Synthesis and thermal properties of side‐chain liquid crystalline poly[1‐({(4‐methoxyazobenzene‐4′‐oxy)alkyl}thio)‐2.3‐epoxypropane]s

A novel series of side‐chain liquid crystalline copolymers, i.e. poly‐[1‐({(4‐methoxyazobenzene‐4′‐oxy)alkyl}thio)‐2.3‐epoxypropane]s, were synthesised in which the number of methylene units in the alkyl group of the side chain varies from 3 to 6. The structures of compounds obtained were characterised by elemental analysis and ¹H NMR spectroscopy. Thermal properties were investigated using polarising optical microscopy, differential scanning calorimetry and X‐ray diffraction analysis. The synthesised thiols and corresponding polyepichlorohydrin‐based copolymers exhibited thermotropic liquid crystalline behaviour and nematic phases with schlieren textures. The thiols have lower transition temperatures than the corresponding copolymers. In addition, the degree of substitution of the copolymers synthesised increased with an increase in number of methylenes in the side chain. The phase transition temperatures increased and the mesomorphic temperature ranges widened with the increasing degree of substitution of the copolymers.     

Synthesis and characterization of luminescent hockey stick‐shaped liquid crystalline compounds

A general synthetic strategy, based on a convergent approach, allowed us to prepare a series of luminescent unsymmetrical bent‐core compounds (2,5‐(disubstituted)‐1,3,4‐oxadiazole derivatives), via the Sonogashira crosscoupling reaction, all possessing a similar hockey stick shape. Their mesophases were characterized using polarizing optical microscopy and differential scanning calorimetry. The observed LC phases possess the classical textures of calamitic liquid crystals. Fluorescence in solution for these compounds exhibits strong blue emission (λ_{max em.} = 390–460 nm) with good quantum yields (50–85%).     

Synthesis of new liquid crystalline compounds containing an α,β-unsaturated ketone and β-chloroketone groups in the side chain

A number of new liquid crystalline compounds containing an ,-unsaturated ketone or -chloro ketone moiety in the side chain were synthesized. The key intermediates in the synthesis were 1-(4-hydroxy-phenyl)-2-octen-1-one and 3-chloro-1-(4-hydroxyphenyl)octan-1-one which were prepared from 5-(4-hydroxy-phenyl)-3-pentyl-4,5-dihydroisoxazole and 3-hydroxy-1-(4-hydroxyphenyl)octan-1-one, respectively.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004, pp. 1526–1531.Original Russian Text Copyright © 2004 by V. Kovganko, N. Kovganko, Bezborodov.     

Synthesis and characterization of achiral banana‐shaped liquid crystalline molecules containing bisnaphthyl moieties

Three analogous series of symmetric banana‐shaped liquid crystalline molecules containing bisnaphthyl units were synthesized and characterized. The effects of linking groups (on the side wings) and lateral meta‐fluoro substitutions (on the middle outer rings) on the mesogenic properties were examined. The type of mesophase depends on the lengths of terminal alkoxy chains. Thus, achiral molecules with shorter flexible chains (n = 8) exhibit a rectangular columnar (B₁) phase, while analogous derivatives with longer flexible chains (n = 12) display the B₂ phase. All lateral meta‐fluoro substituted analogues (series II) possess the lowest isotropization temperatures and the narrowest mesophasic ranges of the B₁ and B₂ phases. The B₁ and B₂ phases were confirmed by X‐ray diffraction, polarizing optical microscopy (POM) and electro‐optical (EO) switching experiments. An electric field‐induced transition from an antiferroelectric (tristable) state to a ferroelectric (bistable) state was observed in the EO measurements. Spontaneous polarization (by switching current response), tilt angle of chiral domains (by POM), and transmittance–voltage measurements of the B₂ phase in related compounds have been surveyed in this study.     

