Smectic Properties Research Articles

Effect of Laterally Substituted Methoxy Group on the Liquid Crystalline Behavior of Novel Ester Molecules

Background: The aim of this research is to study the effect of length-to-width ratio on mesomorphism to enhance the understanding of its potential applications. This will be achieved by synthesizing a unique and innovative series of identical ester molecules, including lateral methoxy groups and terminal ethyl benzoate groups. In this research, we aim to find new insights into the relationship between molecular structures and mesomorphic behaviors, which could have significant implications for the development of advanced materials with adapted properties. : The objective of the study is to investigate the mesophase behavior of new ester mesogens and determine how they are influenced by lateral methoxy groups. By identifying the underlying perspectives and relationships between these variables, we hope to better understand the unique properties and potential applications of these materials. Method: In this research work, the focus is on the synthesis of ethyl(E)-4-((3-(4-alkoxy-3- methoxyphenyl)acryloyl)oxy)benzoate, which is prepared from Steglich esterification method by using (E)-3-(4-alkoxy-3-methoxyphenyl)acrylic acid and ethyl 4- hydroxybenzoate. Synthesis processes involve precise reaction sequences designed to ensure maximum yield and purity of the final product. By providing a detailed report on the experimental process, this study contributes to the ongoing research efforts aimed at the development of innovative compounds with various applications in liquid crystals Result: A new set of liquid crystal derivatives has been synthesized and studied to investigate the effect of molecular structure on the behavior of liquid crystals, with particular attention to the group -OCH3 located laterally. This series was composed of 12 derivatives (C1-C16). Among them, the first six derivatives (C1-C6) did not have the characteristics of a liquid crystal, while the remaining derivatives (C7 and C8) had a monotropic behavior, and C10-C16 had an enantiotropic smectogenic liquid crystal behavior without exhibition of the nematic phase. The average thermal stability of the smectic property was 87.33 °C, and the mesophase range was 2 °C to 14 °C. The molecular structure was confirmed by analytical and spectral analysis. The properties of liquid crystals of this new series were compared with those of other known structurally similar homologous series. The transition temperatures were determined with an optical polarizing microscope equipped with a heating phase. Conclusion: The mesomorphic thermal and optical properties of the compounds have been validated by DSC and POM techniques. The result shows that the length of the alkyl chain has a significant influence on the mesomorphic characteristics and thermal stability of the different mesophases. Evaluation of the compounds studied indicates that the molecules are sensitive to their lateral substituent, which influences the thermal characteristics and stability of the mesophase.

Smectic layering: Landau theory for a complex-tensor order parameter

Composed of microscopic layers that stack along one direction while maintaining fluid-like positional disorder within layers, smectics are excellent systems for exploring topology, defects and geometric memory in complex confining geometries. However, the coexistence of crystalline-like characteristics in one direction and fluid-like disorder within layers makes lamellar liquid crystals notoriously difficult to model—especially in the presence of defects and large distortions. Nematic properties of smectics can be comprehensively described by the -tensor; however, lamellar order can exist independent of nematic alignment. To capture the features of the smectic layering alone, we develop a phenomenological Landau theory for a complex-tensor order parameter , which is capable of describing the local degree of lamellar ordering, layer displacement, and orientation of the layers. This theory accounts for both parallel and perpendicular elastic contributions. In addition to resolving the potential ambiguities inherent to complex scalar order parameter models, this model reduces to previously employed models of simple smectics, and opens new possibilities for numerical studies on smectics possessing many defects, within complex geometries and under extreme confinement.

Synthesis, mesomorphic properties and biological evolution of calamitic-shaped chalcone-based LCs: effect of lateral and terminal group

The mesomorphic properties of linear shaped homologous series based on two linkage group have been designed and synthesized with different side chain substituents (-OR) on the one end of terminal side with presence of lateral nitro group and second terminal iodo substituted group. Novel series consists thirteen members (C1 to C8, C10, C12, C14, C16, C18). Compounds (C1 to C6) showed nonliquid crystalline properties while compound (C7 to C18) displayed smectic and nematogenic mesophase properties. The textures of smectic C and nematic phase are fan, schlieren and droplets type. All these compounds were characterized by spectroscopic techniques such as [FTIR] and 1H Nuclear magnetic resonance [NMR] spectroscopy. The mesomorphic properties of these compounds were observed by POM and further confirmed by DSC and XRD. Chalconyl ester based compounds (C3 to C12) shows good antibacterial as well as antifungal activity compared with corresponding standard drugs.

