Chiral poly {9,9-bis[(3S)-3,7-dimethyloctyl]-2,7-fluorene) shows temperature-induced aggregation in I-octanol. For polymer concentrations of > 0.01 mg/mL and cooling rates of <= 10 degrees C/h, aggregates form, showing characteristics of the beta phase of polyfluorene. At higher cooling rates, lower concentration, or both, another type of aggregates forms (alpha). alpha and beta phases are distinguished by absorption, fluorescence, and circular dichroism (CD) spectroscopy. Temperature-dependent CD and dynamic light scattering show that the beta phase forms only via a precursor aggregate, whose formation is concentration-, temperature-, and time-dependent. The yield of the beta phase can be optimized by choosing processing conditions that favor the formation of the precursor.