Selected examples of recently synthesised non-conventional liquid crystals are highlighted. These are cyclic and open chain oligoamides, molecules containing tetrahedral or octahedral central cores, dendrimers, polyhydroxy amphiphiles, taper shaped molecules, liquid crystals with perfluorinated or oligosiloxane segments, rod-coil molecules as well as special types of polycatenar and laterally branched calamitic molecules. Their mesomorphic properties are discussed as a consequence of incompatibility, micro-segregation and space filling. The analysis is based on the general concept of amphiphilicity, which describes any chemical or structural contrast within a molecule, such as hydrophilic/lipophilic, polar/non-polar, hydrocarbon/fluorocarbon, oligosiloxane/hydrocarbon or rigid/flexible. These non-conventional liquid crystals will be regarded as block molecules. Depending on the degree of chemical and structural difference and the size of the different building blocks micro-segregation can occur with formation of lamellar, columnar or spheroidal aggregates which organise to smectic, columnar and cubic mesophases. The striking analogies between the polymorphism of thermotropic and lyotropic liquid crystals and block-copolymers are pointed out.

Non-conventional liquid crystals—the importance of micro-segregation for self-organisation

Angle-dependent optical effects deriving from submicron structures of films and pigments

Patterning nano-objects is an exciting interdisciplinary research area in current materials science, arising from new optical and optoelectronic properties and the need to miniaturize electronic components. Many techniques have been developed for assembling nanoparticles into two- and three-dimensional arrays. Most studies involving liquid crystals as templates have dealt with colloidal particles and nematic and smectic phases. Here, we demonstrate the long-range ordering of nanoparticle assemblies that adopt the helical configuration of the cholesteric liquid crystalline phase. Because we used glass-forming cholesterics, the nanostructures could be examined by transmission electron microscopy. The platinum nanoparticles form periodic ribbons that mimic the well-known 'fingerprint' cholesteric texture. Surprisingly, the nanoparticles do not decorate the original cholesteric texture but create a novel helical structure with a larger helical pitch. By varying the molar fraction of cholesterol-containing mesogen in the liquid crystal host, we show that the distance between the ribbons is directly correlated to the pitch. Therefore this inherent lengthscale becomes a simple control parameter to tune the structuring of nanoparticles. These results demonstrate how such an assembly process could be modulated, providing a versatile route to new materials systems.

Long-range structuring of nanoparticles by mimicry of a cholesteric liquid crystal

Data on the synthesis, structures and properties of ionic, coordination, organometallic and organoelement compounds with liquid-crystal properties are surveyed. The substances examined are new in the chemistry of the liquid-crystal compounds. Their potential applications are described. The bibliography includes 211 references.

http://iopscience.iop.org/article/10.1070/RC1993v062n04ABEH000019/pdf

Metal-containing liquid-crystal phases

With the goal of developing diverse building blocks for nanocomposite materials, we have now learned to synthesize liquid crystalline materials by appending mesogenic groups to cubic silsesquioxane cores (LC cubes) via hydrosilylation of allyloxy functionalized mesogens (4, 5, 8, and 9) with octakis(dimethylsiloxy)octasilsesquioxane (Q8M8H). On average, hydrosilylation leads to cubes with an average of five LC groups attached, which differ from the more “regular”, fully LC-substituted analogues reported previously. Despite the structural irregularity, three out of the four penta-LC-cube derivatives (II−IV) show LC transitions, with a tendency to form SmA. LC behavior was characterized using differential scanning calorimetry, polarized light microscopy, and X-ray diffractometry.

