SA Phase Research Articles

Sodium alginate emulsion loaded with linalool: Preparation, characterization and antibacterial mechanism against Shigella sonnei

This study aimed to prepare sodium alginate-linalool emulsion (SA-LE) to overcome the low solubility of linalool and explore its inhibitory activity against Shigella sonnei. The results indicated that linalool significantly reduced the interfacial tension between SA and oil phase (p < 0.05). Droplet sizes of fresh emulsions were uniform with sizes from 2.54 to 2.58 μm. The ζ-potential was between −23.94 and -25.03 mV, and the viscosity distribution was 973.62 to 981.03 mPa·s at pH 5–8 (near neutral pH) without significant difference. In addition, linalool could be effectively released from SA-LE in accordance with the Peppas-Sahlin model, mainly described by Fickian diffusion. In particular, SA-LE can inhibit S. sonnei with a minimum inhibitory concentration of 3 mL/L, which was lower than free linalool. The mechanism can be described as damaging the membrane structure and inhibiting respiratory metabolism accompanied by oxidative stress based on FESEM, SDH activity, ATP and ROS content. These results suggest that SA is an effective encapsulation strategy to enhance the stability of linalool and its inhibitory effect on S. sonnei at near neutral pH. Moreover, the prepared SA-LE has the potential to be developed as a natural antibacterial agent to address the growing food safety challenges.

Thermotropic liquid crystalline medicine: establishment of liquid crystalline properties and the X-ray phase structure analysis of immunosuppressant 2-amino-2-[2-(4-alkylphenyl)ethyl]propane-1,3-diol hydrochloride

ABSTRACT From 1995 to 2000, it was found by a pharmaceutical industry that the long-chain-substituted compounds, 2-amino-2-[2-(4-n-alkylphenyl)ethyl]propan-1,3-diol hydrochloride derivatives (abbreviated as Cn-C2-APD (n = 7 ~ 14)), become an excellent immunosuppressant. However, at that time, they only reported that the melting points of these compounds show at ca.107°C irrespective of the chain length (n), and they overlooked that a liquid crystalline phase exists over the melting points. Recently, we have noticed that these immunosuppressive medicines have a molecular structure very similar to a thermotropic liquid crystalline material reported by Borisch et al. in 1998. Therefore, in this work, we have synthesised the same series of the Cn-C2-APD (n = 8 ~ 14) derivatives and investigated the liquid crystallinity and the mesophase structure by using a polarising microscope, DSC, and a temperature-variable X-ray diffractometer. As a result, we have established for the first time that each of the Cn-C2-APD (n = 8 ~ 14) derivative has an SA phase having a bilayer structure in a temperature range from the melting points at ca. 107°C and the decomposition temperature at ca. 230°C, irrespective of the chain length (n).

Téléréalité by Aurélien Bellanger

Reviewed by: Téléréalité by Aurélien Bellanger Walter S. Temple Bellanger, Aurélien. Téléréalité. Gallimard, 2021 ISBN 978-2-07-290299-4. Pp. 243. Throughout the 1990s, the concept of reality television began to take hold with audiences in France as viewers sought a different kind of escape from the mundane. Later adaptations of popular American shows (one such example being Loft story) provided viewers with the possibility of participating in the lives of “real” characters— a new concept for the French market. Yet despite the inherent fragility of the “naturally” filmed comédie humaine, Bellanger confronts a revealing truth in his portrait of téléréalité. Neither a disavowal nor a defense of reality television, the author proposes an analysis of the cultural shift that qualifies a new era of popular culture. In the shadows of the paysage audiovisuel français, this text reads like a bildungsroman that only the most branchés of readers will truly appreciate. The story begins in earnest with the appearance of Sébastien, a modern-day Rastignac who embarks on a journey from the implied provincial Drôme department of southeastern France on a quest to pursue his passion. Reading this text through the lens of Balzac studies gives way to a salient comparison of both writers’ profound understanding of time and space, as well as their observations of a society of contradictions. The occasional veiled cynicism of Bellanger’s protagonist is suggestive of a different kind of social climber, however, as inscribed in Sébastien’s “modern” predicament as identifying as an episodic prisonnier of reality television. Setting the stage for what will unravel as a superficial yet somehow philosophical positioning of sociocultural critique, Bellanger writes: “Sébastien est-il pour autant un enfant de la télévision?” (20). Like many of his contemporaries, he goes on to wonder if he should singularly focus on his career by associating with those who can facilitate his goals and ambitions— “Sébastien était confronté à un dilemme. Devenu l’assistant de Véronique, il apprenait en accéléré le métier de producteur” (59)—thus seemingly concerned by the ramifications of not focusing on his own existence. Or should he succumb to the allure of the antics of Pascal Sevran’s La chance aux chansons, yet another important cultural marker, the narrator proclaiming: “Il était en même temps prisonnier” (59). In what is arguably a curious reflection of the burgeoning disenchantment that will soon be linked to la télé (which Bellanger reminds us time and again through the use of poetically inscribed imagery), Sébastien could fall right out of a Houellebecq novel, a writer who Bellanger has previously studied at length. Near the conclusion of the text, the narrator posits, “La télévision, incontestablement, est entrée dans sa phase de déclin” (218), a powerful observation suggestive of a yet another impending cultural shift—perhaps an occult foreshadowing of the impending role of social media? It is here where Houellebecq’s voice continues to linger in Bellanger’s imaginary despite the silence that qualifies his character’s melancholic (if highly successful) journey. [End Page 239] Walter S. Temple Utah Valley University Copyright © 2022 American Association of Teachers of French

