Layered-silicate polymer microscopy

The nano-scale structures in polymer layered-silicate nano-composites can be thoroughly characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD is used to identify intercalated structures. XRD allows quantification of changes in layer spacing and the most commonly used to probe the nano-composite structure and... 

Gilman JW, Davis RD, BeUayer S et al. (2005) Use of optical probes and laser scanning con-focal fluorescence microscopy for high-throughput characterization of dispersion in polymer layered silicate nanocomposites. PMSE Prepr 92 168-169... 

Morgan AB, Gilman JW.(2003). Characterization of poly-layered silicate (clay) nanocomposites by transmission electron microscopy and X-ray diffraction a comparative study. J Appl Polym Sci, 87 1329-38. 

Atomic force microscopy (AFM) is another technique used to characterize nanocomposites.AFM can provide information about the mechanical properties of a surface at a length scale that is limited only by the dimensions of the AFM tip. AFM tips with 10 nm radius of curvature are readily available from commercial suppliers. When probing mechanical properties, the attractive and repulsive force interactions between the tip and sample are monitored. Schematic depicting the intercalation process between a polymer melt and an organic-modified layered silicate is shown on Figure 6.8. 

H. J. M. Hanley, C. D. Muzny, D. L. Ho, C. J. Glinka, and E. Manias, A SANS study of organoclay dispersions. International Journal of Thermophysics, 22 (2001), 1435 8. A. Morgan and J. Gilman, Characterization of polymer-layered silicate (clay) nanocomposites by transmission electron microscopy and X-ray diffraction A comparative study. Journal of Applied Polymer Science, 87 (2003), 1329-38. 

When a thermoplastic polymer is mixed with layered silicate particles, it either intercalates or exfoliates the layered silicates, as schematically shown in Fig. 1. The state of dispersion (intercalation vs exfoliation) of the aggregates of layered silicate in nanocomposites is commonly assessed by X-ray diffraction (XRD) or transmission electron microscopy (TEM). Generally exfoliation is preferred to intercalation, although exfoliation may not necessarily be required for certain industrial applications (e.g., for an enhancement of flame retardant characteristics). It should be mentioned that the greater the extent of exfoliation of layered silicates, the larger will be the total surface areas of the dispersed layered silicates, giving rise to enhanced mechanical/physical properties of the nanocomposites prepared. 

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