Liquid crystalline polymers V. Thermotropic liquid crystalline poly(azomethine-ether)s containing a cycloalkanone moiety in the polymer backbone

A new homologous series of thermotropic liquid crystalline poly(azomethine-ether)s was synthesized by solution polycondensation of various diformyl-alpha,omega-diphenoxyalkanes, I-VIII with 2,5-bis(m-aminobenzylidene)cyclopentanone, XI and 2,6-bis(m-aminobenzylidene)cyclohexanone, XII. The inherent viscosities of the polymers were in the range 0.34-0.75 dI g^-1. The mesomorphic properties were studied as a function of the diphenoxyalkane spacer length. Analyses by DSC and optical polarized microscopy demonstrated that the poly(azomethine-ether)s form nematic mesophases over wide temperature ranges. The poly(azomethine-ether)s based on the cyclohexanone moiety had better thermal stabilities than the corresponding poly(azomethine-ether)s based on cyclopentanone.     

Liquid crystalline polymers VII. Thermotropic liquid crystalline poly(azomethine-ether)s containing dibenzylidene derivatives in the main chain

A new homologous series of thermotropic liquid crystalline poly(azomethine-ether)s based on dibenzylidene derivatives was synthesized by solution polycondensation of various diformyl-α,ω-diphenoxyalkanes, I-VIII with 2,7-bis-(m-aminobenzylidene)cycloheptanone IX and bis-(m-aminobenzylidene)acetone X. The inherent viscosities of the polymers were in the range 0.23-0.69 dl/g. All the poly(azomethine-ether)s were insoluble in common organic solvents but dissolved completely in concentrated H₂SO₄ and methanesulphonic acid. The mesomorphic properties were studied as a function of the diphenoxyalkane space length. Analysis by differential scanning calorimetry and optical polarized microscopy demonstrated that the poly(azomethine-ether)s from nematic mesophases over wide temperature ranges.     

Studies on photocrosslinkable-cum-flame retardant poly(benzylidene phosphoramide ester)s

Four series of photocrosslinkable-cum-flame retardant poly(benzylidene phosphoramide ester)s were synthesized from bis(4-hydroxy-3-methyoxybenzylidene) acetone, 2,5-bis(4-hydroxy-3-methoxybenzylidene)cyclopentanone, 2,6-bis(4-hydroxy-3- methoxybenzylidene)cyclohexanone and 2,7-bis(4-hydroxy-3-methoxybenzylidene) cycloheptanone with various arylphosphorodichloridates by interfacial polycondensation using a phase transfer catalyst. The resultant polymers were characterized by gpc, FTIR, ¹H, ¹³C and ³¹P-NMR spectroscopy. Thermal behavior of the polymers was evaluated by differential scanning calorimetry and thermogravimetry. Flame retardant properties were ascertained by Limiting Oxygen Index. The photocrosslinking ability of the polymers was studied by ultraviolet spectroscopy. The crosslinking proceeds via 2π + 2π cycloaddition reaction of the benzylidene groups. The rate of crosslinking decreases with increase in the size of cycloalkanone ring, while the thermal stability increases with increase in the size of the alkanone ring. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3285–3291, 1999     

Synthesis and characterization of photosensitive liquid crystalline poly(benzylidene‐ether)s with alkanones and methylene spacers in the main chain

Photosensitive main chain liquid crystalline poly (benzylidene‐ether)s were synthesized by Claisen‐Schmidt polycondensation reaction of 4,4′‐Diformyl‐α,ω‐diphenoxyalkanes with acetone, cyclopentanone and cyclohexanone. The diformyl precursors were synthesized from 4‐hydroxybenzaldehyde and dibromoalkanes of varying spacer lengths. The structure of the monomers and polymers was confirmed by ELEM ANAL , Fourier transform infrared, ¹H NMR and ¹³C NMR spectral analyses. Molecular weight of the polymers was determined by gel permeation chromatography and was found to be moderate. The thermogravimetric analysis data revealed that the polymers were stable up to 280 °C and start degrading thereafter. Cyclopentanone containing polymers are more stable than acetone and cyclohexanone containing polymers. The self‐extinguishing properties of the synthesized polymers were studied by the determination of the limiting oxygen index values with Van Krevelen's equation. The influence of the length of methylene spacer on phase transition was investigated with differential scanning calorimetry and proved that the isotropic temperature decreases as the spacer length increases. Polarized optical microscopic study showed that cyclohexanone containing polymer IIIb exhibit nematic schlieren texture. Crystallinity of the polymers was studied with X‐ray diffractograms. The photolysis of liquid crystalline poly(benzylidene‐ether)s revealed that the entgegen, zusammen (EZ) photoisomerization proceeds in the system. Fluorescence spectra showed violet and green emission maxima. The band gap energy is calculated from absorption spectra are in the range of 3.17–3.40 eV. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Investigation on dual properties of photosensitive thermotropic liquid‐crystalline poly(benzylidene‐ether)s containing alkanones and methylene spacers in the main chain

