Synthesis and ferroelectric properties of chiral swallow-tailed liquid crystals derived from (L)-lactic acid

Three homologous series of chiral swallow-tailed materials derived from (L)-lactic acid were prepared. Structural effects on the mesomorphic and physical properties were investigated in terms of (i) the variation of non-chiral peripheral length chain, (ii) the variation of swallow-tailed groups and straight alkyl chain at the chiral tails, and (iii) lateral halogen substituents in the core of the molecules. The mesophases and their corresponding transition temperatures were identified by optical polarized microscopy and differential scanning calorimetry. The physical properties of the ferroelectric SmC * phases such as switching current, spontaneous polarization and electro-optical response were also measured and compared.     

Synthesis and ferroelectric properties of chiral swallow-tailed liquid crystals derived from (L)-lactic acid

Three homologous series of chiral swallow-tailed materials derived from (L)-lactic acid were prepared. Structural effects on the mesomorphic and physical properties were investigated in terms of (i) the variation of non-chiral peripheral length chain, (ii) the variation of swallow-tailed groups and straight alkyl chain at the chiral tails, and (iii) lateral halogen substituents in the core of the molecules. The mesophases and their corresponding transition temperatures were identified by optical polarized microscopy and differential scanning calorimetry. The physical properties of the ferroelectric SmC* phases such as switching current, spontaneous polarization and electro-optical response were also measured and compared.     

Synthesis and ferroelectric properties of chiral liquid crystals derived from (S)-1-propyloxy-2-propanol

A new optically active chiral moiety, (S)-1-propyloxy-2-propanol, was designed and synthesized by the treatment of 1-propanol with (S)-propylene oxide under basic conditions. Its derivatives, the (R)-1-propyloxy-2-propyl 4-[4-(4-alkoxyphenyl)phenoyloxy]benzoates, PPmPPB (m = 8-12), were prepared for the investigation of mesomorphic properties. All of the chiral materials displayed enantiotropic SmA* and SmC* phases, and the shorter alkyl chain members (m = 8-11) displayed an additional unidentified SmX* phase. The switching current, spontaneous polarization, tilt angle, dielectric constant and electro-optical response for the materials in the ferroelectric SmC* phase were measured. The electro-optic responses in polyimide film-coated homogeneously aligned cells exhibit thresholdless, V-shaped switching in the ferroelectric phase.     

Synthesis and ferroelectric properties of new chiral liquid crystals derived from (S)-lactic acid with alkoxyethanols

A homologous series of chiral materials derived from (S)-lactic acid with alkoxyethanols has been synthesized and their mesomorphic properties investigated. The mesophases and their corresponding transition temperatures were identified by differential scanning calorimetry and polarizing optical microscopy. The spontaneous polarization and electro-optical response of ferroelectric SmC* phase are measured and reported.     

Synthesis and mesomorphic properties of achiral swallow-tailed liquid crystals derived from diethylaminoalkanols

A homologous series of achiral swallow-tailed compounds derived from diethylaminoalkanols was designed and synthesized for the investigation of mesomorphism. Spectral analyses were in accord with the expected structures. Polarizing microscopy showed that all the compounds exhibit SmA and SmC_alt phases. The existence of the SmC_alt phase was confirmed by a significant first-order SmA-SmC_alt phase transition in the DSC traces, and by the appearance of a schlieren texture with a large number of four-brush and a small number of two-brush singularities under microscopy.     

Synthesis and mesomorphic properties of fluoro-substituted chiral liquid crystals derived from (S)-lactic acid with alkoxyethanols

A homologous series of fluoro-substituted chiral liquid crystals derived from (S)-lactic acid and alkoxyethanols were prepared for investigation. Mesophases and their corresponding transition temperatures were identified by polarized optical microscopy and differential scanning calorimetry. The compounds exhibit a broad temperature range in the ferroelectric chiral smectic C (SmC*) phase; in particular, compounds with shorter alkyl chain lengths have an SmC* phase at ambient temperature. The physical properties of the ferroelectric SmC* phase, such as switching current, spontaneous polarization, optical tilt angle and electro-optical response, were also measured. The effects of fluoro substituent on the mesophases and physical properties of the chiral liquid crystals are discussed.     

