Backbone arrangement in "friction-transferred" regioregular poly(3-alkylthiophene)s

The regioregular highly head-to-tail-coupled poly(3-alkylthiophene) (HT-P3AT) films were prepared by a friction-transfer technique. Polarized LTV-vis absorption spectroscopy and grazing incidence X-ray diffraction (GIXD) were used to study the polymer molecular arrangement in the friction-transferred HT-P3AT films, and scanning electron microscopy (SEM) was used to observe the film surface morphology. The polarized LTV-vis absorption spectra show a large dichroism regarding the drawing direction of friction-transfer. The order parameter is evaluated close to unity, which is the ideal orientation state. GlXD measurements show that alkyl side chains lie in the film plane, and the polymer backbones are well-ordered along the drawing direction of friction-transfer within 10degrees for poly(3-hexylthiophene) and 13degrees for poly(3-dodecylthiophene) in the film plane. The polymer backbones form a layered structure with the stacking of thiophene rings normal to the film surface. The polymer molecules in the friction-transferred films are ideally arranged three-dimensionally.