Polarized Optical Microscopy Research Articles

Liquid crystalline self-assembly of mixtures of rod- and wedge-shaped MIDA boronates.

Rod-like MIDA boronates form smectic mesophases, while wedge-shaped MIDA boronates self-assemble into columnar mesophases. However, the phase behavior of mixtures is less understood. In order to obtain further insight on the molecular self-assembly of MIDA boronate mixtures two series of binary mixtures of rod-like and wedge-shaped mesogens were prepared. The phase behavior was studied using differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD). The study revealed a strong dependency of the mesophase structure on the mesogen composition. Usage of a less bulky columnar mesogen suppressed the formation of columnar mesophases in the mixture and led to a decrease in melting and clearing temperatures. The phase behavior is discussed in terms of the packing parameter model typically applied for lyotropic liquid crystals.

Low-cost prototype for real-time analysis using liquid crystal optical sensors in water quality assessment

In the food production sector, quickly identifying potential hazards is crucial due to the resilience of many pathogens, which could lead to wasted production results and, more severely, epidemic outbreaks. E. coli monitoring is essential; however, traditional quality control methods in fish farming are often slow and intrusive, thus promoting an increase in fish stress and mortality rates. This paper presents an alternative method by utilizing a prototype inspired by polarized optical microscopy (POM), constructed with a Raspberry Pi microprocessor to assess pixel patterns and calculate analyte levels. The sensors are based on the immune complexation reactions between E. coli specific antibodies and the disruption of liquid crystal (LC) alignment, which are measured with the POM technique. The prototype yielded a sensitivity of 1.01%±0.17%/log10 (CFU/mL) for E. coli. In this paper, tests using sunlight as the prototype’s light source were also performed, and a user-friendly graphical user interface was designed.

Promoting Effect of Synergetic Nucleating Agent on Crystallization Behavior of Polylactic Acid

ABSTRACTModulating the crystallization behavior of polylactic acid (PLA) is significant for expanding its application range. In this article, a synergetic nucleating agent of talc and D‐sorbitol combination is incorporated into PLA via melt blending to enhance the crystallization of PLA. Then, differential scanning calorimetry (DSC) is employed to study the nonisothermal and isothermal crystallization behaviors, and the analysis of isothermal crystallization kinetics is carried out according to the Avrami equation, which has confirmed that the synergetic nucleating agent can promote the increase of the crystallinity from 3.5% to 43.8% and enhance the crystallization rate. Meanwhile, the analysis of Lauritzen–Hoffman's secondary nucleation theory reveals an obvious decline in the nucleation constant and fold surface free energy of PLA chains, which means a superior nucleating efficiency. Furthermore, the results of polarized optical microscopy (POM) demonstrated that the addition of the synergetic nucleating agent resulted in a greater number of spherical crystals with smaller sizes simultaneously visible in the field of view, indicating the synergetic nucleating agent promotion effect on PLA crystallization.

Hydrogen generation through metal waste corrosion: a systematic investigation on old/post-consumer scrap Al6063-series alloy

In this study, aluminum-based wastes are used as energy carriers for on-demand hydrogen production through sustainable, eco-friendly, and cost-effective controlled electrochemical corrosion in aqueous solution. The electrochemical process is very effective because it (i) uses waste metals to produce hydrogen, (ii) corroborates to circular economy, (iii) produces high purity hydrogen, (iv) is based on simple hydrolysis reaction of metals in relevant solutions, (v) electricity is not required and (iv) recovers part of the chemical Gibbs energy of the electrochemical corrosion usually entirely lost in the environment. We systematically studied the generation of hydrogen from industrial waste Dust Scrap Aluminum Alloy (DSAA) belonging to Al 6063 series for the first time. The process is investigated in a novel hand-made batch reactor with a low-cost commercial body suitable to an easy scale-up. Kinetics of DSAA hydrolysis reaction was explored by measuring the variation of aluminium ion concentration at different immersion times through Inductively Coupled Plasma (ICP) and weight loss measurements at different temperatures and NaOH catalyst concentrations. The effect of hydrolysis reaction on the composition and morphology of the metal surfaces in terms of formed oxide layers was studied in detail using Optical Polarizing Microscopy (OPM), Energy dispersive X-ray (EDX) and Scanning Electron Microscopy (SEM) techniques. The criteria used to evaluate the hydrogen reactor performance were hydrogen (i) yield and (ii) production rate. The experimental results showed that a strong increase in NaOH concentration (from 0.75 to 5 M) corresponding to a slow increase in hydrolysis reaction temperature (from 38.8 to 49.9 °C) lead to an improvement in hydrogen generation rate of one order of magnitude, i.e. from 35.71 to 421.41 ml/(g∙min). Low but constant rate of hydrogen can be generated for longer times at low NaOH concentrations (0.75 M), while fast and variable hydrogen generation rate occurs at higher concentrations (5 M) in short times. In the case study of Al 6063 series waste scrap, the hydrolysis reactor parameters can be regulated to deliver hydrogen generation rates from 35.71 to 421.41 ml/(g min) according to requirements. We expect that the results presented in this work will encourage researchers to study the possible use of other metal-based and multi-material plastic/metal wastes thermodynamically prone to electrochemical corrosion process as possible source of hydrogen.Graphical

