The object of this study has been to investigate the effect of filler dimensionality on morphology and mechanical properties of polymer nanocomposites using various kinds of nanofillers (such as multiwalled carbon nanotubes (1D filler), layered silicate (2D filler), and boehmite (3D filler)) dispersed in the matrix of ethylene-1-octene copolymer (EOC), a polyolefin-based elastomer. The morphological features were studied by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) while mechanical properties were characterized by tensile testing and depth sensitive recording microindentation hardness measurements. It has been demonstrated that the filler dimensionality may have dramatic influence on the mechanical properties of the samples. Based on the results obtained by tensile testing and microhardness measurements, the reinforcing effect of the nanofiller was found to follow the order: 1D filler > 2D filler > 3D filler. 1. Introduction The development of multifunctional engineering materials possessing novel properties has been achieved with the addition of nanosized filler which has overcome several disadvantages of traditional composites. Thus, such novel polymeric materials incorporated with fillers having ultrafine phase dimensions typically of less than 100？nm, which are especially termed as polymer nanocomposites (PNCs), have attracted special research interest [1–9]. Through the variation in particulate dimension from micrometer to nanometer scale, the surface area to volume ratio has been found to alter by three orders of magnitude leading to the drastic changes in morphological features as well as in their properties in such materials [3–9]. The new polymer nanocomposites have been fabricated generally with three categories of reinforcing materials such as particles (e.g., silica, metal, and other organic and inorganic substances), layered materials (e.g., graphite, layered silicate, etc.), and fibrous materials (e.g., nanofibers and nanotubes) [4–10]. Compared to conventional counterparts, these nanocomposites have been found to possess promising mechanical properties such as hardness, tensile modulus, strength, and toughness at both low and high temperatures. In addition, the PNCs are found to have significantly improved barrier properties, thermal stability, and extinguishing characteristics with advantage of light weight of the common polymers [1]. Thus, these are used as excellent prospective materials for food packaging, membranes, adhesives, automotive parts, textiles, and so forth. [11]. Furthermore, the
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