Evidence of partial draining for linear polyelectrolytes; heparin, chondroitin 6-sulfate, and poly(styrene sulfonate)

Abstract

Zero polymer concentration diffusion coefficients, DO, of heparin and chondroitin 6-sulfate were independent of ionic strength C,. Since static dimensions of such linear polyelectrolytes are sensitive functions of C,, the constant DO may represent a partial-draining effect. Similar measurements were made for poly(styrenesulfonate) fractions. For high molecular weights root-mean-square (RMS) radii of gyration (S2)1/2vsCBwere determined. l/Dofollowed (B)llzat high C, (>100mM),climbedlesssteeplyatintermediate C,, ~d reached a plateau below 30 mM. Although tempting to interpret these regimes as nondraining, partial drainmg, and free draining, respectively, 1/Do a iW6 for all C,. Thus, although some type of draining condition seems implicated, a simplistic free-draining condition in the plateau region is inconsistent with the mass scaling. The data show that dynamic light scattering may not be an appropriate particle sizing technique for many linear polyelectrolytes. The 'extraordinary" diffusional phase, present in some samples, could always be permanently removed by filtration through membranes of sufficiently small pore size. IntroductionThe hydrodynamic behavior of macromolecules depends on such factors as linear dimensions, excluded volume, and degree of draining. Numerous theoretical approaches have been taken for calculating such quantities as intrinsic viscosity, sedimentation coefficienta, and translational and rotational friction factors.'-* It is not the object of this report to make critical comparisons of the theories but rather to provide data which bear directly on one of the fundamental issues necessarily addressed in theories of the translational diffusion coefficient: the relationship

The slow relaxation mode: from solutions to gel networks

“…It has been attributed to dynamics of large multichain domains (transient aggregates or clusters) formed due to electrostatic interaction [76][77][78][79][80] or some insoluble chain clusters, or even a trace amount of large particles introduced during the imperfect preparation of solution. [89][90][91][92][93] The transient cluster interpretation was supported by studies of poly(styrenesulfonate) with sodium counterions in aqueous solutions under dialysis. For a long time, this transient cluster has been attributed to the effective interaction between similarly charged segments, namely, the overlapping of the ion clouds of neighboring polyions, so that the more loosely associated small ions are 'shared' by two or more polyions chains, resulting in a fluctuating dipole field that tends to retard the relative motions of those participating polyions.…”

“…[28][29][30][31][32][33][34][35][36][37][38][39] This slow relaxation mode was assigned to different physical origins, such as the reptation of the entire chain inside a 'tube' made of its surrounding chains, 114,115,117 the scattering vector (q)-independent relaxation of a transient network, 29,34,35 the q 2 -dependent translational diffusion of large aggregates or even dust particles, 32,33,37,38,112 and internal motions of large transient chain clusters. 92 Later, it was realized that the reptation is not observable in dynamic LLS because of its nature for homopolymer system.…”

“…The interpretation of the slow mode, especially for those very slow relaxation modes observed in salt-free or low-salt polyelectrolyte solutions, is very controversial. [76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95] It has been attributed to large multichain domains formed because of electrostatic interaction or some insoluble clusters or even a trace amount of dust particles introduced during the imperfect preparation of polymer solution. Actually, not everyone accepts or recognized such a slow mode, even though it has been repeatedly observed in many dynamic LLS experiments for more than three decades, because of some problems or questions related to previous light-scattering experiments, such as some earlier premature data analysis methods and the preparation of dust-free viscous solutions.…”

Probe Diffusion in Sodium Polystyrene Sulfonate−Water: Experimental Determination of Sphere−Chain Binary Hydrodynamic Interactions

“…Before using Pietzsch et al's data, 11 it seems necessary to remark upon a seeming peculiarity in their measurementssof which they were awaresnamely that, for 780 kDa PSS in 2, 15, and 4000 mM NaCl, R g increases by more than 2.5 fold with decreasing ionic strength, but R h increases by no more than 50% over the same range of salt concentrations. These results are not altogether expected, because they imply that R g and R h are independent quantities, contrary to theoretical expectations discussed in ref 11.…”

Review of Light Scattering Literature

“…Peitzsch and coworkers [29] initiated a light scattering study to determine the draining characteristics of linear polyelectrolytes, specifically, the biological polymers heparin (Hep) and chondroitin 6-sulfate (ChS), and a synthetic polyelectrolyte, sodium poly(styrene sulfonate), NaPSS. The three hydrodynamic regimes discussed include free-draining, in which the diffusion coefficient, Do, has an inverse linear relationship with the molecular weight (i.e., independent of radius of gyration, Rg, and hence the ionic strength, Cs); non-draining, in which Do scales as M to the power of -0.5, and thus is a measure of the static size of the polymer, R ; and partialdraining, which is intermediate in behavior between the two extremes.…”