Room-temperature processing of π-conjugated oligomers into uniaxially oriented monodomain films on coumarin-based photoalignment layers

Photoalignment layers comprising Polymer 1 were prepared using linearly polarized UV‐irradiation for chloroform‐vapor annealing of π‐conjugated oligomer films, both processes conducted at room temperature. The resultant uniaxially oriented monodomain films exhibited S = 0.74 (at Pr = 0.90) and 0.82 (at Pr = 0.95) in OF and OF2T films, respectively, apparently limited by film dewetting in comparison to S = 0.82 ± 0.01 from thermal annealing on rubbed polyimide alignment and Polymer 1 photoalignment layers. The time to arrive at maximum S values varied from 5–10 s to 6–8 min on rubbed polyimide alignment layers and Polymer 1 photoalignment layer, respectively, because of favorable π–π interactions enhanced by rubbing. In contrast, PF2T could not be oriented on either type of alignment layers after annealing under saturated chloroform vapor up to 14 h. Annealing of an OF2T film under saturated chlorobenzene vapor at room temperature permitted lyotropic nematic mesomorphism to be observed in situ, which is equivalent to thermotropic nematic mesomorphism as the driving force behind thermal annealing. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 Photoalignment layers are prepared by polarized UV‐irradiation of coumarin‐containing polymer films at room temperature (RT) for solvent‐vapor annealing of π‐conjugated oligomers also at RT. The resultant oriented films have orientational order parameters identical to those on traditional rubbed alignment layers that require high‐temperature processing. This novel technique is ideally suited for making plastic electronics, such aspolarized light‐emitting diodes, anisotropic field‐effect transistors, and polarization‐sensitive photodiodes.