Structures of chiral smectic-<i>C</i>mesophases revealed by polarization-analyzed resonant x-ray scattering

Mach, P.; Pindak, R.; Levelut, A. M.; Barois, P.; Nguyen, H. T.; Baltes, Hubert; Hird, Michael; Toyne, Kenneth J.; Seed, Alexander J.; Goodby, John W.; Huang, C. C.; Furenlid, Lars R.

doi:10.1103/physreve.60.6793

Cited by 157 publications

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“…While the SmC a * features a helical structure analogous to that of the SmC* phase, it is nonetheless a distinct mesophase. Mach et al 3 reported the final structure of the SmC a * phase using resonance x-ray diffraction and found an extremely short incommensurate helical pitch of just a few layers (Figure 1). Since the SmC a * commonly persists only over rather narrow temperature intervals (i.e., a few C), broadening of the SmC a * phase temperature range in a series of mixtures would facilitate a much wider range of experimental studies.…”

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confidence: 99%

Polymer stabilization of the smectic C-alpha* liquid crystal phase—Over tenfold thermal stabilization by confining networks of photo-polymerized reactive mesogens

Labeeb

Gleeson

Hegmann

2015

Applied Physics Letters

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The smectic C*-alpha (SmC a *) phase is one of the sub-phases of ferroelectric liquid crystals that has drawn much interest due to its electro-optical properties and ultrafast switching. Generally observed above the ferroelectric SmC* phase in temperature, the SmC a * commonly shows only very narrow phase temperature range of a few degree Celsius. To broaden the SmC a * phase, polymer stabilization was investigated for thermal phase stabilization. Two different reactive monomers were tested in three mixtures, and all three broadened the temperature range of the SmC a * phase from 3 C to 39 C. The current reversal method was used to determine the phase existence versus temperature. Moreover, the texture and network structure was studied by polarized optical microscopy and scanning electron microscopy, with the latter revealing the confinement of the smectic layer structure within the porous polymer network. V C 2015 AIP Publishing LLC.

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confidence: 99%

Polymer stabilization of the smectic C-alpha* liquid crystal phase—Over tenfold thermal stabilization by confining networks of photo-polymerized reactive mesogens

Labeeb

Gleeson

Hegmann

2015

Applied Physics Letters

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“…Chirality also allows polarizations to form within the layers, causing many phases to exhibit ferroelectric (F) and antiferroelectric (AF) behaviors. In contrast, the INHP found in the Sm-C phase has been measured to be as small as five molecular layers [2]. Recent theoretical advances [3] have predicted the existence of a new form of the Sm-C phase exhibiting INHP structures of less than four layers, whereas only commensurate repeat units of four layers or less have been observed.…”

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confidence: 97%

“…In a different scenario, the n.n.n. AF interactions become greater with decreasing temperature, and the INHP decreases [2,6]. If the n.n.…”

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confidence: 99%

“…To distinguish these two Sm-C phases, we will use Sm-C 1 (Sm-C 2 ) for the phase with INHP > 4 layers (INHP < 4 layers). Typically, measuring such a small length scale in orientationally ordered systems is limited to resonant x-ray scattering (RXS) [2] because the nanoscale structures are well beyond the diffraction limit in usual optical methods. By studying one unique compound, we establish the technique of using differential optical reflectivity (DOR) to determine the INHP.…”

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Optical Characterization of a Nanoscale Incommensurate Pitch in a New Liquid-Crystal Phase

et al. 2003

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As a remarkable orientationally ordered soft-condensed matter system, the smectic-C phase exhibits an incommensurate nanoscale helical pitch of more than four smectic layers. Recent theoretical advances predict the existence of a new phase showing a helical pitch of less than four smectic layers (<16 nm). By applying a novel optical technique to the study of freestanding films with increments in thickness of one smectic layer, we have measured the size of this pitch using 633 nm HeNe laser light. Our results confirm the existence of the newly predicted phase in one unique compound.

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“…The fundamental reason for this is illustrated in Fig. 4 [8]. The free standing smectic film is prepared in a two-stage oven.…”

Section: Antiferroelectric Smectic Liquid Crystals and Related Sub-phmentioning

confidence: 99%

Application of X-ray resonant diffraction to structural studies of liquid crystals

Barois

Gleeson

Huang

et al. 2012

Eur. Phys. J. Spec. Top.

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Abstract. Liquid crystals are soft materials that combine the fluidity of disordered liquids and the long range orientational or positional order of crystalline solids along one or two directions of space. X-ray scattering is widely and generally successfully used to investigate and characterize the microscopic structure of most liquid crystals. In many cases however, the Bragg reflections are forbidden by special symmetries of the unit cell and the low dimensional structure of the liquid crystalline phases are out of reach of conventional X-ray experiments. We show in this paper that this problem can be overcome by resonant scattering of X-rays as it reveals the anisotropy of the tensor structure factor. We review various examples in which the restored forbidden reflections reveal unambiguously the hidden structure of liquid crystalline phases. Moreover, we show that in some cases, a fine analysis of the polarization of the Bragg reflections enables one to discriminate between different structural models. These studies solved long standing questions about biaxial liquid crystal structures and provided new insights into physical phenomena such as supercritical behaviour or commensurate-incommensurate transitions.

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Structures of chiral smectic-Cmesophases revealed by polarization-analyzed resonant x-ray scattering

Cited by 157 publications

References 33 publications

Polymer stabilization of the smectic C-alpha* liquid crystal phase—Over tenfold thermal stabilization by confining networks of photo-polymerized reactive mesogens

Polymer stabilization of the smectic C-alpha* liquid crystal phase—Over tenfold thermal stabilization by confining networks of photo-polymerized reactive mesogens

Optical Characterization of a Nanoscale Incommensurate Pitch in a New Liquid-Crystal Phase

Application of X-ray resonant diffraction to structural studies of liquid crystals

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