ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The first large-scale fractionation method for polyacrylamides is reported. This has been optimized to prepare a series of narrowly distributed polymer standards with molecular weights between 10,000 and 1,000,000. These were subsequently hydrolyzed to between 5 and 35% sodium acrylate content through a saponification reaction. It has been found that the classical light-scattering theory, derived for nonionic scattering bodies, can be applied to polyelectrolytes provided the specific refractive index increment (∂n/∂c) is evaluated at constant electrochemical potential (μ). This is obtained by dialyzing the polymer solution against the dialysate (0.2MNa2SO4 for polyacrylamide-co-sodium acrylate) for a predetermined equilibrium period, specific to the pore size of the membrane used. From such measurements at various copolymer compositions (F), the following empirical relationship is established: \documentclass{article}\pagestyle{empty}\begin{document}$$ \left( {\frac{{\partial n}}{{\partial c}}} \right)_{\mu ,{\rm PAM - NaAc}} = \left( {\frac{{\partial n}}{{\partial c}}} \right)_{{\rm PAM}} \left( {F_{{\rm NaAc}} } \right)^a $$\end{document} where a was found to be -0.076. The validity of the specific refractive index increment at constant chemical potential is established through light-scattering measurements of the weight-average chain length of the hydrolyzed polyacrylamides. These were then compared with the chain lengths of the parent nonionic polymers from which they were derived. Excellent agreement is observed, implying the polyelectrolyte characterization method developed, and specifically the (∂n/∂c)μ's, are accurate and reliable.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1992.070460412
Permalink
