EVIDENCE OF PARTIAL DRAINING FOR LINEAR POLYELECTROLYTES - HEPARIN, CHONDROITIN 6-SULFATE, AND POLY(STYRENESULFONATE)

Zero polymer concentration diffusion coefficients, D0, of heparin and chondroitin 6-sulfate were independent of ionic strength C(A). Since static dimensions of such linear polyelectrolytes are sensitive functions of C(A), the constant D0 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)1/2 vs C(A) were determined. 1/D0 followed (S2)1/2 at high C(A) (> 100 mM), climbed less steeply at intermediate C(A), and reached a plateau below 30 mM. Although tempting to interpret these regimes as nondraining, partial draining, and free draining, respectively, 1/D0 alpha M0.5 for all C(A). 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.