Liquid Crystalline Oligofluorenes

Monodisperse glassy liquid crystalline conjugated§oligomer films are promising for application in§optics, photonics and electronics. This research has§furnished fundamental understanding of the origin of§chiroptical effects in glassy-cholesteric§oligofluorene films and new insight into the§photoalignment of glassy-nematic oligofluorene films.§Specifically, cholesteric films, which emerged upon§thermal annealing of spin-cast films of chiral§oligofluorenes, showed an order-of-magnitude increase§in circular dichroism and a handedness reversal in§circularly polarized fluorescence compared to the§amorphous pristine films. The oligomer chain length§played an important role in solid morphology. The§orientation of monodisperse glassy-nematic§oligofluorenes was characterized on photoalignment§layers comprising a polymethacrylate backbone with§coumarin pendants. A transition from a parallel to a§perpendicular orientation with reference to the§polarization axis of UV-irradiation was observed at a§high extent of coumarin dimerization. A kinetic model§was used to interpret the photodimerization of§coumarin and to evaluate the relative importance of§the factors affecting the crossover behavior.