ISSN:
0022-3832
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
Assuming complete dissociation of the mineral acid in dilute aqueous solutions of a 1:1 vinyltoluene-styrene copolymer sulfonic acid and HCl, the degree of dissociation of the polyacid is apparently a constant independent of the concentration of either solute. On the basis of this result, it is likely that the polysulfonate chain initially contracts in such a manner with increasing HCl content of the solution that a maximum number of sulfonate groups remains on the surface of the coil. The variation of reduced viscosity (ηsp/c) with polyelectrolyte concentration c in the presence of a finite quantity of added “normal” electrolyte is determined mainly by the ratio of the counterions resulting from polyelectrolyte dissociation to the total counterion content of the solution. In regions of high dilution, where counterions from the polyelectrolyte are much less numerous than those from HCl, an apparently linear increase of reduced viscosity with increasing polymer concentration is observed. These data probably can be extrapolated to infinite dilution. Over the range of HCl concentrations 10-4 to 10-2 equivalent per liter the reciprocal square root of such extrapolated polysulfonic acid “limiting viscosity numbers” is proportional to the pH of the solvent. At the maxima of reduced viscosity plots the contribution of the polyelectrolyte to the hydrogen ion activity of the solution is half the contribution of the HCl: i.e., one third of the hydrogen ion activity is the result of polyelectrolyte dissociation. Moreover, the reduced viscosity at the maximum is directly proportional to the pH of the solvent. Curves of ηsp/c vs. c at high dilutions and constant pH are parabolas rather than straight lines. It is permissible to postulate rather convincingly from our data that the reduced viscosity curve of the polysulfonic acid in water possesses a maximum accurately indicated by the intercept of a Fuoss plot (cf. equation (7) in the text). The intercept of a Fuoss plot for any polyelectrolyte can have the significance of a limiting viscosity number only when measurements are made in a nonionizing solvent.
Zusätzliches Material:
12 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1954.120136906
Permalink
