e-caprolactone was polymerized in the presence of neat montmorillonite or organomontmorillonites to obtain a variety of poly(e-caprolactone) (PCL)-based systems loaded with 10 wt % of the silicates. The materials were thoroughly investigated by different X-ray scattering techniques to determine factors affecting structure of the systems. For one of the nanocomposites it was found that varying the temperature in the range corresponding to crystallization of PCL causes reversible changes in the interlayer distance of the organoclay. Extensive experimental and literature studies on this phenomenon provided clues indicating that this effect might be a result of two-dimensional ordering of PCL chains inside the galleries of the silicate. Small angle X-ray scattering and wide angle X-ray scattering investigation of filaments oriented above melting point of PCL revealed that polymer lamellae were oriented perpendicularly to particles of unmodified silicate, while in PCL/organoclay systems they were found parallel to clay tactoids. Calorimetric and microscopic studies shown that clay particles are effective nucleating agents. In the nanocomposites, PCL crystallized 20-fold faster than in the neat polymer. The crystallization rate in nanocomposites was also significantly higher than in microcomposite. Further research provided an insight how the presence of the filler affects crystalline fraction and spherulitic structure of the polymer matrix in the investigated systems. (c) 2007 Wiley Periodicals, Inc.