Liquid Crystalline Properties Research Articles

Aroylhydrazone appended cinnamate based calamitic liquid crystal:Effect of alkoxy side chain and position of terminal pyridine core on mesomorphic properties

Eight newly synthesized liquid crystalline materials containing aroylhydrazone and cinnamate linking units, connected by three phenyl rings and flexible alkoxy side chains, were designed and synthesized. The confirmation of their structures was characterized by using FT-IR, 1H NMR, and 13C NMR, and elemental analysis. The phase behavior of these materials was investigated using crossed polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction techniques. Additionally, their thermal stability was assessed using thermo gravimetric analysis. In the two series of materials studied, those with shorter alkoxy side chains exhibited a smectic C phase along with a nematic mesophase, while compounds with longer alkoxy chains showed only smectic A type mesogenic behavior. The structure-property relationship of these aroylhydrazone-based homologous series was discussed to understand the impact of side alkoxy tail length and the position of the terminal isonicotinic/nicotinic hydrazide core on the liquid crystalline properties. All four materials displayed a wide temperature range of mesophases and exhibited high thermal stability. To gain further insights into their mesomorphic properties, we employed density functional theory to conduct theoretical calculations on various structural and chemical parameters of these materials, including reactivity, energy bad gap, and dipole moment.

Effect of internal energy depletion on active nematic texture and dynamics

ABSTRACTActive nematics represent a relatively new class of materials with liquid crystalline properties that rely on an energy source to maintain their structure and dynamics. In this paper, we focus on the well-known microtubule-kinesin-based active nematic, powered by chemical energy as ATP (Adenosine triphosphate), and report on how ATP depletion impacts active nematic defect dynamics and texture. Using fluorescence microscope video imaging, we measure the time averaged mean defect separations and root mean square velocities of the active flows as a function of time. We also characterise textural changes and the growth of void space in the network after ATP depletion using an image binarization technique.

Dimeric cyanopyridine with methylenebis(oxy)-based linker: A tactic to luminescent molecules exhibiting room temperature liquid crystalline property

The first example of luminescent, room temperature liquid crystalline molecules with methylenebis(oxy)-based linker, namely, 2,2'-(methylenebis(oxy))bis(4,6-bis(4-(alkyloxy)phenyl)nicotinonitrile) has been reported in the present work. The designed molecules have been synthesized using dichloromethane (DCM) as the reagent to obtain the methylenebis(oxy)-based linkers. The structural characterizations of the synthesized molecules were carried out by using ATR-IR, 1H NMR, 13C NMR, MALDI-TOF, and elemental analysis. Photophysical property examination of the molecules in the solution state indicated the deep blue emissive nature of the molecules with a relative quantum yield of about 27–32%. Further, electrochemical studies were performed on the molecules by using cyclic voltammetry and determined their underlying HOMO and LUMO energy levels as well as the associated band gaps. In contrast, DFT analysis was performed on the representative compound bearing methoxy groups in place of flexible alkoxy chains to obtain optimized geometry and further studied the distribution of electron density in its HOMO and LUMO energy levels. Furthermore, the liquid crystalline property examination revealed that all the molecules exhibited a smectic C phase upon cooling from isotropic temperature. Finally, the present study paves the way for the synthesis of dendrimer-type liquid crystals with methylenebis(oxy)-based linkers.

Induction and Stabilization of Columnar Mesophases in Fluorinated Polycyclic Aromatic Hydrocarbons by Arene-Perfluoroarene Interactions.

