Decalin Solutions Research Articles

Oriented shish-kebab like ultra-high molecular weight polyethylene membrane for direct contact membrane distillation

The special bioinspired structure will help membranes to improve the antifouling properties during the membrane distillation (MD) process. Here, a new MD utilized membrane with oriented shish-kebab structure was prepared by stirring the ultra-high molecular weight polyethylene (UHMWPE)/decalin solution to induce the shish-kebab crystals to grow on a polyester mesh along the flow field, and then coated with fluororesin to decrease the surface energy. The multi-stage extraction drying technology was adopted to reduce the membrane shrinkage in the dry process and make the shish-kebab membranes have high porosity (77.5%). More interesting, when the water flows along the shish direction, just like the fish gill works, the membrane has better resistance to NaCl, CaCO3 scaling, due to the nanoscale structure can intensify the interfacial nanoscale turbulent flow and hinder the crystal deposition. Specifically, the membrane has a high-water recovery of 92.5% and a low conductivity increase (from 2.76 to 8.33 μS/cm in 70 h) in the long-term MD process.

Production of ultra-high molecular weight polyethylene-granite composite films by gelation/crystallization

The present study reports on film of ultra-high molecular weight polyethylene (UHMWPE) containing 1 mass% granite composite produced by gelation/crystallization technique at 150 °C from decalin solution. The morphology of UHMWPE-granite composite film was determined by using optical and scanning electron microscope, differential scanning calorimetry and Raman. Uniform dispersion of granite particles within ultra-high molecular weight polyethylene solution was the first step to achieve ultra-high molecular weight polyethylene-granite sheet samples with excellent properties. In differential scanning calorimetry analysis 50.1 % crystallinity of ultra-high molecular weight polyethylene-1 mass% granite composite was calculated from the endothermic peak area occurred around 142 °C which correspond to melting point of composite. Mechanical property of ultra-high molecular weight polyethylene-1 mass% granite composite was tested with tensile test and shown to possess unique properties, in particular an increase of over 2.5 times in Young’s modulus in comparison with pure ultra-high molecular weight polyethylene.

1H relaxation enhancement induced by nanoparticles in solutions: influence of magnetic properties and diffusion.

Magnetic nanoparticles that induce nuclear relaxation are the most promising materials to enhance the sensitivity in Magnetic Resonance Imaging. In order to provide a comprehensive understanding of the magnetic field dependence of the relaxation enhancement in solutions, Nuclear Magnetic Resonance (1)H spin-lattice relaxation for decalin and toluene solutions of various Fe2O3 nanoparticles was investigated. The relaxation experiments were performed in a frequency range of 10 kHz-20 MHz by applying Field Cycling method, and in the temperature range of 257-298 K, using nanoparticles differing in size and shape: spherical--5 nm diameter, cubic--6.5 nm diameter, and cubic--9 nm diameter. The relaxation dispersion data were interpreted in terms of a theory of nuclear relaxation induced by magnetic crystals in solution. The approach was tested with respect to its applicability depending on the magnetic characteristics of the nanocrystals and the time-scale of translational diffusion of the solvent. The role of Curie relaxation and the contributions to the overall (1)H spin-lattice relaxation associated with the electronic spin-lattice and spin-spin relaxation was thoroughly discussed. It was demonstrated that the approach leads to consistent results providing information on the magnetic (electronic) properties of the nanocrystals, i.e., effective electron spin and relaxation times. In addition, features of the (1)H spin-lattice relaxation resulting from the electronic properties of the crystals and the solvent diffusion were explained.

Hydrocracking of 1-methylnaphthalene/decahydronaphthalene mixture catalyzed by zeolite-alumina composite supported NiMo catalysts

