A Dielectric Study of Oligo- and Poly(propylene glycol)

作者：Gainaru Catalin^*; Hiller Wolf; Boehmer Roland

来源：Macromolecules, 2010, 43(4): 1907-1914.

DOI：10.1021/ma9026383

The segmental and normal mode dynamics of poly(propylene glycol) (PPG) were studied using dielectric spectroscopy for a wide range of molecular weights. For intermediate chain lengths the normal mode spectra, unmasked by electrical purging procedures, were described quantitatively using the Rouse model. Based on the ratio of the dispersion strengths of the normal and of the segmental mode, the characteristic ratio C-infinity was determined. The spectral width of the segmental mode evolves smoothly with the number of repeat units N and, except for dipropylene glycol, so does the mean time scale. The exceptional behavior was confirmed by C-13 NMR relaxation experiments. For small N the segmental and the normal modes tend to merge near the glass transformation range. Exploiting the polymer chains its "molecular rulers", the growth of the characteristic length scale associated with the vitrification process is estimated for PPG. In the glassy state two dipolarly active relaxation processes were resolved. The slower one is characterized by an activation energy typical for hydrated systems, and its dispersion strength can be modified by appropriate heat treatment.

• 出版日期2010-2-23