ISSN:
0025-116X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Partially hydrolysed polyacrylamide samples were used as model polyelectrolytes and the variations of the intrinsic viscosities with the extent of hydrolysis and molecular weight were used to determine the relative applicability of the various macroion expansion theories. Expanison coefficients solely attributable to the presence of electrostatic charges were calculated with reference to the intrinisic viscosities of the parent polyacrylamides, assuming that the polyacrylamide corresponds to the discharged state of the macroion from hydrolysed polyacrylamides. Similarly, total expansions and expansions attributable to long-range interactions were evaluated using the estimated intrinsic viscosities at the theta temperature of the parent polyacrylamide and the hydrolysed sample, respectively. The electrostatic expansion coefficients are independent of molecular weight and the long-range expansion coefficients are almost independent of the extent of hydrolysis at high charge densities. In the absence of closed expressions predicting the variation of the expansion coefficients with the concentration of ionizable groups, equivalent expressions based on different theories were deduced assuming that i2/Cs is proportional to the concentration of ionizable groups where i is the extent of ionization of the polyelectrolyte and Cs is the concentration of the added salt. The variation of the electrostatic expansion coefficient with the charge density could not be represented according to any of the theories on macroion expansion. However, attributing the total expansion to the presence of electrostatic charges alone, the Fixman and Chien-Ishihara theories allow a good representation of the data. At very low charge densities, the expansions due to long-range interference effects also can be accounted for by the Fixman and Chien-Ishihara theories.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1984.021850511
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