Synthesis and characterization of organic–inorganic macrocyclic molecular brushes with poly(ε-caprolactone) side chains

In this work, we reported the synthesis of a dodecahydroxyl-functionalized macrocyclic oligomeric silsesquioxane (MOSS). The novel 24-membered hydroxyl-functionalized MOSS was employed as a macroinitiator for the ring-opening polymerization of ε-caprolactone (CL) and the organic–inorganic macrocyclic molecular brushes with poly(ε-caprolactone) (PCL) side chains were successfully synthesized. The organic–inorganic macrocyclic molecular brushes were characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). The results of wide angle X-ray diffraction (XRD) indicate that the architecture of the organic–inorganic macrocyclic molecular brushes did not alter the structure of PCL crystals. Differential scanning calorimetry (DSC) shows that the architecture of organic–inorganic macrocyclic molecular brushes significantly affected the rearrangement of PCL crystals. Compared to linear PCL, the organic–inorganic macrocyclic molecular brushes possessed the improved thermal stability in terms of the temperatures at the maximum of degradation rate and the yields of degradation residues.     

Electrically induced and thermally erased properties of side‐chain liquid crystalline polymer/liquid crystal/chiral dopant composites

The properties of synthesized side‐chain liquid crystalline polymer (SCLCP)/liquid crystal (LC)/chiral dopant composites having a chiral nematic (N*) phase at room temperature were investigated by polarized optical microscopy (POM) and a UV/VIS/NIR spectrophotometer. The composite exhibited a planar texture after it was filled into cells under homogeneous boundary conditions and it was transparent. When an electric field was applied to the composite, a focal conic texture was formed and the composite became light scattering. After the electric field was turned off, the light‐scattering state remained stable for some time, i.e. the light‐scattering state exhibited a memory effect. The focal conic texture changed into the planar texture when the composite was heated and the composite became transparent again. Therefore, the composite had electrically induced and thermally erased properties. The SCLCP had some influence on the memory effect and on the thermo‐electro‐optical properties of the composite.     

Synthesis and characterisation of main‐chain hydrogen‐bonded supramolecular liquid crystalline complexes formed by azo‐containing compounds

A series of azopyridine‐containing hydrogen bonding acceptors (4a–c) with flexible spacers of oligo(methylene) were synthesised. Hydrogen‐bonded polymeric complexes 4/5 and trimeric complexes 4/6₂ , where 5 and 6 are aromatic dicarboxylic acids and monocarboxylic acids, respectively, were prepared and their liquid crystallinity was examined using differential scanning calorimetry and polarising optical microscopy. The study showed that most of the complexes displayed reversible thermotropic nematic phase. The isotropic to nematic phase transition temperatures of polymeric complexes 4/5 and trimeric complexes 4/6₂ in general decreased with the increase in length of spacers and terminal groups in the corresponding proton acceptors 4 and the proton donors 5 and 6, respectively. Hydrogen bonding interactions in complexes 4/5 and 4/6₂ were studied by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.     

Synthesis and characterization of inclusion complexes of aliphatic-aromatic poly(Schiff base)s with β-cyclodextrin (highlight)

This paper describes the formation of polymer inclusion complexes(polymer-CD-ICs) between β-cyclodextrin(β-CD) and aliphatic-aromatic poly(Schiff base)s. Fourier transform infrared(FTIR) spectroscopy, ¹H nuclear magnetic resonance spectroscopy(¹H-NMR), thermogravimetric analysis(TGA) and X-ray diffraction(XRD) have been used to observe the formation of polymer-CD-ICs. In FTIR spectra, the characteristic peaks of β-CD at 3391 cm⁻¹ shifted to 3418 cm⁻¹ and the intense peak at 1602 cm⁻¹ due to the –C = N– stretching vibration diminished after formation of inclusion complexes. Compared the ¹H-NMR of polymer-CD-ICs with β-CD, the chemical shift of the protons H-3, H-5 have shifted to higher field after the formation of inclusion complexes, which is perhaps due to the interaction of these protons with polymers. The TGA analysis revealed that the polymer-CD-ICs had better thermal stability than β-CD, suggesting that the polymer increased the stability of β-CD. The X-ray diffraction patterns displayed that the strong peak for both polymer-CD-ICs at approximately 20.0° (2θ) may confirm their IC formation.     

