Interlayer expansion

Now it is necessary to understand the meaning of the interlayer expansion in the intercalated nanocomposites. As discussed before, we have to take the interdigitated layer structure into consideration. This structure may suggest that a different... 

Differential refraction( ) and colorimetric measurements ) were used to determine the amount of carbohydrate polymer adsorbed from solution. A Phillips X-ray diffractometer was used to quantify the degree of interlayer expansion(60. The cation exchange capacity of the peptized sodium and potassium... 

ADSORPTION AND INTERLAYER EXPANSION OF CELLULOSE ETHERS FROM FRESH WATER ON PEPTIZED SODIUM MONTMORILLONITE... 

The hydration of polyoxyethylene (POE) is dramatically affected by the anion present(J 0) in the aqueous phase. The adsorption of HEC (both 2.0 and 4.3 M.S.) was therefore studied in Na SO and Na PO, at equivalent normalities. The multivalent anions are more effective in precipitating POE than is the chloride ion. The amounts adsorbed and the interlayer expansions at normalities below precipitation conditions are given in Table III. The influence of multivalent anions on the intrinsic viscosity of variable M.S. HECs is illustrated in Figure 6. The increased amounts adsorbed are within experimental error, but the decrease in d. with the 4.3 M.S. HEC is notable. The d. changes in the absence of increased adsorption are not explainable in terms of solvation effects. 

In exfoliated nanocomposites, delaminated structures are obtained if a large number of polymer chains are present between the layers and the layers stand >10 nm apart. Thus, the interlayer expansion is comparable to the radius of gyration of the polymer rather than that of an extended chain, as in the case of intercalated hybrids [35]. 

Morphological structures and properties of a series of poly(ethyl acrylate)/clay nanocomposites prepared by the two distinctively different techniques of in situ ATRP and solution blending were studied by Datta et al. [79]. Tailor-made PNCs with predictable molecular weights and narrow polydispersity indices were prepared at different clay loadings. WAXD and studies revealed that the in situ approach is the better option because it provided an exfoliated morphology. By contrast, conventional solution blending led only to interlayer expansion of the clay gallery. 

The C.E.C. of montmorillonite does not appear to vary with grais size (Osthaus,1955) however, there is a relation between cation type and flake size. In most montmorillonite clays and shales the Na is concentrated in the finer fraction and the Ca in the coarser fraction (McAtee, 1958). This is probably because Na allows much greater interlayer expansion which leads to the shearing-off of thin flakes. 

The second Ni layer is bucklcc (see text). This interlayer expansion is measured from the center-of-mass plane of the second Ni layer. ... 

The interlayer expansions shown in Table 6.2 take into account the removal of the loosely bound layer of water from the gallery space of the host, upon intercalation of the polymer. 

Chen, J. -S., Pohks, M. D., Ober, C. K., Zhang, Y., Wiesner, U., and Giannelis, E., Study of the interlayer expansion mechanism and thermal-mechanical properties of surface-initiated epoxy nanocomposites. Polymer, 43, 4895-4904 (2002). 

The preference of bentonites for heavy metal ions that adsorb by cation exchange decreases in the order Cu > Pb > Zn > Cd > Mn (Lagaly, 1995). According to Lagaly, the selectivity of montmorillonite for cations generally depends on the restriction of interlayer expansion, being minimal for sodium montmorillonites. Metwally et al. (1993) found palygorskite to be more effective than montmorillonite, and very much more effective than kaolinite, for the uptake of Zn, at least under the conditions of their experiments (pH 4.5-7.0). Minerals were tailored to remove particular elements (e g., radioactive... 

Most commonly used layered silicate is montmorillonite clay, which is composed of micron-sized particles. The particles are constructed of platelets with thickness of lnm and width of 100-200 nm. Platelets have permanent negative charge and they are held together by charge balancing cations such as Na" or Ca [2-i] ions. The significant disruption of individual silicate layers in polymer matrix with nanoscopic dimensions (exfoHated structure) leads to improvements of the nanocomposite properties. However, in many cases, the isolated silicate layers are not completely dispersed throughout the polymer matrix, instead, the clay particles in polymer matrix maintain the hierarchical architecture, and an interlayer expansion occurs (intercalated structure). 

Host lattice Guest species Basal Spacing (A) Host interlayer expansion (A) Ref. 

All acids intercalate alkylamines, and the interlayer expansion can be very large for long-chain amines (Table 15). Other types of amines and aromatic bases and the other groups of guest compounds are only intercalated by certain acids. The interlamellar adsorption of urea derivatives, alcohols, nitriles, and ketones is restricted to the most reactive acids (Table 16). The reactivity of guest molecules follows this order alkylamines > N- and 5-oxides > acid amides > various bases > urea derivatives > alcohols. 

Zampori L, Gallo Stampino P, Dotelli G, Botta D, Natali Sora 1, Setti M (2008) Interlayer expansion of dimethyl ditallowylammonium montmorillonite as a function of 2-chloroaniline adsorption. Appl Clay Sci 41(3 ) 149-157... 

Chen et al. [88] studied the interlayer expansion mechanism of MMT in epoxy resins by using time-resolved, high-temperature X-ray diffraction (XRD), DSC and isothermal rheological analyses, and found that the interlayer expansion... 

Sodium montmorillonite binds copper and manganese ions without any preference. The restriction of the interlayer expansion by calcium ions seems to be one of the prerequisites for selectivity of montmorillonite. Sposito and L Vesque [68] illustrated that the adsorption of sodium ions by illite eliminated the preference of the clay minerals for Ca over Mg ions. 

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