Sorption and Isomerselective Properties of Binary Sorbent Based on Supramolecular 4-(3-Hydroxypropyloxy)-4'-Formylazobenzene Liquid Crystal and Partially Methylated β-Cyclodextrin

The sorption and selective properties of a composite sorbent based on the supramolecular liquid crystal 4-(3-hydroxypropyloxy)-4'-formylazobenzene (HPOFAB) and partially methylated β-cyclodextrin heptakis-(2,6-di-O-methyl)-β-cyclodextrin (Me2,6-β-CD) have been studied by inverse gas chromatography. The standard thermodynamic functions of sorption on the smectic A phase of the sorbent for 29 volatile organic compounds of different classes were determined and compared with similar functions obtained on a column with “pure” HPOFAB. The reasons for the increase in the retention of all studied compounds (except for the optical isomers of butanediol-2,3) when Me2,6-β-CD (10 wt. %) added to HPOFAB are discussed. It was found that the mixed SA phase of the binary sorbent in conditions of gas-liquid chromatography has moderate values of structural selectivity and enantioselectivity to both low-polar terpene hydrocarbons and polar optical isomers (butanediols-2,3).

P1797 Left atrial mechanics in patients with stoke: Implications for emprical anticoagulation

Abstract Purpose Detection of atrial fibrillation (AF) after stroke impacts patient management. However, detection of AF is difficult due to its paroxsysmal nature. We sought to test the hypothesis that echocardiographic quantification left atrial (LA) mechanics in patients with stoke can be an imaging biomarker to predict AF. Methods We enrolled prospectively and consecutively 131 patients in normal sinus rhythm with a new diagnosis of ischemic stroke. All patients underwent 48-hour Holter monitorization, transthoracic echocardiography with saline injection in addition to routine work-up of stroke evaluation. Two-dimensional and Doppler studies, together with most up-to-date LA quantification tools were performed including 3-dimensional LA phasic volumes (maxiumum and minimum LA Volume index - LAVImax, LAVImin) and LA strain quantification (average strain from apical 4- and 2-chamber during reservoir (Ss) and contraction (Sa) phases). Patients were followed-up and underwent second 48-hour Holter monitorization 6-12 months later if no etiologic cause was found. Any AF episode lasting &amp;gt;30 seconds was considered significant parosysmal AF. Results In 49 patients, causes other than AF were identified (Noncryptogenic). In 43 patients no discernable cause was found (NoAF Cryptogenic). Paroxysmal AF episodes lasting longer than 30 sec were documented in 27 patients at first 48-hour Holter and in 12 patients during follow-up (9.2 ± 3.1 months) either by second 48-hour Holter monitorization or clinically (AF cryptogenic). LAVImax and LAVImin were significantly increased, Ss and Sa were significantly reduced in patients with AF as compared to No AF and Noncryptogenic groups (Table). LA volumes and strain measures predicted AF development independently of CHA2DS2-VASc score. Better discrimination between No AF and AF groups was obtained after second Holter monitorization that enabled detection of more cases with paroxysmal AF (Figure). Conclusions Our findings underscore the value of echocardiographic assessment of LA function as a marker of AF development and for selection of patients who could benefit from empiric anticoagulation. Noncryptogenic AF cryptogenic No AF cryptogenic 3D LAVI max (ml/m&amp;sup2;) 30.1 ± 9,4 38.1 ± 12.7 28.9 ± 9.2 3D LAVI min (ml/m&amp;sup2;) 13.9 ± 7.5 20.7 ± 10.7 13.4 ± 5.3 3D LA EF (%) 55.5 ± 9.4 50.0 ± 10.5 53.8 ± 10.0 Ss (%) 17.4 ± 8.5 12.7 ± 5.3 17.5 ± 8.5 Sa (%) 12.7 ± 6.3 9.0 ± 5.0 12.8 ± 6.3 CHA2DS2-VASc 4.0 ± 1.6 5.0 ± 1.6 3.9 ± 1.5 Abstract P1797 Figure.

