Design of advanced multicomponent ferroelectric liquid crystalline mixtures with submicrometre helical pitch

New functional multicomponent ferroelectric liquid crystalline mixtures have been designed while searching smart self-assembling materials with submicrometre periodicity of the helical structure responding definite demands for application in electro-optic devices and photonics that exploit the deformed helix ferroelectric effect. The resulting designed mixtures possess the paraelectric smectic A* and the tilted ferroelectric smectic C* phases over a very broad temperature range down below the room temperature. The mesomorphic, electro-optic and dielectric properties have been studied and discussed. The presence of a very stable enantiotropic ferroelectric smectic phase exhibiting almost temperature independent helical pitch within 150–250 nm range and reasonably high values of the tilt angle might allow these mixtures to be applicable for practical purposes.     

Studies on thermotropic liquid crystalline polyurethanes. II. Synthesis and properties of liquid crystalline polyurethane elastomers

Three series of novel thermotropic liquid crystalline polyurethane elastomers (TLCPUEs) were studied. Hard segments were formed by using hexamethylene diisocyanate (HDI) reacted with a mesogenic unit, benzene-1,4-di(4-iminophenoxy-n-hexanol), which also acted as a chain extender. Three diols: 1,10-decanediol,poly(oxytetramethylene) glycol (PTMEG) M _n = 1000 and PTMEG M _n = 2000 were used as the soft segments. The effects of soft segments of polyurethanes on the liquid crystalline behavior were studied. Higher molecular weight TLCPUEs were obtained by adding 30?50 mol % of mesogenic segments to diisocyanates. In contrast to a conventional chain extender such as 1,2-ethylene glycol or 1,4-butyl glycol, the synthesized polyurethane elastomers exhibited a mesophase transition by using a mesogenic unit as the chain extender. Mesophase was found for all synthesized LC polyurethanes except of polymers H2-A-12 and H2-A-7. The structures and the thermal properties of all synthesized TLCPUEs were studied by using FTIR spectroscopy, wide-angle x-ray diffraction (WAXD) and DSC measurements, a polarizing microscope equipped with a heating stage, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). Mechanical properties were also examined by using a tensilemeter. © 1995 John Wiley & Sons, Inc.     

Synthesis and properties of reactive liquid crystal monomers and side-chain liquid crystalline polymers

Two nematic liquid crystal (LC) monomers containing double bonds in the side chain were designed and synthesised. Length of the side groups varied from 1 to 2 methylene units. The side-chain polymers were synthesised by hydrosilylation reaction. The molecular structures of the intermediates and the LC monomers were characterised by Fourier transform infrared, elemental analysis and nuclear magnetic resonance spectroscopy. The thermal phase behaviour of the monomers and polymers were investigated by differential scanning calorimetry and polar optical microscopy coupled with hot stage. The LC monomers showed only one nematic mesophase in the cooling process. And, the two polymers exhibit an enantiotroppic nematic mesophase either in the heating or in the cooling process.     

Studies on thermotropic liquid crystalline polymers. XV. Synthesis and properties of liquid crystalline copoly(imide-ester)s

Three series of the thermotropic liquid crystalline copoly(imide-ester)s were prepared by direct polycondensation. The first two series of the copoly(imide-ester)s were synthesized from N-(4-carboxyphenyl) trimellitimide with N,N-di(hydroxypropyl) pyromellitic diimide and various aromatic diols. The third series of copoly(imide-ester)s were prepared by N-(4-carboxyphenyl) trimellitimide with various imide-diols (methylene spacer = 2–6) and phenyl hydroquinone. The structures and thermal properties of the synthesized poly(imide-ester)s were examined by FTIR spectrum, wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermal optical polarized microscope, and thermogravimetric analysis (TGA). The effects of the structures of the aromatic diols on the thermal properties of the resulting copoly(imide-ester)s were investigated. It was found that most of the copoly(imide-ester)s possessed excellent mesophase stabilities and thermostabilities. The mesophase stabilities of poly(imide-ester)s decreased with the increase of the size of lateral group, and the mesophase range increased with the increase of the amount of PhHQ. No significant odd-even effects were observed between the methylene spacer lengths and transition temperatures. © 1996 John Wiley & Sons, Inc.     

