The synthesis and mesogenic properties of side chain polymethacrylates with terminal branched groups

The synthesis is described of six polymethacrylates attached through oxytetramethylene and oxyhexamethylene spacers to an azobenzene moiety consisting of branched terminal iso -butoxy, iso -amyloxy and n -amyloxy groups. The monomers show a nematic mesophase while their polymers show an additional higher order smectic C phase. The effects of the terminal branched alkoxy group and the spacers on mesomorphic properties are discussed. The phase characteristics, thermal stabilities and molecular masses of the polymers were investigated by DSC, XRD, TGA and GPC. The polymers were also characterized by UV-vis, IR and NMR spectroscopy.     

The synthesis and mesogenic properties of side chain polymethacrylates with terminal branched groups

The synthesis is described of six polymethacrylates attached through oxytetramethylene and oxyhexamethylene spacers to an azobenzene moiety consisting of branched terminal iso-butoxy, iso-amyloxy and n-amyloxy groups. The monomers show a nematic mesophase while their polymers show an additional higher order smectic C phase. The effects of the terminal branched alkoxy group and the spacers on mesomorphic properties are discussed. The phase characteristics, thermal stabilities and molecular masses of the polymers were investigated by DSC, XRD, TGA and GPC. The polymers were also characterized by UV-vis, IR and NMR spectroscopy.     

Template synthesis of a tetraazamacrocyclic ligand with two pendant pyridinyl groups: properties of the isomers of the metal-free ligand and of their first-row transition metal compounds

The one-step reaction of [Cu(en)(2)](2+) (en = 1,2-diaminoethane) with formaldehyde, ethyl 2-pyridyl acetate, and base produces a mixture of [Cu(s-pypymac)](2+) and [Cu(a-pypymac)](2+) (s-pypymac = syn-6,13-bis(2-pyridinyl)-1,4,8,11-tetraazacyclotetradecane, a-pypymac = anti-6,13-bis(2-pyridinyl)-1,4,8,11-tetraazacyclotetradecane; syn-to-anti ratio approximately 1:9) in low yield (6%). Ion exchange chromatography is used for isomer separation, and the two isomers of the metal-free ligand are obtained by reduction of the copper(II) complexes and subsequent ion exchange chromatography. Crystal structure analyses of the metal-free a-pypymac ligand, of two isomeric copper(II) compounds of a-pypymac and one of s-pypymac, and of the cobalt(III) complexes of a- and s-pypymac and nickel(II), as well as zinc(II) complexes of a-pypymac, are reported and discussed on the basis of the expectations from force field calculations and from published experimental data of the transition metal compounds of the bis-pendant amine derivative diammac.     

The influence of grafted functional groups on the adsorption properties of silica

The adsorption properties of silica gel with grafted aminopropyl and guanidinoethanethiol (GET) groups were studied by the techniques of adsorption under static conditions and gas chromatography. It was shown that molecules capable of forming hydrogen bonds are adsorbed on all modified samples more weakly than on the initial silica gel. The grafting of GET radicals on the surface results in a noticiable increase in the dispersion interaction with adsorbed molecules. Calculation of the contributions of molecular groups to the constant of adsorption equilibrium showed that the thermodynamic characteristics of adsorption on aminosilochromes and aminosilicas with a polymeric layer of the modifying agent have similar values. Such adsorbents can be used for investigation of polar compounds, including organic bases. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 452–457, March, 1997.     

New polydimethylsiloxanes with bulky end groups: synthesis and properties

Russian Chemical Bulletin - New polydimethylsiloxanes (PDMS) containing bulky end groups were obtained. The structure of all obtained compounds was confirmed by a combination of physicochemical...     

Mechanical properties of oriented polyvinylchloride composites filled with ultrafine particles

The tensile stress-strain behaviour of undrawn and drawn polyvinylchloride (PVC) composites filled with ultrafine SiO₂ and micron sized glass particles were discussed as functions of filler content and size. For the undrawn PVC composites filled with ultrafine SiO₂ particles, Young's moduli, yield and breaking stresses increased with filler content and decreasing filler size. Whereas for the composites filled with micron sized glass particles, their Young's moduli slightly increased with filler content but both the yield and breaking stresses decreased. Oriented PVC composites were made by uniaxially drawing to × 2.5 at 100 °C. Anisotropic mechanical properties of oriented specimens were discussed in terms of compliance tensor and yield stress measured in the direction of 0°, 45° and 90° to the original stretching direction at room temperature. In the case of 70A SiO₂, all the compliance decreased with filler content, whereas those of 65μ glass, this relation was reversed. The yield stress of the oriented PVC composites showed filler size dependence similar to Young's moduli. The anisotropic yield stress of oriented PVC composites were reasonably analysed by Hill's yield criterion.     