Various zeolite-alumina composites supported NiMo catalysts were prepared and their properties for hydrocracking of a decahydronaphthalene (decalin) solution containing 10wt.% of 1-methylnaphthalene (1-MN) and 0.1wt.% of dibenzothiophene were investigated in order to estimate not only hydrocracking of hydrocarbons but also isomerization and hydrogenation of 1-MN. 1-MN was converted to 2-MN for almost all the catalysts. The hydrogenation activities to form methyltetralin decreased in the order NiMo/Beta(940)60A>NiMo/Beta(980)60A>NiMo/HY(5.5)60A>NiMo/USY(390)60A>NiMo/USY(360)60A>NiMo/ZSM60A at 300°C where Beta(940) β zeolite with SiO2/Al2O3=37, Beta(980) β zeolite with SiO2/Al2O3=500, HY(5.5) Y zeolite with SiO2/Al2O3=5.5, USY(360) dealuminated Y zeolite with SiO2/Al2O3=14, USY(390) dealuminated Y zeolite with SiO2/Al2O3=400, ZSM ZSM-5 zeolite with SiO2/Al2O3=1500, 60A alumina content in a composite support. Hydrocracking was observed at 360°C specifically for β zeolite containing catalysts and the highest yields of benzene, toluene and xylene were obtained for NiMo/Beta(940)35A. It is elucidated that mesopore is favorable for hydrocracking and that the strength of the acid sites as well as homogeneous dispersion of metal species played an important role.

1H relaxation dispersion in solutions of nitroxide radicals: Effects of hyperfine interactions with 14N and 15N nuclei

(1)H relaxation dispersion of decalin and glycerol solutions of nitroxide radicals, 4-oxo-TEMPO-d(16)-(15)N and 4-oxo-TEMPO-d(16)-(14)N was measured in the frequency range of 10 kHz-20 MHz (for (1)H) using STELAR Field Cycling spectrometer. The purpose of the studies is to reveal how the spin dynamics of the free electron of the nitroxide radical affects the proton spin relaxation of the solvent molecules, depending on dynamical properties of the solvent. Combining the results for both solvents, the range of translational diffusion coefficients, 10(-9)-10(-11) m(2)/s, was covered (these values refer to the relative diffusion of the solvent and solute molecules). The data were analyzed in terms of relaxation formulas including the isotropic part of the electron spin - nitrogen spin hyperfine coupling (for the case of (14)N and (15)N) and therefore valid for an arbitrary magnetic field. The influence of the hyperfine coupling on (1)H relaxation of solvent molecules depending on frequency and time-scale of the translational dynamics was discussed in detail. Special attention was given to the effect of isotope substitution ((14)N/(15)N). In parallel, the influence of rotational dynamics on the inter-molecular (radical - solvent) electron spin - proton spin dipole-dipole coupling (which is the relaxation mechanism of solvent protons) was investigated. The rotational dynamics is of importance as the interacting spins are not placed in the molecular centers. It was demonstrated that the role of the isotropic hyperfine coupling increases for slower dynamics, but it is of importance already in the fast motion range (10(-9)m(2)/s). The isotope effects is small, however clearly visible; the (1)H relaxation rate for the case of (15)N is larger (in the range of lower frequencies) than for (14)N. It was shown that when the diffusion coefficient decreases below 5 × 10(-11) m(2)/s electron spin relaxation becomes of importance and its role becomes progressively more significant when the dynamics slows done. As far as the influence of the rotational dynamics is concerned, it was show that this process is of importance not only in the range of higher frequencies (like for diamagnetic solutions) but also at low and intermediate frequencies.

Equilibration of Polymer Films Cast from Solutions with Different Solvent Qualities

We study the effect of film preparation on the equilibration and viscoelastic properties of polymer films. Polystyrene films with a thickness of 14 nm are spun-cast from decalin solutions at different temperatures near the theta temperature to produce films with different chain conformations. We find that the equilibration time of the films increases significantly near the theta temperature. We attribute this to the onset of a rapid collapse in the polymer coil size at the theta condition, along with an increase in the solvent concentration in the films and thereby interchain separation at the time of vitrification. We find that these effects also cause the plateau modulus and equilibrium viscosity of the films to decrease.