Synthesis and characterization of aba-type block copolymer of poly(ϵ-caproplactone) with poly(ethylene glycol), by mean of activation end groups

Poly(?-caprolactone)-b-poly(ethylene glycol)-b-poly(?-caprolactone) (PCL-b-PEG-b-PCL) triblock copolymer were synthesized by mean anionic activation of the hydroxyl end groups of poly(ethylene glycol) in presence of diphenylmethylsodium. Copolymers were characterized by SEC, FT-IR and ¹H-NMR spectroscopy, TGA and DSC. Size exclusion chromatographic analysis of obtained copolymers indicated incorporation of CL monomer into PEG without formation of PCL homopolymer. Characterization by FT-IR and ¹H NMR spectroscopy of the resulting polymeric products, with respect to their structure, end-groups and composition, showed that they are best described as ester-ether-ester triblock copolymers, whose compositions can be adjusted changing the feeding molar ratio of PEG to CL. The thermal stability of triblock copolymers was less that PEG precursor, but higher that PCL homopolymer. Analysis by mean DSC showed that all copolymers were semi-crystalline and their thermal behavior depending on their composition.     

Synthesis of macrocyclic lactones with methoxysulfonyl side chain

Two representative macrocyclic lactones with methoxysulfonyl side chain（5a and 5b）were synthesized employing Michael addition with acrolein and ring enlargement as the key steps,starting from potassium,α-oxocycloaikylsulfonates（1）in total yields of 45 and 57%,respectively.     

Synthesis and characterization of silver—poly(methylmethacrylate) nanocomposites

The optical properties of silver nanoparticles embedded in poly(methylmethacrylate) (PMMA) was investigated as well as the influence of silver nanoparticles on the thermal properties of polymer matrix. The average size and particle size distribution of silver nanoparticles was determined using transmission electron microscopy. The obtained transparent nanocomposite films were optically characterized using UV-Vis and FTIR spectroscopy. Thermal stability of polymer matrix was improved upon incorporation of small amount of silver nanoparticles. Also, silver nanoparticles have pronounced effect on thermo-oxidative stability of PMMA matrix. The glass transition temperatures of nanocomposites are lower compared to the pure polymer.     

Synthesis and characterization of trimethoxysilyl-functionalized poly(phthalazinone ether ketone)

A novel alkoxysilyl-functionalized poly(phthalazinone ether ketone)(PPEK)was prepared for the boundary lubricant application in micro-electro-mechanical system(MEMS).The synthesis of functionalized PPEK was started from the hydro- xylation of PPEK,then following with the corresponding ring-opening reaction of 3-glycidoxypropyltrimethoxysilane(GPTMS). The structures of the functional PPEK were confirmed by FTIR,~1H NMR,~(29)Si NMR,and UV-vis spectrum.     

Synthesis and mesomorphic properties of new chiral banana‐shaped liquid crystals with chiral 3‐(alkoxy)propoxy terminal groups

New chiral banana‐shaped liquid crystals with chiral 3‐(alkoxy)propoxy terminal groups (Pn‐O‐PIMB5*‐4O, n = 7, 8, 9 and 10) were synthesized and their mesomorphic properties and phase structures investigated by means of electro‐optic measurements, polarizing optical microscopy, differential scanning calorimetry, and second harmonic generation measurements. Most of these chiral bent‐core mesogens (n = 7–9) showed the antiferroelectric B2 phase, whereas P10‐O‐PIMB5*‐4O exhibited the B7 phase. Comparing with the previously reported homologue Pn‐O‐PIMB(n‐2)*, we conclude that the terminal chain structure, particularly the position of chiral centres, plays an important role in the emergence of particular phase structures.     

Synthesis and characterization of dendronized poly(methylsiloxane) with appendent Fréchet-type dendrons

A new kind of dendronized poly(methylsiloxane) (3a and 3b) with appendent Fre-chet-type poly(aryl ether) dendrons has been synthesized and characterized by GPC, DSC, TGA, fluorescence and UV-Vis spectra.     

Synthesis and liquid crystalline properties of a series of cholesterol‐based dimesogenic compounds

The synthesis and mesomorphic properties of a series of novel dimesogenic compounds containing the cholesteryl ester unit and a phenyl benzoate group are reported. The two mesogenic units of these compounds are linked through dicarboxylic ester bonds, with alkylene spacer lengths of 2, 4, 6 and 8 methylene units. The chemical structures and liquid crystalline properties of this series of compounds were characterized by FTIR, ¹H NMR, hot stage‐coupled polarizing microscopy and DSC. The results show that this series of compounds are cholesteric liquid crystals over a wide range, both during heating and cooling, and they exhibit iridescent colours in the liquid crystalline state.     

