Temperature dependence of the diffusion coefficient of poly(propylene oxide) in the undiluted state

The temperature dependence of the diffusion of fluorescent-dye-labelled poly(propylene oxide) (PPO) through unlabelled PPO has been investigated for a range of molecular weights of labelled and unlabelled polymer. The technique employed was fluorescence redistribution after pattern photobleaching (FRAPP). It was found that all the diffusion data could be reduced to a single smooth curve as a function of temperature, and that this curve was well represented by the WLF (Williams-Landel-Ferry) equation using parameters determined from rheological measurements on the same PPO fractions. This agreement was independent of the molecular weights of both labelled and unlabelled PPO. At higher temperatures, both the rheological and diffusion data were well fitted by Arrhenius expressions with apparent activation energies of E V =43 kJ mol −1 and E D T =40 kJ mol −1 , respectively. The slightly higher value of E V compared to E D T is qualitatively consistent with Doi-Edwards theory.