Dresden 2011 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 40: Polymer Crystallization and Semicrystalline Polymers
CPP 40.4: Talk
Thursday, March 17, 2011, 11:30–11:45, ZEU 160
Influence of Alkyl Side Chain Length on the Crystallite Orientation of Low-temperature and RT Cast Poly(3-alkylthiophene) Thin Films — •Shabi Thankaraj Salammal1, Souren Grigorian1, Ullrich Pietsch1, Martin Brinkmann2, Nils Koenen3, and Ullrich Scherf3 — 1University of Siegen — 2CNRS, Strasbourg — 3University of Wuppertal
The effect of alkyl side chain length on the orientation of polymer crystallites was studied for a series of poly(3-alkylthiophene)s (P3ATs) like poly(3-pentylthiophene) (P3PT), poly(3-hexylthiophene), poly(3-heptylthiophene) (P3HeptT), and poly(3-octylthiophene) (P3OT). Thin films were cast on the Si/SiO2 substrate at RT and -30°C. The orientation of the crystallites was studied using x-ray and electron diffraction techniques. The 2D diffraction pattern of -30°C cast P3PT film shows the presence of well in-plane stacked edge-on oriented crystallites which are favor for the charge transport. The scattered intensity of -30°C as-cast films are 5 times higher than the RT cast one and it increase to 8 by treating the substrate with OTS. Surprisingly, the -30°C cast P3OT film has few face-on oriented crystallites. But, the mixed edge- and face-on oriented crystallites were observed in RT cast films and showing the powder like distribution of crystallites. Those face-on oriented crystallite was able to resolve through HRTEM. Such an enhancement in ordering of the crystallites with decreasing the growth temperature and side chain length can be explained by the controlled supersaturation ratio as well as the decrease in flexibility of side chain length which may induce the surface nucleation.