Pi-conjugated polymers have attracted considerable attention over the past decade due to the advantageous combination of their electrical, optical and film-forming properties. A major milestone for this emerging technology consists in achieving functional device fabrication by means of large-area printing.[1] As printing involves liquid solutions of functional substances from a limited variety of solvents, multi-layer devices can, in most cases, only be fabricated by alternating printing and curing steps. The latter can both be achieved by cross-linking or removal of solubilizing groups and can be initiated by chemical, thermal or photochemical stimuli or a mixture thereof.

Our work aims at the immobilization of semiconducting molecules by the external stimulus of heat. Inspiration for our approach is acknowledged to work by Fréchet[2] and Krebs[3] who introduced tertiary esters of poly(thiophen-3-carbocyclic acid-2,5-diyl)s which can be transformed into native polythiophene above 300°C for use in organic solar cell devices.

A major drawback of these materials remains the need for high processing temperatures, which delicately limit their application in functional devices. Thus, we focused on developing new thermally cleavable solubilizing groups that allow immobilization of functional polymers. We developed a variety of new polymers and intermediates bearing thermocleavable groups employing an easily scalable synthetic route. Our contribution will discuss synthetic aspects of these new materials as well as studies related to their future application in printable organic electronics.

[1] F. C. Krebs, Solar Energy Materials & Solar Cells 2009, 93, 394.

[2] J. M. J. Fréchet et al., J. Am. Chem. Soc. 2004, 126, 9486.

[3] Bjerring, M.; Nielsen, J. S.; Nielsen, N. C.; Krebs, F. C. Macromolecules 2007, 40, 6012-6013.; S. A. Gevorgyan and F. C. Krebs, Chem. Mater. 2008, 20, 4386.

Torben Adermann

Heidelberg University

Appearances