Synthesis and properties of liquid crystalline polyurethanes

1,4-Bis(p-hydroxybenzoate)phenylene was prepared using 1,4-bis(trimethylsiloxy)benzene and p-hydroxybenzoyl chloride as starting materials. A series of novel 1,4-bis(p-hydroxyalkoxybenzoate)phenylene were synthesized by reaction of 1,4-bis(p-hydroxybenzoate) phenylene with 3-brompropanol and 4-bromobutanol, respectively. The liquid crystal polyurethanes were prepared by 1,4-bis(p-hydroxyalkoxybenzoate)phenylene with MDI (p-methylene diphenylenediisocyanate) and 2,4-TDI(2,4-toluenediisocyanate), respectively. The thermotropic properties, the melting point (T _m) and the isotropization temperature (T _i) of the synthesized polyurethanes were characterized by DSC, IR and POM. It showed that all of the polyurethane polymers exhibited thermotropic liquid crystalline properties between 144°C and 260°C. The transition temperature (T _m and T _i) decreased with an increase in the length of the methylene spacer. __________ Translated from Journal of Qingdao University of Science and Technology, 2006, 27(1) (in Chinese)     

Studies on the thermotropic liquid crystalline polycarbonates. II. Synthesis and properties of fully aromatic liquid crystalline polycarbonates

Four series of fully aromatic polycarbonates were prepared by using melt polycondensation from various novel phenylene diphenyl dicarbonates: 1,4-phenylenc diphenyl dicarbonate, 1,3-phenylene diphenyl dicarbonate, methyl-1,4-phenylene diphenyl dicarbonate, and chloro-1,4-phenylene diphenyl dicarbonate with various diols—4,4′-biphenyl diol, hydroquinone, 2,7-naphthalene diol and 1,5-naphthalene diol, respectively. The thermotropic liquid crystalline properties of synthesized polycarbonates were investigated by: (1) examination of the melt birefringence and stir opalescence by a polarizing microscope equipped with a heating stage, (2) characterization by a differential scanning calorimeter (DSC), and (3) analysis of the wide angle x-ray diffraction. It was found that the 1,3-phenylene unit is compensated for the nonlinearity of the carbonate group, and polycarbonates which contain this bent shape unit showed excellent wide mesophase transition in this study. © 1993 John Wiley & Sons, Inc.     

Synthesis and mesomorphic properties of the nematic mesophase benzoxazole derivatives with big twist angle of difluoro-biphenyl unit

Modifying the position and numbers of lateral fluorine substituent is a common method to design and adjust the mesophase of liquid crystal compounds. Here, a series of 2-(2,2?-difluoro-4?-alkoxy-1,1?-biphenyl-4-yl)-5-substituted benzoxazole with both non-polar (H, CH₃) and polar (NO₂) groups (coded as nPF(2)PF(2)Bx) is synthesised and characterised. All of the compounds show a conspicuous inter-ring twist angle of 38° compared with corresponding reference compounds I and II which are calculated by density functional theory method, and it is interesting to note that the final compounds nPF(2)PF(2)Bx show only nematic mesophase during heating or cooling. Meanwhile, the UV-vis absorption bands and photoluminescence emission peaks both display remarkable blue-shifted. The aforementioned results reveal that lateral difluoro substituents play a key role to stable the nematic mesophase by increasing the dihedral angle of biphenyl.     

官能化苯并菲盘状液晶的合成及不饱柔链对介晶性的影响

合成了12个含不饱和软链的苯并菲盘状液晶化合物,C18H6（OC5H11）6-x（OR）x（x=1,2,3）,R=-C3H6CH=CH2（a）,-C3H6C≡CH（b）,-C2H4OCH=CH2（c）.化合物结构通过核磁共振氢谱和高分辨质谱表征.化合物热致液晶性通过偏光显微镜（POM）,差视扫描热量法（DSC）,和X射线衍射（XRD）进行了研究.结果显示目标化合物呈现有序的六方柱状介晶相.端炔基链化合物b系列熔点最高.乙烯氧基柔链化合物c系列有最高的清亮点和最宽的介晶性温度范围,且随着不饱和醚链数的增多,清亮点明显升高.对称苯并菲化合物sym-C18H6（OC5H11）3（OR）3比不对称化合物asym-C18H6（OC5H11）3（OR）3具有更高的熔点和清亮点.乙烯氧基柔链可极化的偶极相互作用对液晶稳定性有较大贡献.     

Microwave-assisted synthesis of rufigallol and its novel room-temperature liquid crystalline derivatives

An efficient, simple, rapid and economic microwave-assisted synthesis of rufigallol, a molecule of both biological and physical interest, is reported. The acid-catalyzed self-condensation of gallic acid under microwave irradiation produces rufigallol in high yield within 90 s. Alkylation of rufigallol with branched-chain alkyl halides under microwave irradiation provides novel room-temperature discotic liquid crystals in excellent yield.     

