Synthesis and thermal properties of liquid-crystalline polyacrylates containing a carbazolyl group in the mesogen

The new acrylate monomers 4-(ω-acryloyloxyalkyloxy)-N-(9-methyl-2-carbazolylmethylene) anilines containing from 2 to 11 methylenic units in their alkyl group and a carbazolyl group in the mesogenic unit were synthesized and polymerized by azobisisobutyronitrile (AIBN) as radical initiator and by low-energy electron beam (EB) initiation. The thermal properties of the resulting polymers were examined using differential scanning calorimetry and thermal optical polarizing microscopy. The polymer prepared by AIBN with a hexamethylene spacer exhibited a nematic phase from 73 to 170°C and with an undecamethylene spacer exhibited a smectic phase from 55 to 202°C. The isotropization temperature of the polyacrylates increased with increasing the number of carbons of the methylenic spacer. The yield of the resulting polymer was changed by EB irradiation temperature from 4.5 to 41%. The highest yield was obtained when the monomer was polymerized in a liquid-crystalline phase. The same tendency was observed in the molecular weight of the resulting polymers. © 1994 John Wiley & Sons, Inc.     

微波法快速合成光致变色螺(口恶)嗪

螺嗪(Ｓｐｉｒｏｘａｚｉｎｅ)是20世纪70年代在螺吡喃基础上发展起来的一类具有良好光致变色性能的化合物,具有很高的抗疲劳性和光稳定性,具有潜在的商业应用前景[1-4],可用作光信息储存材料和光致变色镜片(ＰｈｏｔｏｃｈｒｏｍｉｃＬｅｎｓ)。6 哌啶取代的吲哚啉螺萘并嗪[5-11]相对于未取代的母体化合物具有更优异的光致变色性能,但是文献中的合成方法步骤繁琐、反应时间长、产率较低。本文利用微波合成了6 哌啶基(氰基)吲哚啉螺嗪,合成路线如下:1　实验部分1.1　仪器和试剂显微熔点仪(四川大学科仪厂),温度计未经校正;美国Ｐ…     

Preparation of a spirooxazine grafted PMMA and its photochromic properties

A novel spirooxazine (SO) compound was designed and synthesized. Macromolecular materials, called SO-g-hPMMAs (where the g means grafting and the h means partial hydrolysis), were prepared using PMMA (polymethylmethacrylate) with different degrees of hydrolysis. SO-g-5%hPMMA was prepared by reacting SO-containing active C-Br bonds with 5% partially hydrolyzed PMMA. The SO was characterized using ¹H NMR and infrared. Beyond that, photochromic properties were studied in detail. We discuss the effects of hydrochloric acids and hPMMAs of different hydrolysis degrees on photochromic properties of SO-g-hPMMA. Additionally, mechanical properties of the material were studied. Results indicate that the colored ring-opening form (PMC) of SO-g-hPMMA exhibits a good performance in terms of thermal stability, in contrast to the homologous SO. Experiments additionally demonstrate that hydrochloric acid improves the PMC’s thermal stability. SO-g-9%hPMMA demonstrated a good performance of photochromic properties compared to those with different degrees of hydrolysis.     

Synthesis and photochromic properties of polymers containing spirooxazine groups

Two spirooxazine (SO) compounds containing bromobutyl substituents on 1-position (SO1) and 9′- position (SO2) have been synthesized and characterized by 1H-NMR, IR and ESI-MS in this paper. SO1-g-PMMA and SO2-g-PMMA polymer were prepared by grafting SO1 and SO2 onto PMMA through C-Br bonding sites. Also, SOs were doped into PMMA matrix to afford SO1-d-PMMA and SO2-d-PMMA. Photochromic behaviors of these compounds have been studied. Compared with SO1, SO2 exhibited better photoresponse and slower bleaching in dichloromethane solution. Inserted into polymer films, the decoloration process of SOs were significantly retarded and it was found that the fading curves fitted a first-order equation; As regard to four polymers, 1-position grafting (SO2-g-PMMA) can cause a higher reduction degree on the thermal fading rate.     

超声波辐射下光致变色螺噁嗪类化合物的快速合成

在超声波辐射条件下,以Fischer碱、1-亚硝基-2,7-二羟基萘为原料,无水乙醇为溶剂快速合成了三个螺嗪类光致变色化合物,通过1 H NMR、IR对目标产物的结构进行了表征,讨论了超声辐射时间对合成产率的影响,利用超声波法合成螺噁嗪类光致变色化合物反应速率快、产率有所提高.     

