PPV precursors were prepared via the precursor route. The free-standing films were stretched at room temperature under an atmosphere of water vapor. Stretch ratios of up to nine could be attained easily. This procedure is less dependent on factors such as film thickness and freshness than hot stretching. Molecular alignment is at least as good as in hot-stretched films, as proved by FTIR dichroism measurements. Detailed IR results are presented. In addition to providing an experimentally easier way to obtain oriented PPV films, this procedure also allows to produce oriented, noneliminated PPV precursor films. This new way of stretching might also be applicable to the precursors of other conjugated polymers.

No abstract

No abstract

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.