Smectic phases in ionic liquid crystals

Ionic liquid crystals (ILCs) are anisotropic mesogenic molecules which carry charges and therefore combine properties of liquid crystals, e.g. the formation of mesophases, and of ionic liquids, such as low melting temperatures and tiny triple-point pressures. Previous density functional calculations have revealed that the phase behavior of ILCs is strongly affected by their molecular properties, i.e. their aspect ratio, the loci of the charges, and their interaction strengths. Here, we report new findings concerning the phase behavior of ILCs as obtained by density functional theory and Monte Carlo simulations. The most important result is the occurrence of a novel, wide smectic-A phase , at low temperature, the layer spacing of which is larger than that of the ordinary high-temperature smectic-A phase . Unlike the ordinary smectic SA phase, the structure of the phase consists of alternating layers of particles oriented parallel to the layer normal and oriented perpendicular to it.

Dielectric studies of a chiral fluorinated organosiloxane liquid crystal

ABSTRACTThe material (LC#11) we are reporting in this communication is a chiral fluorinated organosiloxane liquid crystal which has a long chain hydrocarbon head and ending with a straight trisiloxane terminus. Polarized optical microscopic studies revealed that the material exhibits SC, SA phases along with a co-existent biphasic region. The material responds to electric field; at low temperature the response is slow. Tilt angle measurements as a function of temperature are carried out using optical extinction method. Low frequency dielectric studies are carried out using Wayne Kerr precision impedance analyzer.

Sorbtion and selective properties of supramolecular liquid crystal–β-cyclodextrin sorbent under conditions of gas chromatography

Sorbtion and selective properties of binary sorbent based on polar supramolecular (associated) liquid crystal (LC) 4-(3-hydroxypropyloxy)-4'-formylazobenzene (HPOFAB) and unsubstituted β-cyclodextrin are studied by the method of inverse gas chromatography. Standard thermodynamic functions of sorbtion in smectic phase A of the sorbent are determined for 21 organic compounds belonging to different classes of hydrocarbons and alcohols, which are compared to analogous functions obtained using a column with HPOFAB. The causes of decrease of retention of all studied compounds (excluding n-alkanes C9–C12) upon introduction of β-cyclodextrin into HPOFAB are discussed. It is established that mixed SA phase of the binary sorbent possess high values of para-meta-selectivity and enantioselectivity with respect to optical isomers of camphene.

Synthesis and properties of novel chiral side-chain liquid crystalline polysiloxanes containing different chiral pendant groups

