Séverine Coppee

Influence of chain interdiffusion between immiscible polymers on dewetting dynamics

From dewetting and neutron reflectivity experiments, we demonstrate the major influence of chain interdiffusion on the friction properties for a couple of immiscible polymers. The interface between two immiscible polymers, polystyrene (PS) and polydimethylsiloxane (PDMS), was studied by neutron reflectivity and dewetting by using free PS chains and PDMS brushes. Unexpectedly, we found that the PS chains diffuse in the PDMS brushes at temperatures well below the glass transition temperatures of PS, the dynamics being largely determined by the grafting density of the brush. These observations strongly suggest that the puzzling ageing of PS thin films observed from dewetting experiments can be directly related to modifications of the PS/PDMS interface.

Structuration of Semiconducting Polymer Thin Films by Nanorubbing

In this paper, we study the behavior of thin films of a semiconducting polymer, poly(3-hexylthiophene)-P3HT under the application of a physical constraint. We have rubbed P3HT thin films with a velvet cloth, which leads to the alignment of the polymer chains along the sliding direction at the film surface. Annealing the rubbed films up to the crystallization temperature, leads to the propagation of the surface orientation to the whole film. In order to gain spatial and geometrical control on the rubbing process, we have used nano-rubbing. Using the stylus of an AFM working in contact mode, the nano-rubbing process can be performed locally on an area of defined size. These chain-aligned structures can be permanent thanks to the crystallization process. This study opens interesting opportunities to control the molecular order within the channel of field-effect transistors