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

Abstract

Photoalignment layers comprising Polymer 1 were prepared using linearly polarized UV-irradiation for chloroform- vapor annealing of p-conjugated oligomer films, both proc- esses conducted at room temperature. The resultant uniaxially oriented monodomain films exhibited S ¼ 0.74 (at Pr ¼ 0.90) and 0.82 (at Pr ¼ 0.95) in OF and OF2T films, respectively, apparently limited by film dewetting in comparison to S ¼ 0.82 6 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 p-p interactions enhanced by rubbing. In contrast, PF2T could not be oriented on either type of alignment layers after annealing under satu- rated chloroform vapor up to 14 h. Annealing of an OF2T film under saturated chlorobenzene vapor at room temperature per- mitted lyotropic nematic mesomorphism to be observed in situ, which is equivalent to thermotropic nematic mesomor- phism as the driving force behind thermal annealing. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 725- 731, 2011