Mixed Solvent Of Cyclohexane Research Articles

Growth Mechanism of Hollow Sodium Chloride Single Crystals Grown from a Mixed Solvent of Cyclohexane and Acetone

AbstractRecently, hollow sodium chloride crystals have been proposed as potential high‐value‐added crystals. The crystal growth mechanism of such crystals is elucidated using X‐ray diffraction (XRD), optical microscopic imaging, and analysis of both the chloride ions and water content in the mixed solvent of cyclohexane and acetone. A series of experimental conditions, including the stirring time after injecting the aqueous sodium chloride solutions into the mixed solvent and the ratio of cyclohexane and acetone, are evaluated in detail. Based on experimental data, possible growth mechanisms are proposed to explain the formation of hollow sodium chloride crystals.

Synthesis of regioblock polystyrene by a template monomer technique

In this study, we synthesized for the first time a well-defined model polymer of regioblock polystyrene (PS) comprising pure head-to-tail and head-to-head blocks through living anionic block copolymerisation of styrene and 2,3-diphenyl-1,3-butadiene (DPB), followed by hydrogenation using Na/isopropanol reagent. In the polymerisation of DPB, it was critical to use a mixed solvent of cyclohexane with a small amount of THF to attain high solubility. Since DPB polymerized exclusively in 1,4-addition manner, the resulting block copolymers were readily transformed into the regioblock PS by hydrogenation of the residual double bonds in the main chain. The structure of the regioblock PS thus synthesized were confirmed by carefully characterizing with GPC, 1H NMR, 13C NMR, UV–Vis and Raman spectra.

Anionic polymerization of p-(2,2′-diphenylethyl)styrene and applications to graft copolymers

Well-controlled anionic polymerization of an initiator-functionalized monomer, p-(2,2′-diphenylethyl)styrene (DPES), was achieved for the first time. The polymerization was performed in a mixed solvent of cyclohexane and tetrahydrofuran (THF) at 40 °C with n-BuLi as initiator. When the volume ratio of cyclohexane to THF was 20, the anionic polymerization of DPES showed living polymerization characteristics, and well-defined block copolymer PDPES-b-PS was successfully synthesized. Furthermore, radical polymerization of methyl methacrylate in the presence of PDPES effectively afforded a graft copolymer composed of a polystyrene backbone and poly(methyl methacrylate) branches. The designation of analogous monomers and polymers was of great significance to synthesize a variety of sophisticated copolymer and functionalize polymer materials.

Supramolecular gel based on the cyclodextrin inclusion assembly of Ag-Fe3O4 nanodimers and Pluronic F127

Being considered as building blocks, the inorganic nanodimer particles such as Ag-Fe3O4, Cd-Se and Pt-Fe3O4, have attracted much attention because of their capability of dual surface functionalization and potential applications in field-emission, data storage and photovoltaic devices. For these motivations and as a continuation of our previous study, a gel with flower-like morphology based on Ag-Fe3O4 nanodimers has been constructed with the carboxylated cyclodextrin (MAH-CD) and Pluronic F127 molecules in mixed solvent of cyclohexane and water. The morphology of Ag-Fe3O4 nanodimers and structure of MAH-CD were characterized by transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR) respectively. The mechanism of gel formation is discussed along with the data obtained from rheological measurement, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Each Ag-Fe3O4 particle was coated by lots of MAH-CD molecules, which were threaded by F127 chains. The gel fabrication is controlled by the inclusion of MAH-CD with F127, the interaction between the carboxyl group and the Fe3O4 surface. The cyclohexane molecules in gel were trapped with F127 by cyclodextrin, which may be packed orderly through hydrogen bond. Meanwhile, the Fe3O4 side of nanodimers provides the anchoring position for carboxyl group to induce the formation of gel. Such an Ag-Fe3O4 nanodimer initiated gel can be used either based on Ag side for catalytic and sensing properties, or based on superparamagnetism from Fe3O4 side.

