Organogel network

The junction zones of CAQ organogel networks are lyotropic microdomains that vary from hexagonal in decane to more compact, lamellar-like ordering in 1-octanol 94. Schlieren optical textures confirm the inhomogeneity of the orientation of the threadlike structures (Fig. 16), and CD spectra resemble those of neat CAQ solid, cooled from its mesophase. However, the solid morph obtained from solvent crystallization is packed differently from the gel strands 114. ... 

Huang X, Raghavan SR, Terech P, Weiss RG. Distinct kinetic pathways generate organogel networks with contrasting fractality and thixotropic properties. J Am Chem Soc. 128(47) (2006) 15341-15352. 

Ray S, Das AK, Banerjee A. Smart oligopeptide gels In situ formation and stabilization of gold and silver nanoparticles within supramolecular organogel networks. Chem Commun (Camb). (26) (2006) 2816-2818. 

Figure 3.1 Schematic of small-molecular-weight organogelator networks, (a) Permanent crystalline linkage giving rise to solid fiber network, (b) Transient structural network of fluid fiber matrix formed by reverse micelles which enlarge cylindrically into an entanglement of dynamic lattice that immobilizes solvent to form a gel.

Figure 3.2 Schematic of polymeric organogelator network. Polymers self-assemble through non-covalent bonds and cross-links to form a three-dimensional network that holds organic solvent within and hence leads to gelation of the solvent.

Das AK, Bose PP, Drew MGB, Baneijee A. The role of protecting groups in the formation of organogels through a nano-fibrillar network formed by self-assembling terminally protected tripeptides. Tetrahedron 2007 63 7432-7442. 

FIG. 1 Cartoon representation of (lie four types of junction /ones in the networks of low-mass organogels l. (I) Crystalline (2) lyotropic (3) transient entanglements and seisskm/recombination processes as in "living giant micelles" (4) long-range interactions. From Ref. 120.)... 

For a viscoelastic solid (like an organogel), any rheological description should give a constant finite elastic modulus and infinite viscosity at zero frequency or long times. The situation is somewhat comparable to that of a cross-linked network [2. The equilibrium shear modulus for small deformations is proportional... 

Because of the complexity of the processes involved and the various methods of measuring them, phase diagrams of organogels can be envisioned by different theoretical approaches. In one option, network formation can be considered according to a spinodal decomposition mechanism. Briefly, the spinodal curve in a phase diagram represents the limit of metastability defined by the second derivative of the free energy with respect to concentration Important features of such a mechanism are (1) the phase separation in solute-rich and solute-poor... 

Figure 37 Electron micrographs of self-assembled fibres, (c) Electron micrograph showing the dense network of long helical fibres in a steroid/cyclohexane organogel, (d) Preparation of single fibres, demonstrating their helical superstructure [425]. (e) Cyclic oligopeptides, selfassembling into nanofibres [435,436], Reproduced with permission of The Royal Society of Chemistry and The American Chemical Society. Parts (c) and (d) 1986 American Chemical Society...

Hamilton has published organogelation studies on the family of bis-ureas shown in Fig. 18 [65]. These compounds gel solvents and mixtures of solvents at 5 °C. The crystal structure of compound 30 confirms the extensive formation of one-dimensional hydrogen-bonding networks by both urea groups. The urea hydrogen-bonding distances are within the expected range NH - - CO, 2.18, 2.23 A. 

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