Mesomorphic material

Various covalent and non-covalent approaches for the incorporation of fullerene building blocks into liquid crystalline mesomorphic materials have been developed [35]. Lyotropic mesophases (buckysomes) were obtained upon dissolving globular amphiphilic fullerene dendrimers in water [145]. 

In general, the photoluminescent properties of molecular assemblies depend on their assembled structures [21], Therefore, controlling the structures of molecular assemblies with external stimuli leads to the development of stimuli-responsive luminescent materials. Recently, some photoluminescent materials showing stimuli-responsive properties have been reported [11, 21-34]. However, the number of stimuli-responsive photoluminescent liquid crystals is still limited [11, 21, 28-34], Here we focus on mechano- and thermochromic photoluminescent mesomorphic materials. As the first topic, we focus on LC materials that change their photoluminescent colors by mechanical and/or thermal stimuli. We then describe another... 

Isotropic polymeric systems as well as particulate systems might also show time-dependent moduli after cessation of flow. As long as the shear does not induce structure growth, the moduli always increase with time after flow. An increase of the moduli upon cessation of flow has also been reported for thermotropic PLCs (18) as well as for lyotropic solutions of hydroxy propyl cellulose in water (19) and in acetic add (20). The possibility of changing in either direction seems to be characteristic for mesomorphic materials. A fundamental theory for describing complex moduli does not exist for such materials. The present results, combined with the information about optical relaxation mentioned above, could be explained on the basis of reorientation of domains or defects. The different domains orient differently, even randomly, at rest whereas flow causes an overall orientation. Depending on the molecular interaction the flow could then cause an increase or decrease in moduli as recently suggested by Larson (21). 

Supramolecular helical mesomorphic materials with different proportions of 2,4,6-triarylamino 1,3,5-triazine and (/ )-3-methyladipic acid have been described <05JA458>. 

NMR investigations of mesomorphic materials were initiated by Spence, Moses, and Jain, who observed that the NMR signal from the nematic phase of p-azoxyanisole (PAA) had a line width intermediate between that of a solid and a liquid 32). In later papers 13, 31) they discuss the structure found in the NMR spectrum of this compound and the deu-terated methoxy analog, ascribing the structure to dipole-dipole interactions. In the last of these papers 13) they discuss the temperature dependence of the separation of the triplet structure in PAA. The investigation of the nematic state of PAA and higher homologs was next taken up... 

Display devices can also be constructed using the field effect, the cholesteric memory effect and the cholesteric-nematic phase change effect [259, 262]. The recognition of the useful electro-optical properties of liquid crystals has stimulated efforts in synthesis of new mesomorphic materials. Today, more than 6000 compounds are available but an ideal liquid crystal is still elusive. 

A detailed understanding of the influence of the structure, charge, and counterion on the thermal and mesomorphic properties requires the preparation and further study of ferrocenium materials. The above-reported results prove that liquid-crystalline switches should, in principle, be available by the incorporation of ferrocene/ferrocenium into mesomorphic materials. 

It is commonly accepted that one of the first publications on metallomesogens was by Vorlander, " who reported a number of mercury-based mesomorphic materials,such as the symmetrical Schiff-base complexes of diarylmercury(ll) (160a R = H, NO2, Me, OMe, OEt) and the related, asymmetric, monoaryl mercury chloride complexes 160b. Both series of organometallic compounds exhibited high-temperature smectic phases. 

Liquid crystals are unique molecular materials because of their anisotropic nature and molecular dynamics [1-4]. Over the last three decades, these materials have been developed as advanced materials for electrooptical applications such as display devices. Liquid crystals also have close relationships to biomolecular systems [5]. Cell membranes form dynamic and anisotropic molecular states, which possess liquid-crystalline behavior. Recently, liquid-crystalline complexes of DNAs and liposomes have been considered as potential systems for gene therapy [6]. The design of liquid crystals by using a variety of structures and interactions may lead to wider applicability of mesomorphic materials. 

Antonietti M, Conrad J, Thiinemann A. 1994. Polyelectrolyte surfactant complexes a new type of solid, mesomorphous material. Macromolecules 27 6007 6011. 

Two other di-substituted species were examined by Ohta and coworkers. The tetra alkoxyl-containing 5,15-bis(3,4-didodecyloxyphenyl)porphyrin displayed a discotic lamellar mesophase with a melting point of 60.4 °C and clearing point of 200.7 °C (Figure 23). Four crystalline phases and one undetermined mesophase were delineated for 5,15-bis(4-didodecyloxybiphenyl)porphyrin between initial crystalline phase transitions at 40.1 °C to melting to the mesomorphic material at 430.9 °C (Figure 24). The material was observed to decompose at 450.5 °C. ... 

More systematic work on bipyridines was pubUshed simultaneously by Bruce and Rowe and by Douce et a/. Both groups looked at 5,5 -disubstituted-2,2 -bipyridines Douce et al. looked at monosubstituted derivatives (Figure 91a) while Bruce and Rowe concentrated on diesters (Figure 91b). The bipyridines (a) showed SmA and SmB phases, while the diesters (b) showed N, SmA, and SmC phases, with a particularly wide SmC range. However, metal complexation to either system was rather unsuccessful in generating mesomorphic materials. ... 

Related tris(bipyridine) complexes of Rh were not so stable and so in order to generate mesomorphic materials, it was necessary to use terpyridines which bind more strongly ((316) M = Ru (m = l), Rh (m = 3), X = C1, PFg). In this case, mesomorphic materials were obtained for both Ru and Rh although in some cases it was necessary to use ethylene glycol as the... 

Regular solution theory has been successfully applied to the calculation of binary phase diagrams of mesomorphic materials. Correlation of the parameters required by the theory with simple physical properties of the mixture s components, may offer an empirical way to predict the phase diagrams for mixtures involving members of homologous series. 

There is considerable interest in the properties of new mesomorphic materials, which are composed of molecules with novel architectures. These include rod-coil molecules [1], polyphilic molecules [2, 3], block-copolymers [4] and dendritic molecules [5]. In many of these systems microphase separation can be used to build new materials containing structures that are ordered on the nanoscale. Examples include the formation of spheres or rods within a uniform matrix of dififerent chemical... 

This article explores the possibilities of using simulation to predict the formation of complex structures for two relatively simple classes of mesomorphic materials liquid crystal polymers and liquid crystal dendrimers (figure 1). In the first section of the article we discuss briefly some of the models available currently to the simulator. We then review some of our preliminary work in this area, developing hybrid models composed of a mixture of anisotropic and isotropic sites and using them to study liquid crystal polymers and dendrimers. We point also to some of the problems still faced in this area and some of the likely future developments designed to overcome them. 

---