Cell alignment by smectic liquid crystal elastomer coatings with nanogrooves.

Control of cells behavior through topography of substrates is an important theme in biomedical applications. Among many materials used as substrates, polymers show advantages since they can be tailored by chemical functionalization. Fabrication of polymer substrates with nano- and microscale topography requires processing by lithography, microprinting, etching, and so forth. In this work, we introduce a different approach based on anisotropic elastic properties of polymerized smectic A (SmA) liquid crystal elastomer (LCE). When the SmA liquid crystal coating is deposited onto a substrate with planar alignment of the molecules, it develops nanogrooves at its free surface. After photopolymerization, these nanogrooves show an excellent ability to align human dermal fibroblasts over large areas. The alignment quality is good for both bare SmA LCE substrates and for substrates coated with fibronectin. The SmA LCE nano-topographies show a high potential for tissue engineering.

Synthesis and characterisation of novel chiral smectic liquid crystalline elastomers containing menthol dimer-type side chain

ABSTRACTA series of siloxane-based chiral smectic liquid crystalline elastomers (ChSLCEs) formed by a dimer-type smectic monomer (M1), a dimer-type chiral smectic monomer (M2) and a smectic cross-linker (CL) were reported. M1 and M2 were both new liquid crystals with dimer structures, and their chemical structures and purities were characterised by Fourier transform infrared spectra and 1H NMR. The thermal stability and mesomorphism of monomers, cross-linker and ChSLCEs were examined by different analytical techniques. The results showed both monomers exhibited excellent smectic properties. The combination of different smectic phases from the two liquid crystalline side chains endowed the obtained ChSLCEs with good chiral smectic properties. The effect of different dosages of cross-linkers on the mesomorphic properties of the elastomers was also examined. The temperature ranges of mesophase-isotropic phases was narrowed with increasing addition of the cross-linkers according to the differential scanning calorimetry. All of the ChSLCEs exhibited good thermal stability from thermal gravity analysis results. The effective cross-link densities of ChSLCEs were calculated according to the swelling experiments to give the fact that the molecular weights between the cross-linking points decrease with the increase of the cross-linkers. Novel achiral smectic monomer (M1), chiral smectic monomer (M2), and an achiral smectic crosslinking agent (CL) have been synthesized to form a series of side chain chiral smectic liquid crystalline elastomers (ChSLCEs) LCE1-LCE7 by graft copolymerization with the poly(methylhydrogeno)siloxane backbone

Mesomorphism dependence on terminal polar group in the nonlinear novel azoester series

Synthesis of a novel azoester homologous series is carried out with a view to understand and establish the effect of molecular structure on liquid crystal (LC) behaviors of a substance. Novel series consists of ten LC substances. All the homologs are enantiotropically nematogenic without exhibition of smectic property. Transition and melting temperatures, textures of LC are determined by an optical polarizing microscopy equipped with a heating stage. Textures of nematic phase are threaded or schlieren. Transition curves of a phase diagram behaved in normal manner. Nematic–isotropic transition curve exhibited odd–even effect. Analytical and spectral data supported and confirmed the structures of homologues.

Mesomorphism dependence on central bridge and tail ended polar group

A novel azoester homologous series of laterally and terminally substituted viz, RO–C6H4–CH=CH–COO–C6H3–(CH3) –N=N–C6H4–Cl is synthesized, characterized and studied with a view to understand and establish the relation between molecular structure and thermotropic liquid crystalline property of its homologs. Series consists of twelve homologs. LC properties commence from very first member of a series and continue up to last homolog as enantiotropic nematic with absence of smectic property even in the monotropic condition. Transition temperatures of homologs were determined by polarizing optical microscopy equipped with a heating stage. The transition curves Cr?N and N?I behaved in normal manner. Thermal stability for nematic is 196.7?C whose mesophaselength ranges from 35°C to 131°C.