Synthesis,liquid crystalline properties and fluorescence of polycatenar 1,3,4‐oxadiazole derivatives

A series of hexacatenar liquid crystals containing the 1,3,4‐oxadiazole group as rigid core, i.e. 1,4‐bis[(3,4,5‐trialkoxyphenyl)‐1,3,4‐oxadiazolyl]‐ benzene (P‐P‐oxd‐n), were designed and synthesised. Based on a detailed study of their thermotropic phase behaviour and mesophase structures, it was revealed that columnar phases are generated in these materials. Furthermore, combination of experimental and calculated results enabled a proposal for the molecular packing in the mesophase. The photoluminescent properties of these materials were examined using P‐P‐oxd‐8 as an example. A strong blue light emission (λ_max = 456 nm) was observed in P‐P‐oxd‐8 and a higher quantum yield was obtained in dilute chloroform solution.     

Synthesis of α-tocopherol analogs with unsaturated side chain and their transformation into the corresponding chromans with ω-functionalized side chain

-Tocopherol analogs with double bond-containing side chains were synthesized by condensation of trimethylhydroquinone with optically active (3R/S,4S)-3,4,8-trimethylnona-1,7-dien-3-ol and linalool in the presence of the zeolite-containing Tseokar-10 aluminosilicate. Ozonolysis of these compounds gave the corresponding chromans with -formyl or (after hydride reduction) -hydroxyl groups in the side chain.     

Synthesis of poly(Nε-phenoxycarbonyl-l-lysine) by polycondensation of activated urethane derivative and its application for selective modification of side chain with amines

We report a methodology for the synthesis of Nε-phenoxycarbonyl-protected poly(l -lysine) on the side chain by chain growth polycondensation of Nα,Nε-bis(phenoxycarbonyl)-l -lysine proceeded through the selective elimination of phenol and CO₂ from the Nα phenoxycarbonyl moiety at 50 °C in N,N-dimethylacetamide in the presence of a primary amine used as an initiator. After optimization of reaction condition, the addition of acetic acid during polycondensation proved effective for the realization of the predicted molecular weight and narrow dispersity of the corresponding polypeptide by adjusting the feed ratio of monomer to the amine initiator because of the suppression of interchain coupling that occurs between the amino terminus of poly(l -lysine) and the Nε-phenoxycarbonyl group on the polymer side chains. Furthermore, taking advantage of the potentially reactive Nε-phenoxycarbonyl moiety on the side chain, post-polymerization modification was effectively achieved by the nucleophilic reaction of amine compounds including primary, secondary, and aromatic amines through the formation of urea linkage, providing a useful platform for synthesis of selective side chain functionalization of poly(l -lysine) samples. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2522–2530     

Synthesis of poly(ε-caprolactone) diols and EO-CL block copolymers and their characterization by liquid chromatography and MALDI-TOF-MS

Polymers of ε-caprolactone were synthesized by microwave-assisted polymerization initiated with polyethylene glycols (PEG 200 and PEG 300) and monodisperse diols (mono-, di-, tri-, tetra- and hexaethylene glycol) and tin octoate as catalyst. These polymers were characterized by different chromatographic techniques (SEC, LAC and LCCC) and MALDI-TOF-MS. A comparison with commercially available polycaprolactone diols with molecular weight 530 and 830 showed that the new polymers had a much higher content of triblock structures, while the commercial samples contained considerable amounts of diblocks.     

Synthesis and properties of novel 1,1‐difluoropropoxy‐linked liquid crystalline compounds of negative dielectric anisotropy

A series of liquid crystalline compounds having the difluoropropyleneoxy moiety (–OCF₂C₂H₄–) as a linking group has been synthesized. The physical properties, i.e. dielectric anisotropy, birefringence, viscosity and phase transition temperatures, have been measured. This novel class of compounds shows a larger negative dielectric anisotropy than the corresponding compounds having a propyleneoxy (–OC₃H₆–) linking group. Their dielectric properties may be explained by the combined effect of fluorine atoms with large electron negativities and the electron donating feature of an oxygen atom substituted on the same carbon atom. The semi‐empirical quantum calculation method (AM1) also confirmed this dielectric behaviour of the difluoropropyleneoxy linkage group.