Syndiotactic polystyrene (sPS) was solidified from the melt under drastic conditions according to a continuous cooling transformation rnethodology developed by the authors, which covered a cooling rate range spanning from approximately 0.03 to 3000 degrees C/s. The samples produced, structurally homogeneous across both their thickness and surface, were analyzed by macroscopic methods, Such as density, wide-angle X-ray diffraction (WAXD), and microhardness (MH) measurements. The density was strictly related to the phase content, as confirmed by WAXD) deconvolution. The peculiar behavior encountered (the density first decreasing and. then increasing with the cooling rate) was attributed to the singularity of the phases formed in sPS; that is, one of the crystalline phases (alpha) was less dense than the amorphous phase, and the latter, in turn, was less dense than the other crystalline phase (beta). With an increasing cooling rate, the thermodynamically stable phase (beta) disappeared first, and it was followed by the alpha phase. On the other hand, the MH values remarkably depended on the amount of the beta phase, the alpha-phase content influencing the mechanical properties only to a minor extent. The behavior of the crystallization kinetics was described through a modified multiphase Kolmogoroff-Avrami-Evans model for nonisothermal crystallization. (c) 2007 Wiley Periodicals, Inc.