Effect of Metal Promoters on the Structure and Performance of the Ni_2P/SBA-15 Catalyst for Hydrodesulfurization

Ni2P/SBA-15 catalysts with initial P/Ni molar ratio of 0.8 were prepared by co-impregnation method with mesoporous molecular sieve SBA-15 as support,Ni(NO3)2·6H2O as a source of nickel and(NH4)2HPO4 as a source of phosphorus.Then,a series of M-Ni2P/SBA-15 catalysts were prepared by the addition of Li,Na,K,Mg,Ca,Sr,Ba metal promoters and characterized by X-ray diffraction(XRD).The catalytic performance of the catalysts for hydrodesulfurization(HDS) was evaluated in a fixed-bed microreactor with the decalin solution of 1%(mass fraction) model compound dibenzothiophene.The results indicated that Ni2P particles were the active phase for M-Ni2P/SBA-15 catalysts.Different metal promoters(M) had different effects on the HDS performance of M-Ni2P/SBA-15 catalysts,among which the alkaline earth metal Ca was the best one to improve the HDS activity of the catalysts.Over the Ca-Ni2P/SBA-15 catalyst with Ca mass fraction of 3.5% the conversion of DBT HDS reached 98.6% under the conditions of reaction pressure at 3.0 MPa and temperature at 360℃.In addition,different metal promoters also affect HDS reaction mechanism in different ways.

Synthesis of fullerene-silica hybrid materials

Fullerene/silica hybrid materials were obtained by radiation grafting on silica surface of toluene or decalin solutions of C60. As determined by thermogravimetric analysis, the amount of C60 grafted on silica surface was dependent from the radiation dose administered and independent from the C60 concentration and the nature of the organic solvent. In absence of air, a dose of 48 kGy was sufficient to ensure a grafting level of 30% by weight of C60 in the hybrid material. The fullerene/silica hybrid material shows a remarkable thermal stability, since the early decomposition starts above 300 °C as measured by DTG and DTA. The chemical structure of the fullerene/silica hybrid material was determined by FT-IR spectroscopy and with solid state 13C CP-MAS NMR. The potential application of such materials has been outlined.

Phosphorescent Ir(iii) complexes bearing double benzyldiphenylphosphine cyclometalates; strategic synthesis, fundamental and integration for white OLED fabrication

A new Ir(III) complex [Ir(bdp)2(OAc)] (1) was prepared by the treatment of IrCl3(tht)3 with approx. two equivalent of benzyldiphenylphosphine in refluxing decalin solution, bdpH = benzyldiphenylphosphine and tht = tetrahydrothiophene. Complex 1 proves to be a versatile precursor, which could further react with various triazolate chelates such as 5-pyridyl-3-trifluoromethyl-1,2,4-triazole (fptzH), 3-tert-butyl-5-(2-pyridyl)-1,2,4-triazole (bptzH), 5-(1-isoquinolyl)-3-tert-butyl-1,2,4-triazole (iqbtzH) and 5-(1-phenanthridinyl)-3-tert-butyl-1,2,4-triazole (pbtzH) to afford the emissive complexes [Ir(bdp)2(fptz)] (2), [Ir(bdp)2(bptz)] (3), [Ir(bdp)2(iqbtz)] (4), and [Ir(bdp)2(phbtz)] (5), respectively. Single crystal X-ray diffraction studies of 1 and 5 revealed a distorted octahedral Ir(III) metal core, both possess two mutually orthogonal bdp cyclometalates, and the respective PPh2 donors reside at the cis-orientation. Formation of complexes 2–5 can be envisioned as simple replacement of acetate with the incoming N-heterocyclic triazolate chelates. As for photophysical properties, the structural variation leads to salient difference in emission features among complexes 2–5. Combining theoretical approaches, the results are rationalized by the contribution from the degree of ligand π-conjugation, together with the occurrence of ligand-to-ligand charge transfer (LLCT) and intra-ligand ππ* transition in the lowest lying excited state. The orange-red and white light-emitting OLEDs were then fabricated using 5 as dopant, for which the respective devices gave peak efficiencies of 13.6% photons/electron, 33.3 cd A−1, 29.8 lm/W and with CIEx,y = 0.530, 0.467 at 100 cd m−2, and peak efficiencies of 13.0% photons/electron, 28.0 cd A−1, 22.8 lm/W, and with CIEx,y = 0.356, 0.348 at 1000 cd m−2.