Thermotropic main chain liquid‐crystalline poly (benzylidene‐ether)s were synthesized by Claisen‐Schmidt polycondensation reaction of 4,4′‐diformyl‐2,2′‐dimethoxy‐α,ω‐diphenoxyalkanes with acetone, cyclopentanone, and cyclohexanone. The diformyl precursors were synthesized from 4‐hydroxy‐3‐methoxybenzaldehyde with dibromoalkanes of varying spacer lengths. The structure of monomers and polymers was confirmed by elemental analyses, Fourier‐transform infrared, ¹H NMR, and ¹³C NMR spectral analyses. The thermal properties were studied by thermogravimetric analysis and differential scanning calorimetry. Thermogravimetric analysis (TGA) data revealed that the polymers were stable up to 285 °C and start degrading thereafter. Cyclopentanone‐containing polymers are more stable than cyclohexanone‐ and acetone‐containing polymers. The self‐extinguishing property of the synthesized polymers was studied by calculating the limiting oxygen index values using Van Krevelen's equation. The influence of the length of methylene spacer on phase transition was investigated using differential scanning calorimetry (DSC), and it was proved that the isotropic temperature decreases with an increase in the length of the spacer. Polarized optical microscopic study showed that cyclohexanone‐containing polymers exhibit nematic threadlike and nematic droplet texture. The photolysis of liquid‐crystal poly(benzylidene‐ether)s revealed that the Entgegen, Zusammen (EZ) photoisomerization proceeds in the system. The band gap energy was calculated from absorption spectra and is in the range of 3.05–3.37 eV and proved that the length of spacers has a significant influence on their absorption and emission. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and characterization of new unsaturated polyesters and copolyesters containing azo groups in the main chain

A new interesting class of linear unsaturated polyesters based on dibenzylidenecycloalkanones have been synthesized by interfacial polycondensation of 4,4^′-azodibenzoyl chloride or 3,3^′-azodibenzoyl chloride with: 2,5-bis(p-hydroxybenzylidene)cyclopentanone I, 2,6-bis(p-hydroxybenzylidene)cyclohexanone II, 2,6-divanillylidenecyclohexanone III, or 2,7-bis(p-hydroxybenzylidene)cycloheptanone IV at ambient temperature. The copolyesters are also synthesized from the monomers I, II, III or IV with the diacid chlorides. The resulting polyesters and their copolyesters were characterized by elemental analyses, IR spectroscopy and solubility. Additionally, inherent viscosity of the polyesters in the range 0.32-0.86 dL g⁻¹ and the inherent viscosity of the copolyesters in the range 0.28-0.65 dL g⁻¹ were determined. The UV-visible spectra of certain polymers were measured in m-cresol solution and showed a characteristic absorption band at 435-473 nm due to n-π^* transition. The thermal properties of the polymers were evaluated by thermo gravimetric analysis and differential scanning calorimetry measurements and correlated with their structural units. The crystallinity of some polyesters and copolyesters were tested. In addition, the electrical properties of all polyesters and copolyesters were measured.     

微波辐射相转移催化下水相合成α,α'-双亚苄基环烷酮

芳醛与环戊酮或环己酮在碳酸钠水溶液中, 用微波辐射-相转移催化法合成 α,α'-双亚苄基环烷酮, 反应在0.5～7 min内完成, 产率高达80%～99%, 后处理极为简便, 是一种环境友好的绿色合成.     