The straightforward synthesis of several Fluorinated Polycyclic Aromatic Hydrocarbons by the efficient, transition-metal-free, arene fluorine nucleophilic substitution reaction is described, and the full investigation of their liquid crystalline and optical properties reported. The key precursors for this study, i. e. 2,2'-dilithio-4,4',5,5'-tetraalkoxy-1,1'-biphenyl derivatives, were obtained in two steps from the highly selective Scholl oxidative homo-coupling of 3,4-dialkoxy-1-bromobenzene, followed by quantitative double-lithiation. In situ room temperature nucleophilic annulation with either perfluorobenzene or perfluoronaphthalene leads to 1,2,3,4-tetrafluoro-6,7,10,11-tetraalkxoytriphenylenes and 9,10,11,12,13,14-hexafluoro-2,3,6,7-tetraalkoxybenzo[f]tetraphenes, respectively, in good yields. Exploiting the same strategy, subsequent double annulations resulted in the formation of 9,18-difluoro-2,3,6,7,11,12,15,16-octa(alkoxy)tribenzo[f,k,m]tetraphenes and 9,10,19,20-tetrafluoro-2,3,6,7,12,13,16,17-octakis(hexyloxy)tetrabenzo[a,c,j,l]tetracenes, respectively. Despite the presence of only four alkoxy chains, the polar "Janus" mesogens display a columnar hexagonal mesophase over broad temperature ranges, with higher mesophase stability than the archetypical 2,3,6,7,10,11-hexa(alkoxy)triphenylenes and their hydrogenated counterparts. The improvement or induction of mesomorphism is attributed to efficient antiparallel face-to-face π-stacking driven by the establishment of non-covalent perfluoroarene-arene intermolecular interactions. The larger lipophilic discotic π-extended compounds also exhibit columnar mesomorphism, over similar temperature ranges and stability than their hydrogenated homologs. Finally, these fluorinated molecules form stringy gels in various solvents, and show interesting solvatochromic emission properties in solution as well as strong emission in thin films and gels.

Effect of Surface Functionality on the Rheological and Self-Assembly Properties of Chitin and Chitosan Nanocrystals and Use in Biopolymer Films.

Chitin nanocrystals (ChNCs) are unique to all other bio-derived nanomaterials in one aspect: the inherent presence of a nitrogen moiety. By tuning the chemical functionality of this nanomaterial, and thus its charge and hydrogen bonding capacity, one can heavily impact its macroscopic properties such as its rheological and self-assembly characteristics. In this study, two types of ChNCs are made using acid hydrolysis (AH-ChNCs) and oxidative (OX-ChNCs) pathways, unto which deacetylation using a solvent-free procedure is utilized to create chitosan nanocrystals (ChsNCs) of varying degree of deacetylation (DDA). These nanocrystals were then studied for their rheological behavior and liquid crystalline ordering. It was found that with both deacetylation and carboxylation of ChNCs, viscosity continually increased with increasing concentrations from 2 to 8 wt %, contrary to AH-ChNC dispersions in the same range. Interestingly, increasing the amine content of ChNCs was not proportional to the storage modulus, where a peak saturation of amines provided the most stiffness. Conversely, while the introduction of carboxylation increased the elastic modulus of OX-ChNCs by an order of magnitude from that of AH-ChNCs, it was decreased by increasing DDA. Deacetylation and carboxylation both inhibited the formation of a chiral nematic phase. Finally, these series of nanocrystals were incorporated into biodegradable pectin-alginate films as a physical reinforcement, which showed increased tensile strength and Young's modulus values for the films incorporated with ChsNCs. Overall, this study is the first to investigate how surface functionalization of chitin-derived nanocrystals can affect their rheological and liquid crystalline properties and how it augments pectin/alginate films as a physical reinforcement nanofiller.

Game of Crowns: Na+ Is Coming! Red NIR-Emissive Hybrid Liquid Crystals Containing Discotic Crown Ethers and Na2Mo6X8iCl6 (Xi = Cl or Br).

