A series of azo-type side-chain liquid crystalline polysiloxane–palladium complexes

A series of azo-type side-chain liquid crystalline polysiloxanes (AZLCPs) were synthesized, starting from organic polysiloxane and azo-type mesogenic compounds having an end allyl group. The AZLCPs were further used to coordinate with palladium dichloride and potassium chloride, by which a series of palladium complexes of AZLCPs (Pd–AZLCPs) were prepared. The mesogenic properties of all of the liquid crystalline polymers were characterized by using differential scanning calorimetry, polarized microscope and wide-angle X-ray diffraction. It was found that all of the polymer ligands and their palladium complexes showed thermotropic liquid crystallinity and that the incorporation of the palladium ions gave positive effects to the mesogenic properties of their polymer ligand counterpart. Compared with the corresponding AZLCPs, the Pd–AZLCPs have higher isotropization temperatures and a broader mesophase temperature range. The mesogenic properties of the liquid crystalline polymer ligands and their palladium complexes were also varied gradually by changing the length of the alkoxy groups on the side chain. The polymers that have a color emissive group and a highly flexible polysiloxane main chain may potentially be used as nonlinear optical materials.     

Synthesis and mesomorphic properties of fishbonelike,liquid crystalline polysilsesquioxanes: 4. Pd-coordinating,fishbone-like imine-based liquid crystalline polysilsesquioxane

A new type of Pd-coordinating, imine-based, fishbone-like liquid crystalline polysilsesquioxanes (Pd-FBI) including μ-acetato-bridged Pd-FBI [Pd(μ-oAc)-FBI] and μ-chloro-bridged Pd-FBI [Pd(μ-Cl)-FBI] has been synthesized first by a hydrosilylation reaction to form fishbone-like, imine-based liquid crystalline polysilsesquioxane (H-FBI and MH-FBI respectively,) and then by an ortho-palladation reaction with palladium acetates to obtain Pd(μ-oAc)-FBI. The latter was further subjected to ligand substitution reaction with NaCl to form Pd(μ-Cl)-FBI. Their mesomorphic properties investigated by differential scanning calorimetry (DSC) and optical polarization microscopy (OPM). show that the Pd-FBI is a thermotropic liquid crystalline polymer and its clearing temperatures and mesophase range are much higher than those of the corresponding comb-like imine liquid crystalline polysiloxanes (IMLCP) by about 100 °C. In this paper the influence of the palladium content on mesogenic behavior is discussed.     

Effect of electron donor-acceptor interaction on the thermal stability of supramolecular side chain liquid crystalline polymers based on poly(3-carboxypropylmethylsiloxane)

Supramolecular side chain liquid crystalline polymers were prepared from poly(3-carboxypropylmethylsiloxane) (PSI100) and azobenzene-based derivatives through intermolecular hydrogen bonding between the carboxylic acid groups of PSI100 and the imidazole rings in the azobenzene-based derivatives. The presence of H-bonding was confirmed using FTIR spectroscopy. The polymeric complexes behave as liquid crystalline polymers and exhibit nematic mesophases identified on the basis of the observation of Schlieren textures. The mesogenic behaviour of these complexes was studied by polarizing optical microscopy and X-ray diffraction. The thermal behaviour of the complexes was investigated by differential scanning calorimetry. On increasing the spacer length, the transition temperatures initially increase. A further increase in spacer length, however, leads to a decrease in the transition temperatures. The electron donor-acceptor interaction between unlike mesogenic units in supramolecular copolymeric complexes helps to stabilize the mesophase.     

Effect of electron donor-acceptor interaction on the thermal stability of supramolecular side chain liquid crystalline polymers based on poly(3-carboxypropylmethylsiloxane)

Supramolecular side chain liquid crystalline polymers were prepared from poly(3-carboxypropylmethylsiloxane) (PSI100) and azobenzene-based derivatives through intermolecular hydrogen bonding between the carboxylic acid groups of PSI100 and the imidazole rings in the azobenzene-based derivatives. The presence of H-bonding was confirmed using FTIR spectroscopy. The polymeric complexes behave as liquid crystalline polymers and exhibit nematic mesophases identified on the basis of the observation of Schlieren textures. The mesogenic behaviour of these complexes was studied by polarizing optical microscopy and X-ray diffraction. The thermal behaviour of the complexes was investigated by differential scanning calorimetry. On increasing the spacer length, the transition temperatures initially increase. A further increase in spacer length, however, leads to a decrease in the transition temperatures. The electron donor-acceptor interaction between unlike mesogenic units in supramolecular copolymeric complexes helps to stabilize the mesophase.     

