The nonisothermal crystallization kinetics of a luminescent conjugated polymer, poly(9,9-dihexylfluorene-alt-co-2,5-didecyloxy-1,4-phenylene) (PF6OC10) with three different molecular weights was investigated by differential scanning calorimetry under different cooling rates from the melt. With increasing molecular weight of PF6OC10, the temperature range of crystallization. peak steadily became narrower and shifted to higher temperature region and the crystallization rate increased. It was found that the Ozawa method failed to describe the nonisothermal crystallization behavior of PF6OC10. Although the Avrami method did not effectively describe the nonisothermal crystallization kinetics of PF6OC10 for overall process, it was valid for describing the early stage of crystallization with an Avrami exponent n of about 3. The combined method proposed in our previous report was able to satisfactorily describe the nonisothermal crystallization behavior of PF6OC10. The crystallization activation energies determined by Kissinger, Takhor, and Augis-Bennett models were comparable. The melting temperature of PF6OC10 increased with increasing molecular weight. For low-molecular-weight sample, PF6OC10 showed the characteristic of double melting phenomenon. The interval between the two melting peaks decreased with increasing molecular weight, and only one melting peak was observed for the high-molecular-weight sample. (c) 2007 Wiley Periodicals, Inc.