Schizophyllan viscosity

The zero-shear viscosity r 0 has been measured for isotropic solutions of various liquid-crystalline polymers over wide ranges of polymer concentration and molecular weight [70,128,132-139]. This quantity is convenient for studying the stiff-chain dynamics in concentrated solution, because its measurement is relatively easy and it is less sensitive to the molecular weight distribution (see below). Here we deal with four stiff-chain polymers well characterized molecu-larly schizophyllan (a triple-helical polysaccharide), xanthan (double-helical ionic polysaccharide), PBLG, and poly (p-phenylene terephthalamide) (PPTA Kevlar). The wormlike chain parameters of these polymers are listed in Tables... 

Enomoto, et al measured with conventional and four-bulb Ubbelohde viscometers the low-shear viscosity of seven aqueous schizophyllans(19). Polymer molecular weights ranged from 128 kDa up to 4.3 MDa, for systems having My,/Mfi 1.2. Polymer concentrations approached 200 gA viscosities ranged up... 

Figure 12.3 Low-shear viscosity of aqueous schizophyllan for polymer molecular weights 128 (A), 220 (OX 340 ( ), 460 (V), 960 ( ), 1730 (OX and 4300 ( ) kDa, and fits to stretched exponentials in c, using results from Enomoto, cf aZ.(19).

In the past two to three decades, considerable attention has been paid to rj of semi-flexible-polymer solutions. " Figure 22 illustrates the dependence of relative viscosity ild=flho) on molar concentration c/At for isotropic solutions of triple-helical schizophyllan (in water), double-helical Na xanthan (in 0.1 M aqueous NaCI), CTC (in THF), and PS (in tydohexane) with roughly the same L of 200nm but... 

Figure 22 Relative viscosities ti/rjo plotted against the molar concentration

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