Analytical microscopy, fundamentals

S. Amelincks, D. van Dyck, J. van Landuyt, G. van Tendeloo (eds.) Electron Microscopy Principles and Fundamentals,VCH Verlagsgesellschaft mbH, Weinheim 1997. 4-89 J. J. Hhen, j. I. Goldstein (eds.) Introduction to Analytical Electron Microscopy, Plenum Press, New York, 1979. 

J. Heydenreich, W. Neumann (eds.) Proc. Analytical Transmission electron Microscopy in Materials Science - Fundamentals andTechni-ques, Elbe Druckerei, Wittenberg, 1993. 

Polymer degradation, which reflects changes in the properties of polymers due to chemical processes that occur as a function of a complex set of environmental conditions, is a challenging topic of great fundamental and technological importance. Historically, materials were used long before their properties were fully understood. In recent years, analytical tools such as microscopy, imaging, and computational techniques have made possible the determination of structural and functional details of materials, some of which are hard to obtain by other methods. 

With these emerging applications, there is a critical need for analytical techniques that will provide insights to fundamental questions concerning dendrimer characteristics and properties (e.g. their dimensions, uniformity of size, shape and degree of rigidity, etc.) [8-10], atomic force microscopy (AFM) offers this... 

The interested reader is referred to numerous other compendiums of information on this broad topic (1—5). Particulady noteworthy are the series of Fundamental Reviews on specific techniques that appear biennially in the joumal Analytical Chemistry. These Reviews report developments in specific fields since the previous report, and usually provide an up-to-date perspective of significant advances made in the field. Of particular relevance to this article are the Fundamental Reviews on surface analysis, scanning probe microscopy, and ir spectroscopy which have appeared recendy (5). 

This review article describes progress made in scanning force microscopy of polymers during the last 5 years including fundamental principles of SFM and recent developments in instrumentation relevant to polymer systems. It focuses on the analytical capabilities of SFM techniques in areas of research where they give the most unique and valuable information not accessible by other methods. These include (i) quantitative characterisation of material properties and structure manipulation on the nanometer scale, and (ii) visualisation and probing of single macromolecules. 

Clearly, the structure factor dominates the SAXS patterns. It is relevant to ask whether the cylinder form factor, depending on the pore radius, also plays a significant role in the scattering distribution. The calculated cylinder form factor is defined by a Bessel function [12,15,17] which has zeroes at specific k-values. As shown in Fig 4, the experimental profiles for 40 V membranes (pore diameter 48nm) do not display a clear link to this pattern. The predicted first minimum is close to the broad third-order structure factor peak. It is consequently impossible to derive a value for the pore radius directly from the resuhs without a more detailed analytic treatment. This is disappointing, as the pore size is fundamentally important in the use of AAO membranes in filtration or as templates. Electron microscopy studies show that for the synthetic conditions employed, pore diameters above 12mn are linearly related to anode voltage (1.2 nnW) and so are approximately half the mean pore separation [7,15]. 

In contrast to XRD methods that may introduce sample preparation artifacts (see Jiang et al. 1997 Li et al. 1998), TEM integrated with selected-area electron diffraction (SAED) and energy dispersive spectrometry (analytical electron microscopy, AEM) measurements, provides direct, in situ observations on rock microtextures, crystallite size distributions, lattice imperfections of crystallites and interstratification (see the extensive reviews by Peacor 1992 and Merriman and Peacor 1999). TEM observations on selected portions of thinned (ion-milled) whole rock samples contradict the fundamental particle theory of Nadeau et al. (1984a,b,c summarized recently by Nadeau 1998). The observations show that phyllosilicate domains with interstratified structures form coherent boundaries, and therefore, MacEwan-type crystallites do exist in quasi-undisturbed rocks (Peacor 1998). In addition, AEM studies may provide reliable mineral-chemical data on the phases devoid of any external or internal impurities. 

Since the very first reports on dendrimers in 1984 [62-67], we have proposed the use of these entities as fundamental building blocks for the construction of higher complexity structures on numerous occasions [35,58,198], Early electron microscopy studies [55] and other analytical methods [61] indicated that the supramflcromolecular assembly leading to formation of dimers, trimers, and other multimers of dendrimers occurred almost routinely however, these were largely uncontrolled events. 

Gallezot P, Leclercq C. Characterization of catalysts by conventional and analytical electronic microscopy. In Imelik B, Vedrine JC, editors. Catalyst characterization, physical techniques for solid materials, fundamental and applied catalysis. Heidelberg Springer 1994. p. 509-58. 

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