Study on the thermotropic liquid crystalline polycarbonates. IV. Synthesis and properties of liquid crystalline poly(imide-carbonate)s

Two series of novel thermotropic liquid crystalline poly(imide-carbonate)s were prepared by melt polycondensation from various arylene or alkylene bis(phenylcarbonate)s by using N,N′-bis(hydroxyethyl)pyromellitimide and N,N′-bis(hydroxypropyl)pyromellitimide as monomers. Thermotropic liquid crystalline properties were characterized by a polarizing microscope with a heating stage and a differential scanning calorimeter (DSC). Nematic melts were found for the synthesized aromatic poly(imide-carbonate)s. In order to investigate whether the pyromellitimide unit could be used as a mesogenic unit for preparing LC polymers, a series of aliphatic poly(imide-carbonate)s was prepared in this study. However, no significant LC textures were found under the observation by polarizing microscope. It was suggested that the aspect ratio of the pyromellitimide unit was too short to form liquid crystalline poly(imide-carbonate)s. In addition, it was interesting that the aliphatic poly(imide-carbonate)s with a longer spacer (n = 3) in the pyromellitimide unit showed better crystallinity. Thermostabilities of all synthesized poly(imide-carbonate)s were measured by thermogravimetric analysis (TGA). © 1994 John Wiley & Sons, Inc.     

分子筛固载氟化钾催化芳香醛与环酮的缩合反应

在回流甲醇条件下, 使用分子筛固载氟化钾催化芳醛与环己酮或环戊酮的缩合, 反应80～480 min, 获得56%～95% 产率的α,α'-二取代苯叉环烷酮.     

几个烯胺的邻硝基苯甲酰化和在酸水解中发生的重排

为了了解芳酰基化的效率和双酰基衍生物的形成, 对几个典型醛和酮的吗啉烯胺进行了邻硝基苯甲酰化的探索。丁醛和异丁醛吗啉烯胺的酰化正常, 水解分别生成55%的2-(邻硝基苯甲酰基)丁醛(2)和40%的2-(邻硝基苯甲酰基)异丁醛(3)。3-戊酮和1, 3-二甲氧基丙酮的吗啉烯胺在酰化和水解时分别生成37%和14.8%相应的β-二酮的烯醇邻硝基苯甲酸酯(4)和(5)。4和5的酸水解发生意外的1, 5-和1,3-酰基转位, 分别生成3, 5-二甲基-2, 6-双(邻硝基苯基)吡喃-4-酮(6)和2-甲氧基-2-甲氧乙酰基-1, 3-双(邻硝基苯基)-1, 3-丙二酮(7)。环戊酮和环已酮吗啉烯胺的酰化分别产生9%和34%的双酰基烯胺(9a)和(9b),逐次酸水解得到2-(邻硝基苯甲酰基)环戊酮(11a)和-环已酮(11b)。在总酰化产物的直接水解中, 11a的产率可以达到81%, 而11b只有35%。对双酰化进行了一些讨论。     

Dilute Solution Properties of Poly(Vinyl Chloride)

Light scattering and viscosity studies were made on dilute solutions of poly(vinyl chloride) (PVC) in three solvents: cyclo-hexanone, cyclopentanone, and tetrahydrofuran. Eight samples of PVC (M_w = 25,400 to 145,000) were used to determine the intrinsic viscosities, molecular weights, and the polymer-solvent interaction parameters over a range of temperatures. The solutions were found to behave normally and to exhibit no evidence of aggregate formation. The molecular weights obtained in all three solvents were independent of temperature and agreed well within the experimental errors. The interaction parameters observed were independent of concentration and molecular weight, and functions only of temperature. The intrinsic viscosities were related to molecular weight by the Mark-Houwink equation between 20 and 50°C. The temperature coefficient of the interaction parameter obtained by light scattering agrees well with that found by viscometry. Cyclohexanone, cyclopentanone, and tetrahydrofuran are all good solvents for PVC, and the order of solvent quality is cyclohexanone > cyclopentanone > tetrahydrofuran.     

Synthesis and characterization of processable heat resistant co-poly(ester-amide)s containing cyclopentylidene moiety

New cyclopentylidene ring-containing diamino-diesters, 1,1-bis(3-aminobenzoyloxy phenyl) cyclopentane, was prepared through reaction of cyclopentanone with two moles of phenol to yield 1,1-bis (4-hydroxy phenyl) cyclopentane (BHPP) (I), the resulting diol (I) on reaction with 3-nitrobenzoyl chloride in N,N-dimethyl acetamide (DMAc) and triethyl amine yield 1,1-bis(3-nitrobenzoyloxy phenyl) cyclopentane (II) which on finally reduced by catalytic hydrogenation in presence of 10% Pd/C in DMAc and stirred at room temperature under a 4 kg/cm² hydrogen pressure yields 1,1-bis(3-aminobenzoyloxy phenyl) cyclopentane (III) (m-BABPP). The structure of novel m-diester-diamine was confirmed by FT-IR, ¹H-NMR and ¹³C-NMR. A series of new m-poly (ester-amide)s and co-poly(ester-amide)s were synthesized by using the solution polycondensation method of novel diamine (III) with IPC and TPC in various mole proportion. These novel polymers were characterized by FTIR spectroscopy, solubility, inherent viscosity and thermal analysis and XRD studies. Inherent viscosities of these polymers were in the range 0.30 to 0.46 dL/g indicating moderate molecular weight built-up. These polymers exhibited excellent solubility in various polar aprotic solvents such as NMP, Pyridine. These polymers were partially soluble in DMSO, DMAc, DMF etc.

