Quantitative evaluation of the preferential orientation of para-phenylene vinylene pentamers in polystyrene films by optically detected magnetic resonance

The morphology of drop-casted and spin-coated films of blends of para-phenylene vinylenederived pentamers with polystyrene is investigated by means of X-band optically detected magnetic resonance (ODMR) of the triplet excited states. Adapting an electron spin resonance simulation program to ODMR, the orientation distribution function of the oligomers in the films could be quantified. After drop casting or spin coating the pentamers from a solution, the oligomers tend to lie with their backbones in the plane of the film. The parameters of film preparation and the type of pentamer strongly influence the orientation distribution function. Also, the study of preferentially oriented films allows for the correlation of principal directions of the zero-field splitting tensor with characteristic directions of the molecules.