The synthesis, chemical characterization and liquid crystalline behavior of a series of seven poly(amidoamine) (PAMAM) codendrimers are described. These compounds were obtained by grafting two types of terminal promesogenic units, that carry either one or two decyloxy chains, in various proportions onto the third generation of PAMAM dendrimer. The average number of promesogenic units was determined by using an original interpretation of the NMR spectra. X-ray diffraction studies show that these compounds exhibit lamellar and/or columnar mesophases. The type of mesophase is determined by the number of each kind of promesogenic units present in a given codendrimer and by the temperature. The evolution of the supramolecular organization of the different molecules is explained as a function of the number of alkoxy chains present around the dendritic core and compared to the models developed for the homodendrimers totally functionalized by promesogenic units with either one or two decyloxy chains.

The preparation of optically active poly(isocyanide)s derived from chiral promesogenic monomers is reported. Remarkably, the stereogenic carbon atom in the monomer is able to pass its chiral “information” to the growing polymer backbone which is at least 14 atoms (approximately 16 Å) remote from it. The sense of helical induction in these conformationally rigid polymers is compared to the helical sense of the cholesteric phases, as well as to the helical senses of chiral smectic C phases, induced by the monomers in nematic and smectic C phases, respectively. Both relate to the odd−even rules for chiral sense changes in liquid crystalline phases. The role of noncovalent interactions in the polymerization has been proven by performing the reactions at various concentrations and in different solventsthe chiral induction from monomer to polymer is greatest in most concentrated reactions and in solvents with a balance between high dipolarity−polarizability and low hydrogen bond accepting and cavitational terms, as determined by an LSER analysis.

FT-IR and 2D correlation spectroscopy were employed to study the microstructural changes ocurring during phase transitions of a liquid crystal poly(amidoamine) codendrimer (PAMAM (L1)16(L2)16) generation 3, functionalized on the terminal groups by one-chain promesogenic calamitic units (4-(4'-decyloxybenzoyloxy)salicylaldehyde (L1)) and two-chain promesogenic calamitic units (4-(3',4'-didecyloxybenzoyloxy)salicylaldehyde (L2)). Spectral modifications associated with molecular conformation rearangements allowing for molecular shape change on going from a liquid−crystalline organization to another were found. The transition temperatures were calculated, and they are in good agreement with the DSC data. Spectral analysis gives evidence of the LC phase transitions and to an additional transition associated with the existence of conformers. Various types of hydrogen bonding have been established.

The synthesis and physical characterization (thermotropic and ferroelectric behavior) of eight ortho-palladated dimers [Pd2(ji-C1)2L*2] is reported. They are derived from chiral imines HL* (HL* = />-R1OC6H,(CH=NQH4-OR* 12-p, with R1, R2, or both equal to (R)or (5)-l-methylheptyl). The chiral imines, which contain one or two stereogenic centers, are not liquid crystals themselves. However, the dimeric complexes, which contain two or four stereogenic centers in their structure, exhibit both SmA and SmC* mesophases and enable the first comparative structure-activity study on metal-containing ferroelectric liquid crystals to be made. The ferroelectric properties obtained are better when there are chiral chains on the ortho-metalated aromatic rings, because the fixed conformation of these rings diminishes the chiral tail freedom, thus allowing a better coupling of molecular dipoles. The complexes with two chiral tails show important Psmax values in the range 44-131 nC*cm-2. The complex with four chiral chains (R1 = R2 = (R)-methylheptyl) is the first such compound ever reported containing four stereogenic centers; furthermore, it shows a remarkably high Psmax value of 206 nC-cnr2, the highest value reported so far for a metal-containing liquid crystal.

The present report undertakes a challenge of general interest in supramolecular chemistry: the achievement of helical organizations with controlled structure. To achieve this target we considered the possibility of inducing supramolecular chirality using molecules that were designed to organize into columnar mesophases. The use of oxazoline-derived ligands and metal coordination served as tools to prepare molecules with a phasmidic-like structure, which show columnar organization in the liquid crystalline state. To ensure the formation of chiral mesophases, these complexes bear stereogenic centers in the rigid coordination environment of the metal. X-ray and circular dichroism experiments have revealed that chirality transfer does indeed take place from the chiral molecule to the columnar liquid crystal organization. This chiral columnar organization appears as a helix consisting of stacks of molecules that rotate with respect to one another along the column while maintaining their mean planes parallel to each other. In fact, it has been concluded that packing of these polycatenar molecules must be more efficient upon rotation of a molecule with respect to the adjacent one along the column. Furthermore, the same type of helical supraorganization has been found to be present in the mesophase of the racemic mixture and the mixture of diastereomers prepared from the racemic ligand. In this case, segregation of the optical isomers is proposed to occur to give rise to both types of helix (right-handed and left-handed).

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The synthesis, chemical characterization, and liquid crystalline behavior of two new series of poly(propyleneimine) (DAB) codendrimers are described. Both series were obtained by grafting onto the fourth-generation dendrimer (DAB−(NH2)32) various proportions of two types of promesogenic units:  one of them laterally attached and the other terminally attached. Both series differ in the terminally attached promesogenic unit, being chiral in series 1 and achiral in series 2. X-ray diffraction studies show that these compounds exhibit nematic or lamellar mesophases. For intermediate proportions, the smectic C mesophase, which was not exhibited by the homodendrimers, appears. Thus, the evolution between a nematic and an orthogonal lamellar mesophase occurs through a tilted mesophase. The chiral centers in series 1 permit the appearance of chiral nematic (N*) and chiral smectic C (SmC*) mesophases, which are studied. Deuterium NMR experiments reveal that the nematic formed by one codendrimer is uniaxial and not the anticipated biaxial nematic.

The constitutional marriage between a classical thermotropic discotic molecule and carbohydrate‐based amphiphiles (e.g., see Figure) is shown to result in hybrid compounds, where, for example, a triphenylene unit serves as the central core from which oligomethyleneoxy chains terminated with sugar residues radiate, which have interesting liquid crystal properties.