Two novel chiral liquid crystalline monomers, and a series of their corresponding chiral side-chain polymers (P1–P7) based on poly(methylhydrogeno)siloxane have been prepared. The chemical structures and liquid crystalline properties of the synthesized monomers and polymers have been investigated using various experimental techniques. Thermal analysis shows that all polymers have wide mesophase temperature ranges with a high thermal stability. With the increase of M2 molar ratio in the polymer systems, the isotropic phase transition and glass transition temperatures of all polymers increase, and the temperature ranges of N* phase and mesophase become broad. The effect of cholesteryl mesogens on mesophase behaviors, optical properties, and molecular arrangement of LC polysiloxanes and their advanced applications have also been discussed. For homopolymer P1, it shows a single SA phase. With increasing the content of M2 in the polymer systems, P2 and P3 reveal a SA–N* phase transition when they are heated, and P4–P7 reveal a N* phase. For N* phase polymers P4–P7, the reflection wavelengths exhibit blue shift, suggesting that the pitch decreases with a decrease in the amount of the smectic domains induced by the M1. The reflection wavelengths of P4–P7 are almost across the entire visible region when they are heated, which offer stremendous potential for various optical applications. For P2 and P3, the reflection wavelengths show a very steep change around the temperature of the SA–N* phase transition, which can be used as thermally sensitive liquid crystal devices requiring fast response, such as sensors, and thermally induced tuning.

Phase transition studies in symmetric dimeric liquid crystals

As a part of the systematic studies on symmetric liquid crystal dimer homologous series, α,ω-bis-(4-n-alkylaniline benzylidene-4′-oxy) alkanes, (referred to as m.OnO.m with m = 3, 4, and 5; and n = 8, 9, and 10), we present in this article the nature of phase transitions across isotropic–nematic and nematic–smectic-A (N–SmA) phases exhibited by the just mentioned compounds. The methods employed are differential scanning calorimetry and dilatometry. The compounds studied were 3.O8O.3, 4.O8O.4, and 5.O8O.5; and 3.O9.03, 5.O9O.5, 3.O10O.3, 4.O10O.4, and 5.O10O.5. Different from the case of their corresponding monomers, all these compounds exhibit a nematic phase only with the exception of 5.O8O.5 which exhibits a SA phase in addition to the nematic phase. The phase transitions viz., isotropic–nematic transitions studied in all these compounds were confirmed to be of first-order nature, whereas the N–SmA transition exhibited by the compound 5.O8O.5 only was found to be of second-order nature. We also report in this article the calculated density jumps, thermal expansion coefficient maxima, and pressure dependence of transition temperatures which are analyzed in the light of the available literature data.

The effect of mesogenic and non-mesogenic crosslinking units on the phase behaviour of side-chain smectic and cholesteric elastomers

Chiral monomer (M1 ), mesogenic and non-mesogenic crosslinking agents (C1 and C2 ), and the corresponding liquid crystalline elastomers (P1 and P2 series), have been synthesised. Their chemical structures have been characterised by Fourier transform infrared or 1H nuclear magnetic resonance and their phase behaviour investigated by differential scanning calorimetry, polarising optical miscoscopy, thermo-gravimetric analysis (TGA) and X-ray diffraction. The effect of the crosslinking unit on the phase behaviour of the elastomers has been studied. M1 showed a cholesteric oily streak and focal conic texture. C2 exhibited a nematic enantiotropic thread-like and schlieren texture, and a monotropic fan-shaped texture in the SA phase. Due to the introduction of the mesogenic crosslinking unit, elastomers, P2-1 −P2-5 , exhibited a cholesteric phase, while elastomers, P1-1 −P1-4 , derived from a non-mesogenic crosslinking unit, exhibit a SA phase. As the content of the crosslinking unit increased, the T g of the P1 series initially decreased and then increased, and the T i of the series decreased. In the P2 series the T g increased, but the T i initially increased and then decreased. TGA confirmed that all the elastomers had improved thermal stability.

Therapeutic Efficacy of a Herpes Simplex Virus With Radiation or Temozolomide for Intracranial Glioblastoma After Convection-enhanced Delivery

The herpes simplex virus-1 (HSV-1)-infected cell protein 0 (ICP0) is an E3 ubiquitin ligase implicated in cell cycle arrest and DNA repair inhibition. Convection-enhanced delivery (CED) of either the replication-defective, ICP0-producing HSV-1 mutant, d106, or the recombinant d109, devoid of all viral genome expression, was performed to determine the in vivo efficacy of ICP0 in combination with ionizing radiation (IR) or systemic temozolomide (TMZ) in the treatment of glioblastoma multiforme (GBM). Intracranial U87-MG xenografts were established in athymic nude mice. Animal survival was determined after mice underwent intracranial CED of either the replication-defective d106 or d109 viruses, or Hanks' balanced salt solution (HBSS), before a single session of whole-brain irradiation or TMZ treatment. Median survival for animals that underwent treatment with HBSS alone, d109 alone, d106 alone, HBSS + IR, HBSS + TMZ, d109 + IR, d106 + IR, and d106 + TMZ was 28, 35, 41, 39, 44, 39, 68 (P < 0.01), and 66 days (P < 0.01), respectively. Intracerebral d106 CED resulted in a significant increase in athymic nude mouse survival when combined with IR or TMZ. d106 CED allows for distribution of HSV-1 in human GBM xenografts and persistent viral infection.

