Labeling efficiency molecular weight effects

Figure 3. Effects of molecular weight on labelling efficiency. Three heparins were independently labelled at increasing degrees of substitution. Molecular weight ranges of 3,000 (open square), 4,000-6,000 (solid circle), and 12,000-15,000 (open diamond).

This is the Verdrangungsreaktion with the monomer, and it is catalyzed by the Ziegler catalyst or its consecutive products. Using aluminum alkyls and 14C-labeled ethylene, under conditions not causing any insertion or hydride formation and in the presence of a dead catalyst, an equilibrium distribution of labeled ethylene between the gas phase and the alkyl is reached (33). It has been possible in certain cases to use this effect to reduce molecular weight from over l million to some hundreds by increasing the temperature from 25 to 100°C without any loss in efficiency (34). 

The effectiveness (and efficiency) of two saccharide labeled water treatment polymers as calcium scale inhibitors were then evaluated against low molecular weight poly(acrylic acid), which served as a control. The results of this study are summarized in Table I. The scale inhibition of the labeled polymers was comparable to that of the control at 5 ppm. This indicates that the saccharide tag has no adverse effect on the water treatment performance of the polymer other than, perhaps, to dilute the amount of acrylic acid residues present per unit of polymer present (note the drop in the performance of the experimental polymers relative to that of the control polymer at a concentration of 3 ppm). 

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