Mesomorphic structures

A liquid crystal compound in more cases Ilian not takes on more than one type of mesomorphic structure as the conditions of temperature or solvent are changed. In thermotropic liquid crystals, transitions between various... 

Lupinacci, D., Frosini, V. and Magagnini, P. L. Mesomorphic structure of a homopolymer of N-(4-biphenyl)acrylamide and of copolymers with 4-biphenylacrylate. Makromol. Chem. Rapid Commun. 1, 671 (1980)... 

Hardy, Gy., Cser, F., Nyitrai, K., Samay, G. and Kallo, A. Investigation of the mesomorphic structure of p-alkoxy-phenyl-p-acryloyloxybenzoate polymers. J. Cryst. Growth, 48, 191 (1980)... 

Schneider, N. S., Desper, C. R. and Beres, J. J. Mesomorphic structure in polyphosphazenes in A. Blumstein, ed. Liquid Crystalline Order in Polymers . Academic Press, New York, NY... 

Figure 8. Schematic of mesomorphous structures in phase E, D, and F in the three-component system sodium octanoate-decanol-water (1)...

Figure 1. Schematic of the mesomorphous structure in a lamellar phase. The different coordinate systems used in the text are outlined laboratory frame (L), director frame (D), and molecular frame (M). 0LD and 0DM are angles between the z axis in laboratory-director systems and director-molecular systems, respectively (13).

Control of Mesomorphic Structure and Properties by External Stimulation 139... 

The work presented in the next section concerns the immobilization of retinoic acid by three polyamino acids poly(-L-lysine), poly(-L-arginine) and poly(-L-histidine). The mesomorphous structure of these complexes, which are prepared as nano-particles, has been examined. Then we will report on the physicochemical characteristics of water-soluble complexes formed between PEO-PLL block copolymers and retinoic acid. The structure in the solid-state and solution are discussed. Further the dissociation of the complex when changing the pH is reported. Finally, the immobilization of retinoic acid by PEI with different molecular weights is presented. 

The immobilization of retinoic acid by branched PEI with different molecular weights (6 102 to 2xl06 g/mol) is described in the following section. The main interest is on the formation of mesomorphous structures, the release of retinoic acid from its complexes and the formation of nanoparticles. 

The study by low-angle X-ray diffraction of AB and ABA block copolymers of styrene and isoprene has allowed Gallot et al.1S9-166) to demonstrate that the existence of mesomorphic structures is a quite general property of block copolymers this property is related to the incompatibility of the macromolecular chains11 and the presence in the molecule of a crystallizable (e.g. poly(ethylene oxide)) block is not the condition that governs the formation of mesomorphic structures. 

Amphiphilic lipopeptides with a hydrophobic paraffinic chain containing from 12 to 18 carbon atoms and a hydrophilic peptidic chain exhibit lyotropic meso-phases and good emulsifying properties. The X-ray diffraction study of the mesophases and of dry lipopeptides showed the existence of three types of mesomorphic structures lamellar, cylindrical hexagonal and body-centred cubic. Two types of polymorphism were also identified one as a function of the length of the peptidic chain and the other as a function of the water content of the mesophases. The emulsifying properties of the lipopeptides in numerous pairs of immiscible liquids such as water/ hydrocarbons and water/base products of the cosmetic industry showed that small amounts of lipopeptides easily give three types of emulsions simple emulsions, miniemulsions and microemulsions. 

LC Polvsurfactants. Micelles and vesicles are forms of mesomorphic structures that have until recently been restricted to the world of small molecules. New studies have resulted in the synthesis of micellar polymers... 

X-ray scattering is a very powerful tool for mesophase identification and can provide a great deal of information it is often the only unequivocal means of phase identification. The experiment is rather simple in principle and relies on the faet that mesomorphic structures are periodic and can therefore diffract a schematic cartoon of the experiment is shown in Figure 2. 

In this review, we will focus on ion- and electron-conductive thermotropic LC polymers and oligomers. A variety of mesomorphic structures has been constructed utilizing non-covalent interactions, which influences ionic and electronic carrier transport processes. 