Modification of interlayer space of kanemite with trimethylsilyl groups: structure and adsorption properties

Interlayer hydroxyl groups of layered silicate kanemite have been modified with trimethylsilyl groups by the reaction between the hydroxyl groups and trimethylchlorosilane. Expansion of the interlayer space by intercalation of dimethyldialkylammonium ions into the silicate layers enables the silylating reagent to access the hydroxyl groups. An increase in specific surface areas was observed with increasing concentration of trimethylsilyl groups. This result suggests that the interlayer space of kanemite can be used as an effective molecular adsorption space by weakening the interaction between the interlayer hydrogen bonds of hydroxyl groups. The modification of kanemite with trimethylsilyl groups restricted the adsorption of water below a monolayer capacity and was favorable for benzene adsorption.     

Synthesis and properties of a redox active ligand with bispicorylamino groups and its dinuclear complex

A ligand, 4-methoxy-4′,4″-bis[N,N-bis(2-pyridylmethyl) aminomethyl]triphenyl-amine, and its palladium and copper dinuclear complexes were designed and prepared in order to examine intramolecular interactions between an organic cation radical and the metal ion. Novel NMR techniques, COSY and NOESY, were applied to the palladium complex to examine its conformation in solution. The palladium complex was found to prefer a folded conformation at ambient temperature, indicating the occurrence of intramolecular stacking interaction. CV measurements of the copper complex showed reversible Cu^I/Cu^II and TPA/TPA⁺ redox couples. The spin–spin interaction in the radical pendant copper complex generated upon one electron oxidation of the copper complex was examined by cw-ESR measurements.     

Optical and dielectric properties of polyvinylchloride/polymethylmethacrylate blends

The optical and dielectric properties of prepared polyvinychloride/atactic polymethylmethacrylate (PVA/-PMMA) blends are studied as a function of applied field frequency and PMMA content. The observed optical energy gaps and the energy gap tails were determined from the measured absorption spectra. It was found that the applied frequency and the -PMMA concentration have some effects on the physical parameters such as the optical energy gap, the glass transition temperature (T_g), the dielectric constant, and the refractive index. Correlation between the determined optical energy gaps and the measured T_g is presented. The observed changes in these physical parameters are due to structural changes in the amorphous domains, impurities and space charge within the interfaces in the mixed phases.     

Catalytic and adsorption properties of iron-nickel catalysts in ammonia synthesis

Thermal desorption was used to study the state of chemisorbed nitrogen on the surface of iron-nickel ammonia-synthesis catalysts in the region of the solid solution of nickel and iron. It was shown that the ₁ form of nitrogen should be responsible for catalysis.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 5, pp. 616–618, September–October, 1988.     

The synthesis and ligand properties of the dihydro-bis-(1-indazolyl)borate anion

Summary Potassium dihydro-bis-(1-indazolyl)borate, synthesized from potassium borohydride and indazole, has been used as a reagent to yield complexes with copper(II), nickel(II), cobalt(II), manganese(II) and iron(III) ions. From i.r. spectral studies the ligand is uninegative and bidentate and coordination occurs through the nitrogen atom at position 2 of the indazole ring system in all cases. With the sole exception of the copper(II) complex, the nitrogen atom at position 1 is also involved in forming a bridge with an adjacent metal ion. On the basis of electronic spectral studies and magnetic susceptibility measurements a distorted square planar structure involving chlorine bridges has been proposed for the copper complex. An octahedral geometry with ligand bridges for all complexes is tentatively proposed and it appears that all are polymers.     

Synthesis and properties of a redox active starburst ligand with three bispicorylamino groups and its trinuclear complexes

A starburst-shaped ligand, 4,4′4″-tris[N,N-bis(2-pyridylmethyl) aminomethyl] triphenylamine, and its palladium and copper trinuclear complexes were designed and prepared. NMR techniques, COSY and ROESY, were applied to the palladium complex to examine its conformation in solution. The palladium complex was found to prefer a folded conformation even at 75 °C, indicating the occurrence of strong intramolecular stacking interaction. CV measurements of the palladium complex showed reversible TTA/TTA⁺ redox couples. ETSF measurements showed that the corresponding radical pendant complex is very unstable. Molecular design rules for triarylamine-based spin bearing ligands are discussed.     

Adsorbent grafted on cellulose by in situ synthesis of EDTA-like groups and its properties of metal ion adsorption from aqueous solution

Cellulose - This paper describes the synthesis of a novel chelating material derived from cellulose, and its heavy metal ion adsorption properties from aqueous solution. The first section of this...     

Strontium adsorption properties of an aluminum-pillared montmorillonite carrying carboxylate functional groups

Strontium adsorption was studied in an aluminum-pillared montmorillonite (PILC) carrying organic acid groups. The in situ dissociation of these groups increases the number of negative sites in the modified PILC, promoting thus the uptake of cations from an exchange solution. To investigate the role of solution pH and acid strength in cation uptake phenomena, base titrations were performed for PILCs carrying either oxalate or acetate groups. Comparison with the pristine PILC showed that extra Sr(2+) uptake initiated at pH 6 and 8 in the presence of oxalate and acetate, respectively. The overall increase in Sr(2+) uptake was higher in the presence of oxalate and amounted to about 136% as compared with the pristine PILC, at pH slightly above 8. The effect of the acid's strength was further probed through strontium adsorption isotherms, taken at a constant pH for PILC samples carrying acetate, oxalate, malonate, or citrate groups. The results demonstrate that cation uptake can be optimized by tuning the pH conditions to the acid's strength or vice versa.     