SYNTHESIS AND MESOGENIC PROPERTY OF Pd-COORDINATING AZO-TYPE SIDE CHAIN LIQUID CRYSTALLINE POLYSILOXANE

A novel palladium-coordinating Azo-type liquid crystalline polysiloxane (Pd-AZLCP) has been synthesized by chelation reaction of polymeric ligand, Azo-type liquid crystalline polysiloxane(AZLCP), with palladium dichloride and potassium chloride in the presence of tetrahydrofuran (THF) as reaction medium instead of dioxane/water system, which has been used since Cope first reported the synthesis of palladium-azobenzene in 1965 . The mesogenic behaviors examined by DSC, temperature-variable X-ray diffraction and polarizing microscopy indicate that the incorporation of Pd ions into the liquid crystal polymer can play a positive effect on the mesogenic property of the parent polymeric ligand. It is exhibited that the isotropization temperature T_i is increased and the mesophase range ΔT has been widened, too.     

Influence of chirality on the mesophase of side chain polymers with phenyl benzoate pendant groups

To reveal the structure of an amorphous mesophase with a hidden liquid crystalline structure (ISm*) in a chiral side chain polymer, P8*M, its racemic isomer has been synthesized along with two more RS-copolymers with controlled enantiomer excess. The phase behaviour of the copolymers was studied comparatively by DSC and X-ray scattering. Optical rotatory dichroism was measured for thin films of P8*M and two homologue polymers, differing in the polymeric main chain, by the size of the chiral terminal group and by its absolute configuration. A helical superstructure with pitch of about 250 nm is indicated within the ISm* mesophase. Its structure as a short pitch TGB phase hase been proven conclusively.     

Liquid crystalline side chain polymer with a poly (Geraniol-co-MMA) backbone and phenylbenzoate mesogenic group: synthesis and characterization

A new side chain liquid crystalline polymers have been synthesized and characterized in which [geraniol-co-MMA] polymer are used as a backbone linked via polymethylene spacer to phenyl benzoate mesogenic group. The polymer exhibits enantiotropic liquid crystallinity with nematic phase and does not exhibit side chain crystallization .A clear difference between the nature of the mesophase is evidenced between [Geraniol-co-MMA] main chain and methacrylate polymers .The LC polymer exhibit glass transition at 40 °C. In a comparative analysis, we discuss the relevance of polymer backbone in the synthesis of side chain liquid crystalline polymers.     

Influence of chirality on the mesophase of side chain polymers with phenyl benzoate pendant groups

To reveal the structure of an amorphous mesophase with a hidden liquid crystalline structure (ISm*) in a chiral side chain polymer, P8*M, its racemic isomer has been synthesized along with two more RS‐copolymers with controlled enantiomer excess. The phase behaviour of the copolymers was studied comparatively by DSC and X‐ray scattering. Optical rotatory dichroism was measured for thin films of P8*M and two homologue polymers, differing in the polymeric main chain, by the size of the chiral terminal group and by its absolute configuration. A helical superstructure with pitch of about 250?nm is indicated within the ISm* mesophase. Its structure as a short pitch TGB phase hase been proven conclusively.     

Synthesis and mesomorphic properties of fishbone-like liquid crystalline polysilsesquioxanes V. Pd-coordinating, fishbone-like azo-based liquid crystalline polysilsesquioxanes

New kinds of Pd-coordinating azo-based liquid crystalline polysilsesquioxanes, Pd-H-FBA and Pd-C-FBA, have been synthesized first by hydrosilylation reactions of a vinyl-terminated mesomorphic azo compound with ladder-like homopolyhydrosilsesquioxane (H-T) and copolymethylhydrosilsesquioxane (MH-T) to produce fishbone-like, azo-based liquid crystalline polysilsesquioxanes H-FBA and C-FBA, respectively, followed by a further ortho -palladation reaction with palladium chloride. The mesomorphic properties have been investigated by DSC, optical polarizing microscopy and temperature-variable X-ray diffraction. It is found that their clearing temperatures, Tcl, are much higher and the mesophase ranges, Delta T,are much wider than those of the corresponding comb-like polymers with a single main chain by more than 100 C. This indicates that the double main chain structures of the title polymers have a positive effect on mesomorphic properties. The influence of the contents of Pd2 ions on the liquid crystallinity is also discussed.     

