The concentration dependence of the conformational dynamics of polymer solutions as revealed by measurements of oscillatory flow birefringence (o. f. b. ) has been obtained for narrow-distribution linear, comb and regular-star molecules for concentrations in the range c( eta ) APP 1STH 11. The data obtained show that the relaxation-time spectrum is affected markedly by concentration. The longest relaxation time is affected most; for the linear, comb or 3-armed star polystyrenes studied to date, tau //1 exhibits an exponential dependence on concentration for c( eta ) less than 3. The Muthukumar theory correctly predicts the dependence of tau //1 on concentration for solutions containing linear molecules for which c( eta ) less than equivalent to 5. There is some indication that tau //1 as a function of concentration exhibits two different concentration regimes, one above and one below the onset of significant entanglement effects. The shortest relaxation times are almost unaffected by concentration.
|Title of host publication
|Faraday Symposia of the Chemical Society
|Royal Soc of Chemistry
|Number of pages
|Published - Dec 1 1983