Synthesis and Use of New Substituted 1,3,5‐Hexatrienes in Studying Thermally Induced 6π‐Electrocyclizations

AbstractAn acyclic, two heterocyclic, and two bicyclic alkenylstannanes, 3, 4a, 4b, 8 and 11, respectively, were synthesized in yields ranging from 43 to 97 %, and each was subjected to a sequence of Stille and Heck couplings with 2‐bromocyclohexenyl triflate (13) and alkyl (tert‐butyl and methyl) acrylate to furnish seven new 1,3,5‐hexatrienes 19, 20, 21, 22‐tBu, 22‐Me, 23 and 43, respectively, in 58–84 % yields. For the alkenylstannanes 4a,b, 8 and 11, customized combinations of catalysts had to be used. The Stille–Heck sequence involving 13, 3 and tert‐butyl acrylate could be performed in a one‐pot mode and proceeded in 75 % yield. The hexatrienes were heated in decalin solutions so as to effect 6π‐electrocyclization. Temperatures and reaction times were optimized individually. The hexatrienes 29, 31 and 36 gave the bi‐ and tricyclic cyclohexadienes 28, 30 and 34, incorporating allylic alcohol and allyl ether termini, by 6π‐electrocyclization and subsequent [1,5]‐hydrogen shift, as single products in good yields (85–93 %). In contrast, the hexatrienes 19, 20, 21 and 39 furnished mixtures of the initial electrocyclization products 26, 32, 37 and 40 as well as the products of a subsequent [1,5]‐hydrogen shift 27, 33, 38 and 41, respectively. The tricyclic hexatrienes 22‐tBu, 22‐Me and 23 bearing alkyl (tert‐butyl, methyl) acrylate termini also selectively gave the tetracyclic dienes 48‐tBu, 48‐Me and 50 in 71–77 % yields by electrocyclizations and subsequent hydrogen shifts.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Electrical properties of segregated ultrahigh molecular weight polyethylene/multiwalled carbon nanotube composites

AbstractMultiwalled carbon nanotubes (MWNTs) and ultrahigh molecular weight polyethylene (UHMWPE) composites are prepared using paraffin as solvent. The resulting electrical properties show lower electrical percolation threshold, which is 1.4 vol %, than that of UHMWPE‐MWNT composites prepared by gelation/crystallization from decalin solution. Good reproducibility and higher maximum of electrical conductivity are obtained. The extremely low electrical percolation threshold indicates that the dispersion of MWNTs is segregated, which can be proved by the morphology of the film observed by optical microscopy. The complex planes of electric modulus are useful to analyze the dispersion of MWNTs and the quality of interparticle contacts. In addition, the result of thermogravimetry shows that the retardation of onset of UHMWPE decomposition in inert gas is observed in the mixture with MWNTs. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Research on the molecular entanglement and disentanglement in the dry spinning process of UHMWPE/decalin solution

AbstractThe macromolecular entanglement and disentanglement in the dry spinning process of ultrahigh molecular weight polyethylene (UHMWPE)/decalin solution were investigated. By the fitting results of the theoretical model to the experimental data, it is found that the variation tendency of the NskT value, which reflects the chain slippage at the slip links in the extensional deformation on spinning line of draw‐down process, is in accordance with the fact that each of the relationship curves between the tensile strength, modulus of the UHMWPE fibers through maximized solid state drawing and the draw‐down ratio showed a peak, thus discovering the molecular movement mechanism of “disentanglement on spinning line.” When the entanglements were included in the flow units, their apparent quantity would decrease. Based on this result, the optimum draw‐down ratio can be determined directly by measuring the draw‐down stress at the exit of the spinning duct. The molecular entanglements numbers, which are derived from the theoretical fitting to the experimental data of predrawing and after‐drawing process, abruptly increased in large amounts. It may be concluded that these are mainly not attributed to the topological entanglements, but attributed to the agglomerate entanglements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 864–875, 2006

Clathrate Formation between Syndiotactic Polystyrene and Aromatic Compounds from Solution in Decalin

In order to ascertain whether preferential inclusion of toluene and biphenyl into the δ phase of syndiotactic polystyrene occurs from solution in decalin, we investigate the crystal phase formation of this polymer from solution in decalin/toluene and decalin/biphenyl mixtures of varying composition. To this end, we performed a qualitative analysis of the solid formed upon quenching the solution and drying, with Fourier-transformed infrared spectroscopy and wide-angle x-ray diffraction. In all cases, the formation of T2G2 helical structures was observed. We find that the composition of the solvent mixture can have a strong effect on the X-ray spectrum of the solid, after quenching and drying. For syndiotactic polystyrene samples obtained from decalin/toluene mixtures, we find that little or no toluene inclusion occurs, unless the fraction of toluene in the solvent mixture is quite high. Conversely, biphenyl appears to be preferentially clathrated from solution in decalin, even if it is present in relatively small amounts.