Molecular or supramolecular materials that can self-organize into columns such as discotic liquid crystals are of interest for several applications in the field of optoelectronics. We show in this work that red near-infrared (NIR)-emissive metal cluster compounds of general formula Na2Mo6X8iCl6 (Xi = Cl or Br) can be readily complexed with discotic liquid crystals containing a crown ether. Three cavity sizes have been tested with crown ethers bearing 4, 5, or 6 oxygen atoms. In all cases, 1:1 complexes were formed, thanks to the well-known supramolecular interactions existing between the Na+ cations of the metal cluster salt and the crown ether derivatives. All obtained hybrids are homogeneous, emit in the red NIR region, and show liquid crystalline properties on a wider temperature range than their precursors. Charge transport properties have been investigated by using a space charge limited current device. Obtained results demonstrate that metal cluster compounds can enhance the charge carrier mobility by 5 orders of magnitude compared to the native discotic organic ligands. Considering that the presented organic crown ether derivatives are not the best candidates to design optoelectronic devices because of their inherently low conductivity, but that similar compounds were developed to design proton conductive porous framework, our results open promising perspectives for the use of metal cluster compounds in devices dedicated to such a field.

Effects of Tetrafluorocyclohexa-1,3-Diene Ring Position on Photoluminescence and Liquid-Crystalline Properties of Tricyclic π-Conjugated Molecules

Tetrafluorocyclohexa-1,3-diene ring-containing tricyclic π-conjugated molecules are promising negative-dielectric-anisotropy guest species for vertical-alignment-type liquid-crystalline (LC) displays. Building on our previous work reporting the excellent photoluminescence (PL) properties of tricyclic π-conjugated molecules with central tetrafluorocyclohexa-1,3-diene rings, we herein synthesized four analogous molecules with terminal tetrafluorocyclohexa-1,3-diene rings from commercially available precursors and investigated the effects of substituent type and diene ring position on PL and LC properties using microscopic and spectroscopic methods. One of the prepared molecules exhibited a relatively planar molecular structure and formed herringbone-type aggregates via π/F and CH/π interactions instead of forming stacked aggregates via π/π stacking interactions, thus exhibiting relatively strong PL in solution and crystalline states. Moreover, the PL color of this compound depended on the electronic character of its terminal substituents along the long molecular axis. Of the four prepared species, two featured terminal ethyl groups and formed one or more LC phases. The PL properties of these phases indicated that the related phase transition induced changes in the aggregate structure, PL wavelength, and PL color. Our results expand the applicability of CF2CF2 moiety-containing tricyclic compounds as functional molecules for the fabrication of next-generation PL, LC, and PL-LC materials.

Fabrication of elliptically constructed liquid crystalline elastomeric scaffolds for 3D artificial tissues

Inspired by the orientation and the fibrous structure of human muscle tissues, we fabricated preconstructed porous liquid crystalline (LC) scaffolds through a two-step polymerization and salt leaching method. A novel strategy combining the aligning properties of LCs and the ease of processing of elastomers for the preparation of elliptical scaffolds for muscle cell culture was proposed in this research. Different from the other types of scaffolds, our biocompatible LC scaffold that can be implanted into the human body using a supporting unit to improve the mechanical properties compared with those of natural muscle. To evaluate the synthesized scaffolds, in vitro experiments using normal human dermal fibroblast (NHDF) cells and smooth muscle cells from rats were carried out, and the sample cells were cultured on each sample scaffold. Based on the results of long-term culture of NHDF cells on the LC scaffolds, it can be confirmed that all three kinds of LC scaffolds have good biocompatibility and provide enough space for cell growth. The addition of gelatin can significantly enhance the biocompatibility of the synthesized scaffolds. Evaluation of scaffold morphologies on cell growth indicates that the molecular arrangement on the scaffolds can induce the growth direction of smooth muscle cells to a certain extent, thereby increasing the formation of highly ordered arrangement tissues. The population doubling time of NHDF cells on the different scaffolds suggest that gelatin can improve the attachment and growth of cells. Investigation of cell viability on LC scaffolds shows that the original LC scaffolds already possess excellent biocompatibility. Additionally, the average cell viability of smooth muscle cells was above 90%, showing that the LC scaffolds in this research are suitable for application in muscle tissue engineering. Based on the results, the gelatin-coated scaffolds are more conducive to the growth of cells in this research and provide promising candidates for tissue engineering in biomedical fields and research fields.