Investigation into the crystallization of poly-lactic acid following the application of a novel high molecular weight, high epoxy functionality polymer chain extender

Abstract This research explored the impact of a novel polymer chain extender with high epoxy functionality on the crystallization properties of polylactic acid (PLA). FT-IR and Raman spectrometer were utilized to characterize the structure of PLA after chain extension. The dosage of the chain extender (HSMG) in PLA was varied to investigate its effect on the crystallization behavior of PLA via differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction analysis (XRD). The results indicated that incorporating HSMG into PLA significantly altered its crystallization behavior, without significantly changing its crystal structure.

Hierarchically Structured Stimuli-Responsive Liquid Crystalline Terpolymer-Rhodamine Dye Conjugates.

Optically responsive materials are applied in sensing, actuators, and optical devices. One such class of material is dye-doped liquid crystal polymers that self-assemble into cholesteric mesophases that reflect visible light. We report here the synthesis and characterization of a family of linear and mildly crosslinked terpolymers prepared by the ROMP of norbornene-based monomers. The three monomers were composed of (i) rhodamine dye through one or two norbornene end groups utilizing flexible C10-alkane spacers, (ii) a cholesteryl liquid crystal (LC) using C9-alkane spacers, and (iii) PEG side chains. We investigated how these architectural variations in these terpolymers impacted their hierarchically self-assembled mesophase properties. We probed their composition, morphology, thermal, mechanic, photochromic, and mechanochromic properties using, inter alia, 1H NMR spectroscopy, DSC, temperature-dependent SAXS, diffuse reflectance UV-vis spectroscopy, and optical polarization microscopy. The new terpolymers exhibited architecture-dependent thermochromic, mechanochromic, and piezochromic properties arising from LC-rhodamine dye interactions. We found that a compromise between the rigidity and flexibility of the terpolymer architectures needed to be stricken to fully express stimuli-responsive properties. These terpolymers also showed distinctly different properties compared to those of a previously reported structurally related liquid crystalline copolymer made from two monomers. These findings help to define the design principles for optimally stimuli-responsive liquid crystalline polymers.

Highly selective aptasensor for optical detection of whole cell gastrointestinal pathogen Shigella dysenteriae at label-free liquid crystal–aqueous interface

This paper describes a label-free liquid crystal (LC)-based biosensor for a rapid and straightforward detection of whole cell Shigella dysenteriae at aqueous interfaces using a bacteria-specific aptamer. The stimuli-receptive properties of LCs induce a change in the orientational ordering of molecules at the LC–aqueous interface. This interfacial phenomenon has been utilized to record target binding interactions of the biosensor. The homeotropic LC alignment at the glass–LC and the aqueous–LC interfaces was obtained using the aligning agent dimethyloctadecyl [3-(trimethoxysilyl)propyl] ammonium chloride and the self-assembling property of the cationic surfactant cetyltrimethylammonium bromide, respectively. The introduction of the negatively charged Shigella aptamer causes the homeotropic molecules to morph to a planar/tilted ordering. Upon adding a small quantity of Shigella cells in liquid media, the aptamer–bacterium interaction causes a redistribution of the surfactant at the LC–aqueous interface, restoring the homeotropic alignment. This results in a bright-to-dark optical change observed under a polarizing optical microscope, thus implying the presence of the microbes. This reported aptasensor demonstrates high specificity, with the limit of detection being 30 CFU/ml within a linear range of 1–105 CFU/ml. To test the utility of this system, the sensor was also tested with close taxonomic relatives S. dysenteriae as well as real samples from the food chain. This proposed LC-based sensor offers several advantages over conventional detection techniques for a quick and convenient way for the detection of whole cell targets.

