Characterization of Microstructure

magic-angle spinning (MAS) NMR is becoming an increasingly important spectroscopic tool for the characterization of solids. This is a spectroscopic technique that offers a local probe of the environment ofa target nucleus based on the interactions between the nuclear spins. The versatility of the NMR approach is that it is possible to tune to various NMR interactions, such as the chemical shift (5c), the scalar coupling Jc), the dipolar interaction (Dim), and the quadrupolar interaction (Qi,). M AS-NM R is 

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Microscopic techniques are extensively used to study the surface morphology of reinforcing fibers. The characterization of microstructure of polymer fibers provides an insight into stmcture-property relationship of the fiber. Microscopy techniques have been employed for the... 

Physical metallurgy is concerned with the scientific study of materials. Phase transformations, recovery and recrystallization, precipitation hardening, structure-property correlations, characterization of microstructure by microscopy (optical, electron and field-ion), are some specific examples among the many topics covered under physical metallurgy. 

More recent efforts focused on surface modification of conductive polymers by the SECM, fabrication, and characterization of microstructures. Mandler et al. developed an approach for the formation of a 2D conducting polymer on top of an insulating layer. This approach, based on electrostatically binding a monomer (anilinium ions) to a negatively charged self-assembled monolayer of co-mercaptodecanesulfonate [MDS, HS(CH2)ioS03 ] followed by its electrochemical polymerization. The polyanion monolayer exhibited the properties similar to those of a thin polymer film [167]. 

In terms of characterizing the microstrac-ture of polymer chains, the two most useful techniques are infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) spectroscopy. Commercial infrared spectrometers were introduced after the end of the second world war and quickly became the workhorse of all polymer synthesis laboratories, providing a routine tool for identification and, to a certain degree, the characterization of microstructure (e.g., the detection of short chain branches in polyethylene). In this regard it can no longer compete with the level of detail provided by modem NMR methods. Nevertheless, IR remains useful or more convenient for certain analytical tasks (and a powerful tool for studying other types of problems). So here we will first describe both techniques and then move on to consider how they can be applied to specific problems in the determination of microstructure. 

The textural properties of a fat are influenced by all levels of structure, particularly microstructure. The microstmcture includes the spatial distribution of mass, particle size, interparticle separation distance, particle shape, and interparticle interaction forces (49-51). Methods that can be used for the characterization of microstructure in fat systems include, among others, small deformation rheology and polarized light microscopy, employing a fractal approach (49-51). 

About 15 years ago, the first ultra (low) SANS (USANS) instrument was built. The equipment is complimentary to conventional SANS as it enables measurement to be made at lower Q than conventional SANS. USANS and Super USANS are useful for the measurement of shape and size of particles from a maximum size of 30 pm to either 0.3 pm or 0.01pm, depending upon the particular type of USANS instrument used. When combined with SANS, USANS allows the characterization of microstructure over 11 orders of magnitude and has been used to study the structure and intermicellar interactions in block polyelectrolyte assemblies. ... 

These different contrast mechanisms can all be used to reveal the scale of liquid crystalline polymer microstructures. In specimens that exhibit a mosaic texture, and in those that contain predominantly planar defects, domain size is easily defined in terms of areas that uniformly show extinction between crossed polars. However, if the defects are predominantly linear, as in specimens that exhibit schlieren textures, such simple characterization of microstructural scale is no longer possible. Here it is more convenient to look at the length of disclination line per unit volume, which is equivalent to the number of lines intersecting unit area, and analogous to the dislocation density as defined for crystalline solids. Good contrast is essential in order to obtain an accurate count. Technologically, microstructural scale is of growing interest because of its relevance to processability, mechanical properties and optical transparency. 

Rinaldi et al. introduced the use of correlations for the characterization of microstructures in fluoropolymers by demonstrating that highly dispersed 2D- F, C HMQC and HMBC spectra allowed the identification of different triads and pentads in a 1-chloro-l-fiuoroethylene/isobutylene copolymer, and 3D- H, C, F experiments permitted assignment of the tacticity in polymeric l-chloro-l-fluoroethylene. The latter experiment is interesting because it exploits the unique chemical shift dispersion of F nuclei for the separation of resonances originating from different stereosequences, and then uses the cross-peak multiplicities in the slices... 

Visualization and characterization of microstructure, for example optical or electron microscopy to see ice crystal or air bubble size distributions. 

K. Mader, G. Bade, A. Domb, H.M. Swartz, Characterization of microstructures in drug delivery systems by EPR spectroscopy, in Proceedings of the International Symposium on Control Release of Bioactive Materials, 1995, p. 780. 

Characterization of Microstructure and Permselectivity of Cellulose Acetate Films at Glassy Carbon. 

Xie, R., Chu, L.-Y., Chen, W.-M., Xiao, W., Wang, H.-D. and Qu, J.-B. 2005. Characterization of microstructure of poly(N-isopropylamide)-grafted polycarbonate track-etched membranes prepared by plasma-graft pore-filling polymerization.. 7. Memh. Sci. 258 157-166. 

T Nomura, T Nishio, K Iwanami, K Yokomizo, K Kitano, S Toki. Characterization of microstructure and fracture behavior of polypropyle/elastomer blends containing small crystal in elastomeric phase. J Appl Poly Sci 55 1307-1315, 1995. 

Microemulsions. The shape of the amphiphile, embodied in the v/aT packing parameter concept, along with a subtle interplay of intermolecular forces (van der Waals, electrostatic, hydration, polarizability, specific ion effects, etc) modulate the amphiphilic polar-apolar interface. Exactly as in the L.C. state not only o/w or w/o microdomains exist in Li and L2 microemulsion phases. Indeed a variety of microstructures from discrete to bicon-tinuous nanoaggregates have been identified. Moreover the development and the use of NMR techniques has provided a wide and unique insight of knowledge in the characterization of microstructural features and transitions in microemulsion systems. As reported in the previous volume, the transition of the dispersed phase from a disconnected to an interconnected domain. 

Dawnay E.J.C., Fardad M.A., Green M., Horowitz F., Yeatman E.M., Almeida R.M., Vasconcelos H.C., Guglielmi M., Martucci A. Control and characterization of microstructure in sol-gel films for optical device applications. In Advanced Materials in Optics, Electro-Optics and Communication Technologies. P. Vincenzini, ed. 1995... 

Tsukame, T., Ehara, Y., Shimizu, Y, Kutsuzawa, M., Saitoh, H., and Shibasaki, Y. (1997) Characterization of microstructure of polyethylenes by differential scanning calorimetry. Thermochim. Acta, 299, 27. 

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