Bicontinuous phases liquid crystals

Cr Cub, Cubv d E G HT Iso Isore l LamN LaniSm/col Lamsm/dis LC LT M N/N Rp Rh Rsi SmA Crystalline solid Spheroidic (micellar) cubic phase Bicontinuous cubic phase Layer periodicity Crystalline E phase Glassy state High temperature phase Isotropic liquid Re-entrant isotropic phase Molecular length Laminated nematic phase Correlated laminated smectic phase Non-correlated laminated smectic phase Liquid crystal/Liquid crystalline Low temperature phase Unknown mesophase Nematic phase/Chiral nematic Phase Perfluoroalkyl chain Alkyl chain Carbosilane chain Smectic A phase (nontilted smectic phase)... 

While there have been efforts to polymerize other surfactant mesophases and metastable phases, bicontinuous cubic phases have only very recently been the subject of polymerization work. Through the use of polymerizable surfactants, and aqueous monomers, in particular acrylamide, polymerization reactions have been performed in vesicles (4-8). surfactant foams ), inverted micellar solutions (10). hexagonal phase liquid crystals (111, and bicontinuous microemulsions (121. In the latter two cases rearrangement of the microstructure occured during polymerization, which in the case of bicontinuous microemulsions seems inevitable b ause microemulsions are of low viscosity and continually rearranging on the timescale of microseconds due to thermal disruption (131. In contrast, bicontinuous cubic phases are extremely viscous in genei, and although the components display self-diffusion rates comparable to those... 

All the authors report a decrease in the nano-emulsion droplet size when the surfactant concentration increases, since there is more surfactant available to stabilize more interfaces, and therefore smaller droplets can be obtained. In general, it is observed in the phase diagrams that the region with phases with planar structure, that precedes the region where nano-emulsions are formed, extends to higher water concentrations when the surfactant/oil ratio increases, because when more surfactant is present, it can dissolve more water inside the bicontinuous or liquid crystal structure (as an example, see Eigure 21.6). 

Figure 2a shows a schematic phase diagram for lyotropic liquid crystals. This figure shows the formation of micelles, cubic phases, bicontinuous cubic phases, and lamellar phases as the concentration of surfactant increases. Also shown in this figure is a schematic diagram of an ordered bicontinuous cubic phase (Fig. 2b). Another interesting example in...

This chapter focuses on the fixation of lyotropic liquid crystalline phases by the polymerization of one (or more) component(s) following equilibration of the phase. The primary emphasis will be on the polymerization of bicontinuous cubic phases, a particular class of liquid crystals which exhibit simultaneous continuity of hydrophilic — usually aqueous — and hydrophobic — typically hydrocarbon — components, a property known as bicontinuity (1), together with cubic crystallographic symmetry (2). The potential technological impact of such a process lies in the fact that after polymerization of one component to form a continuous polymeric matrix, removal of the other component creates a microporous material with a highly-branched, monodisperse, triply-periodic porespace (3). 

Siegel DP. The relationship between bicontinuous inverted cubic phases and membrane fusion. In Bicontinuous Liquid Crystals. Lynch ML, Spicer PT, eds. 2005. Taylor Francis Group, CRC Press, Boca Raton, FL. pp. 59-98. 

Holmes MC, Leaver MS (2006) Intermediate phases. In Lynch ML, Spicer PT (eds) Bicontinuous liquid crystals. Surfactant science series, vol 127, Taylor and Francis, Boca Raton, pp 15-40... 

Plots that show the conditions (temperature, composition) at which various phases exist in a system are known as phase diagrams. Figure 3-4 is one type of phase diagram showing the effects of temperature and surfactant concentration on the various solution phases of an aqueous surfactant system. The order of the various liquid crystal phases with increase in surfactarfl concentration—micellar => hexagonal => bicontinuous cubic => lamellar—is found in many surfactant systems. 

Mesophases can be locked into a polymer network by making use of polymerizable LCs [59]. These molecules contain moieties such as acryloyl, diacety-lenic, and diene. Self-organization and in situ photopolymerization under UV irradiation will provide ordered nanostmctured polymers maintaining the stable LC order over a wide temperature range. A number of thermotropic liquid crystalline phases, including the nematic and smectic mesophases, have been successfully applied to synthesize polymer networks. Polymerization of reactive lyotropic liquid crystals also have been employed for preparation of nanoporous polymeric materials [58, 60]. For the constmction of nanoporous membranes, lyotropics hexagonal or columnar, lamellar or smectic, and bicontinuous cubic phases have been used, polymerized, and utilized demonstrated in a variety of applications (Fig. 2.11). 

Liquid crystals (LCs) combine order and mobility on a molecular level and are important both in material and life science [1-9]. Different liquid crystalline phases have provided new methods for the design of supramolecular materials [10-13]. Nematic phases have found widely commercial applications as displays for computers and telecommunications [14], lamellar, coltrmnar, micellar, and bicontinuous cubic phases and even more complicated new phases have also found wide applications as advanced materials [12, 15-17]. 

Figure 3. Sketch of the principal phase behavior of amphiphilic compounds. Usual amphiphiles are represented by a vertical line in this scheme they exhibit only one type of mesophase. Extreme geometries of one of their molecular parts or the addition of solvents (linear alkanes or water) may lead to a deviation from the vertical orientation of that line, thus, amphiphilic compounds in such situations may form various types of liquid crystal phases T = temperature, SmB phase (rotator phase), Cubjn and Cub(,i = cubic discontinuous or cubic bicontinu-ous phases, respectively, Col, i = columnar hexagonal phase, Iso = isotropic phase.

According to Fig. 3, classical thermotropic smectic phases of amphotropic liquid crystals are (SmA ), colunmar hexagonal (Col ), bicontinuous cubic (Cub, i), or discontinuous cubic (Cubjis) [169]. All these meso-phases include a disclination surface between the hydrophilic and the lipophilic parts of the unordered molecules. This surface can be uncurved (SmA), curved in one direction (columnar), curved in two directions with the same sign (discontinuous cubic), or curved in two directions with opposite sign (bicontinuous cubic). 

Figure 2 Phase diagram of a binary amphiphile-water mixture obtained from a Ginzburg- Landau model with a vector order parameter for the amphiphile orientation (50,51]. The phases L and L2 are micellar liquids, is a lamellar phase. H and H denote hexagonal and inverse hexagonal phases, respectively, I is an fee crystal of spherical micelles, and V is a simple cubic bicontinuous phase. (From Ref. 51.)...

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