Formation of Columnar and Lamellar Lyotropic Mesophases by Facial Amphiphiles with Protic and Lipophilic Solvents

Abstract

The influence of water, formamide, and n-dodecane on the liquid crystalline properties of several rodlike 4,4′′-bis(decyloxy)-p-terphenyl derivatives incorporating nonionic hydrophilic groups in a central position was investigated by polarizing microscopy and X-ray scattering. Up to three different rectangular columnar mesophases have been found for molecules with large hydrophilic groups with increasing concentrations of protic solvents. Remarkably only one lattice parameter changes in dependence on the mesophase type and the number of solvent molecules coordinated to the polar groups. We propose that the columns represent ribbons consisting of the rigid terphenyl units, separated laterally by the segregated regions of the hydrophilic groups, whereby the three different columnar mesophases should result from an anisotropic swelling of the polar regions on addition of solvents. Lipophilic solvents (dodecane) destabilize the columnar phases and replace them by smectic layer structures (S A phases).

Heptazine: an Electron‐Deficient Fluorescent Core for Discotic Liquid Crystals

“…Hence, generation of the Sm and Col h phases is attributed to the formation of hydrogen‐bonded ribbon and disc‐like (with no hydrogen bonding) self‐assembled structures. Furthermore, this type of lamellar (Sm)‐to‐hexagonal transformation is also seen in some lyotropic systems …”

Self‐Assembly at Different Length Scales: Polyphilic Star‐Branched Liquid Crystals and Miktoarm Star Copolymers

“…The two‐phase separation is observed down to low concentrations of the bolaamphiphile, although above about 70% solvent concentration, the hexagonal columnar nature of the bolaamphiphile‐rich region is lost. Such simulations should help explain some of the existing163 and future experimental data on binary T‐shaped amphiphile–solvent systems.…”

“…T‐ and X‐shaped amphiphiles usually comprise elongated π‐conjugated aromatics (oligothiophenes,35 oligo(phenylene ethinylenes),54, 174 which are of interest for application as fluorescent, luminescent,175 and semiconducting organic materials,176 capable of self‐assembly into well defined superstructures. They can organize into bulk phases, into aqueous lyotropic LC phases,163 or into fibers and ribbons in a range of other solvents as demonstrated for rod–coil molecules with hydrophilic lateral groups177 (Section 4). Alternatively they can self‐assemble on surfaces, as illustrated in Section 6.3 102, 103.…”

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“…In this respect, ordered structures with liquid-crystalline (LC) properties are of special interest, because they are reversibly formed under thermodynamic equilibrium conditions and combine order and mobility on molecular, supramolecular, and macroscopic levels. [3,4] Examples are bolaamphiphilic biphenyl derivatives carrying a long lateral alkyl chain. [1] In conventional LC materials rod-or disklike anisometric rigid units, which provide long-range orientational order, are connected to flexible alkyl chains, which are largely responsible for positional order and mobility.…”

“…[3,4] Examples are bolaamphiphilic biphenyl derivatives carrying a long lateral alkyl chain. [3,4] Examples are bolaamphiphilic biphenyl derivatives carrying a long lateral alkyl chain.…”