Influence of alkoxy tail length on the phase behaviour of mesogen-jacketed liquid crystalline polymers with fan-shaped pendants

A series of new monomers of 2, 5-bis [(3, 4, 5-trialkoxy benzyl) oxycarbonyl] styrene (denoted as M-tri-OC_mH_2m + 1, m = 1, 2, 4, 6, 8, 10, 12, where m indicated the number of carbon atoms in the alkoxy group) were designed and synthesized. Then, their corresponding polymers P-tri-OC_mH_2m + 1 (m = 1, 2, 4, 6, 8, 10, 12) were synthesized by free radical polymerization. The chemical structure of the monomers was confirmed by elemental analysis, ¹H NMR and ¹³C NMR. The molecular characterization of polymers was performed with ¹H NMR, gel permeation chromatography (GPC). The thermal stability of polymers was investigated by thermogravimetric analysis (TGA). The phase structure and transition behaviours were studied using differential scanning calorimetry (DSC), polarized light microscopy (PLM), one- and two-dimensional (1D and 2D) wide-angle X-ray diffraction (WAXD). We found that P-tri-OC_mH_2m + 1 (m = 1, 2) with short n-alkoxy substituents as the tail form columnar nematic (Φ_N) phase; that with the increasing length of alkoxy tails, P-tri-OC_mH_2m + 1 (m = 4, 6, 8) can demonstrate the hexagonal columnar (Φ_H) phase; however, when the length of alkoxy tails exceeded a threshold, P-tri-OC_mH_2m + 1 (m = 10, 12) only develop into columnar nematic (Φ_N) phase instead of Φ_H phase.     

Structure-property relationship of a series of novel mesogen-jacketed liquid-crystalline polymers containing semirigid side chain with different numbers of alkoxy terminal groups

A series of vinyl monomers, 2, 5-bis [(4-methoxy benzyl) oxycarbonyl] styrene (MBCS); 2, 5-bis [(3, 5-dimethoxy benzyl) oxycarbonyl] styrene (DMBCS) and 2, 5-bis [(3, 4, 5-trimethoxy benzyl) oxycarbonyl] styrene (TMBCS) were synthesized and polymerized via free radical polymerization. The terminal groups of the semirigid side chain were systematically varied to investigate the effects of their numbers on the ability of mesophase formation of the resultant polymers. The chemical structures of the monomers were confirmed by elemental analysis, ¹H NMR and ¹³C NMR. The characterization of the polymers was performed with ¹H NMR, gel permeation chromatography (GPC). The phase structures and transition behaviors were studied using differential scanning calorimetry (DSC), polarized light microscopy (PLM) and one- and two-dimensional wide-angle X-ray diffraction (WAXD). The experimental results suggested that the ability of mesophase formation of the polymers decreased as the rigidity of side-chain group decreased and increased as the number of the alkoxy terminal group increased, and that all the polymers with high molecular weight showed stable columnar nematic phase (Φ_N).     

H NMR study of thermotropic phase transitions in D2O solutions of poly(N-isopropylmethacrylamide)/poly(vinyl methyl ether) mixtures

¹H NMR spectroscopy was used to investigate thermotropic phase transitions in D₂O solutions of poly(N-isopropylmethacrylamide) (PIPMAm)/poly(vinyl methyl ether) (PVME) mixtures. In all studied solutions (polymer concentrations c=0.1-10 wt%) two phase transitions were detected at temperatures roughly corresponding to different lower critical solution temperatures of PIPMAm and PVME. While the phase transition of PVME component (located at lower temperatures) is not affected by the presence of PIPMAm in the mixture, the phase transition temperatures of PIPMAm component (located at higher temperatures) are affected by the phase separation of the PVME component. Measurements of ¹H spin-spin relaxation of residual water (HDO) molecules revealed that above the phase transition, a certain portion of water molecules is bound to polymer globular structures. A major part of bound water is present in globular structures of predominating polymer component in the mixture.     

Reduction of Biocide-Polluted Wastewater Using O3 and H2O2/O3 Oxidation Processes

The objective of the presented study was to test various oxidation processes with the aim being to reduce the concentration and toxicity of biocide wastewater from a Slovenian phytopharmaceutical factory. Laboratory-scale experiments employing two AOP processes – ozonation (O₃) and peroxone (H₂O₂/O₃) – were applied to reduce the concentration of the active components involved, i.e., methylisothiazolone (MI), chloromethylisothiazolone (CMI) and dichloromethylisothiazolone (DCMI). The reduction of the biocide wastewater load for the performed oxidation processes was evaluated using ecological parameters. The H₂O₂/O₃ oxidation procedure using an O₃ flow rate of 1g/L h, at a pH value of 10 and with the addition of 5 ml of H₂O₂ (0.3 M) proved to be the most effective treatment. The toxicity of the biocide-load wastewater with an initial EC₅₀ = 0.38%, decreased to EC₅₀ (24h) >100% and EC₅₀ (48h) = 76%.     

