Liquid crystalline ionomers. II. Main chain liquid crystalline polymers with terminal sulfonate groups

Liquid crystalline ionomers containing sulfonate groups on the terminal unit of the chain were synthesized by an interfacial condensation reaction of 4,4′-dihydroxy-α,α′-dimethyl benzalazine, the monofunctional dye fast yellow (FY), and a 50/50 mixture of sebacoyl and dodecanedioyl dichlorides. The weight-average molecular weights were estimated from inherent viscosity measurements to be between 6000–11,000 and the sodium sulfonate concentrations ranged from 0–18.4 meq/100 g polymer. Elemental analyses, however, indicated much higher molecular weights, which suggested that there was a distribution of chains with one, two, or no FY endgroups. The polymers were semicrystalline and melted at ca. 140°C to form nematic mesophases that were stable over a temperature range of ca. 80°C. They were thermally stable to about 350°C. The ionomeric nature of the polymers was confirmed by the presence of intermolecular associations in nonpolar solvents, as demonstrated by dilute solution viscosity measurements.     

主链型高分子液晶向列相向错观察的进展

综述了主链型高分子液晶向列相向错在实验观察方面的进展。从纹影织构的观察和展曲、弯曲弹性常数相等条件下的二维曲率弹性理论出发探讨了向错结构的几何特征。简要涉及了弹性常数不相等对向错的影响、向错核心的本质和反转墙的观察;给出了拓扑强度s高达4的高阶向错的实验观察结果;归纳出描绘向错周围指向矢场的主要实验方法:1)片晶装饰;2)条带织构装饰;3)表面微裂纹装饰。本文对上述方法进行了讨论和比较,列举了一些电子显微镜和光学显微镜照像的图例。     

Synthesis and properties of liquid crystalline polyurethanes

Liquid crystalline polyurethanes were prepared from 4,4′-bis(2-hydroxyethoxy)biphenyl (BHBP) and 2,4-tolylene diisocyanate (TDI). The effect of partial replacement of BHBP by 25–75 mol % poly(oxytetramethylene) diol (PTMO, M _n = 250) on the liquid crystalline properties was studied. The BHBP/TDI/PTMO polyurethanes were obtained by one- and two-step polyaddition. The polyurethanes were investigated by DSC, polarizing microscopy, x-ray, and IR spectroscopy. The molecular weight distribution was determined by GPC. The morphology of the polymers was investigated by the SALS method. Thermogravimetric investigations of the polyurethanes were also performed. All polyurethanes containing BHBP units have liquid crystalline properties. Partial replacement of BHBP by PTMO-250 considerably changes the phase transition temperatures and the range of mesophase occurrence. More homogeneous polyurethanes were obtained, if the two-step polyaddition method was applied. The polyaddition method affects the phase transition temperatures. © 1993 John Wiley & Sons, Inc.     

Segmented polyurethanes with 4,4′-bis-(6-hydroxyhexoxy) biphenyl as chain extender. I. Synthesis and characterization of 2,4-tdi-polyurethanes

Polyurethanes composed of 2,4-toluene diisocyanate (TDI), poly (butylene adipate) diols (PBA) of different molecular weights, and 4,4′-bis-(6-hydroxyhexoxy) biphenyl (BHHBP) were prepared by a two-step solution polymerization process. The polyurethanes were char-acterized by elemental analysis, NMR, and SEC. The thermal properties were investigated by DSC, DMA, and optical polarizing microscopy. Dependent on the molecular weight of the PBA, a shift in the glass transition temperature T_g of the polyurethanes has been observed by DSC and DMA. Polyurethanes based on poly (butylene adipate)s of M_n ～ 2000 exhibited a T_g nearly independent on the hard-segment content up to 50% LC hard segments, indicating the existence of mainly phase separated soft and hard segments. By shortening the PBA chain length up to 1,000 and further to 600, the T_g of the polyester soft-segment phase increases with growing hard-segment content, a consequence of enhanced interaction between the hard and soft segments. This tendency is observed to the greatest extent at polyurethanes with the shortest, polyester diol and can be interpreted as a partial miscibility or compatibility of hard and soft segments. Although in polyurethanes with PBA 2000 the mesophase can be proven at a hard-segment content of ～ 40%, its appearance in polyure-thances prepared with PBA 1000 or PBA 600 requires a hard-segment content > 60%. © 1995 John Wiley & Sons, Inc.     