Synthesis and mesomorphic properties of chiral liquid crystals derived from (S)-lactic acid with 3-pentanol

The chiral swallow-tailed liquid crystals, 1-ethylpropyl (R)-2-[4-(4'-alkoxybiphenylcarbonyloxy)-phenoxy]propionates, EPmPBPP (m = 8-12), were prepared by using chiral (S)-lactic acid with 3-pentanol as starting materials. Mesophases and their corresponding transition temperatures were determined by polarizing microscopic textures and DSC. The results showed that all the chiral materials exhibited enantiotropic BP, N*, TGBA*, SmA*, and SmC* phases. Spontaneous polarization, dielectric constant and electro-optical response for the materials in the ferroelectric SmC* phase were investigated. It was noted that the electro-optical response of transmittance versus applied voltage obtained from the ferroelectric phase of material EPmPBPP (m = 10) displayed V-shaped switching, while that of other materials displayed the typical characteristics of ferroelectric hysteresis switching or U-shaped switching.     

Synthesis and mesomorphic properties of chiral liquid crystals derived from ( S )-lactic acid with 3-pentanol

The chiral swallow-tailed liquid crystals, 1-ethylpropyl (R)-2-[4-(4′-alkoxybiphenylcarbonyloxy)-phenoxy]propionates, EPmPBPP (m = 8?12), were prepared by using chiral (S)-lactic acid with 3-pentanol as starting materials. Mesophases and their corresponding transition temperatures were determined by polarizing microscopic textures and DSC. The results showed that all the chiral materials exhibited enantiotropic BP, N*, TGBA*, SmA*, and SmC* phases. Spontaneous polarization, dielectric constant and electro-optical response for the materials in the ferroelectric SmC* phase were investigated. It was noted that the electro-optical response of transmittance versus applied voltage obtained from the ferroelectric phase of material EPmPBPP (m = 10) displayed V-shaped switching, while that of other materials displayed the typical characteristics of ferroelectric hysteresis switching or U-shaped switching.     

Synthesis and mesomorphic properties of chiral swallow-tailed thioester liquid crystals with lateral substituents

Two homologous series of chiral swallow-tailed thioester materials, 1-ethylpropyl (R)-2-[3-fluoro-4-(4'-alkyloxybiphenylcarbonylthio)phenoxy]propionates, I-6 (m = 8-12), and 1-ethylpropyl (R)-2-[3-methyl-4-(4'-alkyloxybiphenylcarbonylthio)phenoxy]propionates, II-6 (m = 8-12), have been synthesized and their mesomorphic phases studied. The results show that materials I-6 (m = 8-12) with a fluoro substituent, display the phase sequence I-BPII-N*-SmC*-Cr, whereas materials II-6 (m = 8-12) with a methyl substituent display the phase sequence I-N*-TGBA*-SmA*-Cr during cooling. The physical properties of the SmC* phase in materials I-6 were measured. The results show that the maximum P _s values are in the range 91-95 nC cm^-2 and the maximum tilt angles are about 34-37°.     

Synthesis and mesomorphic properties of chiral liquid crystals derived from (S)-2-(6-hydroxy-2-naphthyl)propionic acid with a methyleneoxy linking group

Three homologous series of chiral materials derived from (S)-2-(6-hydroxy-2-naphthly)propionic acid with a methyleneoxy linking group were synthesized for the investigation of mesomorphic properties. All the materials displayed enantiotropic SmA* and SmC* phases. The spontaneous polarization (P _s) and optical tilt angles in the SmC* phase of the chiral materials were measured. The maximum spontaneous polarizations are in the range 12.3-19.1 nC cm^-2. No significant difference could be found in the P _s values with respect to the various alkyl chiral chain lengths, n. The maximum optical tilt angles are in the range 25-30°. The optical tilt angles decrease with the increase in alkyl chain length, n.     

