benzene at 25 and 30°C , cyclohexane at 34.5°C (0 temperature). From ref. 38, reprinted by permission of John Wiley Sons Inc.

Table 3.3 Selected Mark-M is usually Houwink parameters (limiting viscosity number [ti] = KM t M, the viscosity average molecular weight) ...

---