Synthesis and Characterization of Liquid Crystalline Silsesquioxanes

Die vorliegende Erfindung betrifft cyclische Siloxane, welche mindestens eine an ein Siliciumatom gebundene Gruppe der Formel (1) enthalten The present invention relates to cyclic siloxanes, containing at least one silicon atom bonded to a group of the formula (1) worin x eine ganze Zahl im Wert von mindestens 2, vorzugsweise von 2 bis 10, wherein x is an integer having a value of at least 2, preferably from 2 to 10, R" eine chemische Bindung oder einen zweiwertigen Rest der Formel -COO-, -OOC-, -CH 2 -CH 2 -, -CH = CH-, -C=C-, -N = N-, -N = N(O)-, -CH = N-, -N = CH- oder -Si(R) 2 -, wobei die Reste R "is a chemical bond or a divalent radical of the formula -COO-, -OOC-, -CH 2 -CH 2 -, -CH = CH-, -C = C-, -N = N-, -N = N ( O) -, -CH = N-, -N = CH- or -Si (R) 2 -, where the radicals R gleiche oder verschiedene, gegebenenfalls substituierte Kohlenwasserstoffreste mit 1 bis 18 Kohlenstoffatomen sind, R are identical or different, optionally substituted hydrocarbon radicals having 1 to 18 carbon atoms, L jeweils gleiche oder verschiedenen, gegebenenfalls durch mindestens einen Rest Q in 2-, 3-, 5- und/oder 6-Stellung substituierten 1,4-Phenylen- oder 1,4-Cyclohexylenreste, L are identical or different, optionally substituted by at least one radical Q in the 2-, 3-, 5- and / or 6-position substituted 1,4-phenylene or 1,4-cyclohexylene, Q gleiche oder verschiedene Reste, namlich Wasserstoff-, Fluor- oder Chloratome, Cyano-, Methyl- oder Trifluormethylgruppen, Q identical or different radicals, namely hydrogen, fluorine or chlorine atoms, cyano, methyl or trifluoromethyl, A gleiche oder verschiedene zweiwertige Reste der Bedeutung R" oder der Formel -CH 2 -O- oder -O-CH 2 -, -CH 2 -CH 2 -, -N = N-, - N = N(O)-, -CH = N- oder -N = CH-, A identical or different divalent radicals having the meaning R "or of the formula -CH 2 -O- or -O-CH 2 -, -CH 2 -CH 2 -, -N = N-, - N = N (O) -, -CH = N- or -N = CH-, y eine ganze Zahl im Wert von 0 bis 10, vorzugsweise von 0 bis 2, y is an integer having a value from 0 to 10, preferably from 0 to 2 z eine ganze Zahl im Wert von 0 bis 10, vorzugsweise von 0 bis 2, z is an integer having a value from 0 to 10, preferably from 0 to 2 mit der Masgabe, das die Summe y + mindestens 1 betragt, und with the proviso that the sum of y + is at least 1, and T die in der Beschreibung angegebene Bedeutung hat. T has the meaning given in the description.

Cyclosiloxanes with mesogenic side groups

The present invention relates to cyclic siloxanes which have at least one group of formula (1) bonded to a silicon atom -(CH2)x-R"-[-L-A-]y-(L)z-T (1), in which x is an integer having a value of at least 2, preferably having a value of from 2 to 10, R" is a chemical bond or a divalent radical of the formula -COO-, -OOC-, -CH=CH-, -C?C- or -Si(R)2-, where the radical R is the same or different, and is optionally a substituted hydrocarbon radical having from 1 to 18 carbon atoms, L which is the same or different represents the 1,4-phenylene or 1,4-cyclohexylene radicals which are optionally 2-, 3-, 5- and/or 6-substituted by at least one radical Q, Q is the same or different radical selected from hydrogen, fluorine or chlorine atoms or cyano, methyl or trifluoromethyl groups, A is the same or different and represents divalent radicals R" or radicals of the formula -CH2-O-, -O-CH2-, -CH2-CH2-, -N=N-, -N=N(O)-, -CH=N- or -N=CH-, y is an integer having a value of from 0 to 10, preferably from 0 to 2, z is an integer having a value of from 0 to 10, preferably from 0 to 2, with the proviso that the sum y+z is at least 1, and T is a cholesteryl radical or a sub-stituted or unsubstituted hydrocarbon radical having from 1 to 18 carbon atoms, in which the substituents are preferably selected from the group consisting of halogen atoms, cyano groups, nitro groups, hydrocarbonoxy groups having from 1 to 10 carbon atoms and mixtures thereof.

Cyclosiloxanes containing mesogenic side groups

New silylated benzoic acid derivs. are of formulae R'-Q-COO-R'' (I) and R2-OOC-Q-R1 (II): where Q = a gp. of the formula (III) Z = halogen, CN or OH in the 2-, 3-, 5- or 6-position of the benzene ring; n = 0, 1 or 2; R1 = phenyl or cyclohexyl (opt. substd. by 1-8C alkyl or alkoxy), 1-18C alkyl or 1-18C alkoxy, excluding n-octoxy and n-decoxy, which may have halogen and alkylsiallyl substits.; R2 = a gp. of the formula R'''-(Si(Y)2)(CH2)y-R''''-Q-; R'' = R'''-(Si(Y)2)(CH2)y-R''''-; y = 4-18; R''' = 1-8C alkyl, Y-(Si(Y)2O)v- or L(-O-CO)w-Phe-O-; Phe = p-phenylene; v = 1-10; w = 0 or 1; L = cholesteryl; phenyl, opt. substd. by phenyl, halogen, CN and/or 1-4C alkoxy; or, if w = O, L may also = halogen, CN or 1-4C alkoxy; Y and Z = (substd.) hydrocarbyl(oxy) gps. but Z not = n-octyloxy or n-decyloxy gps.; R'''' = an E gp. attached to the -COO- gp. opt. through a phenylene or biphenylene gp.; E = -O-, not attached directly to the O atom of the -COO- gp., or a divalent -(Si(Y)2)z-gp.; R' = halogen, CN, Z or -C6H4-.

Haeberle Norman Dipl Chem Dr

Papers

Cyclosiloxanes with mesogenic side groups

Cyclosiloxanes containing mesogenic side groups

New partly liq. crystalline silylated benzoic acid cpds.