Smectic A Formation by Twin Dimers Assuming U-shaped Conformation

Abstract Twin dimers with 3-methylpentane spacers behave as U-shaped (folding) molecules if the carbon number of alkyl tail group is longer than 12 and form an SA phase. This behavior is in contrast to that in dimers with linear pentane spacers which assume extended conformation and form the antiferroelectric SCAb. Folding of twin molecules, hence, is another way to accommodate tail groups fairly longer than the spacers, suggesting new potentiality in spontaneous molecular organization.

Mesogenic amido ester with cholesteryl moiety

A new series of mesogenic compounds having a cholesteryl moiety has been synthesized. Thirteen homologues were synthesized by condensing 4-(4′-n-alkoxy benzoyl) amido benzoyl chloride with cholesterol. The methyl to n-hexyl derivatives exhibit only cholesteric mesophases. The n-heptyl to n-dodecyl derivatives exhibit SC and cholesteric phases. The n-tetradecyl to n-octadecyl derivatives exhibit SC, SA and cholesteric phases. The plot of transition temperatures versus number of carbon atoms in the alkoxy chain exibit odd–even effect and falling tendency for cholesteric–isotropic transition temperatures. The mesomorphic and thermal stability is compared with other related homologous series. The results indicate that amide linkage enhances smectic as well as cholesteric thermal stability, but enhancement in smectic phase is much higher.

Does the Solid−Liquid Crystal Phase Transition Provoke the Spin-State Change in Spin-Crossover Metallomesogens?