The effect of supramolecular structure on deformation and relaxation transitions in ethylene-1-hexene copolymers crystallized from solution

Structure and mechanical properties of three samples based on ethylene-1-hexene copolymers prepared by crystallization from decalin solutions were studied. The rate of decrease in the true yield stress was shown to depend on temperature. This behavior was assumed to be due to the involvement in deformation of the “intermediate phase” that is located at the lamellar surface between the crystalline and amorphous phases.

Evidence for a Carbonyl-Containing Intermediate in the 308-nm Photolysis of trans-RhCl(CO)(PMe3)2

Time-resolved infrared absorption spectroscopy is used to monitor the events during the first approximately 100 mus following 308-nm photolysis of trans-RhCl(CO)(PMe3)2 (I) in a C6D6 or Decalin solution. Upon photolysis, the intensity of the carbonyl stretching absorption of I decreases and a new C-O stretching absorption (A) appears at 2006 cm(-1) in C6D6 (2013 cm(-1) in Decalin). Within approximately 100 mus, A disappears concurrently with partial regeneration of I and oxidative addition of a solvent C-D (C-H) bond. Our observation of the prompt formation of a carbonyl-containing intermediate contrasts with prior observations that photolysis at longer wavelengths leads solely to dissociation of CO from I. The implications of the observation of A for the understanding of the mechanisms of photocatalytic reactions of I are discussed.

Grafting of a LLDPE using gamma irradiation

In this investigation, the grafting of a commercial linear low-density polyethylene (LLDPE) with different concentrations of diethyl maleate (DEM, 5 and 15wt.%) was carried out at different absorbed doses from a cobalt-60 source of gamma rays (0, 15, 30, 50, 100, 200kGy). This process was performed in a decalin solution at 10% w/v to obtain a homogeneous dispersion of the monomer into the polyethylene matrix. The grafting degree was estimated by means of FTIR using a calibration curve reported in literature. Thermal properties of the functional polymers were studied by thermogravimetric analysis (TGA). Melt flow index (MFI) values were also taken.The results found indicate that the grafting degree increases as the concentration of DEM in the reaction mixture and the absorbed doses are increased upto 100kGy, as expected. However, the behavior at higher doses is attributed to secondary reactions such as long-chain branching and/or crosslinking, which are faster than radical reactions responsible for the grafting of the DEM onto the polymeric chain. This fact was ascertained by the decrease of the MFI values as the applied irradiation was increased, irrespective of the quantity of DEM used in the grafting reaction. Therefore, in order to obtain a high grafting degree, the absorbed dose should be estimated carefully. Initial degradation temperatures of the grafted PEs decreased when the gamma irradiation dose was higher than 100kGy. This indicates that the thermal stability decreases as higher doses are applied to the material, which is associated to branching and crosslinking. The grafting degree never exceeded 0.3mol%, which demonstrates the low efficiency of the functionalization procedure here presented.

Gamma irradiation effects on the grafting of low-density polyethylene with diethyl maleate

In this work, a low-density polyethylene (LDPE) was grafted with diethyl maleate (DEM) using gamma-rays from a Cobalt-60 source at different absorbed doses and monomer concentrations between 5 and 30wt.%. This process was carried out in a decalin solution at 10w/v% to obtain a homogeneous dispersion of the monomer into the polyethylene matrix. It was found that the grafting degree increases with the absorbed doses, as a consequence of the increased amount of energy given to the system, which made the grafting process more favorable. The grafting degree also increases with the concentration of DEM, because a higher concentration makes the insertion easier due to the increased availability of the free monomer. The highest grafting degree was obtained at 200kGy of absorbed dose and with 30wt.% of DEM. The melt flow index (MFI) values showed a decreasing trend as the absorbed dose was increased. This fact reveals that crosslinking and grafting are taking place simultaneously, this behavior being remarkable at higher irradiation doses. The results from thermogravimetric analysis (TGA) showed that the initial degradation temperatures remained almost unchanged with the absorbed dose.