Compared to block copolymers, there have been relatively fewer examples of using homopolymers for nanofabrication. Nevertheless, some polymers with amphiphilic properties were also used in the fabrication of nanostructures with various metal salts/complexes. For example, polyaniline (PANI) emeraldine base formed self-organized mesomorphic structures when mixed with Zn(DBS)2 by the coordination between Zn2+ and the imine nitrogen atoms on the polymer main chain.100 The resulting supramolecule PANI[Zn(DBS)2]0.5 had a comb-shaped... 

Small-molecule surfactants can give rise to a series of association colloids, including micelles, mesomorphic structures, vesicles, and microemulsions. 

It was observed that a high proportion of template (10%) can be introduced without losing the mesomorphic order [ 199]. Moreover after template extraction, the polymorphism was quite different from that of the non-imprinted material, the variations depending on the structure of the template used and on its concentration [200]. The last point is the manifestation of a significant memory effect of the template, imprinted inside the mesomorphic structure. It arises from the interactions between template and the other parts of the network which can induce conformational constraints inside the networks during cross-linking. It occurs even though the amount of crosslinker is low (5%). Moreover, this point constitutes a means for the direct study of the imprint left in the network by the template. 

The two most common lyotropic mesophases are designated neat and middle 26), Both are members of the family of mesomorphic structures derived by Hermann 12). The neat phase structure is generally accepted as being made up of parallel, equidistant sheets of double molecules separated by solvent 4, 21, 22). Neat phase is optically anisotropic and flows easily. Figure 11 indicates the structure 22) and a cross-sectional view of one of the layers. 

Liquid crystalline products are formed in aqueous soap systems at high concentrations. The existence of different mesophases in such systems was observed by McBain (17,18). Toward the end of the 1950 s Luzzati et al. (.11,1/+, 15,16) discovered by x-ray diffraction various mesomorphous structures in these two-component systems and regarded this as a proof that they contained different mesophases, which, however, they did not separate. 

Schneider NS, Desper CR, Beres JJ Mesomorphic structures in polyphosphazenes. Blumstein A (ed) Liquid Crystrfline order in Polymers. Academic Press, New York NY 1978, p. 299-325... 

Carbohydrates are natural compounds which have hydroxyl groups capable of hydrogen bonding. Amphiphilic sugars with long alkyl chains form layered or columnar mesomorphic structures due to microphase segregation, as shown in Fig. 1 (Type A-I-c) [17-20, 149-153]. Alkylglucosides are representative... 

Ordered (and partially ordered) arrays of metal sites and complexes enable the cooperation of their special electronic, magnetic and optical properties. Such materials have long been sought for their expected physical properties and applications in optics, electrooptics, superconductivity and sensors. The ordering can be by various mechanisms, such as adsorption on surfaces, intercalation into layered structures, formation of mesomorphic structures and liquid crystals, and adoption of specific crystal-packing motifs, all of which are supramolecular phenomena. Organic liquid crystals and their applications are now commonplace, and in recent years the incorporation of metal atoms into mesogenic molecules has demonstrated the occurrence of similar metallo-mesophases [20]. 

The fact that uniform thin films of LC, many microns thick may be produced, as in LCD, give credit to that concept. Barchan has presented some microscopic photos which indicate that the effect of wear, during the running-in of parts in movement, was to produce a layer having a mesomorphic structure. 

A new crystalline form for [NP(OCH2CFj)2]n has been detected leading to a scheme for annealing including two types of mesomorphic structures being proposed.The phase diagram for the [NP(OCH2CFj)2]n/solvent (EtOAc or DMSO) has been constructed. The thermodynamics of the trifluoroethoxy polymer-solvent (acetone, EtOAc) system have been evaluated and... 

Finally, it is possible that side chains in polymers with very long side chains occur in mesomorphous structures, whereas the main chain is amorphous below the glass transition temperature, and behaves like a normal liquid above it. This type of behavior is observed when the movements of the main and side chains are decoupled by flexible spacer groups joining them together. An example of this is a poly(methacrylate) with the monomeric unit ... 

But with polymers, other types of bonding can occur. In certain solvents, and at higher concentrations, poly(7-benzyl-L-glutamates) do not form end-group associated ringlike entities but form laterally arranged bundlelike structures. Mesomorphous structures such as formed by certain stiff low-molar-mass molecules are produced (see also Section 5.5). 

---