Neutron scattering studies morphologies

Several aspects of neutron scattering studies are particularly elegant and unique in terms of the contrast variation method to examine internal structures as well as the external morphology. Thus the protein positions within the 30S ribosomal subunit can be determined by triangulation of deuterated subunits [489,490] the shell-like spherical structures of protein, lipid and nucleic acid within viruses [546,555,566] and lipoproteins can be analysed the distinct disposition of carbohydrates within glycoproteins [197,198,214], membranes within membrane proteins [39], or proteins within protein-nucleic acid complexes [385,387,392] can be elucidated. Likewise X-ray scattering has been of value in protein-lipid systems since these two components can be readily distinguished from one another [75,76]... 

Triolo, A., Russina, O., Keiderling, U., and Kohlbrecher, J. 2006. Morphology of poly(ethylene oxide) dissolved in a room temperature ionic liquid A small angle neutron scattering study. J. Phys. Chem. B 110, 1513-1515. 

Roche and co-workers used SAXS and small-angle neutron scattering (SANS) to study the morphology of 1200 EW Nafion membranes in the acid and neutralized forms with a range of water contents. ... 

Small angle X-ray scattering monitoring the distribution of electron density has been used to probe resin morphology [109]. More recently contrast matched small angle neutron scattering has also been employed [110, 111]. These techniques can also be applied to wet resins and tend to probe the very low dimensions of the polymer matrix structure. More studies are needed to identify the real value of these approaches. 

Since the start of modern interpenetrating polymer network (IPN) research in the late sixties, the features of their two-phased morphologies, such as the size, shape, and dual phase continuity have been a central subject. Research in the 1970 s focused on the effect of chemical and physical properties on the morphology, as well as the development of new synthetic techniques. More recently, studies on the detailed processes of domain formation with the aid of new neutron scattering techniques and phase diagram concepts has attracted much attention. The best evidence points to the development first of domains via a nucleation and growth mechanism, followed by a modified spinodal decomposition mechanism. This paper will review recent morphological studies on IPN s and related materials. 

Even though TEM and SEM played major roles in the study of IPN morphological features, there are various shortcomings, such as staining artifacts, difficulties in sample preparation for very rubbery materials, and the two-dimensional viewing limit for the former. Recently, various scattering techniques have been applied to measure the phase dimensions of IPN s via statistical treatment. The principles of neutron scattering theory as applied to the phase separated materials have been described in a number of papers and review articles [33-36]. 

Luchette, P.A., T.N. Vetman, R.S. Prosser, R.E.W. Hancock, M.P. Nieh, C.J. Glinka, S. Krueger, and J. Katsaras (2001) Morphology of fast-tumbling bicelles a small angle neutron scattering and NMR study. Biochim. Biophys. Acta 1513, 83-94. 

Physical characterization of macromolecular systems strives to determine chemical structure/property relationships. This subfield includes study of thermomechanical performance viscoelastic properties surface properties, adhesion science thermal transitions morphological analysis, including semicrystalline, amorphous, liquid-crystalline, and microphase-separated structures. Structural analysis employs electron microscopy, con-focal microscopy, optical microscopy, x-ray photoelectron spectroscopy, atomic force microscopy, and x-ray and neutron scattering of macromolecular compositions. 

Note that in a subsequent study a similar result of micro-/nanophase separation has been observed in block copolymers of PNIPAAM and Ai-isopropylmetAa-crylamide (PNIPMAM). This small-angle neutron scattering (SANS) study used a scattering analysis with a new form factor model taking into account a nanophase separated internal morphology [50]. 

The structure of PEMs, in particular their phase-separated morphology at nm-scale, has been studied with a number of experimental techniques, including small- and wide-angle X-ray and neutron scattering, infrared and Raman spectra, time-dependent FTIR, NMR, electron microscopy, positron annihilation spectroscopy, scanning probe microscopy, and scanning electrochemical microscopy (SECM) (for a review of this literature see [31]). Structural studies of PEMs have mainly focused on Nafion. A thorough recent review on this particular membrane is provided in [32]. 

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