X-Ray diffraction pattern of polymers showed that introduction of cardo moiety containing ester linkage would disturb the chain regularity and packing, leading to amorphous nature. Thermal analysis by TGA showed excellent thermal stability of polymers. The structure -property correlation among these poly(ester-amide)s were studied, in view of these polymer's potential applications as processable high temperature resistance materials.     

Kinetics of swollen surface layer formation in poly(vinyl chloride)–solvent system

The kinetics of formation of a swollen surface layer by diffusion of liquid solvent into solid poly(vinyl chloride) in the glassy state has been studied. The apparent Fickian diffusion coefficients of cyclohexanone, cyclopentanone, tetrahydropyrane, 1,2-dichloroethane, N,N-dimethyl-formamide, and monohalogen derivatives of benzene in PVC is calculated with the use of Crank's model for discontinuous change of diffusion coefficient with concentration. It is found that the apparent activation energy for diffusion is in the range 6–17 kcal/mole and is dependent on the polarity of the solvent molecule.     

Synthesis and characterization of new cardo poly(bisbenzothiazole)s containing cyclohexylidene units

A new diaminobenzenethiol 1,1-bis(4-amino-3-mercaptophenyl) cyclohexane dihydrochloride (BAMPCH · 2HCl) containing the bulky pendant cyclohexylidene group was synthesized from cyclohexanone in three steps. Its chemical structure was characterized by ¹H NMR, ¹³C NMR, MS, FT-IR and EA. Aromatic poly(bisbenzothiazole)s (PBTs) were prepared from the new monomer and five aromatic dicarboxylic acids by direct polycondensation. The inherent viscosities were in the range of 0.78-2.04 dL/g. These polymers exhibited good solubility and thermal stability. Most of the prepared PBTs were soluble in various polar solvents. The decomposition temperatures at 10% weight loss were in the range of 482-518 °C in nitrogen. X-ray diffractograms of PBTs showed that all polymers were amorphous.     

Novel photo-crosslinkable liquid crystalline polymers containing vanillylidene cycloalkanones and azobenzene units

Two series of novel liquid crystalline photo-crosslinkable bis(vanillylidene-azobenzene) cycloalkanone containing polymers, namely poly(vanillylidene alkyloxy-4,4'-azobenzenedicarboxylic ester)s, have been synthesised from bis[m-hydroxyalkyloxy(vanillylidene)cycloalkanone] (m = 6, 8, 10) with azobenzene dicarbonylchloride by solution polycondensation method at ambient temperature. Polymers with varying spacer lengths have been synthesised and characterised by spectroscopic techniques. These variations have been correlated with the thermal properties and transition temperatures. Thermal transitions were analysed by differential scanning calorimetry (DSC) and the mesophases were identified by hot stage optical polarised microscopy (HOPM). All of the polymers were found to exhibit liquid crystalline properties. Transition temperatures were observed to decrease with increasing spacer length. The thermogravimetric analysis reveals that all of the polymers were stable up to 280°C undergo two-stage decomposition. Using the UV-visible photolysis studies we investigated the simultaneous behaviour of reactivity rates of crosslinking in the vanillylidene unit and isomerisation caused by the azobenzene unit in the photo-crosslinkable main chain liquid crystalline polymers. The photolysis of liquid crystalline bis(vanillylidene)cycloalkanone-based polymers reveals that there are two kinds of photoreactions in these systems: the EZ photoisomerisation of azobenzene unit and 2p+2p addition by vanillylidene units. The EZ photoisomerisation in the liquid crystal phase disrupts the parallel stacking of the mesogens, resulting in the transition from the liquid crystal phase to isotropic phase. The photoreaction involving 2p+2p addition of the bis(vanillylidene)cycloalkanone units in the polymers results in the conjoining of the chains. The cyclopentanone polymers exhibited a faster rate of photolysis than the cyclohexanone polymers.     