Crosslinking-induced compatibility and toughness enhancement in poly(lactic acid)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blends with epoxidized soybean oil.

Polylactide (PLA) is inherently brittle and lacks ductility, which greatly restricts its range of applications. In order to address these issues, we blended PLA with biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)), and introduced epoxidized soybean oil (ESBO) as a reactive modifier to enhance the properties of the PLA/P(3HB-co-4HB) blends. Furthermore, we used theoretical calculations, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Soxhlet extraction, differential scanning calorimetry (DSC), polarising optical microscopy (POM), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and mechanical testing to investigate the compatibility, crystallization behavior, microstructure, thermal and mechanical properties of the PLA/P(3HB-co-4HB)/ESBO blends. The mechanisms underlying these properties were analyzed in detail. ESBO was found to form cross-linking grafts between PLA and P(3HB-co-4HB), strengthening interfacial bonding and thereby enhancing compatibility. The in situ formation of graft copolymers resulted in finer, more uniform dispersion of P(3HB-co-4HB) and ESBO droplets within the PLA matrix, further improving interfacial adhesion and overall material compatibility. With the addition of 5 wt% ESBO, the tensile strain at break of PLA/P(3HB-co-4HB)/ESBO films increased from 114.6 % to 453.3 %, while the notched impact strength improved from 3.75 kJ∙m-2 to 8.75 kJ∙m-2, compared to PLA/P(3HB-co-4HB) films. However, excessive ESBO slightly decreases the mechanical performance of the material.

MODELAGEM DE MISTURAS BINÁRIAS PELA APLICAÇÃO DA EQUAÇÃO DE SCHRÖEDER-van LAAR A UM CONJUNTO DE SUBSTÂNCIAS COM DIVERSIDADE ESTRUTURAL

MODELING OF BINARY MIXTURES BY APPLYING THE SCHRÖEDER-van LAAR EQUATION TO A SET OF SUBSTANCES WITH STRUCTURAL DIVERSITY. The Schröeder-van Laar equation to predict the theoretical eutectic melting temperature values was applied to a set of fourteen binary mixtures (UR1 to UR14). The fourteen binary mixtures belong to a structurally diverse group of organic molecules. They are represented by the 5-membered heterocycles containing N-S and N-O rings, flexible methylene chains (RH), semi-rigid semi-fluorinated chains (RF), and hydrogen bonds (HB). A virtual screening totalizing ninety-one possible theoretical combinations was planned. The UR1 to UR14 were prepared by mixing individual components using the calculated mole fractions. The experimental (Te) and theoretical (Tt) temperatures for the eutectic melting points were determined using polarized optical microscopy (POM) and differential scanning calorimetry (DSC) techniques. Heterogeneous mixtures were formed for components with large structural diversity as seen by POM. During the melting of the mixtures, irregular behavior through the segregation of the components was recorded. The study showed that the similarities in structural diversities favor the formation of homogeneous mixtures, with Te values approaching Tt, as predicted by the Schröeder-van Laar equation and by the theory of eutectic mixtures. Liquid crystal properties were affected in homogeneous binary mixtures containing one of the individual liquid crystal components.

Investigation of the relation between surfactant head group size and formation of different types of lyotropic structures in two surfactants/dye systems

Lyotropic phase properties of novel mixtures of some dodecylalkylammonium bromide surfactants (DAABr) in the mixtures of 1-dodecanol (DDeOH)/Sunset Yellow dye (SSY)/water were investigated. DAABr surfactants were chosen as dodecyldimethylammonium bromide (DDMABr), dodecyldimethylethylamonium bromide (DDMEABr) and dodecyltriethylammonium bromide (DTEABr). In lyotropic mixtures, both surfactants were used in the mixtures, i.e., DDMABr/DDMEABr and DDMEABr/DTEABr to control the average number of the methylene (−CH2) groups in their head groups (navg) at the aggregates’ surfaces. By changing the relative concentrations of each surfactant in the mixtures at constant total surfactant and mixture compositions, lyotropic mixtures presenting lamellar, nematic, and hexagonal phases were obtained. The textures and types of lyotropic phases were analyzed by polarizing optical microscopy (POM), also confirmed by Small-angle X-ray scattering data. Uniaxial-to-biaxial nematic phase transitions were determined from the temperature dependence of the birefringences via laser conoscopy. Temperature-navg partial phase diagrams of the mixtures were constructed by combining the POM and laser conoscopy results. Small-angle X-ray scattering (SAXS) was performed to determine the structural parameters. The results indicate that there is a close relation between the stabilization of different lyotropic structures and the average size per surfactant head group (a0) and the navg values.