Three types of interplay/synergy between spin-crossover (SCO) and liquid crystalline (LC) phase transitions can be predicted: (i) systems with coupled phase transitions, where the structural changes associated to the Cr<-->LC phase transition drives the spin-state transition, (ii) systems where both transitions coexist in the same temperature region but are not coupled, and (iii) systems with uncoupled phase transitions. Here we present a new family of Fe(II) metallomesogens based on the ligand tris[3-aza-4-((5-C(n))(6-R)(2-pyridyl))but-3-enyl]amine, with C(n) = hexyloxy, dodecyloxy, hexadecyloxy, octadecyloxy, eicosyloxy, R = hydrogen or methyl (C(n)-trenH or C(n)-trenMe), which affords examples of systems of types i, ii, and iii. Self-assembly of the ligands C(n)-trenH and C(n)-trenMe with Fe(A)2 x xH2O salts have afforded a family of complexes with general formula [Fe(C(n)-trenR)](A)2 x sH2O (s > or = 0), with A = ClO4(-), F-, Cl-, Br- and I-. Single-crystal X-ray diffraction measurements have been performed on two derivatives of this family, named as [Fe(C6-trenH)](ClO4)2 (C(6)-1) and [Fe(C6-trenMe)](ClO4)2 (C(6)-2), at 150 K for C(6)-1 and at 90 and 298 K for C(6)-2. At 150 K, C(6)-1 displays the triclinic space group P, whereas at 90 and at 298 K C(6)-2 adopts the monoclinic P2(1)/c space group. In both compounds the iron atoms adopt a pseudo-octahedral symmetry and are surrounded by six nitrogen atoms belonging to imino groups and pyridines of the ligands C(n)-trenH and C(n)-trenMe. The average Fe(II)-N bonds (1.963(2) A) at 150 K denote that C(6)-1 is in the low-spin (LS) state. For C(6)-2 the average Fe(II)-N bonds (2.007(1) A) at 90 K are characteristic of the LS state, while at 298 K they are typical for the high-spin (HS) state (2.234(3) A). Compound C(6)-1 and [Fe(C18-trenH)](ClO4)2 (C(18)-1) adopts the LS state in the temperature region between 10 and 400 K, while compound C(6)-2 and [Fe(Cn-trenMe)](ClO4)2 (n = 12 (C(12)-2), 18 (C(18)-2)) exhibit spin crossover behavior at T(1/2) centered around 140 K. The thermal spin transition is accompanied by a pronounced change of color from dark red (LS) to orange (HS). The light-induced excited spin state trapping (LIESST) effect has been investigated in compounds C(6)-2, C(12)-2 and C(18)-2. The T(1/2)LIESST is 56 K (C(6)-2), 48 K (C(16)-2), and 56 K (C(18)-2). On the basis of differential scanning calorimetry, optical polarizing microscopy, and X-ray diffraction findings for C(18)-1, C(12)-2, and C(18)-2 at high temperature a smectic mesophase SX has been identified with layered structures similar to C(6)-1 and C(6)-2. The compounds [Fe(C(n)-trenH)](Cl)2 x sH2O (n = 16 (C(16)-3, s = 3.5, C(16)-4, s = 0.5, C(16)-5, s = 0), 18 (C(18)-3, s = 3.5, C(18)-4, s = 0.5, C(18)-5, s = 0), 20 (C(20)-3, s = 3.5, C(20)-4, s = 0.5, C(20)-5, s = 0)) and [Fe(C18-tren)](F)2 x sH2O (C(18)-6, s = 3.5, C(18)-7, s = 0) show a very particular spin-state change, while [Fe(C18-tren)](Br)2 x 3H2O (C(18)-8) together with [Fe(C18-tren)](I)2 (C(18)-9) are in the LS state (10-400 K) and present mesomorphic behavior like that observed for the complexes C(18)-1, C(12)-2, and C(18)-2. In compounds C(n)-3 50% of the Fe(II) ions undergo spin-state change at T(1/2) = 375 K induced by releasing water, and in partially dehydrated compounds (s = 0.5) the Cr-->SA phase transition occurs at 287 K (C(16)-4), 301 K (C(18)-4) and 330 K (C(20)-4). For the fully dehydrated materials C(n)-5 50% of the Fe(II) ions are in the HS state and show paramagnetic behavior between 10 and 400 K. In the partially dehydrated C(n)-4 the spin transition is induced by the change of the aggregate state of matter (solid<-->liquid crystal). For compound C(18)-6 the full dehydration to C(18)-7 provokes the spin-state change of nearly 50% of the Fe(II) ions. The compounds C(n)-3 and C(18)-6 are dark purple in the LS state and become light purple-brown when 50% of the Fe(II) atoms are in the HS state.

Synthesis and properties of new liquid crystalline polyurethanes containing mesogenic side chain

The segmented and unsegmented polyurethanes (PUs) containing hexamethylene diisocyanate (HDI), poly (tetramethylene oxide) (PTMO), and 2,2-bis (hydroxymethyl)propionic acid (DMPA) as chain extender at three molar ratios were synthesized through conventional technique. Furthermore, three, new side chain polyurethanes (PUM6s) containing 4-ω-hydroxyhexyloxycarbonyl-4-hexyloxyphenylbenzoate (M6) mesogenic pendant group on the DMPA chain extender were synthesized through esterification reaction of PUs. The M6 mesogen was successfully synthesized via multi step routes from 4-hexyloxybenzoic acid and 6-hydroxyhexyl-4-hydroxybenzoate. Characterization of all synthesized compounds was carried out by FT-IR and 1H NMR. The content of carboxylic groups of polyurethanes and the degree of M6 attachment on the chain extender were determined by titration and 1H NMR methods. The properties of polyurethane were also examined by solubility tests and inherent viscosity measurements using Ubbelhode viscosimeter. Thermal behavior of the M6 and PUM6s was investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). The POM observation of M6 showed a focal conic texture formation of the SA phase on heating and cooling processes. The effect of the soft segment and M6 content on the liquid crystallinity of polymers was studied. The mesomorphic properties of PUM6 polyurethanes made up of both nonmesogenic pendant carboxyl group in the chain extender and mesogenic side chain were dependant polymer composition. Optical microscopy showed textures characteristic of the smectic A phase for PUM6-0.5 and PUM6-1 polyurethanes. The rigidity of the backbone along with the presence of the mesogenic side chains results in high Tg value for PUM6-1. Thermogravimetric analysis (TGA) displayed better thermal stability for the unsegmented polyurethane with high content of mesogenic side chain.