Effect of ferroelectric liquid crystalline quaterphenyl structure and handedness on helical pitch length in bicomponent mixtures

The aim of this paper is characterisation of mesomorphic properties and helical structure parameters: handedness and helical pitch, of two laterally substituted ferroelectric compounds and mixtures based on them. These compounds have the same quaterphenyl rigid core and the same length of non-chiral chain – eight carbon atoms, as well as the absolute configuration of chiral centre (‘R’). Base compounds differ in the kind of a substituent in a rigid core (–Cl, –CH₃). Both of them have rather low melting temperature in comparison to most of quaterphenyls, and it affects the lowering of this temperature in binary mixtures. Thus they can be used for preparation of multicomponent ferroelectric mixtures useful for application.     

Synthesis and mesomorphic properties of three-benzene-ring-containing banana-shaped liquid crystals

A homologous series of three-benzene-ring-containing banana-shaped compounds, N,N-bis(4-alkylcarbonyloxybenzylidene)benzene-1,3-diamine, were synthesised by esterifying aliphatic acids with the three-benzene-ring bent core 1,3-phenylene-bis(4-hydroxybenzylideneamine). As the number of carbon atoms in the aliphatic acids increased from 1 to 12, 12 novel banana-shaped compounds resulted with increasing lengths in their terminal tails. The mesomorphic properties of this homologous series of three-benzene-ring-containing banana-shaped compounds were characterised by means of polarised optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical studies. Our results have demonstrated that this series of banana-shaped compounds can form mesophases, although each of their bent cores contains only three benzene rings.     

Studies on thermotropic liquid crystalline polymers. XIV. Synthesis and properties of liquid crystalline poly(imide-ester)s by the direct polycondensation

A series of semi-aromatic poly(imide-ester)s were prepared by the direct polycondensation of N-(4-carboxyphenyl) trimellitimide or N-(3-carboxyphenyl) trimellitimide with various pyromellitic diimide diols containing methylene spacer = 2–6, respectively. The effect of the amount of LiCl, pyridine, and the kinds of condensation agents on the direct polycondensation were studied. The structures and thermal properties of the synthesized poly(imide-ester)s were examined by FTIR spectrum, wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermal optical polarized microscopic observation, and thermogravimetric analysis (TGA). It is found that P1 series [derived from N-(4-carboxyphenyl) trimellitimide] with even number methylene spacer (n = 4, 6) exhibit smectic mesophase, but P2 series [derived from N-(3-carboxyphenyl) trimellitimide] do not show LC phase. © 1996 John Wiley & Sons, Inc.     

新型噻二唑类液晶的合成与研究

合成了以酰胺键为中心桥键的三芳环1,3,4-噻二环系共8个新化合物。液晶性质测试证明它们均为具有高相变温度和宽相变范围的稳定的液晶化合物。     

Synthesis of thermotropic liquid crystal polyimide and its properties

Thermotropic liquid crystal polyimide which has neither an ester linkage nor a carbonate linkage was prepared by the polymerization of 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA) and 1,3-bis[4-(4′-aminophenoxy)cumyl)]benzene (BACB). This polyimide shows the liquid crystal phase at 549-593 K. Mixing this liquid crystal polyimide or copolymerizing BACB decreases the melt viscosity of the thermoplastic polyimide (Aurum). © 1994 John Wiley & Sons, Inc.     

Synthesis and liquid crystal properties of new banana-shaped cinnamoyl derivatives

Three new achiral five-ring banana-shaped homologous series have been synthesized and their liquid crystalline properties studied by polarizing microscopy, differential scanning calorimetry, and electro-otpical analysis. The compounds consist of two identical mesogenic structures of bis (alkoxycinnamoyloxybenzoates) linked on a different central ring (unsubstituted or methyl-substituted). The length of the terminal alkoxy groups was varied from heptyloxy to dodecyloxy; the hexadecyloxy group was also included in the study. It was found that the polymorphism of compounds can be strongly dependent upon molecular structure in this class of compound. In particular, substituents on the central ring may exert a significant effect on the type of mesophase observed.     