Tuning the optical properties of gold nanoparticles via photoactive liquid crystalline azo ligands.

In the field of modern nanoscience, the ability to tailor the properties of nanoparticles is essential for advancing their applications. A key approach for achieving this control involves manipulating surface plasmon resonance (SPR) to modify optical properties. This study introduces a novel method for synthesizing gold nanoparticles capped with photoactive liquid crystalline azo ligands, accomplished without reducing agents. Comprehensive structural characterization was performed using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), ultraviolet-visible (UV-Vis) spectroscopy, powder X-ray diffraction (PXRD), and high-resolution transmission electron microscopy (HRTEM). Photophysical investigations, including time-dependent UV-Vis and fluorescence spectroscopy, provided insights into the modulation of SPR. The mesomorphic behavior of the azo ligands was examined through polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD), revealing a chiral lamellar superstructure confirmed by circular dichroism (CD) spectroscopy. Notably, the photoactive azo ligands demonstrated significant control over SPR peak modulation, enabling precise manipulation of nanoparticle size and arrangement. This research highlights the potential of photoactive ligands in the design of nanoparticles with tailored optical properties, paving the way for innovative applications in various fields.

Gum Arabic induced assembly of cellulose nanocrystals in aqueous media.

Entropy-driven assembly of nematic liquid-crystal phases of cellulose nanocrystals (SCNCs) in aqueous suspensions results in the emergence of a cholesteric liquid crystalline phase (N* phase). We report that a solvated, non-adsorbing, highly branched natural polysaccharide, Gum Arabic (GA), strongly affects the assembly of the SCNCs and modifies the phase diagram: GA leads to significant crowding of the SCNC rods and induces a new liquid-liquid phase transition, where SCNC-rich and GA-rich droplets coexist. The solvated GA does not induce coagulation or gelation of the suspended SCNCs (at low concentrations of 1-3 wt% of GA). In the SCNC-rich droplets, finite-sized nematic nano-islands assemble and further evolve into cholesteric tactoids and nucleate the formation of the N* phase at significantly lower concentration (about 1.5 wt%) than in GA-free suspensions. We observe that the inter-particle distance and the chiral pitch of the N* phase are determined by the concentration of GA (for a given SCNC concentration). The resulting mesophases are characterized via transmission electron microscopy at cryogenic temperatures (cryo-TEM), small-angle X-ray scattering (SAXS), and polarized optical microscopy (POM). Our findings indicate that GA can be used to tune the phase diagram and optical properties of SCNC suspensions, and overcome kinetic barriers that lead to gelation or kinetic arrest.

Synthesis, Trans-Cis Photoisomerization, Fluorescence Decay Studies of Methoxy Ester Functionalized Alkoxy Side Chain Azobenzene Compounds and Their Photoluminescence Dynamics.

In this study, a series of new methoxy ester functionalized core fluorinated, chloro-fluorinated azobenzene derivatives were synthesized. The molecular structures of the azobenzene derivatives (3a-3c and 4a-4c) were confirmed through various analytical methods, with variations in the alkoxy chain length on one end of the aromatic ring. Optical absorption studies of 3a, 3b revealed π-π* transitions around 368-392nm. Further, polarizing optical microscope (POM) studies of 3a, 3b revealed birefringent textures, and their phase transitions were investigated using differential scanning colorimetry (DSC) studies. The trans-to-cis photoisomerization of 3a, 3b transpired over 3600s whereas, thermal back relaxation (cis-to-trans) isomerization took 0.75h. Room temperature photoluminescence (RTPL) studies of 3a-3c and 4a-4c unveiled weak emission intensity peak at ~ 450nm (blue region) when excited at 400nm. Steady-state photoluminescence (SSPL) studies of 3a-3c, 4a-4c revealed a broad emission band in the violet region of the visible spectrum with significantly large Stokes shifts, indicating the presence of highly energized excited states and formation of additional energy levels during photoexcitation. Fluorescence decay (FLD) studies of 3a-3c, 4a-4c unveiled average lifetime (τ) dwells between 8.2 ps and 70.4 ps. The average lifetime (τ) was found to increase with the increase in the length of the alkoxy chain. Phosphorescence decay (PD) profiles of 3a-3c, 4a-4c showed average lifetime (τ) fluctuate around 373 ns to 463 ns. The obtained core fluorinated, chloro-fluorinated azobenzene derivatives having different lengths of the alkoxy side chain can find potential applications in optical storage and display technologies.