Synthesis of Silicon Dioxide Optical Films Mixed with Acrylic Series Monomers by Sol-gel Process

In this study, silicon dioxide (SiO₂) particles are mixed with acrylic series monomers (methyl metacrylate (MMA) and 2-hydroxyethyl methacrylate (2-HEMA)) by sol-gel process to prepare inorganic-organic hybrid materials for the optical film. The other optical film has the same composition and process as the above but tri(ethylene glycol) dimethacrylate (TEGDMA) is added.

An infrared spectrometer, differential scanning calorimeter, thermo gravimetric analysis, ultraviolet-visible spectrophotometer, and spectroscopic-ellipsometer have been used to explore the effect on optical, hardness, and thermal properties of the two series of thin films. TEGDMA used as a bonding resin in this study showed that not only a better hardness and thermal properties, but also maintain good optical properties in the SiO₂ hybrid materials by sol-gel process.     

Reactive extraction for preparation of hydrogen peroxide under pressure

The preparation of hydrogen peroxide from anthrahydroquinone by reactive extraction was investigated. The integration process of oxidation of anthrahydroquinone by air and extraction of hydrogen peroxide from the organic phase with water was carried out in a sieve plate column under pressure. The conversion of anthrahydroquinone increased with increasing pressure resulting in an increase of hydrogen peroxide concentration in the aqueous phase. However, no change in extraction efficiency of hydrogen peroxide was observed. A mathematical model for gas-liquid-liquid reactive extraction was established. In themodel, the effects of pressure and gas superficial velocity on reaction were considered.With increasing gas superficial velocity, the conversion of anthrahydroquinone increased, and the fraction of hydrogen peroxide extracted reached a plateau with a maximum of 72.94%. However, both the conversion of anthrahydroquinone and the fraction of hydrogen peroxide extracted decreased with increasing organic phase superficial velocity. __________ Translated from Petrochemical Technology, 2007, 36(1): 49–54 [译自: 石油化工]     

Self-assembly of C60 containing poly(methyl methacrylate) in ethyl acetate/decalin mixtures solvent

[60]Fullerene (C₆₀) was mono-substituted with well-defined poly(methyl methacrylate) (PMMA-b-C₆₀) using the atom transfer radical polymerization (ATRP) technique. The self-assembly behaviors of PMMA-b-C₆₀ in ethyl acetate (EA) and decalin mixtures were studied using laser light scattering (LLS) and transmission electron microscopy (TEM). Homogeneous solutions of PMMA-b-C₆₀ can be obtained in the solvent mixtures containing more than 40 wt% EA, where the molar ratio of decalin to EA is close to 1. For each solvent mixture, unimers coexist with micelles and large aggregates. The sizes of PMMA-b-C₆₀ micelles and aggregates are independent of polymer concentration, confirming that they are produced via the closed association mechanism. For the various solvent mixtures, the weight-averaged molecular weights, M_w of the PMMA-b-C₆₀ aggregates range from 4.1×10⁷ to 12.5×10⁷ g/mol. The hydrodynamic radii of the large aggregate, R_h, vary from 90 to 136 nm, while the z-averaged radii of gyration, R_g, range from 210 to 311 nm. The R_g/R_h value for each solvent mixture is ∼2.3, which is independent of decalin contents in the mixed solvents. The morphological study using the transmission electron microscope suggests that the large aggregates are composed of porous large compound micelles (LCM) in solution.     

Coordination Polymers of 1,9-Bis(8-Hydroxyquinolin-5-yl)-2,5,8-Trioxanonane

ABSTRACT

Coordination polymers of a novel bis(oxine) bidentate ligand, namely 1,9-bis(8-hydroxyquinolin-5-yl)-2,5,8-trioxanonane (BHQTN) (H₂L) have been prepared with the metal ions Zn⁺², Cu⁺², Ni⁺², Co⁺², and Mn⁺². The novel bis(bidentate) ligand BHQTN was synthesized by condensation of 5-chloromethyl-8-hydroxyquinoline hydrochloride with diethylene glycol in the presence of a base catalyst. All of these coordination polymers and the parent ligand were characterized by elemental analyses and IR spectral studies. The diffuse reflectance spectral studies and magnetic susceptibilities of all of the coordination polymers have also been performed. Thermogravimetric parameters such as T_o, T₁₀, T_max., IPDT, and the activation energy of the thermo-degradation process were calculated.     