Self-Assembly of a Pyridyl Derivative and its Silver Complex: Formation of a Liquid Crystalline Phase and Organogels

Self-assembling behavior of N,N′-didodecyl-3,5-pyridinedicarboxamide and its silver complex has been studied. They act as gelators in solution and gelate a variety of organic solvents. Though the silver complex exhibits lower gelation abilities for halogenated and aromatic solvents, long-term stability is achieved for ethanol and acetone gels. Moreover, the silver complex exhibits a smectic A phase on cooling while a single component of N,N′-didodecyl-3,5-pyridinedicarboxamide exhibits no mesomorphic behavior. The XRD pattern for the complex shows that the layer spacing of the SA phase is 37 A˚.

DTA and Dielectric Studies of a Substance with the Nematic, Smectic A, and Smectic C Polymorphism at Ambient and Elevated Pressures

For the first time the low frequency relaxation process in two smectic phases (smectic A and smectic C) was studied at elevated pressures with the aid of DTA and dielectric spectroscopy. The substance studied, 2-(4-hexyloxyphenyl)-5-octyl-pyrimidine (6OPB8 in short) exhibits the nematic (N) - SA - SC phase sequence. The p-T phase diagram was established with DTA. However, the SA - SC transition was not observed in the DTA, but could be detected by dielectric relaxation measurements. The dielectric relaxation time measured as function of temperature and pressure, τ∥(p,T), enabled us to calculate the activation volume, Δ#V =RT(∂lnτ /∂p)T, and activation enthalpy, Δ#H = R(∂lnτ /∂T−1)p. It was found that Δ#V(SA) &gt; Δ#V(SC) and Δ#H(N) ≫ Δ#H(SA) &gt; Δ#H(SC), indicating that the molecular rotations around the short axes are more feasible in the tilted SC than in the orthogonal SA phase.

Comparison of the liquid crystalline properties of dimesogenic compounds bearing alkoxy and perfluoroalkoxy tails

The liquid crystalline properties of two series of nonsymmetric dimesogenic compounds consisting of cholesterol and Schiff base, azobenzene or stilbene mesogens interlinked by a pentamethylene spacer are compared. Compounds in the first series bear the fluorinated OCH2(CF2)6CF3 tail, whereas those in the second series bear the corresponding alkoxy tail. In general, compounds with the fluorinated alkoxy tail exhibited mesophases over a much wider temperature range than those with the alkoxy tail. Moreover, the former favored the formation of smectic phases (either chiral smectic C (Sc*) and SA phases, or SA phase) and suppressed the formation of the cholesteric phase. All of the three compounds of the second series were able to form the cholesteric phase. It was also observed that the layer spacing in compounds with the fluorinated tail was greater by 3 Å than those with the alkoxy tail. The compounds that form the Sc* phases exhibited very high spontaneous polarization, 400–500 nC cm−2. The compound with the fluorinated tail has a much shorter response time, 80 µs, than those with the alkoxy tail, 400–500 µs.

Synthesis and Thermal and Photoluminescence Properties of Liquid Crystalline Polyacetylenes Containing 4-Alkanyloxyphenyl trans-4-Alkylcyclohexanoate Side Groups

Two series of polyacetylenes containing 4-alkanyloxyphenyl trans-4-n-alkylcyclohexanoate were synthesized using [Rh(nbd)Cl]2, MoCl5, and WCl6 as initiators. Polymers 1P−3P, which contain no flexible spacer, show no mesomorphic properties due to the rigid poly(phenylacetylene) backbone. Polymers 4P−9P, which contain three or four methylene units in their spacers, exhibit both SA and Sc phases. X-ray diffraction diagrams reveal that the liquid crystalline polyacetylenes display an interdigitated bilayer structure for the smectic phases. Polymers 4P−9P are photoluminescent, and their emission wavelengths are about 500 nm. The photoluminescence intensity increased dramatically when a liquid crystalline polyacetylene was blended with poly(methyl methacrylate).