Dependence of mesomorphism on geometrical shapes of isomeric and nonisomeric series of chalconyl esters

ABSTRACTA meta substituted chalconyl ester homologous series: RO‒C6H4‒COO‒C6H4(meta)‒CO‒CH˭CH‒C6H4‒OC12H25(n)(para) is synthesized and studied with a view to understanding the effect of molecular substitution at meta position in a molecular structure on thermotropic liquid crystal properties. The novel homologous series consists of thirteen homologues (C1 to C18). All the homologues except the nonliquid crystal homologues C1, C2, C3 are enantiotropic nematic with the absence of smectic properties. The transition and melting temperatures were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren. Transition curves (Cr-N/I and N-I) behave in normal manner except homologues between C10 and C14 of N-I curve, which show negligible deviation from normal and a smooth descending tendency. The N-I transition curve exhibits an odd-even effect up to C10 homologue and then the odd-even effect disappears for higher homologues. Analytical and the spectral data support the molecular structures. Thermal stability for nematic is 107.3°C and the mesophase lengths range between 13.0°C and 35.0°C at the C18 and C12 homologues respectively. Group efficiency order for nematic is derived on the basis of thermal stability as ‒OC12H25(n) (linear) > ‒OC12H25(n) (nonlinear) > ‒OC16H33 (nonlinear).

Study of mesomorphism and its relation to molecular structure through molecular rigidity and flexibility

ABSTRACTNovel liquid Crystalline (LC) substances of chalconyl ester derivatives from Vinyl aromatic carboxylic acids are synthesized and studied with a view to understanding and establishing the relation between molecular structure, RO-C6H4-CH=CH-COO-C6H4-CH=CH-CO-C6H4-F (para) and LC properties of the thermotropic variety. Homologous series consists of eleven members (C1 to C16). C1 and C2 members of novel series are nonliquid crystals (NLC) and the rest of the homologues (C3 to C16) are enantiotropic nematic with absence of smectic property throughout. Transition temperatures and textures of homologues were determined by an optical polarizing microscope (POM) equipped with a heating stage. Textures of nematic phase are threaded or Schlieren. The transition temperatures of novel homologues are relatively lower than the corresponding dimeric trans n-Alkoxy Cinnamic acids from which, novel homologues are synthesized. Thermal, analytical, spectral data confirmed molecular structures of novel homologues. Cr-N/I and N-I transition curves behaved in normal manner except C8 to C14 homologues which deviated from normal descending tendency in N-I transition curve. N-I transition curve exhibited odd-even effect up to C6 homologue and odd member's N-I transition curve occupied lower position than even member's N-I transition curve. Thermal stability for nematic is 118.2°C; with its total mesophase length ranging from 12.0 to 50.0°C. Thus, it is a middle ordered melting type series with absence of smectic property. Group efficiency order derived on the basis of thermal stability using comparative study of present novel series with structurally similar analogous series as mentioned below.Smectic: Series-Y > Series- X = Series-1 andNematic: Series-X > Series- 1 > Series-Y

The effect of molecular rigidity and flexibility on the mesomorphism of azoesters

ASBTRACTAn Azoester novel homologous series RO-C6H4-COO-C6H4-N˭N-C6H4-OC4H9(n) (para) of liquid crystalline (LC) materials are synthesized and studied with a view to understanding and establishing the effects of molecular structure on liquid crystal behavior with reference to lateral, terminal, or central group or groups on the basis of molecular rigidity and/or flexibility. The novel homologous series consists of thirteen (C1 to C18) homologues. C1 to C5 homologues are nonmesogenic and the rest of the homologues are enantiotropically mesogenic. C8 to C18 homologues are smectogenic plus nematogenic and the remaining two C6 and C7 homologues are only nematogenic without exhibition of smectic property. Analytical, thermal and spectral data confirms the molecular structures. Textures and transition temperatures of homologues were determined by an optical polarizing microscope (POM) equipped with a heating stage. Textures of a nematic phases are threaded or Schlieren and that of a smectic phase are of the type of A or C. The average thermal stabilities for smectic and nematic are 111.3°C and 124.7°C, respectively. The smectic and nematicmesophase lengths from 10.0°C to 28.0°C and 7.0°C to 16.0°C, respectively. The transition temperatures are compared with known series.

