DIFFUSION OF SPHERES IN ENTANGLED POLYMER-SOLUTIONS - A RETURN TO STOKES-EINSTEIN BEHAVIOR
- Authors
- WON, J; ONYENEMEZU, C; MILLER, WG; LODGE, TP
- Issue Date
- 1994-12-05
- Publisher
- AMER CHEMICAL SOC
- Citation
- MACROMOLECULES, v.27, no.25, pp.7389 - 7396
- Abstract
- Dynamic light scattering has been used to follow the tracer diffusion of polystyrene spheres (R approximate to 200 nm) in dilute, semidilute, and entangled solutions of poly(vinyl methyl ether) (M(w) = 1.3 x 10(6)). Over this range of matrix concentrations, 0 less than or equal to e[eta] less than or equal to 36, the diffusivity drops by almost 5 orders of magnitude. Near c(*) (approximate to[eta]-(1)) for the matrix, the diffusivity exceeds that estimated from the bulk solution viscosity via the Stokes-Einstein relation by a factor of about 3. Such ''positive deviations'' from Stokes-Einstein behavior have been reported previously in several systems. However, once the matrix concentration is sufficiently high for entanglements to be effective, Stokes-Einstein behavior is recovered. This new result was. confirmed via forced Rayleigh scattering. In-addition, these data can reconcile measurements of sphere diffusion with reptation-based models fdr chain mobility in well-entangled systems. The behavior near c(*) is discussed,is terms of the matrix correlation length, xi, which has a maximum at xi approximate to R(g) for c approximate to c(*). It is noted that the fluid; layer within a distance w of the sphere surface will, in general, differ in composition from the bulk solution, and consequently the sphere mobility may well not sense the macroscopic solution viscosity, particularly near c(*). As a corollary, for large matrix chains, dynamic light scattering may not monitor the long-time diffusion of the spheres near c(*), because q xi approximate to qR(g) x 1, rather than q xi << 1.
- Keywords
- POLYSTYRENE LATEX SPHERES; DYNAMIC LIGHT-SCATTERING; POLYVINYL METHYL-ETHER) SOLUTIONS; HYDRODYNAMIC SCALING MODEL; POLY(ACRYLIC ACID) WATER; PROBE DIFFUSION; TRACER-DIFFUSION; SELF-DIFFUSION; LINEAR POLYSTYRENES; TRANSLATIONAL DIFFUSION; POLYSTYRENE LATEX SPHERES; DYNAMIC LIGHT-SCATTERING; POLYVINYL METHYL-ETHER) SOLUTIONS; HYDRODYNAMIC SCALING MODEL; POLY(ACRYLIC ACID) WATER; PROBE DIFFUSION; TRACER-DIFFUSION; SELF-DIFFUSION; LINEAR POLYSTYRENES; TRANSLATIONAL DIFFUSION
- ISSN
- 0024-9297
- URI
- https://pubs.kist.re.kr/handle/201004/145428
- DOI
- 10.1021/ma00103a020
- Appears in Collections:
- KIST Article > Others
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