Ferroelectric liquid crystal materials synthesized from 2(S)-[2(S)-methylbutyloxy]propanol

A new chiral alcohol, 2(S)-[2(S)-methylbutyloxy]propanol (3), containing two chiral centres has been synthesized from ethyl lactate and (S)-1-iodo-2-methylbutane. It was used as a chiral building block for the preparation of ferroelectric liquid crystal materials. Several of the new materials exhibit an enantiotropic S*_c phase with a wide temperature range. The results indicate that the molecular structure of 3 is useful for synthesizing ferroelectric liquid crystal materials.     

Ferroelectric liquid crystal materials synthesized from 2(S)-[2(S)-methylbutyloxy]propanol

Abstract

A new chiral alcohol, 2(S)-[2(S)-methylbutyloxy]propanol (3), containing two chiral centres has been synthesized from ethyl lactate and (S)-1-iodo-2-methylbutane. It was used as a chiral building block for the preparation of ferroelectric liquid crystal materials. Several of the new materials exhibit an enantiotropic S*_c phase with a wide temperature range. The results indicate that the molecular structure of 3 is useful for synthesizing ferroelectric liquid crystal materials.     

Synthesis and frustrated phases of chiral liquid crystals derived from (R)-3-alkoxy-2-methylpropionic acids

A homologous series of chiral compounds, (R)-6-(3-alkoxy-2-methylpropionyloxy)-2-naphthyl 4-alkoxybenzoates, nMPNmB (n = 2-5, m = 6-13), derived from methyl (R)-3-hydroxy-2-methylpropionate, was prepared for the study of mesormorphic phases. The mesophases were determined mainly by their microscopic textures and identified by the racemic modification. The results show that most of these compounds displayed frustrated phases BP, TGB_A* and TGB_C*, and the N*phase. Moreover, the thermal stability of the frustrated phases is significantly affected by the length of the alkyl chain in both achiral and chiral groups of the compounds. The spontaneous polarization in the TGB_C* phase of compounds nMPN10B in a surface-stabilized geometry was measured, giving P_s values of about 20 nC cm^-2.     

Stable frustrated phases in chiral liquid crystals derived from optically active (R)- and (S)-3-ethylmercapto-2-methylpropionic acids

Highly optically pure (R)- and (S)-3-ethylmercapto-2-methylpropionic acids were synthesized by using optically active (D)- and (L)-2,10-camphorsultams as chiral auxiliaries, respectively. Their derivatives, (R)- and (S)-EMMPNmB (m=6-12), were prepared for investigation. Microscopic texture observations demonstrated that the materials possess three stable frustrated phases: BP, TGB_A* and TGB_C* phases. Interestingly, it was found that the N* phase behaves as an intermediary phase between BP and TGB_A* phases in a rather narrow temperature range (calc. 0.5-1.4°C). A study of the racemic mixture, (±)-EMMPNmB (m=10), indicated that the chirality of the molecule could suppress the formation of smectic phases in the heating process. An increase of alkyl chain length favoured the formation of the TGB phases particularly, in accompaniment with a change of TGB phases from monotropic to enantiotropic. Moderate maximum P _S values (calc. 14-19 nC cm^-2) and apparent tilt angle (calc. 20°) were obtained for the TGB_C* phase in a surface stabilized ferroelectric liquid crystal geometry.     

Synthesis and ferroelectric properties of laterally substituted fluoro liquid crystals derived from 4-mercaptobenzoic acid

Several new ferroelectric liquid crystals with thiobenzoate mesogenic cores have been synthesized and the influence of a single fluorine atom ortho to the alkyloxy tail on the mesomorphic properties of some two and three benzene ring core compounds has been studied. The two benzene ring derivatives do not display the ferroelectric smectic C phase but the three phenyl ring compounds exhibit a wide temperature range S_c* phase. The transition temperatures and enthalpies of transition for these compounds have been determined; the spontaneous polarization, response time and tilt angle have also been measured and are discussed as a function of the structure near to the chiral centre.     

