Epitaxial Growth of Highly Oriented Fibers of Semiconducting Polymers with a Shish-Kebab-Like Superstructure

Highly oriented fibers of regioregular poly(3-alkylthiophene)s (P3ATs) showing a shish-kebab morphology are prepared by oriented epitaxial crystallization in a mixture of 1,3,5-trichlorobenzene (TCB) and pyridine. The superstructure of the P3AT fibers consists of an oriented thread-like core several hundreds of micrometers long, the shish, onto which lateral crystalline fibrils made of folded polymer chains, the kebabs, are connected in a periodic way with a periodicity in the range 18-30 nm. The P3AT-chain axis is oriented parallel to the fiber axis whereas the pi-stacking direction is oriented perpendicular to it. The oriented character of the shish-kebab fibers results in polarized optical absorption and photoluminescence. The formation of oriented precursors by epitaxial orientation of polymer chains onto long needles of a molecular crystal-TCB in the present case-appears to be an original alternative to the crystallization usually performed under external flow conditions.