Nanocomposites lamellar

Ruland and Smarsly [84] study silica/organic nanocomposite films and elucidate their lamellar nanostructure. Figure 8.47 demonstrates the model fit and the components of the model. The parameters hi and az (inside H ) account for deviations from the ideal two-phase system. Asr is the absorption factor for the experiment carried out in SRSAXS geometry. In the raw data an upturn at. s o is clearly visible. This is no structural feature. Instead, the absorption factor is changing from full to partial illumination of the sample. For materials with much stronger lattice distortions one would mainly observe the Porod law, instead - and observe a sharp bend - which are no structural feature, either. 

Layered materials are of special interest for bio-immobilization due to the accessibility of large internal and external surface areas, potential to confine biomolecules within regularly organized interlayer spaces, and processing of colloidal dispersions for the fabrication of protein-clay films for electrochemical catalysis [83-90], These studies indicate that layered materials can serve as efficient support matrices to maintain the native structure and function of the immobilized biomolecules. Current trends in the synthesis of functional biopolymer nano composites based on layered materials (specifically layered double hydroxides) have been discussed in excellent reviews by Ruiz-Hitzky [5] and Duan [6] herein we focus specifically on the fabrication of bio-inorganic lamellar nanocomposites based on the exfoliation and ordered restacking of aminopropyl-functionalized magnesium phyllosilicate (AMP) in the presence of various biomolecules [91]. 

Structural characterization of the biomolecule-AMP lamellar nanocomposites using FTIR and circular dichroism (CD) spectroscopies showed no change in the... 

The biochemical activity and accessibility of biomolecule-intercalated AMP clays to small molecules was retained in the hybrid nanocomposites. For example, the absorption spectrum of the intercalated Mb-AMP nanocomposite showed a characteristic soret band at 408 nm associated with the intact prosthetic heme group of the oxidised protein (Fe(III), met-myoglobin) (Figure 8.9). Treatment of Mb with sodium dithionite solution resulted in a red shift of the soret band from 408 to 427 nm, consistent with the formation of intercalated deoxy-Mb. Reversible binding of CO under argon to the deoxy-Mb-AMP lamellar nanocomposite was demonstrated by a shift in the soret band from 427 to 422 nm. Subsequent dissociation of CO from the heme centre due to competitive 02 binding shifted the soret band to 416nm on formation of intercalated oxy-Mb. 

The above studies indicated that intercalation of GOx during re-assembly of exfoliated AMP sheets produced lamellar nanocomposites that retain their... 

Whilton. N.T., Burkett, S.L. and Mann, S. (1998) Hybrid lamellar nanocomposite based on organically functionalized magnesium phyllosilicate days with interlayer... 

Patil, A.J., Muthusamy, E. and Mann, S. (2005) Fabrication of functional protein-organoclay lamellar nanocomposites by biomolecule-induced assembly of exfoliated aminopropyl-functionalized magnesium phyllosilicates. Journal of Materials Chemistry, 15, 3838-3843. 

Ruland, W. Smarsly, B. 2004. SAXS of self-assembled oriented lamellar nanocomposite films An advanced method of evaluation../. Appl. Cryst. 37 575-584. 

An additional route consists of using the reconstruction ability of some LDH materials after a moderate thermal treatment. This is a pecuharity of LDH systems called the memory effect the LDH lamellar framework is reconstructed in the presence of the polymer with concomitant intercalation. Finally, a post-synthesis hydrothermal treatment can be applied in all cases, which may improve the inter- and intralamellar organization of the LDH/polymer nanocomposites. 

X-ray diffraction (XRD) has been poorly used to characterize the carbon phase of intumescent structure. Indeed, as shown previously, the carbon structure resulting from the development of the intumescent system is mainly disordered whereas XRD characterizes ordered structure. However, this technique may be of interest to study the carbonization process in the case of flame-retardant systems containing layered additives, such as expandable graphite,28,42 or even more in the case of lamellar nanocomposites, such as MMT-based nanocomposites. 

FTIR spectra of all nanocomposites also confirm the presence of An nanoparticles in the lamellar space of the clay. Au nanoparticles did not affect the structure of silicate layers. F urthermore, the BET measurement provides complete information about changes which occur during intercalation. 

