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Characterization of DEAE‐dextran by means of light scattering and combined size‐exclusion chromatography/low‐angle laser light scattering/viscometry
Author(s) -
Hanselmann Ralf,
Burchard Walther,
Lemmes Rolf,
Schwengers Dieter
Publication year - 1995
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1995.021960715
Subject(s) - radius of gyration , chemistry , viscometer , light scattering , intrinsic viscosity , virial coefficient , molar mass distribution , analytical chemistry (journal) , size exclusion chromatography , hydrodynamic radius , molar mass , static light scattering , viscosity , dynamic light scattering , multiangle light scattering , branching (polymer chemistry) , scattering , chromatography , thermodynamics , polymer , materials science , aqueous solution , optics , organic chemistry , micelle , physics , nanoparticle , enzyme , nanotechnology
Ten DEAE (2‐(diethylamino)ethyl) dextran samples were investigated by means of static and dynamic light scattering, viscometry and size‐exclusion chromatography (SEC) in combination with on‐line small‐angle laser light scattering (LALLS) and viscometry (VISC). In dilute solution the behavior of DEAE‐dextran was compared with that of unsubstituted dextran and the molecular weight M dependences of the radius of gyration R g , hydrodynamic radius R h, intrinsic viscosity [η], second virial coefficient A 2 and z‐average diffusion coefficient D z were determined. The relationships for DEAE‐dextran dissolved in a 0,8 molar sodium nitrate solution were nearly the same as for dextran dissolved in water with 0,05 wt.‐% sodium azide and gave the same exponents. The molecular weight dependence of the intrinsic viscosity cannot be described by a Kuhn‐Mark‐Houwink relationship with a constant exponent. The slope in the plot of log [η] versus log M decreases with increasing molecular weight which indicates the occurrence of branching. By means of SEC/LALLS/VISC measurements the molecular weight distributions were determined. The distributions were calculated (1) directly from the light scattering signal, (2) from a calibration line obtained by light scattering data of a DEAE‐dextran sample with a broad distribution and (3) from the intrinsic viscosity distribution obtained by the on‐line viscosity/refractive index detector in combination with the [η]‐ M relationship. In order to get the correct molecular‐weight dependence of the intrinsic viscosity it is necessary to determine the molecular weight distribution directly by LALLS (technique 1) and to combine this with the appropriate intrinsic viscosity data from the viscometer. Only the third technique, which is an extension of technique 1, gave satisfactory results over the whole molecular weight region observed.