Multicomponent gels

Morris, V.J. (1986). Multicomponent gels. In Phillips, G.O., Wedlock, D.J., Williams, P.A. (Eds). Gums and Stabilisers for the Food Industry 3, London Elsevier Applied Science, pp. 87-99. 

Morris, V. J. 1986. Multicomponent gels, in Gums and Stabilisers for the Food Industry 3, eds. G. O. Philips, D. J. Wedlock, and P. A. Williams, pp. 87-99, Elsevier Applied Science Publishers, London. 

Tolstoguzov, V.B., Some physico-chemical aspects of protein processing foods. Multicomponent gels, Food Hydrocoil., 9, 317, 1995. 

In the gel network there are zones, where the polymers interact, and large segments, where the macromolecules are randomly extended. The lattice is responsible for the elasticity and the textural strength of the product. In multicomponent gels all constituents may form separate or coupled networks, or else one component, not involved in network formation, may indirectly affect the gelling by steric exclusion of the active molecules. Such exclusion increases the concentration of the active component in the volume of the solution where the gel is formed. In gels made from the mince of squid meat at 1.5% NaCl, the added carrageenan and egg whites form separate networks that support the structure made of squid proteins, while added... 

Sonogels Gel exposed to ultrasound in the 20-kHz range prior to autoclave treatment Assists in the formation of multicomponent gels... 

A wide range of ceramic and glass compositions have been prepared by sol-gel processing and details of the experimental procedure can be found in the literature (see, for example. Ref. 44 for a partial list). We will not repeat the procedure for the preparation of specific gel compositions. Instead, the common techniques will be outlined with the aid of a few specific examples. To keep the discussion at a suitable level, we shall limit the consideration of multicomponent gels mainly to the case of gels containing two metal cations only. 

Figure 12.7 Natural logarithm of the shrinkage versus the reciprocal of the temperature for a multicomponent gel during constant heating rate sintering calculated curves (MODELED) and measured data (MEASURED). (From Ref. 5.)...

In the field of sol-gel derived materials, multicomponent gel evolves, after densification process and thermal annealing, to mixed oxide. However, in the synthesis of multicomponent... 

Multicomponent Silicates briefly discusses synthetic schemes employed to make multicomponent gels and presents the results of several structural studies that examine polymer growth in binary silicate systems. 

It is certainly beyond the scope of this book to discuss in any detail the solution chemistry pertinent to the large number of multicomponent silicate systems described in the literature. However, it is necessary to address at the minimum the synthetic strategies employed in multicomponent gel synthesis. In aqueous systems coprecipitation is so commonly used that it warrants no further discussion here. In alkoxide systems, there are two general approaches 1) hydrolysis of mixed-alkoxide or metal organic precursors and 2) sequential addition of alkoxides to partially hydrolyzed precursors. 

Isothermal plots of /K and viscosity (//) versus bulk density, obtained by analyzing sintering kinetics of multicomponent gel in terms of cylinder model K =... 

Isothermal plots of l/X and viscosity versus residual OH content, found by analyzing sintering kinetics of multicomponent gel using cylinder model. (Reprinted by permission of the publisher from Gallo et al. [65], copyright 1984, Elsevier Science Publ. Co., Inc.)... 

In situ FTIR spectroscopy experiments [101] performed on binary borosilicate compositions indicate that boron is primarily responsible for nitridation in the multicomponent gel referred to in Fig. 25. Figure 26 shows a series of spectra obtained for a 20 B2O3 - 80 Si02 (mol%) film heated in flowing ammonia between 20 and 700°C. Dissociative chemisorption... 

In(shrinkage) versus /T(K) during heating at constant rate curves calculated from cylinder model (MODELED) and measured data ( ) for multicomponent gel (MEASURED). From Brinker et al. [70]. 

Stability than the gels obtained from the 20 1 mixture of 10 and 11. Careful analysis of the CuAAC product 14 by MALDl-TOF revealed that it consisted mainly of short oligomers. This example hence showed that such oligotriazole compounds could be used to reinforce the strength of multicomponent gels. 

Most ceramics and glasses are based on silica. The problem then is to form Si-O-M bonds in the molecular precursor and to keep them during the whole hydrolysis and condensation processes. However, silicon has a rather high electronegativity (XSi=L74) and does not show any tendency toward coordination expansion. Its chemical reactivity toward hydrolysis and condensation is therefore quite low. Silicon alkoxides Si(OR)4 always exhibit a monomeric tetrahedral molecular structure and very few heterometallic alkoxides or oxo-alkoxides are formed with silicon (4). It is therefore difficult to prepare homogeneous multicomponent gels in silicate systems... 

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