An efficient synthesis of benzylidene-2-alkoxy-4-aryl-2,3-cycloalkenopyridine-3-carbonitrile derivatives

An efficient procedure for the synthesis of a novel class of benzylidene-2-alkoxy-4-aryl-6,7-dihydro-5H-cyclopenta[b]pyridine-, -5,6,7,8-tetrahydroquinoline and/or -6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridine-3-carbonitrile was introduced through the one-pot multi-component reaction of cyclopentanone, cyclohexanone, and/or cycloheptanone with different aromatic aldehydes and malononitrile. The same products were also produced by classical route by the two-component reaction of dibenzylidine cyclopentanone, cyclohexanone, and/or cycloheptanone derivatives with malononitrile. The reactions were achieved using sodium alkoxide solution as catalyst and reagent.     

Preparation and characterization of new photosensitive and optically active poly(amide-imide)s from N-trimellitylimido-L-amino acid and dibenzalacetone moiety in the main chain

Six new photosensitive and optically active poly(amide-imide)s 8a–8f with good inherent viscosities based on dibenzalacetone moiety were synthesized from the direct polycondensation reaction of N-Trimellitylimido-L-amino acids 3a–3f with 2,5-bis(4-aminobenzylidene)cyclopentanone 7 by two different methods such as direct polycondensation in a medium consisting of N-methyl-2-pyrrolidone/triphenyl phosphite/calcium chloride/pyridine and direct polycondensation in a tosyl chloride/pyridine (py)/N,N-dimethylformamide system. Diamine 7 was synthesized by using a two-step reaction. At first 2,5-bis(4-nitrobenzylidene)cyclopentanone 6 was prepared from the reaction of two equimolars 4-nitrobenzaldehyde 5 and one equimolar cyclopentanone 4 and dinitro compound 6 was reduced by using Na2S. Also N-trimellitylimido-L-amino acids 3a–3f were synthesized by the condensation reaction of trimellitic anhydride 1 with two equimolars of various L-amino acids 2a–2f in an acetic acid solution. The polymerization reactions produced a series of photosensitive and optically active poly(amide-imide)s with high yield and good inherent viscosity. The resulted polymers were fully characterized by means of FTIR and ¹H-NMR spectroscopy, elemental analyses, inherent viscosity, specific rotation, solubility tests, UV-VIS spectroscopy, differential scanning calorimeter, thermogravimetric analysis, and derivative of thermogravimetric. These macromolecules exhibited maximum UV-VIS absorption at around 395 and 265 nm in a N,N-dimethylformamide solution.     

Efficient solvent-free synthesis of thiazolidin-4-ones from phenylhydrazine and 2,4-dinitrophenylhydrazine

An efficient solvent-free synthesis of thiazolidinones from reaction of mercaptoacetic acid, aldehydes (benzaldehyde and valeraldehyde) or ketones (cyclopentanone and cyclohexanone), and hydrazines (phenylhydrazine and 2,4-dinitrophenylhydrazine) is reported. The compounds were generally characterized by spectroscopic techniques and specifically for 2-cyclohexanyl-3-(N-phenyl)-1,3-thiazolidin-4-one by X-ray crystallography.     

Studies on the thermotropic liquid crystalline polymer. VI. Synthesis and properties of homo- and co-poly(amide-azomethine-ether)

Two series of poly(amide-azomethine-ether)s and poly(ester-azomethine-ether)s were prepared by the condensation of dialdehydes with N,N'-bis(aminobenzamide)s and 4,4′-bis(p-aminophenyl)terephthalester, respectively. The thermotropic liquid crystalline properties were examined by DSC microscopic observations. Almost half of the synthesized polymers exhibit thermotropic liquid crystalline properties which are in the nematic phase since threaded and/or Schlieren textures are observed under polarizing microscope. The effects of the number of amide group and the nature of the nonlinear bibenzamide moiety, which link in the rigid segment, on the thermotropic liquid crystalline properties of the homo- and co-poly(amide-azomethine-ether)s were also investigated.     

Diselenienyldenecycloalkanones

Crotonoid condensation of 2 moles of 2-selenophenaldehyde and 1 mole of acetone, cyclopentanone, cyclohexanone, or cyclheptanone, gave diselenienylidenacetone and the corresponding diselenienylidinecycloalkanones. The electronic absorption spectra in ethanol and in sulfuric acid-glacial acetic acid were measured, and are discussed, similarly with the IR spectra of the solids over the range 1800-600 cm^–1. All the compounds investigated showed halochromism.