Photochromic liquid-crystalline copolymers containing crown ether groups

An approach was developed for the synthesis of new multifunctional photosensitive liquid-crystalline copolymers of the acryl series containing azobenzene, ionophoric, and mesogenic groups in the same macromolecule. The phase behavior of the copolymers was studied. Most of these copolymers were demonstrated to form nematic mesophases. An increase in the concentration of crown-containing groups to 26 mol.% leads to amorphization of the copolymers. The influence of complexation of the crown ether groups of the copolymers with potassium perchlorate on the mesomorphic properties of the systems was investigated. A comparative study of the photooptical properties of the copolymers in solution and thin films was performed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2332–2242, December, 2007.     

螺噁嗪类光致变色化合物的合成研究进展

光致变色螺噁嗪;双光致变色螺噁嗪;螺噁嗪聚合物;合成;微波合成     

Preparation and photochromic properties of oligomeric poly(dimethylsiloxane) with the spiropyran or spirooxazine moiety in the side chain

Spirobenzopyran 1 , with the 3-(diethoxymethylsilyl)-propyl group at the N atom, was synthesized. The condensation reaction of the spiropyran 1 and diethoxydimethylsilane gave oligomeric poly(dimethylsiloxane) with the spiropyran moiety in the side chain. The oligomer was photochromic; its colour changed from colorless to purple-red on uv irradiation and the color faded on visible irradiation or on standing in the dark. The half-decay time of the thermal decoloration was about twice that of monomeric spiropyran dissolved in the dimethylsiloxane oligomer. Photochromic poly(dimethylsiloxane) with the spirooxazine moiety in the side chain was also prepared.     

Synthesis of functionalized spiropyran and spirooxazine derivatives and their photochromic properties

Three series of functionalized spiropyrans and spirooxazines derivatives were synthesized and their photochromic properties were investigated in particular regard to the fatigue resistance, the lifetime of the colored merocyanine form and the interaction of the colored form molecule. (1) Spiropyrans 5 and spironaphthooxazines 6 having an antioxidant group as a pendant exhibited higher fatigue resistance than that of the parent spiro compounds in solution. In particular, spiropyrans 5 showed higher resistance than parent compound 1 in the presence of an equimolar amount of the corresponding antioxidant. (2) bis-Spironaphthooxazines 8a–8i and 10 connected through a phosphoryl group exhibited higher fatigue resistance and longer lifetime of the colored merocyanine form than those of the parent spirooxazine 7. (3) Symmetrical bis-spiro photochromic compounds 15 and 16 and unsymmetrical bis-spiro compounds 13, 14 and 17 were synthesized. The bis-spiro photochromic compounds were found to undergo intramolecular interaction between the colored merocyanine forms.     

New chiral liquid crystal monomers and cholesteric polyacrylates: synthesis and characterisation

The synthesis of new chiral monomers (M₁ ?M₃ ) based on menthol and the corresponding polyacrylates (P₁ ?P₃ ) is described. The chemical structures, formula and phase behaviour of the obtained monomers and polymers were characterised with FT-IR, ¹H-NMR, elemental analyses, differential scanning calorimetry (DSC), polarising optical microscopy (POM) and X-ray diffraction (XRD). The effect of the mesogenic core rigidity, spacer length and menthyl steric effect on the phase behaviour of M₁ ?M₃ and P₁ ?P₃ is discussed. The expected mesophase of the compounds based on menthol can be obtained by inserting a flexible spacer between the mesogenic core and the terminal groups. For the chiral monomers and polyacrylates, their corresponding melting temperature (T _m), glass transition temperature (T _g) and clearing temperature (T _i) increased with an increase of the mesogenic core rigidity; while the T _m, T _g and T _i decreased with increasing the spacer length. M₁ and P₁ showed no mesophase, while M₂ and M₃ all revealed a SmC* and cholesteric phases. P₂ and P₃ only showed a cholesteric phase.     

Photoorientation in hydrogen-bonded blends of liquid-crystalline polymers with a low-molecular photochromic dopant

A series of hydrogen-bonded blends of nematic liquid-crystalline copolymers with a low-molecular photochromic dopant and their covalent analogs were prepared. Their phase behavior and photooptical properties were studied. The introduction of a dopant increases considerably the isotropization temperatures of the systems. A comparative study of photoorientation processes in the blends and copolymers analogous to them was carried out. The induced dichroism in covalent systems is more pronounced than in similar hydrogen-bonded blends. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 322–328, February, 2008.     

Structure and photochromic properties of a single-crystalline spiro[indolinepyranopyridinium] salt

The molecular and crystal structure of single crystalline 5’-hydroxymethyl-1,3,3,7’, 8’-pentamethylspiro[indoline-2,2’-[2H]-pyrano[3,4-b]pyridinium] iodide (1) was studied. The crystal structure is composed of cation layers separated by iodide ions and provides a sufficient volume for the phototransformation of compound 1. The spectroscopic and photochromic properties of this compound in the crystalline state were investigated. Upon irradiation with light at 270–370 nm, up to 600 layers of single crystals are subjected to photochromic transformations. The quantum yield of formation of the open form is ∼0.1, and the quantum yield of decoloration is 0.04. After ten reversible photocyclizations, the absorption of the colored form was decreased by 10%. The photochromic properties were related to the single-crystal structure. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2050–2055, September, 2005.     

