Effect of long-range hydrodynamic and direct intermacromolecular forces on translational diffusion

✍ Scribed by Wylie I. Lee; J.Michael Schurr

• Publisher: Elsevier Science
• Year: 1976
• Tongue: English
• Weight: 386 KB
• Volume: 38
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(76)80258-8

✦ Synopsis

Within the francwork of recently formulated microscopic theories of nlacromolecular diffusion it is shown that Rydrodynamic forces act dways to diminish the influence of direct fbrces, but never to rc~crsc the sign of the correction term due to direct forces alone. Although the correction term D(k) to the intrinsic diffusion coefficient may vary with scattcring vector I&l, it is shown that a reversal in sign of the correction term with increasing Ikl. if it occurs. must be associated with an amplitude of less than 10% of the carrcction term at Ikl = 0. At I kl = 0 direct repulsive forces xc predicted to QlWQyS increase the nppCxent diffusion constant, even after accounting fur hydrodynamic interactions. Ahbough expcriments on polylysinc (1 mglml) at salt concentrations above 0.01 M are in qualitative accord with ttrc theory, h&w 1V3 I4 salt the apparent diffusion coefficient is reduced by il Fictor of nbol;t 20, concomitant with ;L much nduced intensity oi scattered light. The strong conlraciicrion of the theory imp&xl by this obscrvntion is attributed to 3 drnmntic rise ir, Stokes friction xi+, from long-range interionic forces in the low-salt solutions.