A volume-corrected Kratky model and the influence of the shape of the orientation distribution function on the molecular orientation in PPV and its precursor
Dermaut, W × Van den Kerkhof, T Goderis, Bart Mertens, R Dolbnya, I van der Veken, BJ Blockhuys, F Geise, HJ #
Amer chemical soc
Macromolecules vol:37 issue:1 pages:110-117
The molecular orientation in cold-stretched PPV films was studied with synchrotron WAXD. The results showed that the degree of orientation is comparable to that of hot-stretched films and that it exceeds the latter's orientation for the lower stretch ratios. The values from WAXD and those from previous FTIR dichroic and DECODER NMR measurements are in agreement with each other, but the observed orientation is far higher than predicted by the Kratky model. Therefore, a volume-corrected Kratky model was derived, which takes into account the extra orientation induced by the volume reduction of the polymer during the thermal elimination process. To fully explain the observed orientation values, however, the shape of the orientation distribution function had to be considered as well. It is concluded that this shape should be close to a Gaussian rather than to a Kratky distribution. The orientation in stretch-aligned noneliminated precursor films is discussed as well.