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Research Brinkmann

Morphogenesis of π-conjugated polymers and small molecules

This research topic is led by M. Brinkmann. It is motivated by the understanding of the correlations existing between opto-electronic properties (charge transport, photophysics, photovoltaic activity) in organic thin films of pi-conjugated materials and the structure/morphology at multiple length scales of these materials. The team around M. Brinkmann has developped a strong experience in : morphogenesis of conjugated polymers and small molecules using epitaxial growth [1], and multi-scale structural analysis of pi-conjugated materials (pentacene, regioregular polythiophenes and polyfluorenes) using transmission electron microscopy (TEM) (electron diffraction, High-resolution TEM, dark filed imaging).[1]
The original combination of TEM and epitaxial growth of pi-conjugated polymers was used to address following important issues in the field of plastic electronics :
the correlation between macromolecular parameters (Mw, PDI) and crystallization mode (extended vs folded) of various polymers like P3HT, PBTTT and polyfluorenes (PF2/6) (2),
the determination of structural models using electron diffraction [2],
the investigation of the semi-crystalline structure/nanomorphology of P3HT films using HR-TEM [2] and
the growth of highly oriented and nanostructured P3HT fibers with a shish-kebab structure [3]. The recent research activity is also focused on the elaboration of oriented/nanostructured hybrid films comprising semi-conducting polymers and inorganic nanoparticles (CdSe, metals) to obtain highly oriented and nanostructured thin films suitable for photovoltaic applications.

To this aim, the group develops new orientation and growth methods e.g. by zone melting applied to directional epitaxial crystallization, orientation via rubbing and also new structural approaches based on electron diffraction in rotation/tilt. Tomographic studies of the 3D distribution of CdSe NPs in nanostructured hybrid layers is also performed in collaboration with O. Ersen (IPCMS).

Figure caption : 1) HR-TEM image of an oriented film of regioregular poly(3-hexylthiophène) grown by directional epitaxial crystallization. The inset illustrates the arrangement of P3HT chains in the crystal. 2) Bright Field TEM image of an oriented P3HT film showing the periodic alternation of crystalline lamellae (dark stripes) and amorphous interlamellar zones (brighter areas), 3) Diffraction pattern of an oriented PF2/6 film grown onto an oriented PTFE substrate, 4) Bright Field TEM image of a P3HT fiber showing a shish-kebab structure, 5) Bright Field TEM image of a highly oriented and nanostructured hybrid film made of a semi-crystalline matrix of P3HT harboring CdSe nanorods in the amorphous interlamellar zones.

[1] M. Brinkmann and P. Rannou, Adv. Funct. Mat., 2007, 17, 101.
[2] M. Brinkmann and P. Rannou, Macromolecules, 2009, 42, 1125.
[3] M. Brinkmann, F. Chandezon, C. Julien-Raban and R. P. Pansu, Adv. Funct. Mat. 2009, 19, 2759.

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