Polymer Nanocomposites Characterization by Microscopy

Electron microscopy (EM), complemented by other techniques, has played a very important role in the elucidation of morphology and structure-property correlations of polymers including homopolymers, copolymers, blends, and composite materials. When employed vigilantly by an experienced microscopist with proper care during sample preparation, electron microscopy most reliably characterizes every detail concerned with the morphology of polymers on various length scales. EM identifies the structure and properties of specific locations of polymers and the information is not restricted to the average values. The significance of the EM in nanocomposites science and technology arises principally from two causes. First, electron microscopic information is much more detailed than that from other sources. Using electron microscopy, information of the morphology of polymer matrix as well as of the filler and the adhesion between them can be simultaneously assessed with nanometer resolution. Second, electron microscopy allows studying the response of all the structural details of the composite towards applied load (sometimes even in situ) enabling the design of tailored materials. Electron microscopy is the only technique which provides very direct evidence of intercalation and exfoliation of the filler in the polymer matrix allowing straightforward quantification of morphological features of the polymer nanocomposites. This paper aims at highlighting the importance of different microscopic techniques in the study of the structure and properties of polymer nanocomposites (PNCs) with special reference to electron microscopy and scanning force microscopy as nanoanalytical tools. It will be shown that the selection of specific microscopy technique and preparation methods is crucial for the artifacts free imaging of the PNCs. The choice of the microscopic technique depends basically on the class of composite materials at hand. Besides the discussion of classical nanocomposites based on inorganic fillers, a brief account of polymer-polymer composites and bionanocomposites will be presented.