Synthesis and phase transition behaviours of laterally substituted liquid crystals containing methylhydroquinone: emerging of smectic C phase for higher homologues

ABSTRACTA series of laterally substituted low-molar-mass liquid crystals with molecular geometry were constructed with three phenyl rings bridged through ester central groups as the rigid core and a lateral methyl group as the flexible part of a molecule, with a view to understanding and establishing the effect of molecular structure on liquid crystal behaviour. Low-molar-mass mesogens known as 1,4-bis[(4′-n-alkyloxybenzoyl)oxy]toluene with different number of carbon (n) at the alkyl chain have been prepared. Their molecular structures were proposed via physical measurements and spectroscopic techniques. Mesomorphic properties were studied by using differential scanning calorimetry, optical polarizing microscopy and powder X-ray diffraction techniques. The results showed that the melting points as well as the clearing temperatures decreased upon lengthening of the terminal alkyloxy chain lengths. Members with the shorter chain (n = 2–10) exhibited nematic phase. As for higher homologues, members with n = 12, 14, 16 and 18 showed polymorphism, whereby these compounds displayed both smectic and nematic properties.

Study of mesomorphism and laterally substituted nitro group

ABSTRACTA novel thermotropically mesomorphic, meta-substituted nitro group of chalconyl ester series, RO-C6H4-COO-C6H3-(NO2)-CO-CH=CH-C6H4OC12H25(n) (para) is synthesized and studied with an aim to establish the relation between molecular structure and the mesomorphism with reference to changing molecular flexibility in presence of nitro lateral group. Novel homologous series consist of thirteen homologs (C1–C18) whose mesomorphism commences from C5 homolog as enantiotropic nematogenic with absence of smectic property, even in the monotropic condition. Transition temperatures of novel substances were determined by an optical polarizing microscope, equipped with a heating stage (POM). Textures of a nematic phase are threaded or Schlieren. N-I transition curve exhibited narrow, sharp and short odd-even effect; with deviating trend in a phase diagram. Analytical, spectral and thermal data confirmed the molecular structures of homologs. Thermal stability for nematic is 182.89°C, whose mesophase lengths minimum to maximum ranges from 17°C to 45°C and it is an upper middle ordered melting type series. Group efficiency order for nematic is series 1 > series Y > series X, as derived from comparative study of structurally similar analogous series.

Synthesis and mesomorphic behavior of liquid crystal chalconyl esters

ABSTRACTA chalconyl homologous novel series of thermotropic liquid crystals (LC) have been synthesized and studied with a view to understand and establish the effects of molecular structure on LC properties in thermotropic behaviors. Homologous series consists of 13 homologs (C1–C18), C1–C4 homologs are nonliquid crystals and the rest of the homologs are enantiotropically nematogenic without exhibition of smectic property. Transition temperatures and the textures of the nematic phase were determined by an optical polarizing microscopy, equipped with a heating stage (POM). Texture of a nematic phase are threaded or Schlieren. The Spectral and analytical data confirms the molecular structures of homologs. Cr-N/I and N-I transition curves behaved in normal manner except C7 homolog which shows negligible abnormality for N-I transition temperature or curve with exhibition of odd-even effect.

