ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
A series of copolymers, of 4-vinylpyridine and styrene, covering the range 1.5 to 100% vinylpyridine were prepared in 20% toluene solution at 80°. Strong electrolytes were then made by the addition of n-butyl bromide in nitromethane solution. The salts with high vinylpyridine content were soluble in water, alcohols, nitromethane, and other polar solvents. Viscosities of the parent copolymers in methyl ethyl ketone were in the range 0.15-0.20; osmotic pressures gave molecular weights in the range 50,000-80,000. The polyelectrolytes in nitromethane and nitromethane-dioxane mixtures gave viscosity-concentration curves which were strongly concave upwards: at 1 mg./100 cc., the reduced viscosity of the salt of polyvinylpyridine in nitromethane was 6.0. The salts of the different copolymers did not differ much in their viscosities at concentrations above a few tenths of a gram per 100 cc., a fact which shows a high degree of ionic association; only as zero concentration is approached, can the detailed polymer structure be seen. The extent of association at a given concentration is controlled by the amount of vinylpyridine in the copolymer and by the dielectric constant of the solvent. Addition of simple one-one electrolytes, such as tetrabuty lammonium bromide, suppresses the electrostatic increase in viscosity which otherwise appears at low concentrations. The following empirical equation: \documentclass{article}\pagestyle{empty}\begin{document}$$ {{\eta _{{\rm sp}} } \mathord{\left/ {\vphantom {{\eta _{{\rm sp}} } {\rm C}}} \right. \kern-\nulldelimiterspace} {\rm C}} = {{\rm A} \mathord{\left/ {\vphantom {{\rm A} {\left( {1 + {\rm B}\sqrt {\rm C} } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {1 + {\rm B}\sqrt {\rm C} } \right)}} + {\rm D} $$\end{document} was found to fit the data for the different systems studied. The constant A depends on copolymerization ratio and probably on molecular weight; it is a measure of the extent to which the polymer coil can spread out at infinite dilution as a consequence of the intramolecular Coulomb repulsion between charges attached to the chain. It is roughly several orders of magnitude larger than the intrinsic viscosity of the parent polymer. The constant B is a measure of the electrostatic forces and increases with decreasing dielectric constant of the solvent.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1949.120040201
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