Changes in solution viscosity

The progress of the reaction can be followed by measuring the amount of water condensed. The water can be collected in a tube with calcium chloride or alternatively collected in a small flask.59 The reaction can also be followed by taking samples ( 0.5 g, with a spatula) at different intervals and analyzing them. In this way, the change in solution viscosity (molecular weight) can be determined as a measure of reaction progression. 

The striking changes in solution viscosity produced by the cobalt-60 y-ray irradiation of dry Polyox are shown in Table I. 

It should also be noted that the viscometric technique can detect the presence of star-shaped aggregates, having the ionic active centers. The addition of ethylene oxide to hydrocarbon solutions of poly(isoprenyl)lithium leads to a nearly two-fold increase in viscosity144). Conversely, this results in an approximately twenty-fold decrease in solution viscosity, after termination by the addition of trimethylchloro-silane. This change in solution viscosity is reflected in the gelation which occurs when difunctional chains are converted to the ionic alkoxy active centers 140,145,146). Branched structures have also been detected 147> by viscometry for the thiolate-lithium active center of polypropylene sulfide) in tetrahydrofuran. 

Saturated hydraulic conductivity may also be influenced by dramatic changes in solution viscosity as well as the soil s dispersive potential. The data in Figure 10.5 represent saturated hydraulic conductivity as a function of EC. It appears that as EC increases, hydraulic conductivity decreases. The soil material in this study represents a Kentucky mine spoil. The predominant salt in the solution was an acid, MgS04. Suspension data showed that as MgS04 concentration increased, colloid dispersion increased. This could be due to an increase in solution viscosity, which also has a suppressing effect on saturated hydraulic conductivity (see Eq. 10.2). 

Large differences in solvent power effect large changes in solution viscosity. Data presented by Reynolds (8) show that Beckosol 7 viscosities increase sharply on going from a solvent with a solubility parameter matching the resin (9.7) to one a few units lower. Similar behavior is predicted by the present model, as shown in Figure 8. The solubility parameters are related to the activity coefficients by (9)... 

Preliminary studies indicated that PFAP(II) undergoes a loss in molecular weight at temperatures above 149°C (1,2). The degradation process was followed by monitoring the change in solution viscosity of samples aged at 150°C in air. The viscosity exhibited a rapid loss during the first 200 hr, then leveled off to a slower rate. 

Investigation of the Thermal Degradation of PFAP(II). PFAP(II) was aged in air at varying time intervals (0-700 hr) at 135°, 149°, 177°, and 200°C. The change in solution viscosity with aging time at these temperatures is shown in Figure 1. The viscosity exhibits an initial rapid decrease, then levels off and approaches a constant value which appears... 

Figure I. Change in solution viscosity of PFAP(II) with time at different temperatures...

Figure 5. Change in solution viscosity of PFAP(II) (with 0, 1, 2, and 3 wt % bis(8-oxy-quinolate)zinc(II) with time at different temperatures...

Figure 4. Changes in solution viscosity as a function of reaction time for simple model compound systems (a) the effect of change the ratio of phenol to formaldehyde reactive sites (r) for constant (f) and (p) (f=3, p=l), (b) the effect of changing the functionality of the phenolic model compound (f) for constant (r) and (p) (r=l, p=l), and (c) the effects of adding a monofunctional phenolic to the reactive system (p) for constant (f) and (r) (f=l, r=l).

To explain the molecular origin of the change in solution viscosity with... 

Martin et al (9) investigated 1. the change in solution viscosity as a function of sodium chloride concentration and 2. copolymer susceptibility to shear degradation for poly((1-amidoethylene)-co-sodium(l-carboxylato-ethylene)). Table II gives the results from this investigation and shows that as carboxylate content of copolymer increases, 1. viscosity of a fixed concentration solution of the copolymer in sodium chloride brine decreases... 

Figure 5.12 Temporal changes in solution viscosity for acid- and base-catalyzed TEOS systems. Crosses indicate gel points. Samples I-V are identified in Table 5.5. (From Ref. 28.)...

Left relative change in solution viscosity Right relative change in gel content... 

The kinetics of polymer photodegradation in solutions can be studied by measuring the change in solution viscosity during irradiation (cf. section 10.9). 

Despite the open structure of the hyperbranched stiff macromolecules, they are rather compact with radius of gyration, Rq, far smaller than that for the linear analogues. The compactness is mirrored in the modest change in solution viscosity upon the addition of more than 1 g Li-carboxylate terminated polyphenylene to 1 ml water [363], and in the brittleness and inability to form films [383] exhibited by these polymers. A similar very modest effect on solution viscosity was previously observed by Aharoni et al [370] on solutions of the highly branched and very compact poly((x,e-L-lysine) molecules prepared by Denkewalter et al. [332]. 

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