DIFFERENT ORIENTATION AND POLYMORPHISM OF POLY(9,9'-DIOCTYLFLUORENE-CO-BENZOTHIADIAZOLE) IN THIN FILMS DEPOSITED ONTO VARIOUS SUBSTRATES

Poly(9,9'-dioctylfluorene-co-benzothiadiazole) is known for application in LED and FET devices [1-3], although a reliable crystal structure has not definitely reported. Thin films of the material deposited onto different self-assembled monolayers and annealed at different temperatures, were examined by synchrotron radiation in grazing incidence and compared with optimized powder of same material. By applying the variable cell direct space method of ref. [4] to the diffraction profile obtained from the thermally optimized powders of the polymer, and combining the observations of confocal optical microscopy at different temperatures on the films, the polymorphic character of the polymer in the films was definitely assessed, in terms of a 3D phase and a mesophase form. These results allow for the accurate determination of both orientation and crystallinity of various films. Subtle differences among films deposited on surface layers displaying various polarity, namely SiOx, hexamethyldisilazane, divinyltetramethyldisiloxane-bis(benzocyclobutene), sodium poly(styrenesulphonate), could be exploited and will be addressed.