Synthesis, mesomorphic and fluorescent properties of 1,3,4-oxadiazoles/thiadiazoles with a terminal 3-fluoro-4-cyanophenyl group

A series of new liquid crystalline 1,3,4-oxa/thiadiazoles with a terminal 3-fluoro-4-cyanophenyloxy group were synthesized, and their structures were characterized by nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS). The liquid crystal properties were studied by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). All of the 1,3,4-oxadizoles exhibited only Nematic mesophase, while the 1,3,4-thiadiazole analogues displayed Smectic A (SmA) and Smectic C (SmC) over a wide temperature range. The fluorescent properties were investigated using ultraviolet–visible spectrophotometer (UV–Vis) and fluorescence spectrometer. The solutions of all final compounds in CH2Cl2 individually displayed one absorption band with λabs-max values at 319–340 nm, and exhibited an intense emission with λem-max values at 432–448 nm, and the photoluminescence quantum yields reached 0.52–0.66. The effects of the heterocyclic structural units, the terminal alkoxy chain length and the lateral fluorine atom on liquid crystalline and fluorescent properties were comparatively discussed.

Thermotropic Colloidal Liquid‐Crystalline Hydroxyapatite Nanorod Hybrids Containing a Forklike Mesogen

AbstractWe here report the development of new thermotropic colloidal liquid‐crystalline (LC) organic/inorganic hybrids consisting of a hydroxyapatite (HAp)/poly(acrylic acid) (PAA) nanorod and a dendritic forklike mesogen. Complexation of the HAp/PAA nanorod covered with negatively charged PAA and a cationic forklike mesogen through electrostatic interactions and cation metathesis results in the surface modification of the HAp/PAA nanorod with the forklike mesogen. While the HAp/PAA nanorod forms a lyotropic colloidal LC phase in the aqueous dispersion, the HAp/PAA nanorod modified with the forklike mesogen exhibits thermotropic colloidal LC phases in the solvent‐free states. The biomineral‐based organic/inorganic colloidal liquid crystals exhibiting thermotropic LC properties have potential for the development of new stimuli‐responsive sustainable materials.

Liquid Crystalline Magneto-Optically Active Peralkylated Azacoronene.

Organic Faraday rotators have gained significant attention in recent years as a promising alternative to traditional inorganic magneto-optical (MO) materials as a result of their lower cost, superior mechanical properties, and potential for large-scale deployment. This interest is peaked by the fact that a number of high symmetry, rigid, strongly optically absorbing organic chromophores display Verdet constants an order of magnitude higher than commercial inorganic Faraday rotators. Critical to the development of new generations of organic materials is the ability to organize them in optimal structures for optical coupling/measurements. We report herein the synthesis of a dodecyl-substituted hexapyrrolohexaazacoronene (C12-HPHAC) displaying discotic liquid crystalline (LC) properties and large Faraday rotation. Thin films with a redox mixed C12-HPHAC/C12-HPHAC+2 composition display a discotic columnar LC phase, are stable to air and moisture in the solid and solution states, and achieve a maximum Verdet constant of 3.36 × 105 deg T-1 m-1 at 700 nm. This result is consistent with Serber's model of magnetic circular birefringence and displays one of the largest reported Verdet constants for organic materials in the UV-Vis range. The LC phase aligns the molecules and leads to gains in Verdet constants of up to 105% through the favorable orientation of the molecules' magnetic and electric transition dipole moments with respect to the applied magnetic field.