Molecular Dynamics of a Polymer in Mixed Solvent: Atactic Polystyrene in a Mixture of Cyclohexane and N,N-Dimethylformamide

Local structural and dynamic properties of atactic polystyrene in a mixed solvent of cyclohexane (CH) and N,N-dimethylformamide (DMF) have been investigated using molecular dynamics simulations. We measure local conformations in the polymer and classify them by distance and angle distribution histograms. End-to-end distances and structure factors are employed to describe the static structure of polystyrene chains. Polystyrene concentration, including 1.6%, 4.8%, and 14% (by weight), and solution temperatures of 300, 330, or 360 K are used to elucidate the concentration and temperature dependencies of the solvation by the two solvents. Both solvent molecules preferentially approach the phenyl rings. At lower temperatures, polystyrene dissolves more favorably in cyclohexane. With rising temperature DMF molecules approach more closely with the oxygen oriented toward the phenyl rings. Additionally, the global and segmental relaxation times of the chains decrease and the system becomes more homogeneous. The segmental and global dynamics of polystyrene show different concentration behaviors: the reorientation times of solvent molecules and segments of polystyrene increase with concentration while the global dynamics of polystyrene decelerates as the concentration is changed from 1.6% to 4.8% but accelerates when the concentration rises to 14%. We conclude that the change of concentration from 4.8% to 14% qualitatively marks the change from a dilute to a semidilute solution. The diffusion constants of the small molecules and corresponding activation energies have also been measured. Our simulation data are compared with available experimental results and we find a satisfactory agreement.

Polymer chain conformation in the phase separation process of a binary liquid mixture

A polymer chain conformation change near the critical point of liquid–liquid phase separation was investigated. Poly( N-isopropylacrylamide) labeled with a small amount of carbazolyl group for a fluorophore (P(NIPA-Cz)) was prepared. A ternary system of P(NIPA-Cz)+cyclohexane+methanol was investigated by the fluorescence spectroscopic technique. A mixed solvent of cyclohexane+methanol (CH/MeOH) shows phase separation at the upper critical solution temperature. Light scattering intensity, fluorescence emission intensity and fluorescence anisotropy ratio, as a function of temperature, were measured with quasi statically approaching to the critical demixing point. The fluorescence intensity of the carbazolyl groups attached to the polymer chain decreases with approaching to the critical temperature. This result suggests that the radius of gyration of the polymer decreases upon approaching to the critical demixing point of the solvent. We discuss the collapse and aggregation processes of the polymer based on the fluorescence quenching method. The rotational diffusion coefficient of carbazolyl groups attached to the polymer chain was estimated by the fluorescence depolarization technique. The rotational motion of carbazolyl groups is slowed down upon approaching the critical point.

Effect of Chain Architecture on Adsorption from Dilute Solution: ω-Functionalized Linear and Mono-, Di-, and Tri-ω-functionalized Three-Arm Star Polybutadienes

The adsorption behavior of ω-functionalized linear and mono-, di-, and tri-ω-functionalized three-arm star polybutadiene (PB) samples from the mixed solvent of cyclohexane and toluene (50% by volume) on silicon wafers is investigated by means of null-ellipsometry at 20.0 °C. Under these conditions no association of the sulfozwitterionic functional groups is detected in solution with dynamic light scattering, and there is sufficient contrast for in situ ellipsometric adsorption measurements. The adsorbed end-functionalized linear PB chains have a “brushlike” conformation. In the case of the functionalized star PB, the adsorbed amount increases when the number of functionalized arms increases from 1 to 3. However, the grafting density is more influenced by the molecular weight than by the number of functional groups. The adsorbed stars are less stretched than the linear chains. The adsorption energy is calculated as (9 ± 1)kT. The diffusion coefficient and hydrodynamic radius are determined with dynamic lig...