Role of n-alkoxy terminal end groups on mesomorphism

ABSTRACTA homologous series RO-C6H4-CH:CH-COO-C6H4-CO-CH:CH-C6H4-OC6H13 (n) of novel liquid crystals (LC) has been synthesized and studied with a view to understanding and establishing the relation between molecular structure of a substance and the LC properties or behavior of thermotropic LC materials. Novel series consist of 11 homologues. C1 and C2 homologue derivatives are non-LCs and the rest of homologues (C3 to C16) are nematogenic without exhibition of smectic property. Transition temperatures were determined by an optical polarizing microscopy equipped with a heating stage. Transition curve Cr-N/I of a phase diagram behaved in normal manner. N/I transition curve partly deviated at C6 and C10 homologues from normal descending behavior, and exhibited very narrow and sharp odd-even effects. Textures of nematic phase are threaded or Schlieren. Thermal, analytical, and spectral data confirmed the molecular structures of novel chalconyl ester derivatives. Thermal stability for nematic is 95.77°C and the upper and lower mesophase lengths vary from 35 to 16°C at C5 and C8 homologues respectively. Group efficiency order derived for nematic on the basis thermal stability is -OC10H21 (n) > -OC8H17(n) > -OC6H13(n).

Study of the mesomorphism of benzoates and cinnamates

ABSTRACTTwo ester homologous series of carboxy (-COO-) and ethylene-carboxy (-CH=CH-COO-) mesogens, viz. α-4-[4’-n-alkoxybenzoyloxy] phenyl β-4’’-methoxy benzoyl ethylenes (1) and α-4-[4’-n-alkoxy cinnamoyloxy phenyl β-4’’-methoxy benzoyl ethylenes (2)] are discussed. Series (1) and (2) differ at their central linking group. Mesophase are observed at four and five number members in both homologue series. Enantiotropic nematogenic property is observed in both series (1) and (2), while some smectic property is exhibited in series (2). Thermal stability of nematic-isotropic in series (1) is relatively low as compared to (2), smectogenic property is totally absent in series (2). In phase diagram, solid-nematic, solid-isotropic, and nematic-isotropic curve follow zigzag path rising and falling. Transition temperatures are observed through hot stage polarizing microscope. Analytical data supports the structure of molecules. Threaded, Schlieren-type textures of homologues are observed through microscope.

Molecular structural flexibility dependence of mesomorphism through ortho-substituted bromo group

ABSTRACTA novel series of liquid crystal (LC) materials of Schiff's bases viz. RO-C6H4‒CH˭CH‒COO‒C6H4‒N˭CH‒C6H4‒Br (ortho) is synthesized and studied with a views to understanding and establishing the effect of molecular structure on liquid crystal properties and to provide novel thermotropic LC material to the scientific and technological community of research interest. The novel series consists of thirteen members (C1 to C8, C10, C12, C14, C16 & C18). All the members of a series are enantiotropic liquid crystals. Smectic (C10‒C18) and nematic (C1‒C18) property commence from C10 and C1 homologue respectively. Transition temperatures and the textures of homologues were determined using a polarizing optical microscope (POM) equipped with a heating stage. Transition curves Cr-M, Sm-N and N-I of a phase diagram behaved in normal manner. Odd–even effect is absent for Sm-N transition curve, but it is present for N-I curve. Sm-N transition curve is extrapolated to C8 and C6 nonsmectogenic homologues to determine and predict their latent ability for exhibition of smectic property. Analytical and spectral data confirms the molecular structures of homologues. Thermal stabilities of smectic and nematic are 85.4°C and 130.1°C °C whose upper and lower total mesophase length vary from 58.0°C to 06.0°C at the C10 and C1 = C5 = C6 homologue, respectively. Textures of nematic phase are threaded or Schlieren and smectic phase are of type A or C. LC properties of present novel series are compared with structurally series known series. Thus, present novel series is predominantly nematogenic and partly smectogenic with middle ordered melting type and considerable total mesophase length range.

Mesomorphism dependence on tail group

ABSTRACTA chalconyl homologous novel series of thermotropic liquid crystals (LC) have been synthesized and studied with a view to understand and establish the effects of molecular structure on LC properties in thermotropic behaviors. Homologous series RO-C6H4-COO-C6H4-CO-CH=CH-C6H4-OC14H29 consists of 13 homologs (C1–C18), C1–C6 homologs are nonliquid crystals and the rest of the homologs are enantiotropically nematogenic without exhibition of smectic property. Transition temperatures and the textures of the nematic phase were determined by an optical polarizing microscopy, equipped with a heating stage. Texture of a nematic phase are threaded or schlieren. The Spectral and analytical data confirms the molecular structures of homologs. Thermal stability for nematic is 123.0°C and its mesogenicphaselength ranges between 13°C and 34°C. Cr-N/I and N-I transition curves behaved in normal manner except C14 homolog which shows negligible abnormality for N-I transition temperature or curve with exhibition of odd-even effect. Some LC properties are compared with the structurally similar homologous series. Thus, present homologous series is nematogenic and middle ordered melting type.