Mesophase transition-induced reorientation in a stretched side-chain liquid crystalline polymer

The orientation relaxation behavior of a stretched side-chain liquid crystalline polymer (SCLCP) on a poly(vinyl alcohol) (PVA) film under strain was investigated through infrared dichroism at temperatures near its phase transitions. We found a reorientation of the aligned mesogens over the smectic to nematic transition of the SCLCP, changing the alignment from an initially, mechanically induced perpendicular orientation to a parallel orientation with respect to the film-stretching direction. This reorientation was found to be irreversible during subsequent nematic to smectic transition, with the parallel orientation preserved. We show that it is possible to stop the reorientation process by cooling the SCLCP back to its smectic phase just before the change in the alignment direction. Moreover, this interruption can result in a stable, zero macroscopic orientation of the mesogens in the stretched SCLCP, and a subsequent heating to the smectic-nematic transition allows the reorientation process to restart and to be completed. We discuss the possible mechanisms for this mesophase transition-induced reorientation and the factors that could influence the process. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1491–1499, 1997     

Annealing effects on the thermal properties of liquid crystalline polyurethanes

This work is a continuation of our earlier investigations of liquid crystalline polyurethanes prepared from 4,4′-bis(2-hydroxyethoxy) biphenyl (BHBP), 2,4-tolylene diisocyanate (TDI), and poly (oxytetramethylene) diols (PTMO). The annealing effects on the thermal properties of the investigation polyurethanes are presented for three samples with the same BHBP content, different flexible spacer length, and different molecular weight of the polyurethanes. The annealed polyurethanes were investigated by means of DSC, and polarizing microscopy. The results of the thermal analysis show that the temperatures of phase transitions depend on the annealing temperature and time. These dependences are different for different molecular weights. © 1994 John Wiley & Sons, Inc.     

Photo and electrically switchable behavior of azobenzene containing pendant bent‐core liquid crystalline polymers

New class of photo and electrically switchable azobenzene containing pendant bent‐core liquid crystalline monomers ( AZBM 1, 2 , and 3 ) and their polymers ( AZBP 1, 2 , and 3 ) are reported. The synthesized precursors, monomers, and polymers were characterized by FT‐IR, ¹H, and ¹³C NMR spectroscopy. Thermal stability of polymers was examined by thermogravimetric analysis and revealed stable up to 260 °C. The mesophase transition of monomers and polymers are observed through polarized optical microscopy (POM) and further confirmed by differential scanning calorimetry (DSC). The electrically switching property of monomers and their polymers were studied by electro‐optical method. Among the three monomers AZBM 1, 2 , and 3 , AZBM 1 and 2 exhibit antiferroelectric (AF) switching and AZBM 3 exhibits ferroelectric (F) switching behavior. On the other hand, low molecular weight polymers ( AZMP 1, 2 , and 3 ) show weak AF and F switching behavior. The photo‐switching properties of bent‐core azo polymers are investigated using UV‐vis spectroscopy, trans to cis isomerization occurs around 25 s for AZBP‐1 and 30 s for AZBP‐2 and 3 in chloroform, whereas reverse processes take place around 80 and 90 s. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Main-chain liquid crystalline copolymers: synthesis and comparative study of the mesomorphic properties and non-linear optical properties

Linear main-chain polymers (P1, P2 and P3) have been synthesised and characterised. The polymers were designed to understand the rigidity of the mesogen’s linking groups and its effect on transition temperature. The liquid crystalline behaviour of these polymers was investigated using polarised optical microscopy and differential scanning calorimetry. All polymers exhibited phase transition on heating and cooling runs. The mesophase stability decreases with the decrease of rigidity of the second mesogen (P2>P1>P3). Similarly, the enthalpy and entropy changes are dependent on the rigidity of the second mesogen (Mesogen B). Polymer P1 undergoes photoisomerisation under UV-visible light irradiation and it attains a photo-stationary state at 275 s. This provides an opportunity to investigate the third-order non-linear optical properties. The non-linear behaviour of polymer P1 in chloroform presents a distinct deviation in a different concentration, where polymer P1 also exhibits a negative non-linear refractive index. Thus, polymer P1 can be used as a potential candidate for optical device applications such as optical limiters.     

Molecular engineering of photoactive liquid crystalline polyester epoxies containing benzylidene moiety

A series of photoactive liquid crystalline polyester epoxies incorporating bisbenzylidene segments as photoactive mesogenic cores were synthesized by polyaddition of diepoxy monomers and terephthalic acid/trimesic acid. To investigate the influence of structural parameters such as, molecular architecture, structural rigidity of mesogenic unit and substituents on thermal, mesogenic, and photoactive properties, the bisbenzylidene segment was incorporated into one acyclic and two cycloalkanone units with two and four substituents, respectively in both linear and hyperbranched architectures. Degree of branching of hyperbranched polymers was found to be in the range of 0.49–0.62. All polymers exhibited nematic mesophase (nematic droplets). Photo induced (2π + 2π) cycloaddition reaction, upon exposure to light at 365 nm, was examined. Inter molecular photocycloaddition was confirmed by photoviscosity measurement of UV irradiated polymer solutions. Faster photo induced reactivity of polymers in hyperbranched architecture was observed when compared to linear structure. Acyclic units facilitated photocycloaddition, and five‐membered ring showed higher photoactivity compared to six‐membered ring. The steric hindrance caused by substituents decreased the photoactivity of polymers. Refractive index change was found to be in the range of 0.015–0.024. Substantial variation of refractive index indicates that these polymers could be used for optical recording. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7637–7655, 2008     

