Wide-Angle X-Ray Diffraction in the Characterization of Polymer-Based Nanocomposites

Wide-Angle X-Ray Diffraction in the Characterization of Polymer Based Nanocomposites 

The most extensive use of WAXD in the field of nanocomposites was done with clay-polymer nanocomposites. Such fillers are composed of inorganic layers stacked one above another. The layers are characterized by a high aspect ratio since they have thicknesses of about 1 nm and diameters ranging from 30 to over 500 nm. Weak van der Waals forces keep together hundreds or thousands of these layers, stacked in structures called tactoids. The performance of day-based nanocomposites is strongly dependent on the breaking-up of day partides in the polymer matrix. 

In general, authors consider three possible systems, which occur as a function of the degree of interaction between the polymer and the filler 

The exfoliated system is almost always quoted as the most desirable, since nanometric dispersion of day platelets maximizes the interfacial region between the filler and the polymer matrix, thus allowing to exploit the excellent mechanical properties of the individual day layers. Moreover, when exfoliation is attained, the number of reinfordng components is dramatically increased, since each day particle contains a very large number of day sheets. To further complicate matters, often a mixed dispersion is observed for day with different populations of tactoids or with partial exfoUation of single layers. Transmission electron microscopy (TEM) and WAXD are by far the most employed characterization techniques that assess the morphology of PLSN. 

1) To favor the interaction between ihe polymer (usually nonpolar) and the day layers, which are polar in nature, an organic molecule, often an alkylammonium salt, is intercalated within 

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