Shear-induced Stabilization of the Nematic Phase in a Side Group-containing Poly (aryl ether ketone) Copol ymer

IntroductionPolarized optical microscopes (POM) are commonly used to identify liquid crystalline tex-tures. However, it is often found problematic to employ this technique in investigating themesophase transition of polymeric materials due to their higher viscosities. Rheological mea-surements at this juncture could provide us with valuable information about the mesophase- transition of liquid crystalline polymers[1]. Accordingly, there have been some rheological in-vestigations reported on …     

Lightly crosslinked,mesomorphic networks obtained through the reaction of dimeric,liquid‐crystalline epoxy–imine monomers and heptanedioic acid

We reacted various dimeric, liquid‐crystalline epoxy–imine monomers, differing in the length of the central aliphatic spacer or the dipolar moments, with heptanedioic acid. The resulting systems showed a liquid‐crystalline phase in some cases, depending on the dimer and on the reaction conditions. The systems were characterized with respect to their mesomorphic properties and then were submitted to dynamic mechanical thermal analysis in both fixed‐frequency and frequency‐sweep modes in the shear sandwich configuration. The arrangement in the liquid‐crystalline phase seemed to be mainly affected both by the polarization of the mesogen and by the reaction temperature, which favored the liquid‐crystalline arrangement when it was lying in the range of stability of the dimer mesophase. In agreement with other recent literature data, dynamic mechanical thermal analysis results suggested that the presence of the mesogen directly incorporated into the main chain increased the lifetimes of the elastic modes both in the isotropic phase and in the liquid‐crystalline phase with respect to side‐chain liquid‐crystalline elastomers and that the time–temperature superposition principle did not hold through the liquid‐crystalline‐to‐isotropic transition. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44:6270–6286, 2006     

Effects of the H-bond donor structure on the properties of supramolecular side chain liquid crystalline polymers based on poly(3-carboxypropylmethylsiloxane-co-dimethylsiloxane)s and stilbazoles

Supramolecular side chain liquid crystalline polymers (SCLCPs) based on poly(3-carboxypropylmethylsiloxane-co-dimethylsiloxane) (PSIX, X=100, 76, 60, 41 or 23, denoting the mole percentage of 3-carboxypropylmethylsiloxane unit in the polymer) and stilbazole derivatives have been obtained through intermolecular hydrogen bonding (H-bonding) interactions between the carboxylic acid and the pyridyl moieties. The formation of H-bonding and self-assembly results in the formation of new mesogenic units, in which H-bonds function as molecular connectors. FTIR shows the existence of H-bonding in the complexes. The polymeric complexes behave as single component liquid crystalline polymers and exhibit stable and enantiotropic mesophases. The liquid crystalline properties of the supramolecular SCLCPs were studied using differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction, and were found to exhibit smectic A phases with focal-conic textures. The thermal stability of the SCLCP increases on increasing the carboxylic acid content in the polysiloxane and the concentration of the stilbazole derivative in the complex. However, the thermal stability decreases on increasing the chain length of the stilbazole derivative. The crystal phase was not formed even on cooling to the glass transition temperature of the polymeric complex.     

新型侧链液晶M5MPP/MMEANB高聚物的合成与表征

以4,4'-二羟基联苯、4-硝基苯胺、二溴己烷、甲基丙烯酸、氯代乙醇为原料合成了单体甲基丙烯酸[5(4'-甲氧基联苯4氧基)戊基]酯(M5MPP)、4-硝基偶氮苯基甲基-2-甲基丙烯酸酯基乙胺(MMEANB),并完成了单体的聚合和共聚,得到了含有非线性光学活性基团(NLO)的侧链液晶高分子,对其结构进行了表征.结果表明,均聚物PM5MPP及共聚物(M5MPP/MMEANB)属双向液晶高分子;PMMEANB属于非晶性高分子.证实了分子间吸电子与给电子基团相互作用有利于提高液晶高分子热稳定性,共聚物(M5MPP/MMEANB)具有较宽的液晶相温度范围.     

胆甾型侧链液晶共聚物的研究

合成并表征了两个胆甾型液晶烯类单位以及它们分别与辛烯－１，二氧化硫进行自由基共聚合得到的一系列不同组成的胆甾型侧链液晶三元共聚砜。研究结果表明：该共聚砜的两个液晶热转变温度均随其中辛烯－１单体单元组份含量的增加而降低。     

Mesomorphic properties of copolyesters of 3,6-linked triphenylene-based units and polymethylene spacers

Main chain discotic liquid crystalline polymers consisting of triphenylene-based units and alkyl spacers (C8, C10 and C12), connected by ester linkages in the 3- and 6-positions of triphenylene, have been synthesized and their mesomorphic properties were studied by DSC, polarizing optical microscopy and X-ray diffraction. It was found that these polymers exhibit a hexagonal columnar (Col h ) mesophase with intracolumnar order over a wide temperature range. The clearing temperature decreases on increasing the spacer length. It was found that the clearing temperatures are rather higher than that of the corresponding triphenylene monomer having six hexyloxy chains. These polymers form an ordered columnar mesophase, while the corresponding monomeric mesogen shows a disordered columnar phase. In the polymeric system, the fluctuations of the disc-like units in the mesophase are restricted by the connection of the mesogenic units, which stabilizes the columnar mesophase.     