Study of the Effects of Lateral Substitution (Bromo) on Mesomorphic Behaviours of Chalconyl Ester Derivatives

Novel homologous series: RO-C6H4-COO-C6H3-Br-CO-CH=CH-C6H4-OC18H3(n) (ortho bromo to –COO-) is synthesized and studied with a view to understand and establish the relation between mesomorphic properties and the molecular structure with reference to lateral substitution of bromine (-Br) at middle phenyl ring. Chalconyl homologous series consists of thirteen between (C1to C18) homologues. Nematogenic mesomorphism commences from C5homologue and continue up to C18homologue in enantiotropic manner. Transition and melting points were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Textures of nematic phase are threaded or schlieren. Transition curve Cr-N/I behaved in normal manner. N-I transition curve exhibited odd-even effect up to C8homologue. It (N-I) rises and fall with negligible deviations from its normal descending tendency which appears in case of homologues C10to C18. Thermal stability for nematic is 142.89 °C and the mesophase lengths vary minimum 8.0 °C to maximum 26.0 °C at the C7and C8homologue respectively. Liquid Crystal properties of present series are evaluated and compared with structurally analogous series and relative group efficiency order derived. Thus ,present series is predominantly nematogenic with absence of Smectic property. Analytical and spectral data supported moleculars of homologues.

Study of the Effects of Lateral Substitution (Bromo) on Mesomorphic Behaviours of Chalconyl Ester Derivatives

Novel homologous series: RO-C6H4-COO-C6H3-Br-CO-CH=CH-C6H4-OC18H3(n) (ortho bromo to –COO-) is synthesized and studied with a view to understand and establish the relation between mesomorphic properties and the molecular structure with reference to lateral substitution of bromine (-Br) at middle phenyl ring. Chalconyl homologous series consists of thirteen between (C1to C18) homologues. Nematogenic mesomorphism commences from C5homologue and continue up to C18homologue in enantiotropic manner. Transition and melting points were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Textures of nematic phase are threaded or schlieren. Transition curve Cr-N/I behaved in normal manner. N-I transition curve exhibited odd-even effect up to C8homologue. It (N-I) rises and fall with negligible deviations from its normal descending tendency which appears in case of homologues C10to C18. Thermal stability for nematic is 142.89 °C and the mesophase lengths vary minimum 8.0 °C to maximum 26.0 °C at the C7and C8homologue respectively. Liquid Crystal properties of present series are evaluated and compared with structurally analogous series and relative group efficiency order derived. Thus ,present series is predominantly nematogenic with absence of Smectic property. Analytical and spectral data supported moleculars of homologues.

Mesomorphism dependence on molecular rigidity and flexibility

ABSTRACTA novel homologous series of mesogens was synthesized and studied with a view to understanding and establishing the relations between molecular structure and liquid crystal properties. Eleven members of the series were synthesized. Mesogenic behavior commences from the C6 member and continues up to the C14 member. The rest of the members, C1 to C5 and C16, are non-mesogenic. Mesogenic homologues (C6 to C14) are enantiotropically nematogenic. Textures of nematic phase are threaded or Schlieren. Transition temperatures were determined by an optical polarizing microscope equipped with a heating stage. Analytical and structural data confirm the molecular structures of homologues. Thermal stability for nematic phase is 198.0°C. Mesomorphic phase length ranges from 11.0°C to 50.0°C. Cr-I/N and N-I transition curves of a phase diagram behave in normal manner from C1 to C12 members, and higher members C14 and C16 deviated from normal behavior. Mesogenic properties of present novel ester series are compared with the structurally similar series. Odd-even effect is missing for the N-I transition curve. Thus, the present series is partly nematogenic without exhibition of smectic property whose transition temperatures vary between 153°C and 210°C.