Structural defects in polyvinylchloride—II Structure and properties of polyvinylchloride prepared in presence of oxygen and carbon monoxide

To investigate oxygen-containing structures in PVC, arising for example from the presence of air in technical polymerization vessels, vinyl chloride (VC) suspension polymerizations were performed with various amounts of added oxygen. Quantitative investigations demonstrated that the low molecular peroxides formed in the induction period decompose, resulting in hydrogen chloride, formaldehyde and carbon monoxide. Residual peroxides have been determined in the final copolymers and found to be mainly responsible for the considerable reduction in the thermal stability. Considerable evidence is provided that carbon monoxide, copolymerized with VC, is incorporated as a carboxylic acid sidegroup. It is considered to arise from a 1,2 chlorine shift to the carbonyl radical chain-end. The resulting acryloyl chlorides are capable of reacting with water, alcohols or amines to yield the corresponding acids, esters or amides. A new i.r. band at 1770 cm^?1 after alkali treatment of VC-CO copolymers containing acrylic acid groups is suggested as caused by the formation of butyrolactone structures. Butyrolactone formation by methyl chloride evolution was also observed in thermal degradation of VC-CO copolymers containing methyl acrylate units. The rates of dehydrochlorination of the copolymers are not very different from those of pure suspension PVC.     

Europium complex of a tridentate ligand: synthesis and spectroscopic properties

A new europium complex containing the chelate tridentate ligand and imidazole terpyridine (itpy), was synthesized. The complex was characterized by elemental analysis, mass, FT-IR and photoluminescence spectroscopic techniques. The europium complex in solution showed characteristic luminescence properties. The room temperature photoluminescence spectrum of this complex was composed of typical Eu³⁺ red emission assigned to ⁵D₀ → ⁷F₂ transition. The metal-centered red emission seemed to be promoted by the ligand-assisted energy transfer, namely antenna effect.     

Amphiphilic poly(N-propargylamide) with galactose and lauryloyl groups: synthesis and properties

An amphiphilic poly(N-propargylamide) with galactose and lauryloyl groups was synthesized by copolymerization of the corresponding N-propargylamide monomers using a Rh catalyst. The obtained copolymer formed a one-handed helical conformation and molecular aggregates in water. The observations by fluorescence microscopy in a cell culture experiment in the presence of dye-labeled copolymer indicated that the copolymer was incorporated into the cells.     

Hydrothermal synthesis of MoS2 with controllable morphologies and its adsorption properties for bisphenol A

The effect of preparation conditions (molar ratio of S/Mo, hydrothermal temperature and time) on the morphologies of MoS₂ was investigated. The as-synthesized materials were characterized by X-ray diffraction (XRD), field emission scanning microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectra and Brunauer–Emmett–Teller’s (BET) surface area measurement. Results showed that the three kinds of morphologies of MoS₂ were obtained. Morphologies varied gradually from the coral-like aggregated particles to flower-like spheres to wrapped nano-sheet structure with increasing hydrothermal temperature and time. It is meaningful for specific morphology demand in different fields. Moreover, the prepared materials were used as tentative adsorbents for the removal of bisphenol A (BPA) as a representative of endocrine disruptors. The results showed that the prepared MoS₂ materials with wrapped nano-sheet structure had good adsorption capacity (39.03 mg/g) and fast adsorption rate (0.0053 g/(mg/min). The adsorption process was thermodynamically exothermic and spontaneous. The study indicated that electrostatic interaction is strong and π-π interaction between BPA and the MoS₂ materials play an important role for BPA adsorption.     

The synthesis and mesomorphic properties of liquid crystals with bulky terminal groups designed for bookshelf geometry ferroelectric mixtures

The synthesis and mesomorphic properties of a systematic range of ortho difluoroterphenyls with a bulky terminal chain are detailed. The bulky terminal chain consists of either a tertiarybutyl group or a trimethylsilyl unit, each separated from the core by a short (dimethylene) chain, with the other terminal chain being either octyloxy or heptyl. The synthesis of the materials was affected efficiently using a combination of low temperature lithiations and palladium-catalysed cross-coupling reactions. Unusually for liquid crystals with bulky terminal chains, the smectic phase stability (particularly smectic C) is upheld by more than the nematic phase stability, and in most cases the smectic C phase stability is actually higher than comparable analogues with conventional unbranched terminal chains. It is postulated that the surprisingly high smectic C phase stability results from a phase separation effect due to the incompatibility of the spherical bulky group and the conventional unbranched terminal chain, hence implying that the smectic ‘layers’ are well defined, and such definition of the layers bodes well for bookshelf geometry in ferroelectric mixtures.