DIFFUSION OF SOLVATED POLYSTYRENE CONFINED IN A POROUS-MEDIUM AT NEAR-THETA CONDITIONS

Citation
Zm. Zhou et al., DIFFUSION OF SOLVATED POLYSTYRENE CONFINED IN A POROUS-MEDIUM AT NEAR-THETA CONDITIONS, Macromolecules, 27(25), 1994, pp. 7402-7405
Citations number
18
Categorie Soggetti
Polymer Sciences
Journal title
ISSN journal
00249297
Volume
27
Issue
25
Year of publication
1994
Pages
7402 - 7405
Database
ISI
SICI code
0024-9297(1994)27:25<7402:DOSPCI>2.0.ZU;2-X
Abstract
The dynamic light scattering (DLS) technique was applied to polystyren e fractions of different molecular weights dissolved in the near-Theta solvent trans-decahydronaphthalene and confined in a porous glass bea d. Diffusion coefficients were measured for the polymer in the interio r of the porous medium and in the surrounding free solution. Diffusion , when normalized to take into account solvent viscosity and temperatu re, was slower in the Theta solvent than in the good solvent 2-fluorot oluene, a result being ascribed to a stronger hydrodynamic interaction for a compact Gaussian chain in the pore channels than for a chain wi th excluded volume. At higher temperatures, the decrease in the reduce d diffusivity was larger than expected for the increased radius of gyr ation of the polystyrene chain in the better solvent. At the same time , the DLS autocorrelation function exhibited a pronounced deviation fr om a single-exponential decay. Enhanced interaction between swelling p olymer chains in the narrow pore channels is considered to have increa sed the concentration coefficient of the friction coefficient for tran slational motion and thus to have resulted in the decrease of the diff usion coefficient at a low, but nonzero, polymer concentration.