In polymer–clay nanocomposites, to truly reach the ultimate in property improvements requires full exfoliation. A fully exfoliate composite yields the maximum interfacial interaction between the nanoparticle and polymer matrix. In order to produce optimally exfoliated systems requires that direct methods be available to measure the level of exfoliation. The ideal analytical method should be rapid, nondestructive, applicable to many sample matrices, low cost, and should require minimal sample preparation. The only method that fits these criteria is wide-angle X-ray diffraction (WAXD). This method, however, has some major drawbacks that will be discussed in detail in this chapter.

The other analytical methods for confirming the level of exfoliation include scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The utility and limitations of these three microscopy techniques for measuring exfoliation in nanocomposites will be discussed in detail with specific examples in this chapter.

There are also a number of indirect methods to measure the level of exfoliation but all of them require a direct method with which to standardize them. As examples, two methods, melt viscosity and tensile modulus, will illustrate the indirect methods. Unfortunately, the overall area has not received a great deal of attention, with limited numbers of publications on the subject [1–3].