Abstract
We use small angle neutron scattering (SANS) to study the aggregation of an electroluminescent polymer, poly(9,9-dioctylfluorene)(PFO), in toluene solution. The scattering profile display the asymptotic behavior of q-1, associated with the rod-like character of the PFO chain on local scale (q-1 > lps = persistence length). The low-q intensity shows strong upturn, signifying prevalent inter-chain aggregation of the polymer. The middle-q intensity decreases with increasing the polymer concentration caused by the chain mashng. And PF chains were mostly uniformly dissolved in toluene. The chains were virtually rod-like, such that the corresponding mesh size in the semidilute regime exhibited c-1/2 dependence. A small fraction of the rod segments aggregated to form nanoscale microdomain, which was responsible for the intensity upturn at low-q. The aggregation was spontaneous, as demonstrated from the thermal reversibility experiment.