Synthesis and characterisation of thermotropic liquid-crystalline properties of azomethine dimers

A series of azomethine dimers were prepared by condensation reactions of benzaldehyde, biphenylcarboxaldehyde and 9-anthraldehyde with various aromatic diamines of varying flexibility in ethanol in the presence of tosic acid. Their chemical structures were determined by Fourier transform infrared and ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopies, as well as elemental analysis. Their thermal properties were also examined by using a number of experimental techniques, including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarising optical microscopy (POM) and variable temperature X-ray diffraction (VTXRD). Azomethine dimer, prepared from benzaldehyde and 1,9-bis(4-aminophenoxy)nonane, exhibited a monotropic, nematic liquid-crystalline (LC) phase. The majority of the azomethine dimers containing biphenyl moieties exhibited enantiotropic, nematic LC phase on melting at relatively low temperatures, since they developed typical Schlieren, threaded or marbled textures in their LC phase. They also had accessible isotropisation temperatures well below their decomposition temperatures. Azomethine dimers containing anthracene moieties did not exhibit LC properties, but exhibited polymorphism as determined by POM and VTXRD in two cases. All of these azomethine dimers in the series had excellent thermal stability that was in the broad range of temperatures of 307–400°C depending on their degrees of aromaticity index.     

Efficient synthesis and photochromic properties of 2,3-position hybrid diarylethene derivatives

An efficient synthetic method was proposed to synthesize some 2,3-position hybrid diarylethene derivatives. In these compounds, one of thiophene rings was attached to the ethylene moiety at 2-position, the other at 3-position. These asymmetric diarylethenes are sensitive at wavelengths in the region of 400 and 500 nm. They can undergo thermally irreversible and fatigue-resistant photochromic reactions in solution, some of them even in the solid state. Substituent effects on their photochromism were examined.     

Liquid crystalline behavior and fluorescent property of calix[4]arene containing azobenzene photochromic group

The reaction of 4′-hydroxy-4-methyl azobenzene (1) and 1,6-dibromohexane afforded 6-bromo-1-((4-((4-met hylphenyl)azo)phenyl)oxy)hexane (2), which further reacted with p-tert-butylcalix[4]arene to give the calix[4]arene derivative (3) whose lower rim had been modified by the azobenzene photochromic group. The structure of 3 was characterized by ¹H-nuclear magnetic resonance (NMR) and electrospray ionization-mass spectrometry (ESI-MS). The fluorescence intensity of compound 3 was two to four times higher than that of compounds 1 and 2 as the azobenzene group concentration in the range of 1.6 × 10⁻⁵ to 8.0 × 10⁻⁴ mol/L, indicating that the fluorescence quantum yield of the azobenzene group had been improved through being attached to the calix[4]arene skeleton. The liquid crystalline behavior of compound 3 was studied by polarized microscopy (POM) and differential scan calorimeter (DSC). Compound 3 exhibited the enchased texture of a smectic liquid crystal from 209.4°C to 219.5°C on heating, while 2 exhibited a liquid crystalline phase from 87.4 to 83.2°C on cooling. It was found that the calix[4]arene skeleton was a good platform for conformation immobilization of azobenzene photochromic group and the formation of liquid crystalline. Translated from Chinese Journal of Applied Chemistry, 2006, 23(9): 1023–1026 [译自: 应用化学]     

Synthesis and characterization of chiral azo LCPs with optical properties

ABSTRACT

In this study, we designed, synthesised and characterised two series of cholesteric liquid crystal polymers, QP series and ZP series. With polymethylhydrosiloxane as the main chain, QP series were synthesised by copolymerisation between the monomer M₁ containing a cholesteryl mesogenic unit and the monomer M₂ with a hydroxyl. ZP series, meanwhile, were synthesised by esterification between QP series members and the monomer M₃, a carboxylic acid with an azo mesogenic unit. We characterised chemical structures of all the monomers and polymers by FT-IR and ¹H-NMR, which proved that the target monomers and polymers had been obtained. We observed dramatic colour changes after the introduction of monomer M₃ and Grandjean textures from both QP series and ZP series using POM. In addition, strong selective reflection could be observed as well. Then, we characterised the thermal properties of polymers by DSC, TGA and XRD to explore their phase transition behaviours further. Their photoresponsive and photochromic properties were characterised by UV-Vis spectrum.     