Hybrid supercapacitor battery-type electrode potential of electrospun PAN-porphyrin CNFs

In this study, electrospun polyacrylonitrile-(5,10,15,20-tetra(4-tert-butylphenyl))-porphyrin nanofibers (PAN-Por NFs) were carbonized to obtain carbonized PAN-Por NF/carbon-felt electrodes (PP2C/CFE), which were then investigated for their performance as battery-type hybrid supercapacitor (SC) electrodes. To the best of our knowledge, the doping of a hybrid SC electrode with (5,10,15,20-tetra(4-tert-butylphenyl)porphyrin has not been previously investigated. Subsequently, a series of physicochemical analyses were conducted, including scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and polarization optical microscopy. Electrochemical analyses were performed using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy. The PP2C/CFE exhibited battery-type characteristics in the CV and GCD tests. From the CV data, the maximum specific capacitance was calculated to be 220 F g − 1 at 0.5 mV s − 1 . At a current density of 0.5 A g − 1 , a specific capacitance of 177 F g − 1 and a specific capacity of 284 mAh g − 1 were calculated from the GCD curve. The highest coulombic efficiency, 110.60%, was observed at 3 A g − 1 . At 0.5 A g − 1 , the maximum energy density was 98.3 Wh kg − 1 , and the power density was 348.6 W kg − 1 . In the cycle-stability test, 50 charge-discharge cycles were performed at 3.5 A g − 1 , resulting in an 88% increase in the specific capacitance value. This study demonstrates, for the first time, that PP2C/CFE doped/carbonized with Por is a promising and improvable hybrid SC battery-type electrode.

Developing energy-efficient cool roof coatings using microencapsulated eutectic phase-change material and poly(methyl methacrylate-co-methacrylic acid) copolymer shell emulsion

ABSTRACT The rise in the construction of modern structures of buildings has increased the demand for energy sources to cool indoor and outdoor temperatures. Cool coating is a highly effective roofing technology for absorbing less heat and reflecting more sunlight than conventional coating. These coatings are made from a special type of material with high solar reflectance, allowing them to reflect more sunlight. The cool coating is applied over the building roofs, which gives an efficient way to cool the building inside passively and the surrounding environment. In this context, incorporating phase-change material (PCM) into cool coating enhances its capacity for regulating temperature by storing and releasing heat as required. Combining these two would improve the coating’s overall cooling capabilities, increasing its efficacy in maintaining a lower surface temperature and lowering the cooling energy consumption in buildings. There is a lack of research studies incorporating PCM into a cool roof coating. The present work fills this gap. In this study, we have developed an easy-to-maintain thermal storage cool roof coating using microencapsulated phase-change material (MPCM) latex and white cement. This coating integrates a cooling effect, making it ideal for building applications. Lauric acid (LA), palmitic acid (PA), and stearic acid (SA) eutectic PCM as core were microencapsulated with polymethyl methacrylate-co-methacrylic acid (PMMA-co-MAA) shell using oil-in-water emulsion polymerization. The microcapsule was prepared by altering the core-to-shell ratio. The microcapsules were characterized using various techniques such as thermogravimetric analysis (TGA), polarized optical microscopy (POM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The melting temperature of LA-PA-SA eutectic PCM, MPCM 1, and MPCM 2 was 32.66°C, 31.47°C, and 32.73°C, respectively. The TGA analysis indicates that the prepared microcapsules have good thermal stability and degrade in two steps. Microcapsules’ average particle size diameter was observed in the 3–9 µm range. The cool roof coating was fabricated by partially replacing the acrylic copolymer latex with prepared MPCM 1 latex. This study evaluates the influence of MPCM 1 latex loading on the coating’s mechanical and thermal properties. The temperature changes from the building’s exterior to the interior have been recorded using thermal energy transfer analysis. General coating properties such as water resistance, stain resistance, alkali resistance, and gloss were investigated. DSC result shows that the thermal storage enthalpy of the coating has been improved from 17.85 J/g to 37.45 J/g by partially replacing MPCM 1 latex with acrylic copolymer from 50 to 70 wt.%. Coating with 70 wt.% MPCM 1 latex reduced the rise in the room’s temperature, showing it to be a promising candidate for utilizing thermal energy within building technologies.