Examination of acid-base properties of alumina treated with silane coupling agents, by using inverse gas chromatography

This study examined the specific component of the free energy of adsorption, − ΔG_A^SP, of the untreated and four types of silane coupling agent-treated alumina powders using inverse gas chromatography (IGC) by employing the adsorption of several polar and non-polar probes onto their surfaces at various temperatures. The acid-base properties of the untreated and surface-treated alumina powders were quantified using their K_A and K_D parameters, which reflect the ability of a surface to act as an electron acceptor and donor, respectively. The surface of the untreated alumina was found to be amphoteric and was able to function as both an electron acceptor and donor. The acid-base properties of the alumina surfaces treated with γ-glycidoxy propyl trimethoxy silane (GMS) and γ-amino propyl triethoxy silane (AES) were slightly basic, and those of the alumina surfaces treated with γ-methacryloxy propyl trimethoxy silane (MTMS) and γ-mercapto propyl trimethoxy silane (MCMS) were amphoteric.     

The Preparation of Molybdenum Oxynitride by Hydrazine Reduction of MoO3 at Moderate Temperature and Its Application in the Selective Hydrogenation of Long-Chain Linear Alkadienes

Molybdenum oxynitride was prepared by hydrazine reduction of MoO₃ at moderate temperatures. The anhydrous condition was favorable to production of amorphous molybdenum oxynitride, and the presence of hydrogen favored the reduction of Mo⁶⁺ and Mo⁴⁺ species to Mo ⁺ (0 < < 4) species. These molybdenum oxynitrides exhibited activity for hydrogenation which depended on the amount of Mo ⁺ (0 < < 4) species produced under reaction conditions. The amorphous molybdenum oxynitride MoO_1.83N_0.36 catalyst showed a good catalytic activity, selectivity, and resistance to poisoning of H₂S for liquid-phase hydrogenation of longer-chain alkadienes.     

Decolorization and Modeling of Synthetic Wastewater Using O3 and H2O2/O3 Processes

This research deals with the decolorization of synthetic wastewater, prepared with the acid 1:2 metal-complex textile dye C.I. Acid Blue 193, using the ozonation (O₃) and H₂O₂/O₃ processes. To minimize the number of experiments, they were performed using the 2^k factorial design. Five influential parameters were examined: initial dye concentration, ozone flow rate, initial pH value, decolorization time and H₂O₂ addition. The decolorization efficiency was 95% in 20 minutes (pH = 7; O₃ flow rate of 2 g/L.h) and a higher increase in the toxicity after the ozonation process (39%) indicates the formation of carcinogenic by-products. According to the variance test analysis, the initial dye concentration, the ozone flow rate, the initial pH value and the decolorization time and their first- and second-order interactions are significant, while the H₂O₂ addition was not important with respect to the discussed range. With the help of these significant factors a regression model was constructed and the adequacy of the model was checked. The obtained regression polynomial was used to model the relation between the absorbance and the influential parameters by fitting the response surface. This response surface may be used to predict the absorbance result from a set of influential parameters, or it can be rearranged in such a way as to predict the set of process decolorization parameters necessary to reduce the absorbance of wastewater with the given initial dye concentration, below the prescribed limit. It is also shown that the 2^k factorial design can be suitable for predicting the operating expenses of the ozonation.     

Excess molar enthalpies for the binary and ternary mixtures of ether compounds (di-isopropyl ether, di-butyl ether, propyl vinyl ether) with ethanol and isooctane at 298.15 K

Excess molar enthalpy (H ^E ) data at 298.15 K are reported for the binary systems di-isopropyl ether (1)+ethanol (2), di-isopropyl ether (1)+isooctane (2), ethanol (1)+isooctane (2), di-butyl ether (1)+ethanol (2), di-butyl ether (1)+isooctane (2), propyl vinyl ether (1)+ethanol (2) and propyl vinyl ether (1)+isooctane (2). These data were obtained by using an isothermal flow calorimeter. The experimental binary H ^E data were well correlated with the Redlich-Kister model, and infinitely dilute partial excess molar enthalpies for each binary were calculated with the fitted Redlich-Kister parameters. Additionally, the isoclines of H ^E for ternary systems di-isopropyl ether (1)+ethanol (2)+isooctane (3), di-butyl ether (1)+ethanol (2)+isooctane (3) and propyl vinyl ether (1)+ethanol (2)+isooctane (3) at 298.15 K were calculated by using the Radojkovič equation. H ^E for all the measured systems in this work shows that mixing is endothermic.     

