Synthesis and Phase Behavior Studies of Two New Chiral Liquid Crystals of Schiff Base——The Influence of Intramolecular Hydrogen Bond on the Phase Behavior

Two new chiral liquid crystals of schiff-base type have been synthesized.This series of compounds contain α-chloro acidic ester chain prepared from commercially available L-valine.Both of the compounds exhibit tilted smectic phases;their phase transitions were studied using DSC and polarized optical microscopy;the influence of intramolecular hydrogen bonds on the phase behavior was studied as well.

Chiral liquid crystals based on pillararene and supramolecular self-assembly-induced chirality amplification

Macrocyclic liquid crystals combine the unique property of liquid crystals and excellent supramolecular assembly ability of macrocyclic compounds.It is a significant challenge to make rational use of the advantages of macrocyclic compounds to prepare new macrocyclic mesogens.Pillararenes,a type of macrocycles with rigid pillar-shaped frameworks and easy-tofunctionalize property,are excellent building blocks to fabricate liquid crystal materials.However,the site-selective modification property of pillararene has been rarely exploited to tailor liquid crystal behaviors.Previously reported pillararene-based liquid crystal systems are almost prepared by per-functionalized pillararenes.Herein,we report the regulation of chiral liquid crystal behaviors by different derivatization of pillararene.Lyotropic and thermotropic liquid crystals with different chirality were obtained by self-assembly of pillararene with different numbers of cholesterol groups.The bridge between thermotropic liquid crystal and lyotropic liquid crystal based on pillararene is built.In addition,the chirality of the mesogens can be amplified through supramolecular self-assembly driven by noncovalent interactions.Based on the different liquid crystal behaviors,the optical signal of the pillararene-based chiral liquid crystals was used to fabricate an information encryption system.This work provides a simple strategy to regulate liquid crystal behaviors via pillararene-based mesogens and realizes information encryption through the combination of different types of liquid crystals.

Field-induced phase transitions in chiral smectic liquid crystals studied by the constant current method

In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the（E, T） phase diagram of the studied product can be obtained.In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.

SYNTHESIS OF DIAZA CROWN ETHER CHIRAL LIQUID CRYSTAL

A chiral liquid crystal crown ether containing diaza-18-crown-6 was synthesized with the help of CPK atomic model and in the meantime a nonchiral liquid crystal crown ether of alike structure was also synthesized for comparison, indicating that only the former was asymmetric. The present work represents the first attempt of the investigation in chiral liquid crystal crown ether, thus providing basis for further research into problems as such.

STUDY ON MAGNETIC FIELD-INDUCED 0RIENTATI0N OF A CHIRAL SIDE-CHAIN LIQUID CRYSTAL POLYACRYLATE USING INFRARED DICHROISM

Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate(P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown thatthe magnetic alignment takes place over the entire temperature range between its meltingpoint and clearing point and the orientation level is strongly temperature-dependent, thedevelopment with time of the magnetic orieatation follows an exponeotial-type relation,and the smectic phase state influences the thermal relaxation process in the absence of themagnetic field.

Synthesis and Properties of Some Novel Liquid Crystals: Chiral 4′-(4-alkoxy-2,3-difluorobenzoyloxy)-4-biphenyl Carboxylates

A series of laterally o difluoro substituted chiral liquid crystals, S(+) 2 methyl 1 butyl 4′ [(4 alkoxyl 2, 3 difluoro)benzoyloxy] 4 biphenyl carboxylates, have been synthesized using a simple process. Their molecular structures were determined using IR, NMR, MS, and EA. Their transition temperatures were measured using DSC(Differential Scanning Calorimeter). All of the compounds exhibit the N * phase and their clearing points vary regularly with the increase in the number of terminal group carbons. The influence of lateral fluoro substituents on the properties was also investigated.

Upconverting and downshifting circularly polarized luminescence in a superstructural helix

The modulation of circularly polarized luminescence(CPL) has become an increasingly prominent area of research. In this study,we propose a unique “one-excitation-to-three-emissions” CPL system through the co-assembly of an upconversion system,incorporating one sensitizer(Pt(II) mesotetraphenyl tetrabenzoporphyrine, Pt TPBP) and two annihilators(R/S-DPA and R/SBDP) within liquid crystals. The chiral nature of the annihilators induces a transformation of the nematic liquid crystal into chiral nematic liquid crystals(N*LC), establishing an excellent chiral matrix. Upon the incorporation of the sensitizer Pt TPBP and subsequent excitation at 635 nm, the system demonstrates two independent triplet–triplet annihilation photon upconversion(TTA-UC) with the emission in blue and yellow, aided by thermally activated triplet–triplet energy transfer(TTET). This is accompanied by the simultaneous generation of upconverting circularly polarized luminescence(UC-CPL) and downshifting near-infrared circularly polarized luminescence(DS-CPL) originating from the residual luminescence of Pt TPBP. Remarkably,fine-tuning the ratio between the two annihilators allows the TTA-UC system to exhibit multicolor CPL emission with an amplified luminescence dissymmetry factor(glum, reaching up to 0.6). Our study unveils a previously unreported “one-excitation-to-three-emissions” system and provides a versatile strategy for modulating CPL emissions, surpassing conventional methodologies.