Adjacent functional group effects on the assembly of columnar liquid crystals

Although the impact of individual functional groups on the self-assembly of columnar liquid crystal phases has been widely studied, the effect of varying multiple substituents has received much less attention. Herein, we report a series of dibenzo[a,c]phenazines containing an alcohol or ether adjacent to an electron-withdrawing ester or acid. With one exception, these difunctional mesogens form columnar phases. The phase behavior appeared to be dominated by the electron-withdrawing substituent; transition temperatures were similar to derivatives with these groups in isolation. In most instances, the addition of an electron-donating group ortho to an ester or acid suppressed the melting temperature and elevated the clearing temperature, leading to broader liquid crystal thermal ranges. This effect was more pronounced for derivatives functionalized with longer chain hexyloxy groups. These results suggest a potential strategy for controlling the phase ranges of columnar liquid crystals and achieving room temperature mesophases.

Rapid Tissue Clearing in Pre-warmed Xylene Without Compromising Staining Adequacy and Histoarchitecture

Aims: To determine the adequacy of nucleo-cytoplasmic staining characteristics and preservation of nucleo-cytoplasmic morphology of mouse liver tissue cleared in pre-warmed xylene at predetermined temperatures and durations using haematoxylin and eosin staining procedure. Study Design: Tissues for clearing were first divided into 3 broad experimental groups (A, B and C) based on pre-determined tissue clearing temperature. Each broad group were further divided into 4 sub-groups (A1 to A4, B1 to B4 and C1 to C4) based on duration of tissue clearing. Place and Duration of Study: Department of Medical Laboratory Science, Babcock University, Ilishan-Remo, Nigeria and Department of Oral Pathology, College of Medicine, University of Ibadan, Nigeria. January-June, 2015. Methodology: Tissues assigned to sub-groups A1 to A4 were cleared in pre-warmed xylene at 25°C for 30, 45, 60 and 90 minutes respectively, while tissues assigned to sub-groups B1 to B4 were cleared in pre-warmed xylene at 30°C for 30, 45, 60 and 90 minutes respectively and tissues assigned to sub-groups C1 to C4 were cleared in pre-warmed xylene at 35°C for 30, 45, 60 and 90 minutes respectively. As a consequence of this procedure, adequacy of nucleo-cytoplasmic staining characteristics and preservation of nucleo-cytoplasmic morphology were subsequently determined. Results: Adequacy of nuclear and cytoplasmic staining were both assessed using a 2-point grading scale of 0 being inadequate and 1 being adequate, while preservation of both nuclear and cytoplasmic morphology were also assessed using a 2-point grading scale of 0 being poorly preserved and 1 being well preserved. Adequate nuclear and cytoplasmic staining were observed in tissues cleared in pre-warmed xylene at 25°C for 45 and 60 minutes, at 30°C for 30 and 45 minutes, at 35°C for 30, 45, 60 and 90 minutes. Well preserved nuclear morphology were observed in tissues cleared in pre-warmed xylene at 25°C for 30, 45 and 60 minutes, at 30°C for 30 and 45 minutes and at 35°C for 30, 45, 60 and 90 minutes. However, only tissues cleared at 35°C for 30, 45 and 90 minutes exhibited well preserved cytoplasmic morphology. Conclusion: Adequate nucleo-cytoplasmic staining and well preserved nucleo-cytoplasmic morphology of tissues for histopathologic demonstration may be achieved rapidly by clearing tissues in 35°C pre-warmed xylene for as short as 30 minutes.

Study of variation in thermal width of nematic and induced smectic ordering phase of citric acid (CA) and 4-heptyloxybenzoic acid (7OBA) hydrogen bonded liquid crystal complexes

Hydrogen-bonded liquid crystals (HBLCs) have been derived from nonmesogenic citric acid (CA) and mesogenic 4-heptyloxybenzoic acid (7OBA) yielding a highly ordered smectic C (Sm C) phase along with the new smectic X (Sm X) phase which has been identified as fingerprint-type texture. Optical (polarizing optical microscopy), thermal (differential scanning calorimetry) and structural (Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy) properties are studied. A noteworthy observation is that the intermolecular H-bond (between CA and 7OBA) influences on its melting point and clearing temperature of the HBLCs which exhibits lower value than those of the individual compounds. A typical extended mesophase region has been observed in the present complex while varying the mixture ratio (1:1 to 1:3) than those of individual compounds. The change in the ratio of the mesogenic compound in the mixture alters thermal properties such as enthalpy value and thermal span width in nematic (N) region of HBLC complex. Optical tilt angle measurement of CA+7OBA in Sm C phase has been discussed to identify the molecular position in the mesophase.

Rupture of Polydomain and Monodomain Liquid Crystal Elastomer

Liquid crystal elastomer (LCE) has been recently explored extensively to make diverse active structures and devices. Depending on synthetic process, LCE can be made either polydomain or monodomain when ambient temperature is below isotropic clearing temperature. In the applications, LCE may be subjected to large mechanical stretch or force and break apart. The capability of predicting the rupture of LCE under different loading conditions is crucial for the applications. However, according to our knowledge, there is no report on fracture energy measurement of LCE. In this paper, we measured fracture energy of both monodomain and polydomain LCEs using pure shear test. We found that polydomain LCE has significantly higher fracture energy than monodomain one. We suggest that the increase of fracture energy in polydomain LCE is attributed to stretch-induced polydomain-to-monodomain transition near the crack tip of the material.

Doping liquid crystals with nanoparticles. A computer simulation of the effects of nanoparticle shape

Molecular-scale Monte Carlo simulations of liquid crystal-nanoparticle dispersions show the effect on the orientational order and on the clearing temperature of shape and concentration of the dopant nanoparticles.

Influence of main-chain and molecular weight on the phase behaviors of side-chain liquid crystalline polymers without the spacer

The main-chain and molecular weight affects the clearing temperature of side-chain liquid crystalline polymers based on biphenyl mesogen without the spacer.

Synthesis and Characterization of Bowl-Shaped Liquid Crystals with a Core of Calix[6]arene

A new kind of bowl-shaped liquid crystals were designed and synthesized by esterification. They used a calix[6]arene as central unit and ω- cholesteric alkyl diacid monoester as mesogenic arms. Their chemical structures were confirmed by FTIR and 1HNMR spectra, their mesomorphic properties and phase behavior were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-Ray Diffraction (XRD) measurements. The results showed that the kind of calix[6]arene bowl-shaped liquid crystals N1-N3 exhibited broad range liquid crystalline phases at moderate temperature, and they displayed cholesteric phase focal-conic texture in liquid crystal states. With increasing the flexibility of monomers M1-M3, the melting point and the clearing temperature decreased in the macromolecules.