The self assembly of the rod-rod block copolymer poly(3-hexylthiophene)-b-poly(g-benzyl-L-glutamate) (P3HT-b-PBLG) thin film on organic field effect transistors (OFETs) has been studied. Chloroform and 1,2,4-trichlorobenzene (TCB) were used as solvents for the diblock copolymer. The P3HT-b-PBLG diblock copolymer solution either in chloroform or TCB was deposited on OFETs by drop-casting. The OFET devices were annealed under vacuum at three different temperatures (80 �C, 120 �C, and 150 �C) after the polymer deposition. We attempted to correlate the field-effect mobilities with the surface morphology of the P3HT-b-PBLG films deposited on OFETs. The surface morphologies of thin films were investigated by TMAFM in the channel region of the OFET devices. X-ray diffraction studies were also carried out on thin films cast from both the solvents to investigate the crystallinity of polymer thin film. The films formed from both chloroform and TCB displayed field effect mobilities in the order of 10-4 cm2/Vs. However, the TMAFM images of the films displayed a substantial change in morphology upon annealing. The non-annealed film showed densely packed ribbon-like domains. An incremental change in the length of the nanoribbons was observed upon annealing the films at 80 �C and 120 �C. The independence of the field-effect mobility with respect to the film morphology indicates that the P3HT block self-assembles near the SiO2dielectric surface where charge transportation occurs whereas PBLG block assembles at the top of the thin film.

Self-assembly and optoelectronic properties of a rod-rod semiconducting liquid crystalline block copolymer containing poly(3-hexylthiophene)

245th National Meeting (2013)

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