These examples demonstrate clearly that charge densities of uranyl-based sheets are in general smaller than charge densities of metal phosphate and vanadate units in lamellar compounds. However, the very existence of nanocomposite vanadates and metal phosphates means that the charge-density matching principle in these compounds is observed. Then how does it work for... 

Fig. 25 Transmission electron micrographs (TEM) of a ternary nanocomposite of PS-poly(ethyl propylene) (PEP) diblock copolymer with two types of nanoparticle-Ugand systems AuR]- and SiO2R2-ftmctionalized (R i, R2 are alkyl groups) nanoparticles of total volume fraction 0.02. The former appear along the interface of the lamellar microdomains, whereas the latter reside in the center of PEP microphases. Schematically, the nanoparticle distribution is shown in the inset. Taken from [308]...

The application of a 11-ferrocenylundecyl-ammonium bromide/hexa-decylammonium bromide surfactant mixture as structure-directing agent resulted in a lamellar mesostructured silica film, which showed electronic conductivity due to electron transport in the ferrocenyl chains. Lyotropic lithium triflate-silicate liquid crystals have been utilized as supramolecular templates in the synthesis of ionically conducting nanocomposite films. ... 

We can show by DMTA and DSC that lamellar clays partially restrict the mobility of the starch chains [PAR 02], Nanoclays are also known for having an impact on the permeabihty to water vapor of the corresponding nanocomposites, particularly when they are correctly oriented. Park et al. looked at the permeabihty of nanobiocomposites to water vapor with different types of clay [PAR 02]. According to those authors, all the films analyzed showed decreased permeability to water vapor in comparison to the matrix alone. Such results were not confirmed in the case of OMMT-CS, which has a very highly plasticized matrix [CHI 10a]. In this case, the high affinity of the clay platelets with starch-rich phases creates preferential diffusion pathways through the glycerol-rich phases, in which the platelets tend to be absent. 

L. Wang, J. Schindler, C. R. Kannewurf, and M. G. Kanatzidis, Lamellar polymer-LixMo03 nanocomposites via encapsulative precipitation, J. Mater. Chem., 7, 1277-1283 (1997). 

S.K. Sahoo, D.W. Kim, J. Kumar, A. Blumstein, and A.L. ChoUi, Nanocomposites from in-Situ pol3fmerization of suhstituted polyacetylene within lamellar surface of the montmorillo-nite a solid-state NMR study. Macromolecules, 36, 2777-2784 (2003). 

Z)eff,dark) nd under UV irradiation (Z)eff,uv) were estimated to be 9.5 x 10 s and 1.7 X 10 s respectively. These values are much smaller than the effective diffusivity of FDM in Brij 56-templated photoresponsive nanocomposite membranes (Deff.dark = 1.1 X 10 " m s Deff,uv = 1-6 X 10 " m s ). As the pore size and probing molecule size are comparable in the two cases, the pore accessibility plays a major role. It was demonstrated that the photoresponsive nanocomposite membrane had a BCC mesostructure whereas the photoresponsive nanocomposite particles had an onionlike lamellar structure. Only the defects located on the particle surfaces could provide the pathway for uptake and release of OBN probe molecules, which lowered the effective diffusivity considerably. 

Before discussing the flow behavior of polymeric nanocomposites (PNCs), the nature of these materials should be outlined. As the name indicates, PNCs must contain at least two components, a polymeric matrix with dispersed nanoparticles [Utracki, 2004]. PNCs with thermoplastics, thermosets, and elastomers have been produced. The nanoparticles, by lUPAC s definition, must have at least one dimension that is not larger than 2 nm. They can be of any shape, but the most common for structural PNCs are sheets about 1 nm thick with the aspect ratio p=D/t= 20 to 6000, where D is the inscribed (or equivalent) diameter and t is the thickness of the sheet. These inorganic lamellar solids might be either natural or synthetic [Utracki et al., 2007]. 

Lamellar nanostructures can be obtained by hydrolyzing TEOS in acidic mixtures ofperfluoroctane sulfonic acid, C8Fi7S03H, and3-aminopropyltriethoxysilane, APTES. The silica layers in the materials are very thin, and contain a relatively high concentration of attached aminopropyl groups. These hybrid fluorocarbon-silica nanocomposites are thermally stable, hydrophobic and show a low dielectric constant (around 2.8) which is almost independent of frequency [68]. 

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