A series of intercalated poly(trimethylene terephthalate) (PTT)/clay nanocomposites were prepared in a twin-screw extruder by the melt mixing of PTT with either quaternary or ternary ammonium salt-modified clays. The morphology and structure, along with the crystallization and melting behavior, and the dynamic mechanical behavior of the composites were characterized by X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, and dynamic mechanical thermal analysis. The results showed that the PTT chains could undergo center-mass transport from the polymer melt into the silicate galleries successfully during the blending and extrusion process. More coherent stacking of the silicate layers was reserved at higher clay concentrations and shorter blend times. Compared with conventionally compounded composites, the nanoscale-dispersed organophilic clays were more effective as crystal nucleation agents. The influence of the nanosilicates on the crystallization and melting behavior of PTT became distinct when the concentration of clay was around 3 wt %. The changes in the crystallization behavior of the polymer/clay nanocomposites depended not only on the size of the silicates but also on the intrinsic crystallization characteristics of the polymers. The resulting nanocomposites showed an increase in the dynamic modulus of PTT and a decrease in the relaxation intensity (both in loss modulus and loss tangent magnitude). (C) 2003 Wiley Periodicals, Inc.