Influence of molecular weight on some properties of liquid crystalline polyurethanes

This investigation extends our previous investigations of liquid crystalline polyurethanes prepared from 4,4′-bis(2-hydroxyethoxy)biphenyl (BHBP), 2,4-tolylene diisocyanate, and poly(oxytetramethylene)diols as the flexible spacers. The influence of molecular weight of investigated polyurethanes on their properties is discussed for two series with the same content of BHBP and different lengths of flexible spacers. The polyurethanes were investigated by means of DSC, polarizing microscopy, x-ray diffractometry, and IR spectroscopy. The molecular weight distribution was determined by GPC. Morphology was studied by the SALS method. The molecular weight of polyurethanes and the length of flexible spacer influence the phase transition temperature and the range of mesophase occurrence. © 1993 John Wiley & Sons, Inc.     

Synthesis and properties of mesogen‐jacketed liquid crystalline polymers containing bistolane mesogen

On the basis of the concept of mesogen‐jacketed liquid crystalline polymers, a series of new methacrylate monomers, (2,5‐bis[2‐(4′‐alkoxyphenyl) ethynyl] benzyl methacrylate (MACn, n = 4, 6, 8, 10, and 12) and 2,5‐bis[2‐(6′‐decanoxynaphthyl) ethynyl] benzyl methacrylate (MANC10), and their polymers, PMACn (n = 4, 6, 8, 10, and 12) and PMANC10 were synthesized. The bistolane mesogen with large π‐electron conjugation were side‐attached to the polymer backbone via short linkages. Various characterization techniques such as differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized light microscopy were used to study their mesomorphic phase behavior. The polymer PMACn with shorter flexible substituents (n = 4) forms the columnar nematic (?_N) phase, but other polymers with longer flexible tails (n = 6, 8, 10, and 12) can develop into a smetic A (S_A) phase instead of a ?_N phase. The PMANC10 containing naphthyl can also form a well‐defined S_A phase. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

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.     

Fully aromatic thermotropic liquid crystalline polyesters of 3-phenyl-4,4′-biphenol with 4,4′-benzophenone dicarboxylic acid

A series of fully aromatic, thermotropic polyesters, derived from 3-phenyl-4,4′-biphenol (MPBP), nonlinear 4,4′-benzophenone dicarboxylic acid (4,4′-BDA), and various other comonomers was prepared by the melt polycondensation method and characterized for their thermotropic liquid crystalline behavior by a variety of experimental techniques. The homopolymer of MPBP with 4,4′-BDA had a fusion temperature (T_f) at 240°C, exhibited a nematic liquid crystalline phase, and had a narrow liquid crystalline range of 60°C. All of the copolyesters of MPBP with 4,4′-BDA and either 30 mol % 4-hydroxybenzoic acid (HBA), 6-hydroxy-2-naphthoic acid (HNA) or 50 mol % terephthalic acid (TA), 2,6-naphthale-nedicarboxylic acid (2,6-NDA) and low T_f values in the range of 210–230°C, exhibited a nematic phase, and had accessible isotropization transitions (T_i) in the range of 320–420°C, respectively. As expected, each of them had a broader range of liquid crystalline phase than the homopolymer. They had a “frozen” nematic, glassy order as determined with the wide-angle X-ray diffraction (WAXD) studies. The morphology of each of the “as-made” polyesters had a fibrous structure as determined with the scanning electron microscopy (SEM), which arises because of the liquid crystalline domains. Moreover, they had higher glass transition temperatures (T_g) in the range of 167–190°C than those of other liquid crystalline polyesters, and excellent thermal stabilities (T_d) in the range of 500–533°C, respectively. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of side-chain liquid crystalline polymer containing dichroic dye monomer

A series of side-chain liquid crystalline polysiloxanes containing 1-(p-toluidino)-4-anthraquinone undecylenate (TAU) (dye-monomer) and 4-allyloxybenzoyl-4^′-(p-propyl-benzoyl)-p-benzenediol bisate (ABB) (liquid crystalline monomer) side groups were synthesized by copolymeraztion. The molecular structures of the monomers and polymers were confirmed by FT-IR spectroscopy. The optical characterization of the monomer ABB and polymers was made by using polarizing optical microscopy (POM) technique, and their thermal behaviour was investigated by thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC). The conjugate action of the dye (1-(p-toluidino)-4-hydroxyl anthraquinone) and the monomer was analyzed by fluorophotometry. Polymers and monomer ABB revealed nematic phase. And DSC results demonstrated that the glass transition temperatures (T_g) of the polymers increased with the increase in dye-monomer. TGA result showed that the temperatures at which 5% mass loss occurred () for all the polymers were above 270 °C.     

