Self-assembly of gels

Aggeli A, Bell M, Boden N et al (1997) Responsive gels formed by the spontaneous self-assembly of peptides into polymeric beta-sheet tapes. Nature 386 259-262... 

Successive H-bond urea self-assembly of 4 and sol-gel transcription steps yield preferential conduction pathways within the hybrid membrane materials. Crystallographic, microscopic and transport data confirm the formation of self-organized molecular channels transcribed in solid dense thin-layer membranes. The ionic transport across the organized domains illustrates the power of the supramolecular approach for the design of continual hydrophilic transport devices in hybrid membrane materials by self-organization (Figure 10.8) [42-44]. 

Fig. 10.12 (A) The cation-templated hierarchic self-assembly of guanine alkoxysilane gives the C-quartet and (B) the G-quadruplex transcribed in solid hybrid materials by the sol-gel process.

Aggeli, A., Bell, M., Boden, N., Keen, J. N., Knowles, P. F., McLeish, T. C., Pitkeathly, M., and Radford, S. E. (1997). Responsive gels formed by the spontaneous self-assembly of peptides into polymeric beta-sheet tapes. Nature 386, 259-262. 

Electrode surfaces can be modified by redox polyelectrolytes via a sol-gel process, yielding random redox hydrogels or by layer-by-layer self-assembly of different redox and nonredox polyelectrolytes by alternate electrostatic adsorption from solutions containing the polyelectrolytes to produce highly organized redox-active ultrathin multilayers. 

Veerman, C., Sagis, L.M.C., van der Linden, E. (2003). Gels at extremely low weight fractions formed by irreversible self-assembly of proteins. Macromolecular Bioscience, 3,243-247. 

Ipsen, R., Otte, J., Qvist, K.B. (2001). Molecular self-assembly of partially hydrolysed alpha-lactalbumin resulting in strong gels with a novel microstructure. Journal of Dairy Research, 68, 277-286. 

Pronounced self-assembly of 281 and 282 in nonpolar solvents (e.g., aliphatic and aromatic hydrocarbons) takes place as a result of hydrogen bonding between amide groups to result in the formation of gels above a critical gelation concentration. 

An excellent example that shows the potential of combining various bottom-up techniques is the joint work by Whitesides and Stucky [4]. Hierarchical metallic oxides were produced by combining (i) sol-gel self-assembly of neutral surfactants, (ii) spherical polystyrene templates, and (iii) molds with micrometric cavities (micromolding). Figure 3.12 shows how the described materials are hierarchically organized at several scales ranging from a few nanometers to hundreds of micrometers. 

Percolation is widely observed in chemical systems. It is a process that can describe how small, branched molecules react to form polymers, ultimately leading to an extensive network connected by chemical bonds. Other applications of percolation theory include conductivity, diffusivity, and the critical behavior of sols and gels. In biological systems, the role of the connectivity of different elements is of great importance. Examples include self-assembly of tobacco mosaic virus, actin filaments, and flagella, lymphocyte patch and cap formation, precipitation and agglutination phenomena, and immune system function. 

When the composite-matrix is formed with a polystyrene solution as a dispersion medium, the self-assembly of silica particles is influenced by the adsorption of macromolecules on their surface. During adsorption, both solitary macromolecules and their aggregates transfer simultaneously onto the adsorbent surface. Depending on solution concentration, not only the conformation of adsorbed molecules but also the number and size of macromolecular aggregates in the solution change on adsorption. This leads to the formation of complex-shaped structures, which are linked by a system of nonvalent interactions and consist of polymeric-inorganic blocks[8,14] this is of interest in the preparation of a nanostructured medium (polystyrene-silica gel) as a precomposite for the fabrication of carbon structures in a matrix of silica particles. 

Self-Assembly of PPEs on Surfaces From Jammed Gel Phases to Nanocables... 

Grosso, D., Babonneau, F., Sanchez, C., Soler-Ulia, G., Crepaldi, E. L., Albouy, P. A., Amenitsch, H., Balkenende, A. R. and Brunet-Bruneau, A. (2003). A first insight in the mechanisms involved in the self-assembly of 2D-hexagonal templated Si02 and TiOj mesostructured films during dip-coating. J. Sol-Gel Sci. Technol. 26(1-3), 561-565. 

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