Proposed biosensor for the detection of Bovine Serum Albumin using 7CB liquid crystals: A preliminary study.

Liquid crystal (LC) based biosensors offer a sensitive platform for detecting biomolecules due to their ability to respond to molecular interactions through changes in LC orientations. In this paper, we introduce a novel LC biosensor using 4-heptyl-4-biphenyl carbonitrile (7CB) to detect Bovine Serum Albumin (BSA). The interaction between BSA and 7CB was investigated using polarising optical microscopy (POM), molecular docking (MD), and Raman spectroscopy. Time, temperature, and concentration-dependent POM experiments revealed that 7CB-BSA interaction induced a change in the LC texture producing bipolar and radial textures, with the biosensor demonstrating high selectivity for BSA at concentrations as low as 25 μM. A strong linear response to BSA concentration was observed, with a coefficient of determination (R2 = 0.97973), indicating the biosensor's quantitative capabilities. Molecular docking analysis showed that 7CB binds to BSA with a minimal binding energy of -6.06 kcal/mol, supporting the strong interaction between the two. Raman spectroscopy revealed that specific amino acid residues, such as Phenylalanine (Phe) and Leucine (Leu) in BSA, significantly influence the symmetric and asymmetric stretching of the CH chains in 7CB leading shift in peak position (PP), line width (LW) and integrated intensity (II). The sensitivity, specificity, and label-free detection capability of this biosensor underscore its potential to enhance the performance of LC-based biosensing systems for protein detection.

Synthesis and Mesomorphism of New Calamitic Schiff Bases-Ester Possessing Dialkylamino Terminal Substituent

: New calamitic liquid crystals, 4-[{[4-(diethylamino)phenyl]methylidene}amino]phenyl 4- alkyloxybenzoate (nEABAA) containing mesogenic core system which made of three phenyl rings were reported. The ester and imine linkages connected the phenyl rings. At one end of the molecule, the core system was attached to an alkyloxy chain with a variable length -(CH2)n- (where n = 2-10, 12, 14, 16 and 18). At the other end of the molecule, the para position of the phenyl ring is bonded to the diethylamino group. The molecular structure of the current compounds was confirmed by using spectroscopic methods. The mesomorphic characteristics of the title compounds were studied by using a differential scanning calorimeter and a polarizing optical microscope attached to a heating stage. Through observation under microscopy, it was found that all synthesized compounds exhibited only a single (nematic) phase. The exhibition of the monophase variance (nematic) in the current compounds is caused by the presence of the diethylamino group that is attached to the terminal position of the benzylideneaniline core system. The diethylamino group has caused the molecular breadth to increase and this results in a weaker overall lateral intermolecular attraction. Subsequently, it depressed the mesophase thermal stability of the compounds. Thermal properties of the current compounds were compared with the earlier reported analogous and the structure-property relationships of the current compounds have been inferred through this comparison.

Enhancing Hole Transport and Autonomous Healing Properties of Supramolecular Columns in Unsymmetrical Discotics.

Designing smart autonomous healing soft materials is crucial to attaining cost-efficiency and optimal performance in organic semiconductors. In this context, we design an unsymmetrical thiophene-fused phenazine (TFP)-based discotic liquid crystal (DLC) with the goal of creating an active organic semiconductor that encompasses favorable attributes, such as polarizability, mobility, and processability. Aligned with our objective, we successfully synthesized two unsymmetrical TFP core-based DLCs by linking alkyl chains of variable lengths at the periphery through a coupling reaction. These DLCs show room temperature columnar oblique (Colob) mesophase as evident from temperature-dependent studies employing polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS). We performed space charge-limited current (SCLC) techniques to evaluate the hole mobility of TFP-based DLCs and found that they have high hole mobility (∼10-3 cm2/V s). Additionally, the film morphology and its self-healing nature have been examined using atomic force microscopy (AFM) and stress relaxation test. One of the unsymmetrical DLCs exhibited an ability to relax stress over time while maintaining a constant strain (up to 1-3%). The rational design of these unsymmetrical discotics, exhibiting reduced threshold voltage (as confirmed by conductivity studies) highlights their possible potential in various organic semiconductor devices.

