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David Kreher, assistant professor

Novel Liquid Crystal Polymers for Organic Electronics

The control of both the mesoscopic and nanoscale organization within thin semiconducting films is the key issue for the improvement of charge transport properties and achievement of high charge carrier mobilities. In this context, we will take advantage of our recent results to investigate the self-organization of novel sidechain liquid crystal (SCLC) semiconducting polymers : we will keep the essential structure, with (i) a p-conjugated polymer backbone and (ii) p-conjugated mesogens side groups. But this time we will target ambipolar materials and we will continue to try to obtain lamella-lamellar self-organization.

Consequently, in priority and quite soon, we will replace the p-type triphenylene discotic group by different ntype entities such as :

Moreover, we want to replace discotic mesogens by calamitic ones, still targeting ambipolar materials. An example of calamitic derivative tested and typical structure expected is described :

To conclude on this current and future project, we won't detail too much our strategy as this is not published yet, but if our preliminary results are confirmed, later on we plan to synthesize the other high performance columnar side-chain liquid crystal homo and alternating (co)polymers described below, these different kinds of architectures being once again prepared following the Grignard methathesis (GRIM), allowing the control of the side group ratio along of the polymer chains, and leading to tunable electronic properties and nanostructures.

In the first scheme, the electronic performances will be enhanced, we hope, by the choice of the disc and by controlling its ratio of incorporation along the chain.

In the second scheme, we both change the nature of the backbone (introduction of fused thiophenes entities) and play with the type of mesogenic side groups.