Pd(II)-complexes of telluro-substituted Schiff base ligands: Effect of the pendant alkyl group on Suzuki and Heck coupling through in situ generated palladium nanoparticles

Two telluro-substituted Schiff bases L1/L2 having different pendant carbon chains (−Me in L1 and − C10H21 in L2) and their corresponding square planar Pd(II)-complexes (1/2) have been synthesized and their structural characterization has been carried out using multinuclear NMR and elemental analysis. The ligand L2 showed a Smectic liquid crystalline phase and melts at 81 °C into isotropic liquid whereas L1 and complexes (1/2) did not show any liquid crystalline property. The square planar Pd(II)-complexes (1/2) have been formed through the coordination of ligands (L1/L2) respectively in mono-anionic tridentate mode (Te,N,O−) and the fourth coordination sphere at the palladium center is occupied with chloride ion. Both complexes 1/2 (1 to 2 mol%) have beenexamined as a catalyst for Suzuki and Heck coupling reactions and their activity depends significantly on the length pendant alkyl chain. The results obtained from Hg-/PPh3-poisoning and three phase test on Suzuki-Miyaura coupling indicate the participation of both homogeneous as well as heterogeneous palladium species protected with the ligand or its fragment.

Investigation of luminescent and liquid crystalline properties of the supramolecular hydrogen bonded complexes formed from non-mesogenic pyridine derivatives and lauric acid

Hydrogen bonds are the best non-covalent interactions for building supramolecular structures. Nowadays, hydrogen bonded supramolecular liquid crystals are quickly evolving into a versatile, simple, and affordable method for new smart materials. Therefore, through intermolecular hydrogen bond interactions, a homologous series of supramolecular mesogenic systems are prepared in the present study. The non-mesogenic hydrogen bond acceptors i.e. 2-(4-alkoxyphenyl)-5-(pyridin-4-yl)-1,3,4-oxadiazoles (OXn) are synthesized, the structures are confirmed using various techniques (1H NMR, 13C NMR, ESI-MS, and elemental analysis) and their photophysical properties are studied in the solid state as well as in solution state. Moreover, the DFT study indicated the planar structure with greater intramolecular charge transfer between donors and acceptors. In addition, these molecules (OXn) are made to form a hydrogen bond with the non-mesogenic fatty acid i.e. Lauric acid (LA). The formation of the hydrogen bonds in the prepared supramolecular complex (OXn/LA) is confirmed by using the ATR-IR analysis. Further, red shifted solid state emission spectra are noted for the complexes (OXn/LA) compared to the parent molecules (OXn). The mesogenic properties of the prepared OXn/LA complexes are studied via differential scanning calorimetry, polarized optical microscopy, and X-ray diffractometry. It was found that the complexes OX-8/LA and OX-10/LA exhibit monotropic SmA mesophase, however, the remaining complexes are non-mesogenic in nature.

The influence of the ring system with mono/diester and imine links, and terminal unsaturated carbon chains on mesomorphism and their quantum-mechanical study

ABSTRACT Five homologous series of low molar mass liquid crystals containing mono/diester and imine-linked cores with terminal unsaturated carbon chains and/or a carboxylic group were synthesised. They were characterised with IR, UV and 1H-NMR spectroscopies. Liquid crystalline properties of all the derivatives were studied by polarised optical microscopy and their mesophase transition enthalpies and entropy changes measured by DSC. The 4-((4-n-alkoxybenzoyl) oxy) benzoic acids (n OPBA) exhibit enantiotropic smectic A and nematic mesophases, while all the 4-allyl-2-methoxyphenyl 4-n-alkoxybenzoates (n OBEg) and 4-allyl-2-methoxyphenyl (E)-3-(4-n-alkoxyphenyl) acrylates (n OCEg) do not show any liquid crystalline properties. Intermediate members of the 4-allyl-2-methoxyphenyl (E)-4-((4-n-alkoxybenzylidene) amino) benzoate series (n OPMABEg) and the 4-((4-allyl-2-methoxyphenoxy) carbonyl) phenyl 4-n-alkoxybenzoate series (n OB2Eg) exhibited only enantiotropic nematic mesophase behaviour. The optimised geometry of all the liquid crystalline compounds was calculated by density functional theory (DFT), and the effect of the twist angle ϴ of the ring system, the length of the core, HOMO-LUMO energies and electrostatic potential of the compounds on mesomorphism was examined. The effects of the linking groups, the ring systems, the length of the core and the terminal unsaturated carbon chain on mesophase behaviour were studied. The mesophase transitions of the five series were compared with each other and with structurally similar compounds to evaluate the effects of the ring systems on their mesophase behaviour.

