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The results of an investigation, which shows that the chirality of SmC phase derives from surface interactions, are described. No evidence for the presence of a ferroelectric polarization in the SmC phase of 4'-octyloxyphenyl-4-octyloxybenzoate, a necessary result of chiral symmetry of the phase, could be found, even though very sensitive tests for such polarization are applied.

We have investigated the various morphological changes of helical nanofilament (HNF; B4) phases in multiscale nanochannels made of porous anodic aluminum oxide (AAO) film. Single or multihelical structures could be manipulated depending on the AAO pore size and the higher-temperature phase of each molecule. Furthermore, the nanostructures of HNFs affected by the chemical affinity between the molecule and surface were drastically controlled in surface-modified nanochannels. These well-controlled hierarchical helical structures that have multidimensions can be a promising tool for the manipulation of chiral pores or the nonlinear optical applications.

Azobenzene-based molecules forming a self-assembled monolayer (SAM) tethered to a glass surface are highly photosensitive and readily reorient liquid crystals in contact with them when illuminated with polarized actinic light. We probe the coupling of such monolayers to nematic liquid crystal in a hybrid cell by studying the dynamics of liquid crystal reorientation in response to local orientational changes of the monolayer induced by a focused actinic laser with a rotating polarization. The steady increase in the azimuth of the mean molecular orientation of the SAM around the laser beam locally reorients the nematic, winding up an extended set of nested rings of splay-bend nematic director reorientation until the cumulative elastic torque exceeds that of the surface coupling within the beam, after which the nematic director starts to slip. Quantitative analyses of the ring dynamics allow measurements of the anchoring strength of the azo-SAM and its interaction with the nematic liquid crystal.

We report a bent-core liquid crystal (LC) compound exhibiting two fluid smectic phases in which two-dimensional, polar, orthorhombic layers order into three-dimensional ferroelectric states. The lower-temperature phase has a uniform polarization field which responds in an analog fashion to applied electric field. The higher-temperature phase is a new smectic state with periodic undulation of the polarization, structurally modulated layers, and a bistable response to applied electric field which originates in the periodically splay-modulated bulk of the LC rather than by surface stabilization at the cell boundaries.

The growth of helical filaments in the B4 liquid-crystal phase was investigated in mixtures of the bent-core and calamitic mesogens NOBOW and 8CB. Freezing-point depression led to nucleation of the NOBOW B4 phase directly from the isotropic phase in the mixtures, forming large left- and right-handed chiral domains that were easily observed in the microscope. We show that these domains are composed of homochiral helical filaments formed in a nucleation and growth process that starts from a nucleus of arbitrary chirality and continues with chirality-preserving growth of the filaments. A model that accounts for the observed local homochirality and phase coherence of the branched filaments is proposed. This model will help in providing a better understanding of the nature of the B4 phase and controlling its growth and morphology for applications, such as the use of the helical nanophase as a nanoheterogeneous medium.

Self-assembled monolayers (SAMs) were prepared from solutions with different proportions of a photoactive, azobenzene-based, silanized derivative of disperse red one (dDR1), and octyltriethoxysilane (OTE), a shorter, nonphotoactive molecule. The in-plane photoinduced orientational ordering of the resulting two component monolayers was monitored via precision measurement of in-plane birefringence using a dedicated high-extinction polarimeter. Measurements of contact angle, absorption, and birefringence show that introduction of OTE into the dDR1 deposition solution produces a continuous reduction of the surface density of dDR1 in the SAM, enabling the study of photowriting and relaxation dynamics in monolayers ranging from 100% dDR1 to samples where the dDR1 coverage is about 35%. The orientational dynamics depend strongly on the areal density of dDR1. As the fractional area of dDR1 is reduced, the rates of photowriting, photoerasing, and thermal relaxation increase, and the local orientational confinement of the molecules becomes more heterogeneous.

Mixtures of 8CB (a calamitic mesogen) and NOBOW (P-9-O-PIMB, a bent-core mesogen) have been investigated using differential scanning calorimetry, nuclear magnetic resonance spectroscopy, and freeze fracture transmission electron microscopy. On cooling the isotropic mixture, the NOBOW component phase separates, forming a dilute, random network of helical nanofilaments in the B4 phase with isotropic 8CB material filling the interstitial volume. At lower temperature, but still far above the bulk isotropic-nematic transition of pure 8CB, a significant fraction of the 8CB becomes prealigned on the filament surfaces. We propose that this pretransitional ordering is induced by short-range interactions of the polar 8CB molecules with the NOBOW filaments, leading to the formation of an adsorbed film of orientationally frozen 8CB around each filament.

We describe a new type of optically controlled liquid crystal alignment layer that demonstrates unprecedented performance. It consists of an aminoazobenzene-type material with a very simple molecular structure, which is derived from methyl red by a one-step synthesis. We have devised a method of forming covalently attached monolayers of this material on glass by an amine-assisted condensation reaction involving the triethoxysilane end of the molecule. A nematic liquid crystal (LC) cell made with the monolayer and a rubbed polymer layer was switched from a uniform state to a twisted state with a polarized 450 nm control beam having a dose of 5.5 mJ/cm(2). This is equivalent to an average of only one absorbed photon per azobenzene group. Through atomic force microscopy, absorption spectroscopy, spectroscopic ellipsometry, and second harmonic generation experiments, we have confirmed that layers of this type are smooth and uniform with a surface coverage consistent with a monolayer and that the azobenzene groups are tilted, on average, 55 degrees with respect to the surface normal. These characteristics lead to a large interaction energy density between the layer and LC. The monolayer's rapid response in developing anisotropy in this property can be attributed to a large absorption cross section, as well as the favorable tilt angle, which allows for sufficient photoisomerization free volume in a dense layer.