Lamellar crystals of polydisperse poly (9,9-di-n-octyl-2,7-fluorene)s were obtained from dilute solution. By means of scanning electron microscopy (SEM) and atomic force microscopy (AFM), we found that polymer chains formed lamellar single crystals through fractionated crystallization, in which components of the largest mass fraction crystallized first and remained extended in the first lamella. With the depletion of the species, other components continued the crystal growth and deposited on the already formed surface, which gave rise to the variation in lamellar thicknesses. Therefore, our study not only confirmed the feasibility of our previously crystallization mechanism of the binary mixture on the polydisperse Fn but also provided an extension of the research on the crystallization behavior. (c) 2013 Elsevier Ltd. All rights reserved.