Photoalignment of monodisperse glassy-nematic oligofluorenes

The photoalignment of a series of monodisperse glassy-nematic oligofluorenes was investigated on coumarin-containing polymer films in the parallel regime. The orientational order parameter of a spin-cast oligofluorene film, SOF, was found to decrease with an increasing oligofluorene length because of the increasing demand on YdSd, the product of coumarin dimers' concentration and orientation order parameter. In addition, an increased annealing temperature demanded by a longer oligofluorene caused an orientational relaxation of coumarin dimers to a greater extent. Nonetheless, under favorable conditions SOF values of penta, hepta-, and nonafluorenes are comparable to those achieved on rubbed polyimide films.