Sandwich structure containing liquid crystal polymer grafted on polymer support

Graft post-polymerization of mesogenic monomers onto fluorine-containing polymer support was initiated by the simultaneous action of vacuum ultraviolet radiation and atomic oxygen. The resultant two-layer structure possesses the combined physical–mechanical properties of the polymer-supporting film and the optical characteristics of the anisotropic liquid crystal layer.     

Fully aromatic thermotropic liquid crystalline homopolyesters of 3,4′-benzophenone dicarboxylic acid

A series of fully aromatic, thermotropic homopolyesters, derived from 3,4′-benzophenone dicarboxylic acid and various aromatic diols, was prepared by the melt polycondensation method and examined for thermotropic behavior by a variety of experimental techniques. The aromatic diols used in the study were hydroquinone, 2,6-, 1,4-, 1,5-, 2,3-, and 2,7-naphthalenediol isomers. All of the homopolyesters of 3,4′-benzophenone dicarboxylic acid with aromatic diols (except that with 2,7-naphthalenediol) formed a nematic LC phase in the melt. They had the glass transition temperatures (T_g) in the range of 133–164°C, the melting transitions (T_m) in the range 305–360°C and the high thermal stabilities (T_d) in the range of 410–483°C. The 2,6-naphthalenediol based homopolymer had the highest T_m (360°C) and the 2,3-naphthalenediol based homopolymer had the lowest T_m (305°C) among all of the homopolymers of naphthalenediol isomers. © 1994 John Wiley & Sons, Inc.     

Side-chain liquid crystalline polymers with silphenylene-siloxane main chains. III. Synthesis and characterization of polymers with phenyl benzoate mesogenic groups

Side-chain liquid crystalline (SCLC) silphenylene-siloxane polymers with a phenyl benzoate mesogenic group and polymethylene spacers were prepared and characterized, and their properties were compared with those of equivalent SCLC polymers, SCLCPs, with a biphenyl mesogenic group. With identical spacers and terminal substituents, the melting temperatures of the former were much lower, but the isotropization temperatures were lowered to a lesser extent, than those of the latter, and, consequently, a more thermally stable nematic phase was obtained for the former. Both types of SCLCPs formed nematic phases, while polymethylsiloxanes with the same side-chain mesogens exhibited smectic phases with wider temperature ranges. The lower thermal stability of the mesophases in the silphenylene-siloxane SCLCPs compared to those of the SCLC polymethylsiloxanes can be attributed to both the rigidity of the backbone and the greater separation of the side-chains along the main chains of the former.     

Effect of the poly(oxytetramethylene)diol spacer length on some properties of liquid crystalline polyurethanes

Previous studies on liquid crystalline polyurethanes prepared from 4,4′-bis(2-hydroxyethoxy)biphenyl (BHBP) and 2,4-tolylene diisocyanate (TDI) were continued. In this article, a series of polyurethanes, which differ in the flexible spacer length and BHBP content is described. Poly(oxytetramethylene)diols of different molecular weights (PTMO, M _n = 250, 650, 1000, 2000) were used as flexible spacers. The polyurethanes were investigated by DSC, polarizing microscopy, x-ray diffractometry, and IR spectroscopy. The molecular weight distribution was determined by GPC. The morphology of the polyurethanes was investigated by the SALS method. Partial replacement of BHBP by 25–75 mol % PTMO and the flexible spacer length influence the liquid crystalline properties, the phase transition temperatures, and the range of mesophase occurrence. © 1993 John Wiley & Sons, Inc.     

Mesophase structure of low‐wetting liquid crystalline polyacrylates with new perfluoroalkyl benzoate side groups

The synthesis, thermal behavior, bulk microstructure, and wettability of new polyacrylates carrying spaced 4‐perfluorohexylpropyl benzoate and 4‐perfluorooctylpropyl benzoate units in the side groups were investigated. X‐ray diffraction analysis proved the formation of different smectic mesophases (SmI₂, SmF₂, and SmC₂) and the evolution of their structures and lattice parameters with temperature. The mesophase polymorphic behavior depended on the length of the perfluorinated chain segment in the repeat unit. The electron density profiles along the smectic layer normal were drawn and provided a deeper insight into the packing of the side chains in a tilted, double layer structure. Thin polymer films were cast from solution, and their low wettability was established by measurements of contact angles with different probing liquids. We suggest that the hydrophobicity and lipophobicity of the films are enhanced by the mesophase surface structure which is mediated by the high‐order, mesophase bulk structure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4128–4139, 2010