Effect of the variation of swallow-tailed groups on the mesomorphic and electro-optical properties of chiral compounds derived from (S)-2-(6-hydroxy-2-naphthyl)propionic acid

Three homologous series of chiral swallow-tailed compounds, alkyl (S)-2-{6-[4-(4′-alkoxyphenyl)benzoyloxy]-2-naphthyl}propionates, (S)HNP(p,n,q) derived from (S)-2-(6-hydroxy-2-naphthyl)propionic acid in conjugation with a variety of swallow-tailed groups, attached to the external side of the chiral centre, have been synthesized and their mesomorphic and electro-optical properties studied. Both (S)HNP(p,1,2) and (S)HNP(p,1,3) exhibited an enantiotropic antiferroelectric SmC*_A phase. This implys that the swallow-tailed groups in the molecules favour zigzag pairing of the molecules in the smectic phase. The maximum P _S values of compounds (S)HNP(p,1,2) in the antiferroelectric phase were measured in the range 21–30 nC cm^-2; those of compounds (S)HNP(p,1,3) were in the range 15–23 nC cm^-2, indicating that these chiral compounds possess low polarity. The electro-optical response of the compounds in the antiferroelectric SmC*_A phase displayed thresholdless V-shaped switching.     

Mesogenic properties of chiral compounds derived from 2( S )-[2( S )-ethylhexyloxy] propionic acid and its ( S, R )-diastereomer

Two acids, 2( S )-[2( S )-ethylhexyloxy] propionic acid and 2( S )-[2( R )-ethylhexyloxy] propionic acid, were used as the chiral building block for the preparation of four liquid crystals 5, 6, 7 and 8 . The diastereomers of the biphenyl ring system, 5 and 6 , possess the phase sequence I-N * -SmC * -Cr1-Cr2, while the diastereomers of the naphthalene ring system, 7 and 8 , exhibit the sequence I-SmA-SmC * -Cr. The temperature ranges of the SmC * phase for 5 and 6 are wider than those for 7 and 8 ; the phase transition temperatures of the SmC * phase for 7 and 8 are lower than those for 5 and 6 . In the case of the diastereomers of naphthalene ring system, the larger the size of the lateral substituent at the second chiral centre, i.e. ethyl or methyl group, the wider the temperature range of the SmC * phase.     

(S)-Isoleucine and (R)-2-octanol as chiral precursors of new chiral liquid crystalline thiadiazoles: synthesis, mesomorphic and ferroelectric properties

New chiral Schiff bases with a 1,3,4-thiadiazole unit in the rigid core were synthesized (SB1-SB4). These compounds contain a chiral chain derived from (S)-isoleucine and (R)-2-octanol. Their liquid crystalline properties were studied by polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. Thereby it was found that most of the new compounds exhibit a chiral Smectic C phase. A study of the ferroelectric properties is described.     

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

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

Synthesis and mesomorphic properties of new chiral banana-shaped liquid crystals with chiral 3-(alkoxy)propoxy terminal groups

New chiral banana-shaped liquid crystals with chiral 3-(alkoxy)propoxy terminal groups (Pn-O-PIMB5*-4O, n = 7, 8, 9 and 10) were synthesized and their mesomorphic properties and phase structures investigated by means of electro-optic measurements, polarizing optical microscopy, differential scanning calorimetry, and second harmonic generation measurements. Most of these chiral bent-core mesogens (n = 7-9) showed the antiferroelectric B2 phase, whereas P10-O-PIMB5*-4O exhibited the B7 phase. Comparing with the previously reported homologue Pn-O-PIMB(n-2)*, we conclude that the terminal chain structure, particularly the position of chiral centres, plays an important role in the emergence of particular phase structures.