The Valence Band Structure of the [Ni(Salen)] Complex: An Ultraviolet,Soft X-ray and Resonant Photoemission Spectroscopy Study

The valence band photoemission (VB PE) spectra of the [Ni(Salen)] molecular complex were measured by ultraviolet, soft X-ray and resonant photoemission (ResPE) using photons with energies ranging from 21.2 eV to 860 eV. It was found that the Ni 3d atomic orbitals’ (AOs) contributions are most significant for molecular orbitals (MOs), which are responsible for the low-energy PE band at a binding energy of 3.8 eV in the VB PE spectra. In turn, the PE bands in the binding energies range of 8–16 eV are due to the photoionization of the MOs of the [Ni(Salen)] complex with dominant contributions from C 2p AOs. A detailed consideration was made for the ResPE spectra obtained using photons with absorption resonance energies in the Ni 2p_3/2, N 1s, and O 1s Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectra. A strong increase in the intensity of the PE band ab was found when using photons with an energy 854.4 eV in the Ni 2p_3/2 NEXAFS spectrum. This finding is due to the high probability of the participator-Auger decay of the Ni 2p_3/2⁻¹3d⁹ excitation and confirms the relationship between the PE band ab with the Ni 3d-derived MOs.     

The synthesis of poly(vinyl chloride) nanocomposite films containing ZrO2 nanoparticles modified with vitamin B1 with the aim of improving the mechanical,thermal and optical properties

In the present investigation, solution casting method was used for the preparation of nanocomposite (NC) films. At first, the surface of ZrO₂ nanoparticles (NPs) was modified with vitamin B₁ (VB₁) as a bioactive coupling agent to achieve a better dispersion and compatibility of NPs within the poly(vinyl chloride) (PVC) matrix. The grafting of modifier on the surface of ZrO₂ was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA). Finally, the resulting modified ZrO₂ (ZrO₂–VB₁), was used as a nano-filler and incorporated into the PVC matrix to improve its mechanical and thermal properties. These processes were carried out under ultrasonic irradiation conditions, which is an economical and eco-friendly method. The effect of ZrO₂–VB₁ on the properties and morphology of the PVC matrix was characterized by various techniques. Field emission scanning electron microscopy and transmission electron microscopy analyses showed a good dispersion of fillers into the PVC matrix with the average diameter of 37–40 nm. UV–Vis spectroscopy was used to study optical behavior of the obtained NC films. TGA analysis has con?rmed the presence of about 7 wt% VB₁ on the surface of ZrO₂. Also, the data indicated that the thermal and mechanical properties of the NC films were enhanced.     

Examination of the surface properties of kaolinites by inverse gas chromatography: Acid-base properties

The specific component of the free energy of adsorption,-ΔG _A ^SP , of untreated kaolinite and kaolinites surface-treated with isopropyl triisostearoyl titanate (ITT) and isopropyl tri(dioctylpyrophosphato) titanate (ITDT) was estimated, using the adsorption of several polar and non-polar probes on these surfaces at various measuring temperatures, by the inverse gas chromatography (IGC) method. The acid-base properties of the untreated kaolinite and surface-treated kaolinites were quantified by K _A and K _D parameters, reflecting the ability of the surface to act as an electron acceptor and donor, respectively. In the result, all kaolinite surfaces were amphoteric and were able to function as both an electron acceptor and an electron donor.     

Electrochemically reduced titanocene dichloride as a catalyst of reductive dehalogenation of organic halides

We have studied a reaction between the reduced form of titanocene dichloride (Cp₂TiCl₂) and a group of organic halides: benzyl derivatives (4-XC₆H₄CH₂Cl, X = H, NO₂, CH₃; 4-XC₆H₄CH₂Br, X = H, NO₂, PhC(O); 4-XC₆H₄CH₂SCN, X = H, NO₂) as well as three aryl halides (4-NO₂C₆H₄Hal, Hal = Cl, Br; 4-CH₃O-C₆H₄Cl). It has been shown that the electrochemical reduction of Cp₂TiCl₂ in the presence of these benzyl halides leads to a catalytic cycle resulting in the reductive dehalogenation of these organic substrates to yield mostly corresponding toluene derivatives as the main product. No dehalogenation has been observed for aryl derivatives. Based on electrochemical data and digital simulation, possible schemes of the catalytic process have been outlined. For non-substituted benzyl halides halogen atom abstraction is a key step. For the reaction of nitrobenzyl halides the complexation of Ti(III) species with the nitro group takes place, with the electron transfer from Ti(III) to this group (owing to its highest coefficient in LUMO of the nitro benzyl halide) followed by an intramolecular dissociative electron redistribution in the course of the heterolytic CHal bond cleavage.The results for reduced titanocene dichloride centers immobilized inside a polymer film showed that the catalytic reductive dehalogenation of the p-nitrobenzyl chloride does occur but with a low efficiency because of the partial deactivation of the film due to the blocking of the electron charge transport between the electrode and catalytic centers.     