Spatial configuration of chain molecules incorporated in liquid crystals and thermodynamic significance

The conformation of chain molecules participating variously in the formation of liquid crystalline mesophase has been elucidated. Two examples are mentioned: (1) the side chain flanking the α-helical backbone of polypeptides, and (2) the spacer joining mesogenic units in mainchain liquid crystals. Flexible segments play an important role in determining thermodynamic properties of these systems.     

Vinyl‐terminated side‐chain liquid‐crystalline polyethers containing mesogenic benzylideneaniline moieties

The synthesis of two vinyl‐terminated side‐chain liquid‐crystalline polyethers containing benzylideneaniline moieties as mesogenic cores was approached in two different ways: by chemically modifying poly(epichlorohydrin) with suitable mesogenic acids or by polymerizing analogous glycidyl ester or glycidyl ether derivatives. In all the conditions tested, the first approach led to materials in which the imine group was hydrolyzed. The second approach led to the desired polymers PG2a and PG2b , but only from the glycidyl ether derivatives and when the initiator was the system that combined polyiminophosphazene base t‐Bu‐P₄ and 3,5‐di‐t‐butylphenol. These polymers were chemically characterized by IR and ¹H and ¹³C NMR spectroscopies. The estimated degrees of polymerization ranged from 30 to 36. The liquid crystalline behavior of the synthesized polymers was studied by differential scanning calorimetry, polarized optical microscopy (POM) and X‐ray diffraction. Both polymers behave like liquid crystals and exhibited a single mesophase, which was recognized as a smectic C mesophase, probably with a bilayer arrangement, i.e., a smectic C₂ mesophase. The crosslinking of both polymers was performed with dicumyl peroxide as initiator, which led to liquid crystalline thermosets. POM and X‐ray diffraction confirmed that the mesophase organization mantained on the crosslinked materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1877–1889, 2006     

A STUDY ON CONFORMATIONAL STRUCTURE OF MODEL COMPOUND OF NOVEL SIDE CHAIN LIQUID CRYSTALLINE POLYMER BY USING HIGH RESOLUTION SOLID STATE ~(13)C-NMR

~(13)C-NMR chemical shifts of model compound of a novel side chain liquid crystalline polymer, poly 2.5-his (4-alkoxybenzoyloxy) styrene , have been assigned in this study. Moreover, by using high-resolution solid-state CP/MAS (cross polarization/magic angle spinning) technique, the spectrum shows that in the crystalline state the ester linkage has a conformation nearly perpendicular to the either side of ring planes, and that the alkoxy groups are not fully in zigzag form. The possible conformational changes around the mesogens from the solid state to the mesophase are discussed.     

一种侧链液晶高分子的合成与表征

合成了一种主链为甲基丙烯酸酯 ,侧链是三个苯环以酯键相连的介晶基元 ,柔性间隔段为两个亚甲基的新的侧链液晶高分子 .聚合物和单体的化学结构、液晶相转变和液晶态织构采用红外光谱、核磁共振、偏光显微镜、差热分析和广角X光衍射进行了表征 .研究表明 ,单体呈现近晶相和向列相两个液晶相 ,聚合物在很宽的温度范围内呈向列相 .该单体和聚合物在一定条件下可形成固化诱导条带织构     

Mesomorphic properties of copolyesters of 3,6-linked triphenylene-based units and polymethylene spacers

Main chain discotic liquid crystalline polymers consisting of triphenylene-based units and alkyl spacers (C8, C10 and C12), connected by ester linkages in the 3- and 6-positions of triphenylene, have been synthesized and their mesomorphic properties were studied by DSC, polarizing optical microscopy and X-ray diffraction. It was found that these polymers exhibit a hexagonal columnar (Col_h) mesophase with intracolumnar order over a wide temperature range. The clearing temperature decreases on increasing the spacer length. It was found that the clearing temperatures are rather higher than that of the corresponding triphenylene monomer having six hexyloxy chains. These polymers form an ordered columnar mesophase, while the corresponding monomeric mesogen shows a disordered columnar phase. In the polymeric system, the fluctuations of the disc-like units in the mesophase are restricted by the connection of the mesogenic units, which stabilizes the columnar mesophase.