A method for determination of thermodynamic and solubility parameters of polymers from temperature and molecular weight dependence of intrinsic viscosity

An equation using the temperature dependence of intrinsic viscosity of a polymer was proposed for the determination of the partial molar entropy and enthalpy changes of the polymer for mixing in dilute solution. It was found that the partial molar entropy change of a polymer for mixing at a given temperature is proportional to the hydrodynamic volume or segment number of the polymer. The partial molar enthalpy change of the polymer for mixing was determined from the thermodynamic equilibrium property of polymer phases. The solubility or cohesion parameter of a polymer fraction was calculated by using the partial molar enthalpy change and repeat unit volume of the polymer. The solubility parameter of high molar mass polymer at a given temperature was determined by extrapolating solubility parameter values of polymer fractions to high molar mass by using the solubility parameter-segment number relation of polymer fraction. This relation gives a straight line. The solubility parameter of the polymer at a given temperature and the effective interchange energy parameter for polymer–solvent pair were obtained directly from the intercept and the slope of this line, respectively. These equations were applied to the intrinsic viscosity–temperature data of polystyrene fractions in decalin solutions, and polystyrene fractions in decalin, cyclohexane and dioctyl phthalate solutions at the theta temperatures and in toluene solutions at the given temperatures. The results obtained in this study coincide with the literature values. In addition, it was given a relation, which is derived from the blob theory for the temperatures above the theta point, for the estimation of the thermodynamic parameters of polymers for mixing.

Picosecond conformational relaxation of singlet excited polyfluorene in solution

Poly[9,9-di(ethylhexyl)fluorene] was studied by steady-state and time-resolved fluorescence techniques in solution in cyclohexane, methylcyclohexane, tetrahydrofuran, and decalin over the temperature range from 343 to 77 K. A decrease in temperature leads to a decrease in the inhomogeneous broadening of the emission band. Fluorescence decays were biexponential, consistent with a two-state model involving two different polymer conformers. Global analysis of the time profiles of luminescence collected at different emission wavelengths shows a long decay-time of 371.5±1.5 ps, which is temperature and solvent independent. The second shorter time (29±3 ps at 313 K and 100±3 ps at 233 K in methylcyclohexane) appears as a decay-time at the onset of the emission spectrum and as a risetime at longer wavelengths. Whilst the slow process was independent of temperature, the fast process showed Arrhenius type behavior, with an activation energy value of 0.10 eV found in both methylcyclohexane and decalin solutions. However, the risetime in the more viscous decalin was longer than that in methylcyclohexane. The observed behavior is interpreted in terms of fast conformational relaxation of the initially excited polymer, leading to a more planar conjugation segment.

Nucleation of Polypropylene Crystallization by Single-Walled Carbon Nanotubes

Nonisothermal and isothermal crystallization experiments were performed on polypropylene mixed with carbon nanotubes produced by disproportionation of CO on Co−Mo catalysts. Functionalization of the nanotubes with octadecylamine made the tubes hydrophobic and allowed the tubes to be solubilized in an organic solvent. Mixing of the nanotubes with the polymer was accomplished by adding the nanotubes to a Decalin solution that contained dissolved polypropylene, followed by evaporation of the solvent. Dynamic mechanical analysis indicated very little difference in the small-strain mechanical properties between filled and unfilled polymers at the very low solid levels that were tested. By contrast, the crystallization behavior of the filled and unfilled polymer was quite different. Nanotubes promoted growth of the less-preferred beta form of crystalline polypropylene at the expense of the alpha form. In nonisothermal crystallization, the total amount of crystalline material in the sample was the same for the filled and unfilled materials. However, for isothermal crystallization experiments, the percent crystallinity in the filled materials was slightly higher. Most importantly, the rate of crystallization was substantially higher in the filled system. The results presented in this paper clearly show that carbon nanotubes nucleate crystallinity in polypropylene.