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The molecular weight average obtained by combining quasielastic light‐scattering and intrinsic viscosity measurements
Author(s) -
McDonnell M. E.,
Jamieson A. M.
Publication year - 1977
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1977.070211207
Subject(s) - dispersity , intrinsic viscosity , polystyrene , molar mass distribution , viscosity , diffusion , polymer , light scattering , molecular mass , thermodynamics , materials science , tetrahydrofuran , polymer chemistry , toluene , macromolecule , chemistry , scattering , organic chemistry , optics , physics , composite material , biochemistry , solvent , enzyme
For “monodisperse”, randomly coiled macromolecules, we find that the molecular weight, intrinsic viscosity, and diffusion coefficient are accurately related by\documentclass{article}\pagestyle{empty}\begin{document}$$ \left[ \eta \right]M_{D,\eta } = 3.0 \times 10^{ - 27} \left( {D_t^0 {{\eta _0 } \mathord{\left/ {\vphantom {{\eta _0 } T}} \right. \kern-\nulldelimiterspace} T}} \right)^{ - 3} {{\left( {{{{\rm erg}} \mathord{\left/ {\vphantom {{{\rm erg}} {^\circ {\rm K}}}} \right. \kern-\nulldelimiterspace} {^\circ {\rm K}}}} \right)^3 } \mathord{\left/ {\vphantom {{\left( {{{{\rm erg}} \mathord{\left/ {\vphantom {{{\rm erg}} {^\circ {\rm K}}}} \right. \kern-\nulldelimiterspace} {^\circ {\rm K}}}} \right)^3 } g}} \right. \kern-\nulldelimiterspace} g} $$\end{document} This equation holds for denatured proteins in 6 M GuHCl(aq) as well as for narrow polystyrene fractions in tetrahydrofuran. For a Schulz distribution of molecular weights, the weight measured from combining diffusion and viscosity data is closely approximated by\documentclass{article}\pagestyle{empty}\begin{document}$$ M_{D,\eta } = M_w^{0.425} M_z^{0.575} $$\end{document} These equations are verified with measurements of wide molecular distributions of polystyrene in toluene and data from the literature. These relations provide a rapid, nondestructive method to determine a well‐specified molecular weight average of small quantities of polymers in a wide diversity of solvents using quasielastic light scattering techniques to evaluate polymer diffusion coefficients.