N-乙基-9′-溴丁氧基螺噁嗪的合成及其化学改性PMMA的结构与光致变色性能

合成了分子结构中含活性C—Br键的N-乙基-9′-正溴丁氧基螺噁嗪(Br-SO),利用Br-SO分子结构中的化学基团C—Br与部分水解的聚甲基丙烯酸甲酯(hPMMA)反应制备含SO的PMMA高分子化合物(SO-hPMMA)。采用1 HNMR和IR对Br-SO结构进行了表征,研究了Br-SO、SO-hPMMA的光致变色性能及其影响因素。研究表明:Br-SO、SO-hPMMA均具有良好的光致变色性能,且SO-hPMMA的热稳定性明显高于Br-SO。     

Mesomorphic and luminescent properties of side chain nematic liquid-crystalline polymers containing Ir(III)

Iridium-containing liquid-crystalline polymers were obtained by graft copolymerisation using poly(methylhydrogeno)siloxane, 1-methyl-4-(4-(4-vinylcyclohexyl)cyclohexyl)benzene (M₁) and an iridium complexes monomer (Ir-M₂). The series of polymers contained different molecular fractions of Ir-M₂ from 0% to 1.2%. All of these polymers showed mesomorphic behaviours. The introduction of small amount of iridium ions endowed liquid-crystalline polymers with luminescent properties. The chemical structures were characterised by IR and ¹H NMR. The mesomorphic properties and phase behaviour were investigated by differential scanning calorimetry, thermal gravimetric analysis, polarising optical microscopy and X-ray diffraction. With an increase of iridium complexes units in the polymers, the glass transition temperature (T_g) did not change significantly; the isotropic temperature (T_i) decreased. All polymers showed typical nematic marble textures, which was confirmed by X-ray diffraction. The temperatures at which 5% weight loss occurred (T_d) were greater than 300°C for the polymers. The introduction of iridium complexes units did not change the liquid-crystalline state of polymer systems. With Ir³⁺ ion contents ranging between 0.6 and 2.4 mol%, luminescent intensity of polymers gradually increased.     

Synthesis and characterization of graft copolymers containing poly(p-phenylene) main chains and mesogen-jacketed liquid-crystalline polystyrene side chains

A series of novel comblike mesogen-jacketed liquid-crystalline graft copolymers, poly(p-phenylene)-g-poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PPP-g-PMPCS) copolymers, have been designed and successfully synthesized by a Yamamoto coupling reaction and subsequent atom transfer radical polymerization (ATRP). ¹H NMR spectroscopy, ultraviolet–visible spectra, and gel permeation chromatography (GPC) have been used to confirm the molecular structure of the macroinitiator and the copolymers. A study of the polymerization kinetics of ATRP has shown that the molecular weight of the copolymer increases linearly with the conversion of the monomer, whereas the polydispersity remains narrow (≤1.28), indicating that the ATRP of 2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene is well controlled. Thermogravimetric analysis and differential scanning calorimetry (DSC) measurements have indicated that the PPP-g-PMPCS copolymers have better thermal stabilities than the macroinitiator, and their thermal stabilities increase with increasing molecular weight. The liquid-crystalline behavior has been examined with polarized optical microscopy, DSC, one-dimensional wide-angle X-ray diffraction (1D WAXD), and two-dimensional wide-angle X-ray diffraction (2D WAXD). The results show that all the comblike copolymers exhibit obvious liquid-crystalline behaviors, even though the GPC molecular weight of the segments of poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS) have been determined to be far less than the critical value of linear PMPCS. Moreover, 1D WAXD measurements show that the temperature at which the comblike mesogen-jacketed liquid-crystalline copolymers can transform into a liquid-crystalline phase is low; about 20 °C in comparison with the linear ones. 2D WAXD analysis has revealed that these comblike copolymers should be assigned to a hexatic columnar nematic (Φ_HN) phase. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2543–2555, 2007     

Side‐chain liquid crystalline polyacrylates containing 3,4‐disubstituted pyrrole moiety

Polymerization of liquid crystalline bifunctional monomer N‐{{ω‐{4‐[4‐(11‐acryloyloxy)undecanoxybenzoyl]biphenyleneoxy} alkyl}}‐3,4‐dimethylpyrrole gave a side‐chain liquid crystalline polyacrylate containing 3,4‐dimethylpyrrole group. Liquid crystallinity was determined by DSC and optical polarizing microscope measurements. The monomers having pentylene, hexylene, and decylene as the alkylene spacer group between the mesogenic unit and the 3,4‐dimethylpyrrole group exhibited smectic and nematic phases on the heating and cooling stages. The radically polymerized polyacrylate derivatives containing the 3,4‐dimethylpyrrole group showed nematic phases on the heating and cooling stages. These polymers are the first example of side‐chain liquid crystalline polymers containing 3,4‐dimethylpyrrole as functional group for further reaction. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1214–1221, 2000