Synthesis of Porous Metal Oxides Utilizing Nanosheet Colloid with Liquid Crystallinity

Activated carbon, a high specific surface area microporous carbon(>2000 m2 g–1), has been used as the electrode material for electrochemical double layer capacitors.1 The structure of activated carbon is characterized by a three-dimensional network consisting of graphene-like layers. Preparation of metal oxides with a similar porous structure is anticipated to behave as pseudocapacitive electrode materials with high energy density. However, the hierarchical porous structure of activated carbon is obtained by gas-phase or chemical activation treatment and is applicable only to carbonaceous materials. Thus, an alternative strategy is necessary to prepare metal oxides with porous architectures similar to activated carbon.Assembly of inorganic oxide nanosheets is one of the promising methods to prepare hierarchical porous metal oxides. Here, we focus on the phenomenon where inorganic oxide nanosheets form liquid crystal structures in colloids and align macroscopically under an electric field. A highly concentrated hexaniobate nanosheet ([Nb6O17]4 –(ns)) colloid is known to exhibit liquid crystalline behavior.2 Additionally, the orientation of nanosheet with micro-mesoscale sheet spacing (< tens of nm) forms a hierarchical macroscopic structure (< several hundred µm) under an electric field.3 Therefore, the liquid crystalline structure and its responsiveness to electric fields in nanosheet colloids are effective for controlling the hierarchically nanosheet-assembled structure. In this study, we applied the freeze-drying method of nanosheet liquid crystals (NLC) to transfer the structure within the fluid nanosheet colloid to the dried aggregates (Figure 1).[Nb6O17]4 –(ns) colloids with developed liquid crystal domains form stripe-shaped macrostructures by applying an alternating current (AC) electric field (10 Vp–p, 50 kHz) perpendicular to the direction of gravity.3 Figure 1(a) shows the polarized optical microscopy (POM) image of the stripe-shaped macrostructures with a width of 100 µm and intervals of 200 µm composed of [Nb6O17]4 –(ns). In the birefringent regions, NLC oriented perpendicular to the direction of the AC electric field and parallel to the direction of the gravity. After applying an electric field to the cell, the cell was immersed in liquid nitrogen with applying the electric field and then dried in vacuum, resulting in the formation of a sponge-like nanosheet aggregate between the electrodes. The bright-field optical microscope image of the freeze-dried aggregates shows the similar stripe-shaped macrostructures to that of NLC under the electric field (Figure 1(b)). Therefore, the macrostructure of NLC oriented in an electric field can be transferred into the porous nanosheet aggregates by freeze-drying method. These results indicate that the liquid crystalline and electric field responsive properties of nanosheet colloids are useful for structural design of nanosheet-assembled materials. References P. Simon and Y. Gogotsi, Nat. Mater., 7, 845 (2008).N. Miyamoto and T. Nakato, Adv. Mater., 14, 1267 (2002).T. Nakato, Y. Nono, E. Mouri and M. Nakata, Phys. Chem. Chem. Phys., 16, 955 (2014). Figure 1

New alkoxyphenyl azomethine phenyl toluate liquid crystals

ABSTRACT A series of alkoxyphenyl azomethine phenyl toluates was synthesised and investigated for thermal and liquid crystalline behaviour. All the synthesised compounds were characterised using FT-IR, 1H NMR and 13C NMR spectroscopy. The materials demonstrated high thermal stability in thermogravimetric analysis (TGA), undergoing decomposition above 280°C. Mesomorphic properties were investigated using a combination of differential scanning calorimetry (DSC) and polarising optical microscopy (POM). All final compounds exhibited liquid-crystalline properties, displaying textures characteristic of calamitic liquid crystals. There was a tendency for lower homologs to display enantiotropic behaviour (N), while higher homologs exhibited dimesomorphic behaviour (N and SmC). The mesophases were confirmed through X-ray diffraction studies. A comparison with similar compounds revealed that interchanging the positions of methyl and alkoxy end groups influenced the nematic phase stabilities in lower homologues and led to a transition from SmA to SmC in higher homologues.