Synthesis, LC self-assembly and photophysical behavior of stimuli responsive cyanostilbene-based hexacatenar mesogens with multicolour switching

A novel series of cyanostilbene-based hexacatenar mesogens consisting of two cyanostilbene units and one central pyridine in the π-conjugated rigid core were obtained by Suzuki coupling and Knoevenagel reactions. POM, DSC, SAXS, UV–vis spectrophotometer and fluorescence spectrophotometer were employed to explore the liquid crystalline, photophysical and stimuli responsive properties. All the biscyanovinyl diphenylpyridine-based hexacatenars can self-assemble into rectangular columnar phase with P2mm symmetry in bulk state. All the mesogens display weak solvatochromism due to the weak intramolecular charge transfer (ICT) and aggregation-induced enhanced emission (AIEE) due to non-planar structure and the long π-conjugated core. Temperature inducing hypochromatic shifts of fluorescence spectra, fluorescence quenching and the change in fluorescence color due to the phase transition and molecular planarization was well demonstrated. In addition, volatile acids could induce reversible changes of dual solid color, dual fluorescence color, fluorescence quantum yield and fluorescence lifetime owing to the protonation and deprotonation of pyridine. DFT analysis demonstrated that the protonation could induce more distinct molecular distortion and ICT, causing bathochromic-shifted absorption and emission spectra. Therefore, the introduction of different functional building blocks into liquid crystalline molecules is beneficial for the development of multifunctional materials.

Multi-functional buried interface engineering derived from in-situ-formed 2D perovskites using π-conjugated liquid-crystalline molecule with aggregation-induced emission for efficient and stable NiOx-based inverted perovskite solar cells

The poor and limited-functional NiOx/perovskite buried interface has hindered the development of NiOx-based perovskite solar cells (PSCs). Herein, a π-conjugated liquid-crystalline organic spacer with aggregation-induced emission (AIE), (Z)-2-([1,1′-biphenyl]-4-yl)-3-(4-(3-aminopropoxy)phenyl)acrylonitrile (BPCSA), is employed for the multi-functional NiOx/perovskite buried interface engineering. The functional groups of BPCSA spacer can coordinate with NiOx and induce the in-situ formation of 2D perovskite at the NiOx/perovskite interface. The in-situ-formed 2D perovskite interlayer can passivate interface defects, strengthen interface interconnection and optimize energy level alignment between NiOx and 3D perovskites. More markedly, the π-conjugated liquid-crystalline molecular structure and AIE property of BPCSA spacer can guide the high-quality crystal growth of upper 3D perovskite films, release interfacial strain, facilitate interfacial carrier transport and realize efficient photosensitization process concurrently. Consequently, such 3D/2D PSCs can acquire a champion power conversion efficiency (PCE) of 23.45% with improved stability. Besides, high-performance flexible 3D/2D PSCs are also successfully demonstrated.

Color-tunable photoluminescent discotic liquid crystal based on perylene – Pentaalkynylbenzene triad

This article describes the design and development of a discotic triad, where perylene is sandwiched between two pentaalkynyl benzene units, linked via a flexible alkyl spacer. The thermotropic liquid crystalline properties of the compound were analyzed by differential scanning calorimetry (DSC), polarising optical microscopy (POM), and wide-angle X-ray diffraction (WXRD) techniques. The compound exhibits columnar oblique (Colob) mesophase that sustains over a significant temperature range. The corresponding electron density map was derived from the intensities observed in the diffraction pattern. The photophysical behaviour of the compound in various solvents of varying polarity has been studied. The compound shows positive solvatochromism with a significant increase in Stoke's shift of around 91 nm between toluene and ethanol. The compound shows high fluorescence quantum yield in non-polar solvents and the lowest in polar solvents. The presented luminescent material with positive solvatochromism will reveal its potential application in fluorescence imaging and the field of optoelectronic organic materials.

