Mesomorphic Characteristics of Induced Chiral Nematic Phase of[Smectic LCP,PS(4BC/DM)/Nematic LC,E7/Chiral Dopant,CB-15]-Ternary Composite System

The phase transition behavior and aggregating states of [smectic LCP, PS(4BC/DM)/nematic LC, E7/chiral dopant, CB 15] ternary composite system were investigated on the basis of differential scanning calorimetry (DSC) measurement, polarizing optical microscopy (POM) observation and wide angle X ray diffraction (WAXD) patterns. It was demonstrated that if the weight ratio of the chiral dopant was fixed as 4.8wt%, an induced chiral nematic (N *) phase existed in the ternary system when PS(4BC/DM) ratio was below 47.6 wt%. Moreover, smectic like long range ordering appeared in the induced N * phase in a certain temperature range just above the smectic A(S A) N * phase transition when PS(4BC/DM) ratio was between 19.1wt% and 47.6wt%.

Optically Ambidextrous Reflection and Luminescence in Self-Organized Left-Handed Chiral Nematic Cellulose Nanocrystal Films

Defect-embedded chiral nematic organizations are attractive due to their light manipulation ability that is crucial for photonic applications.Self-assembly of cellulose nanocrystals(CNC)forms a left-handed chiral nematic structure,which makes simultaneous reflection of left-handed circularly polarized(LCP)and right-handed circularly polarized(RCP)light a challenging task.Herein,we present unprecedented evidence that self-organized CNC films with left-handed helical sense and photonic bandgaps(PBG)display ambidextrous CP light reflection with peak reflectivity up to 68%and transform spontaneous photoluminescence to RCP and LCP luminescence with respective|glum|values up to 0.796 and 0.120.These ambidextrous chiroptical properties originate from a left-handed chiral nematic structure consisting of a nematic-like phase,acting as a half-wave retarder,sandwiched between two PBG layers.The latter are spontaneously intercalated into the left-handed helicoids by rapid gelation of CNC colloidal suspensions.We demonstrate that the ambidextrous chiroptical properties can be manipulated by changes in evaporation temperatures,concentrations,and characteristics of CNC suspensions.We showcase the potential of defect-embedded chiral nematic CNC films for the sustainable and scalable development of anti-counterfeiting optical labels.

Helical twisting properties of new chiral dopants with double (S)-1,2-propanediol units for nematic liquid crystals

A novel series of chiral dopants synthesized from(S)-1,2-propanediol and mesogenic carboxylic acids were characterized by FT-IR,~1H NMR,elemental analysis and their helical twisting properties were investigated by doping the chiral dopants into a nematic liquid crystal host(SLC-1717).The results show that,the helical pitch of N~*-LC mixture exhibited a terminal alkyl chain length dependence and the molecular twisting power β also exhibited a temperature dependence(increasing β with increasing temperature).

Tuning the helical twisting power of nematic liquid crystals induced by chiral 1,2-propanediol derivatives using varied substituents

In this study,a novel series of chiral 1,2-propanediol derivatives with different electron-donating and electron-withdrawing groups were synthesized and characterized by FT-IR and ~1H NMR.The helical twisting properties of all the chiral dopants were investigated by doping the chiral dopants into a nematic liquid crystal host（SLC-1717）.The results indicate that the donor-acceptor electron effect have a prominent influence on helical twisting property of the chiral nematic phase induced by the chiral dopants. Introducing electron-withdrawing groups into the terminal ends of chiral 1,2-propanediol can decrease the absolute values of the helical twisting power.In addition,the helix inversion temperatures of the induced chiral nematic phase are variational with the change of terminal groups.

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.

Low and Wide Phase Transition Temperature Dimesogenic Compounds Consisting of a Cholesteryl and 4-（trans-4-n-Alkylcyclohexyl）phenoxy Mesogens

Unsymmetrical dimesogenic compounds with cholesteryl and 4-（trans-4-n-alkylcyclohexyl）phenoxy parts were synthesized by condensation of cholester-3-yl 6-bromohexanoate with appropriate 4-（trans-4-n-alkylcyclohexyl）- phenols. Structures and thermal phase behaviour of these dimesogenic compounds have been confirmed by IR, IH NMR, elemental analysis, DSC, polarity microscopy and XRD measurements. Their thermal phase behaviour was significantly different with that of other cholesterol-based dimesogens while they exhibited low and wide phase transition temperature.