Effects on molecular orientation and phase transition of addition of carbon nanotubes into liquid crystalline matrix

For practical guest–host applications, it is important to choose dyes with a high ability of orientation in the liquid crystal (LC) matrix. In this experimental work, two different azo-structured dyes (disperse yellow 3 and 7) were separately doped to each of two different nematic LCs (E7 and ZLI-1132). Their solubilities, textures, phase transition temperatures and order parameters were determined. At the second stage, single-walled carbon nanotubes (SWCNTs) in a small amount were separately added to each of these solutions, and the experiments were repeated as similar to the previous ones. The solubilities of dyes in the LC E7 were lower than those of ZLI-1132. Moreover, the highest order parameter value was attained with yellow 7 dye in ZLI-1132 nematic host. Co-use of nanoparticles (CNTs) as dopant resulted in notable increases in order parameters. These dyes and CNTs did not significantly destabilise the mesomorphic phase of nematic hosts. An appreciable change in textures was not monitored with addition of dopant(s). In addition, it was observed that the narrowing on the temperature range of the LC did not take place with the addition of dopants to the crystal; on the contrary, an increase was recorded.     

Orientational and electro-optical properties of liquid crystal aligned with a directly spinnable carbon nanotube web

We investigated the orientational and electro-optical properties of a nematic liquid crystal (LC) aligned with a directly spinnable carbon nanotube (CNT) web functioning both as an electrode and as an alignment layer. The LC molecules were uniformly oriented along the drawing direction of the CNT web and the spatially averaged birefringence was comparable to a rubbed polyimide sample. The CNT web sample also showed smaller residual DC and hysteresis compared to the polyimide sample.     

The effects of some factors on the rheological properties of the lyotropic liquid crystals formed in Brij97/NaDC/IPM/water system: compositions,temperature and polyphenols

In this paper, interaction between Brij97 and NaDC in mixed micelles was studied by surface tension method. Phase behavior for Brij97/NaDC/IPM/H₂O system was investigated at the desire molar ratio of α_NaDC?=?0.42 and the human body temperature of 37?°C. Hexagonal and cubic liquid crystal were found in this system analyzed by small angle x-ray scattering (SAXS). some factors were changed to affect the rheological properties of liquid crystal. Rheological investigations showed: The higher content of water and lower experimental temperature favored the greater values of shear viscosity and viscoelastic modulus; The sample was closer to the plastic fluid and was more likely to recover from disturbed state to equilibrium state at lower ratio of NaDC; The curcumin and TP can influence the shear viscosity, viscoelastic properties and phase transition temperature, even change the structure of liquid crystal. This supplies a way to adjust rheological properties, structure and even phase transition by altering those factors.     

The structure and physical properties of in situ composites based on semiflexible thermotropic liquid crystalline copolyesteramide and poly(butylene terephthalate)

Liquid crystalline polymer–poly(butylene terephthalate) (LCP/PBT) blends were prepared by melt mixing. The LCP employed was a thermotropic copolyesteramide based on 30 mol % of p‐amino benzoic acid (ABA) and 70 mol % of poly(ethylene terephthalate) (PET). The thermal, dynamic mechanical and rheological properties, morphology, and crystal structure of LCP/PBT blends were studied. The results showed that the semiflexible ABA30/PET LCP is miscible in the melt state with PBT, and they are partial miscible in the solid state. Differential scanning calorimetric measurements showed that the introduction of the semiflexible LCP into LCP/PBT blends retards the crystallization rate of PBT. However, the LCP dispersed phase acted as the sites for the nucleation of spherulites and enhance the degree of crystallinity of PBT. Hot‐stage optical microscopy examination revealed that the LCP microfibers with random orientation are dispersed in the PBT matrix of compression molded LCP/PBT blends. Under the application of a shearing force, the LCP domains in the PBT matrix tended to deform into microfibers, and to orient themselves along the flow direction. The formation of microfibers resulted in an increase of the storage modulus. The torque measurements indicated that the melting viscosity of the LCP/PBT blends is much lower than that of the pure PBT. Finally, the wide‐angle X‐ray diffraction patterns indicated that PBT shows no structural change with the incorporation of LCP, but the apparent crystal sizes of several diffraction planes change significantly. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 403–414, 2000     

Novel luminescent liquid crystalline polyazomethines. Synthesis and study of thermotropic and photoluminescent properties

Novel semiflexible polyazomethines containing chromophoric units into azomethine mesogenic core have been synthesised by condensation of a flexible dialdehyde with mesogenic diamines containing fluorene, antraquinone, pyrimidine, azobenzene and benzophenone. The thermotropic behaviour of the resulting polyazomethines was assessed by differential scanning calorimetry, polarised light microscopy and investigations of the miscibility relations. While the pure polyazomethines showed a birefringent viscous texture difficult to be ascribed, by mixing with a liquid crystal dimer, clear Schlieren or marbled textures were observed, indicating a nematic mesophase. The polymers exhibited violet, blue or yellow light emission.