Columnar Liquid Crystals of Copper(I) Complexes with Ionic Conductivity and Solid State Emission.

Two neutral copper(I) halide complexes ([Cu(BTU)2X], X = Cl, Br) were prepared by the reduction of the corresponding copper(II) halides (chloride or bromide) with a benzoylthiourea (BTU, N-(3,4-diheptyloxybenzoyl)-N'-(4-heptadecafluorooctylphenyl)thiourea) ligand in ethanol. The two copper(I) complexes show a very interesting combination of 2D supramolecular structures, liquid crystalline, emission, and 1D ionic conduction properties. Their chemical structure was ascribed based on ESI-MS, elemental analysis, IR, and NMR spectroscopies (1H and 13C), while the mesomorphic behavior was analyzed through a combination of differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and powder X-ray diffraction (XRD). These new copper(I) complexes have mesomorphic properties and exhibit a hexagonal columnar mesophase over a large temperature range, more than 100 K, as evidenced by DSC studies and POM observations. The thermogravimetric analysis (TG) indicated a very good thermal stability of these samples up to the isotropization temperatures and over the whole temperature range of the liquid crystalline phase existence. Both complexes displayed a solid-state emission with quantum yields up to 8% at ambient temperature. The electrical properties of the new metallomesogens were investigated by variable temperature dielectric spectroscopy over the entire temperature range of the liquid crystalline phase. It was found that the liquid crystal phases favoured anhydrous proton conduction provided by the hydrogen-bonding networks formed by the NH…X moieties (X = halide or oxygen) of the benzoylthiourea ligand in the copper(I) complexes. A proton conductivity of 2.97 × 10-7 S·cm-1 was achieved at 430 K for the chloro-complex and 1.37 × 10-6 S·cm-1 at 440K for the related bromo-complex.

Four-Dimensional Printing of Temperature-Responsive Liquid Crystal Elastomers with Programmable Shape-Changing Behavior.

Liquid crystal elastomers (LCEs) are polymer networks that exhibit anisotropic liquid crystalline properties while maintaining the properties of elastomers, presenting reversible high-speed and large-scale actuation in response to external stimuli. Herein, we formulated a non-toxic, low-temperature liquid crystal (LC) ink for temperature-controlled direct ink writing 3D printing. The rheological properties of the LC ink were verified under different temperatures given the phase transition temperature of 63 °C measured by the DSC test. Afterwards, the effects of printing speed, printing temperature, and actuation temperature on the actuation strain of printed LCEs structures were investigated within adjustable ranges. In addition, it was demonstrated that the printing direction can modulate the LCEs to exhibit different actuation behaviors. Finally, by sequentially conforming structures and programming the printing parameters, it showed the deformation behavior of a variety of complex structures. By integrating with 4D printing and digital device architectures, this unique reversible deformation property will help LCEs presented here apply to mechanical actuators, smart surfaces, micro-robots, etc.

Multichromic Behavior of Liquid Crystalline Composite Polymeric Films

In this study, we describe the synthesis of a cholesterol-linked cyanostilobazole salt dye and the tuning of its luminescence by physical stimuli such as electricity and grinding. The dyes exhibited liquid-crystalline properties at temperatures above 170 °C. Some of the solutions were transformed into orange luminescent gels upon the addition of poor solvents. When the solvent was evaporated, the resulting solid xerogel exhibited mechanochromism, its color changed, and its luminescent color changed from orange to red. Furthermore, we investigated the construction of functional gels (mechanochromic gels) that can respond to two stimuli, damage detection by abrasive responsiveness, and electrical response using ionic liquid complexes of polymers as dispersing media. This study provides a new strategy for tuning and switching luminescence using non-chemical stimuli in a single-component system using aggregation.