Form and Function

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Science  25 May 2001:
Vol. 292, Issue 5521, pp. 1453
DOI: 10.1126/science.292.5521.1453c

The method of fabrication of a conjugated polymer film influences the packing of the polymer chains and the morphology of the film; it also can affect the electronic properties that are critical for device applications. For example, films of the polymer MEH-PPV that are spin cast from a good solvent show a flat texture but exhibit numerous nanometer-sized bumps and have poorer photoluminescence than films cast from a poor solvent.

Nguyen et al. have used near-field scanning optical microscopy to examine the correlations between morphology and electronic structure and wear resistance. They find that there are direct correlations between the topography and morphology of the film and the local electronic properties, and that the diminished properties associated with the bumps are due to enhanced interchain interactions in these areas. However, these more densely packed areas suffer less damage during photo-oxidation. Annealing of the films can remove these spatial features, but once cooled, the chains pack with a large number of interchain interactions to produce a film with weak photoluminescence. — MSL

J. Phys. Chem. B, in press.

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