Interaction between Pyrazine and Halomethanes. II. Effects of Halomethanes on the Phosphorescence of Pyrazine at 77 K

Abstract The phosphorescence and phosphorescence excitation spectra of pyrazine have been studied at 77 K in various mixed solvents of cyclohexane and halomethanes such as carbon tetrachloride, chloroform, and dichloromethane. When the halomethane concentration was low (below 10−2 mol dm−3), only the cyclohexane-phase phosphorescence was observed at 77 K; the lower energy components of the well-known doublet band series in the cyclohexanephase phosphorescence were found to decrease in intensity relative to the higher energy components, with increasing concentration of halomethane. When the halomethane concentration was raised to a range higher than 10−1 mol dm−3, where the complex formation between pyrazine and the halomethanes was confirmed through absorption spectroscopy, new phosphorescence bands appeared in the 373–375 nm region for all the systems studied. With further increase of the halomethane concentration, the new bands decreased in intensity or disappeared, and the phosphorescence approached to those in the pure halomethanes. Comparison of the absorption and phosphorescence excitation spectra shows that the new phosphorescence bands result from the 1 : 1 pyrazine–halomethane complexes. The possibility of hydrogen-bonding species formation with chloroform and dichloromethane has been discussed in the light of the phosphorescence spectra studied in the ethanol–cyclohexane mixed solvents.

Interaction between Pyrazine and Halomethanes. I. Complex Formation between Pyrazine and Halomethanes at Room Temperature

Abstract The absorption spectrum of pyrazine has been studied at room temperature in various mixed solvents of cyclohexane and halomethanes such as carbon tetrachloride, chloroform and dichloromethane. With increasing concentration of halomethane, the singlet-singlet (S-S) and singlet-triplet (S-T) n→π* absorptions decrease in intensity and become structureless, whereas the S-S π→π* absorption remains essentially unchanged. The observations are attributed to the complex formation between pyrazine and halomethanes involving the non-bonding electrons in pyrazine. From the concentration and temperature dependences of the n→π* absorption spectra, the equilibrium constants, enthalpy and entropy changes have been obtained for the complex formation in all the systems studied. The equilibrium constants obtained from the S-S and S-T n→π* absorptions are in good agreement with each other.

Order of Quencher Participation in Photochemistry. I. Proton Transfer from the Excited p-Hydroxybenzophenone in Mixed Solvents of Cyclohexane and Alcohols

Abstract The change in the absorption spectrum of p-hydroxybenzophenone (HOBP) and relative quantum yields Φrel for the photoreduction of HOBP have been studied in mixed solvents consisting of cyclohexane and four kinds of alcohol. The change in absorption spectrum occurs in two steps with methanol, ethanol, and 2-propanol, suggesting the following equilibria, HOBP+S\leftrightharpoonsA, and A+S\leftrightharpoonsB (S, alcohol molecule). Φrel changes in two steps with methanol and ethanol and in one step with 2-propanol and amyl alcohol roughly in line with the spectral change. The changes in Φrel have been interpreted to be due to the deprotonation of HOBP. Φrel=1⁄(1+K[S]n) holds for them with n=5.5 for 2-propanol and n=1 for other alcohols. A linear relation holds between 1⁄(n−1)logK and Hammett’s constant of alkyl group of alcohols, suggesting that the deprotonation tendency depends upon the specific interaction between alcohol molecules. The reactivity of A-species is considered to depend largely on the dielectric nature of the solvent.

Ethylene-Cyclohexane-Telomer System

In the previous reports, we have suggested that the radiation-induced reaction of ethylene in a mixed solvent of cyclohexane and carbon tetrachloride may consist of two succeeding steps ; firstly, the formation of ethylene-carbon tetrtrachloride telomer, and secondly, the grafting reaction of ethylene onto the telomer. Therefore, when the telomer is used instead of carbon tetrachloride, it may be expected that only the second reaction occurs.In the system of ethylene, cyclohexane, and an ethylene-carbon tetrachloride telomer, the yield of solid products increased linearly with increasing dose. Results of the differential thermal analysis showed that the products contained two components corresponding to the products of high melting points obtained in ethylenecyclohexane-carbon tetrachloride systems.Results suggested that only grafting reactions occurred and that the grafted branch grew fairly long.