Electrosynthesis and properties of poly(3,4-ethylenedioxythiophene) films functionalized with titanocene dichloride complex

Synthesis of a titanocene dichloride derivative functionalized with 3,4-etylenedioxythiophene group, Tc1EDOT (Cl₂TiCpC₅H₄(CH₂) (3,4-ethylenedioxythiophene)) has been described. Redox behavior of the monomer in tetrahydrofuran (THF), dichloromethane (DCM) and acetonitrile (AN) at different scan rates has been discussed in terms of different ability of these solvents to coordination with the reduced titanocene (Tc) complex and the solvation of Cl⁻ anions. Electrooxidation of Tc1EDOT to get a conducting polymer film with immobilized titanocene dichloride centers and electrochemical properties of its polymer matrix in background acetonitrile solution have been compared with those of non-substituted PEDOT and PEDOT-methanol derivative (PEDOTMet), to elucidate the effect of substituents both on polymerization and redox potentials of the matrix. STM and AFM images of p(Tc1EDOT) films obtained with potentiodynamic and potentiostatic regimes are compared to illustrate that the films deposited at constant potential are better ordered and more compact than those obtained by cyclic voltammetry. A comparison of the cyclic voltammograms of p(Tc1EDOT) and poly(titanocene-propyl-pyrrole) (p(Tc3Py)) films in 0.1 TBAPF₆ in THF has shown that the electroactivity of the polymer matrix of p(Tc1EDOT) is extended to more negative potentials in comparison to that of p(Tc3Py). This results in the anodic shift of redox potential of Tc centers immobilized in p(Tc1EDOT) film with respect to that of the centers fixed in p(Tc3Py).     

PolyHIPEs: Recent advances in emulsion-templated porous polymers

Porous polymers with well-defined porosities and high specific surface areas in the form of monoliths, films, and beads are being used in a wide range of applications (reaction supports, separation membranes, tissue engineering scaffolds, controlled release matrices, responsive and smart materials) and are being used as templates for porous ceramics and porous carbons. The surge in the research and development of porous polymer systems is a rather recent phenomenon. PolyHIPEs are porous emulsion-templated polymers synthesized within high internal phase emulsions (HIPEs). HIPEs are highly viscous, paste-like emulsions in which the major, “internal” phase, usually defined as constituting more than 74% of the volume, is dispersed within the continuous, minor, “external” phase. This review focuses upon the recent advances in polyHIPEs involving innovations in polymer chemistry, macromolecular structure, multiphase architecture, surface functionalization, and nanoparticle stabilization. The effects of these innovations upon the natures of the resulting polyHIPE-based materials (including bicontinuous polymers, nanocomposites, hybrids, porous ceramics, and porous carbons) and upon the applications involving polyHIPEs are discussed. The advances in polyHIPEs described in this review are now being used to generate new families of porous materials with novel porous architectures and unique properties.     

Polymer membranes for high temperature proton exchange membrane fuel cell: Recent advances and challenges

Proton-exchange membrane fuel cells (PEMFCs) are considered to be a promising technology for efficient power generation in the 21st century. Currently, high temperature proton exchange membrane fuel cells (HT-PEMFC) offer several advantages, such as high proton conductivity, low permeability to fuel, low electro-osmotic drag coefficient, good chemical/thermal stability, good mechanical properties and low cost. Owing to the aforementioned features, high temperature proton exchange membrane fuel cells have been utilized more widely compared to low temperature proton exchange membrane fuel cells, which contain certain limitations, such as carbon monoxide poisoning, heat management, water leaching, etc. This review examines the inspiration for HT-PEMFC development, the technological constraints, and recent advances. Various classes of polymers, such as sulfonated hydrocarbon polymers, acid-base polymers and blend polymers, have been analyzed to fulfill the key requirements of high temperature operation of proton exchange membrane fuel cells (PEMFC). The effect of inorganic additives on the performance of HT-PEMFC has been scrutinized. A detailed discussion of the synthesis of polymer, membrane fabrication and physicochemical characterizations is provided. The proton conductivity and cell performance of the polymeric membranes can be improved by high temperature treatment. The mechanical and water retention properties have shown significant improvement., However, there is scope for further research from the perspective of achieving improvements in certain areas, such as optimizing the thermal and chemical stability of the polymer, acid management, and the integral interface between the electrode and membrane.