Syndiotactic polystyrene (sPS) samples melt-crystallized into neat alpha" hexagonal modifications were prepared at various temperatures thoroughly for the extensive morphological studies. Lamellar morphologies of the as-prepared sPS samples were investigated using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Absence of a discernible scattering peak was found for SAXS conducted at room temperature, resulting from a negligible difference in the electron density between the lamellar and amorphous layers. To enhance the scattering contrast and strength, SAXS was carried out at 180 degreesC to obtain more reliable morphological parameters. Due to the broad thickness distribution of morphological features as revealed from the TEM observations, a pronounced variation is found for the long periods derived from the Bragg's law, one-dimensional correlation function, and interface distribution function of the SAXS data. In addition, relatively irregular packing of lamellar stacks with short lateral dimensions was detected in the as-prepared alpha"-form sPS, leading to the absence of spherulitic birefringence under polarized optical microscopy. Based on the interface distribution function analysis of the SAXS intensity profiles, the lamellar thicknesses were estimated. Using the Gibbs-Thomson relation, the ratio of fold surface free energy (sigma(e)) to the fusion enthalpy (DeltaH(f)(0)) for alpha"-form sPS was successfully deduced to be ca. 0.057 nm, which is lower than that of beta'-form sPS, ca. 0.12 nm. On this basis, a comparison of critical lamellar thicknesses for alpha"- and beta'-form sPS at various crystallization temperatures is provided and the crystal stability associated with the lamellar thickness is discussed as well. (C) 2004 Published by Elsevier Ltd.