Kento Okoshi

First observation of a smectic A–cholesteric phase transition in a thermotropic liquid crystal consisting of a rigid-rod helical polysilane

A smectic A–cholesteric phase transition for a rigid-rod helical polymer, poly[n-decyl-(S)-2-methylbutylsilane] (PD2MBS), with a narrow molecular weight distribution, has been observed for the first time. Polarizing optical microscopy showed that the fan-shaped texture of the smectic A phase turned into the characteristic planar texture of the cholesteric phase upon heating. The positive CD band, which corresponds to the reflection band of the cholesteric phase, gradually decreased in intensity within a range 30°C below the transition temperature on cooling, while the peak maximum shifted towards shorter wavelengths. It was concluded that the system has a very wide temperature region over which the cholesteric–smectic A phase transition occurs and in which the cholesteric pitch varies with temperature.

Smectic Liquid Crystal Observed in Thermotropic System of Rigid-Rod Poly(γ-octadecyl L-glutamate)

We investigated the thermotropic phase behavior of rigid-rod poly(γ-octadecyl L-glutamate) (PG18) with an average molecular weight Mw=36,000. Two polymers with narrow molecular weight distributions (Mw/Mn), PG18-A with Mw/Mn=1.12 and PG18-B with Mw/Mn=1.05, were prepared by gel permeation chromatography (GPC) fractionation. Both were found to form a smectic A phase by means of microscopic observations of the focal conic texture and by the small-angle X-ray method. The smectic A phase of PG18-A was transformed into a cholesteric phase at approximately 140–170°C while that of PG18-B stably existed in the entire thermotropic temperature range from 60°C to 220°C (decomposition temperature). This dependence of smectic stability on the molecular weight polydispersity qualitatively corresponds to the theoretical prediction based on the excluded volume effect.

Anomalous thermotropic liquid crystalline phase behaviour in poly[n-decyl-(RS)-2-methylbutylsilane]s with narrow molecular weight distributions

The thermotropic liquid crystalline (LC) phase behaviour of a rod-like polymer, poly[n-decyl-(RS)-2-methylbutylsilane], with narrow molecular weight distributions, was studied by optical microscopic observations and X-ray diffraction measurements. This polymer exhibited a very unusual LC phase sequence of smectic A (SmA)–reentrant isotropic (Ire)–nematic (N). Upon heating, the Ire phase prevails in the SmA phase, and then the N phase goes over into the Ire phase, while upon cooling, the Ire phase enantiotropically grows in the N phase. Moreover, the orientation of the polymer and smectic layer reflection simultaneously disappeared during the transition to the Ire phase, so that the anchoring transition to the pseudo-isotropic homeotropic alignment can be ruled out. To the best of our knowledge, this is the first example of a rod-like LC polymer exhibiting a reentrant isotropic phase without a drastic conformational change, although the exact molecular origin of the Ire phase is still unclear.

Small-Angle X-Ray Analysis of Smectic a Cholesteric Liquid Crystal Phase Transition in Rigid-Rod Helical Polysilane

The smectic A Cholesteric liquid crystal phase transition of rigid-rod helical polysilane was studied by means of synchrotron radiation small-angle X-ray scattering (SR-SAXS). The information on the smectic trans-layer electron density distribution was clarified by fitting the model of electron density distribution to the diffraction data. Each of the layers was approximated by the boxlike function to introduce the molecular form factor of the polymer. The distribution of the molecular center of gravity within the layers due to the thermal motion was taken into consideration by convolution with the Gaussian function. The elucidated smectic layer structure was not like the conventional structure with their ends packed into the interlayer space. The layers with bumpy surfaces interdigitate in a key-and-keyhole manner to pack the molecules with different lengths into layers due to their finite molecular weight distribution.

27.4L: Late‐News Paper: A New Mode LCD with Intrinsic Continuous Grayscale Memory Using Ferroelectric Liquid Crystalline Polymer

A new mode LCD has been developed by rubbing methods with a ferroelectric liquid crystalline polymer (FLCP). It has good balanced characteristics such as a fast response time of less than 1 ms, a high contrast ratio at the same level as in-plane switching (IPS) mode, bi-stability, continuous grayscale, and high durability against external shock. In addition, it displays intrinsic continuous grayscale memory. This new mode LCD has significant potential as a substitute for IPS or vertically aligned (VA) mode LCDs, and also as an electronic paper by which video content can be displayed.