Static and dynamic solution properties of monodisperse oligofluorenes

Dynamic light scattering techniques were employed for the study of molecular and collective properties of newly synthesized oligomers (n = 3-7) of the polyfluorene in toluene solutions. At low concentrations, the molar mass, interaction parameter, optical anisotropy and the transport coefficients for translational and rotational diffusion provide a consistent description using a rigid rod model with thickness b = 0.6 nm and length L = nl (l = 0.75 nm). This description is in agreement with the persistence length (6-7 nm) reported for the fluorene polymers. In the non-dilute regime, the estimated concentration for the lyotropic transition further supports the proposed molecular shape and the second slow process in the intermediate scattering function relates to the formation of almost spherical clusters above about 30%.