To more accurately investigate the nucleation, crystallization and dispersion behaviors of silica particles in polymers, the composites of PET with monodisperse SiO2-PS core-shell structured particles were prepared with SiO2 size from 380 nm to 35 nm. For these SNPET samples, DSC results showed that the nucleation rate of silica particles increased as their size decreased, in which 35 nm SiO2 particles produced the most obvious nucleation effect. At 2.0 wt.% load of 35 nm silica, Avrami equation proved that the isothermal crystallization rate G of SNPET was ca. 30% higher than that of pure PET and the crystallization activation energy for SNPET was -218.7 kJ mol(-1) lower than -196.1 kJ mol(-1) for PET. While, the non-isothermal crystallization Delta E for SNPET was -199.8 kJ mol(-1) lower than -185.5 for PET. On non-isothermal crystallization, Jeziomy equation presented the primary and secondary crystallization stages in PET and SNPET, in which nano SiO2 accelerated the crystallization rate. Their Ozawa number m was from 2.1 to 2.7, which was smaller than that of Avrami number n. The nucleation and dispersion behaviors of SiO2 particles were directly observed. POM results demonstrated that SNPET samples crystallized more quickly from melt and their crystallization rate increased as silica load increases but accelerated at 2-3 wt.%. The spherulites grew well in PET but their size was smaller in SNPET due to the silica barrier on their growth. SEM and TEM observed the homogeneous silica dispersion morphology and the vivid ordered patterns formed in SNPET. The monodisperse particles are highly expected to give more accurate and valuable references than multi-scale ones in obtaining novel advanced PET composites. (c) 2007 Elsevier Ltd. All fights reserved.