Diffusion Of Pentane Research Articles

Expansion Properties and Diffusion of Blowing Agent for Vinylidene Chloride Copolymer Thermally Expandable Microspheres.

Vinylidene chloride copolymer microspheres were synthesized by in situ suspension copolymerization of vinylidene chloride (VDC), methyl methacrylate (MMA), and/or acrylonitrile (AN) in the presence of a paraffin blowing agent. The effects of shell polymer properties including compositions, glass transition temperature (Tg), crosslinking degree, blowing agent type, and encapsulation ratio (Er) on the expansion properties of copolymer microspheres were investigated. Moreover, the diffusion properties of blowing agent in copolymer microspheres were studied. The results show that VDC-MMA-AN copolymer microspheres exhibited excellent expansion properties, and the volume expansion ratio (Ev) and the apparent density were decreased over 40 times, but it was difficult to expand for the VDC-MMA copolymer microspheres. In addition, the moderately crosslinked inside of the polymer shell enhanced the Ev more than 30 and the stable expansion temperature range (Tr) was about 30 °C by adding 0.2–0.4 wt% of divinyl benzene. The Tg of the shell polymer must be higher than the boiling point of the blowing agent as a prerequisite; the lower the boiling point of the blowing agent, the higher the internal gas pressure driven microsphere expansion, and the wider the Tr. By increasing the Er of blowing agent improved the Ev of the microspheres. The diffusion of pentane blowing agent in VDC-MMA-AN copolymer microspheres were divided into Fick diffusion and non-Fick diffusion.

Mer-Tri-chlorido-tris-(tetra-hydro-thio-phene-κS)iridium(III): preparation and comparison with other mer-tri-chlorido-tris-(tetra-hydro-thio-phene-κS)metal complexes.

The title complex, [IrCl3(C4H8S)3], was prepared according to a literature method. A suitable crystal was obtained by diffusion of pentane into a di-chloro-methane solution and analyzed by single-crystal X-ray diffraction at 100 K. The title complex is isotypic with mer-tri-chlorido-tris-(tetra-hydro-thio-phene-κS)rhodium(III). However, the orientation of the tetra-hydro-thio-phene rings is different from an earlier report of mer-tri-chlorido-tris-(tetra-hydro-thio-phene-κS)iridium(III) deposited in the Cambridge Structural Database. The IrS3Cl3 core shows a nearly octa-hedral structure with various bond angles within 1-2° of the perfect 90 or 180° expected for an octa-hedron. The structure of the title compound is compared with the previous iridium complex as well as the rhodium and other octa-hedral metal tris-tetra-hydro-thio-phene compounds previously structurally characterized. DFT calculations were performed, which indicate the mer isomer is significantly lower in energy than the fac isomer by 50.1 kJ mol-1, thereby accounting for all compounds in the CSD being of the mer geometry. Powder X-ray diffraction of the bulk material showed that the preparation method yielded only the isomorph reported in this communication.

Translation and Rotation of Penetrants in Ultrapermeable Nanocomposite Membrane of Poly(2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole-co-tetrafluoroethylene) and Fumed Silica

Diffusion of pentane, cyclohexane, and toluene in nanocomposite films of fumed silica and poly(2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole-co-tetrafluoroethylene) is observed by pulse field gradient NMR. The apparent diffusion constant determined in this experiment depends on the time over which the diffusion measurement is made. The pure copolymer and the nanocomposites based on it are inhomogeneous materials phenomenologically similar to a porous system with the fast diffusion domains having an apparent pore size in the micron size range. In this regard the diffusion can be considered to be anomalous with slopes as low as 0.6 in plots of the logarithm of mean-square displacement vs the logarithm of time at short observation times and at lower silica content. The slower diffusing toluene and cyclohexane are influenced to a greater extent by the inhomogeneous structure when motion is considered over the same time. The addition of nanoparticles increases the diffusion constants of the penetrants subs...

Effects of Conditioning, Aging, and Copolymer Content on the Diffusion of Propane and Pentane in Amorphous Glassy Perfluorodioxole by Pulse Field Gradient NMR

The diffusion of pentane and propane in TFE/PDD copolymer was studied using pulse field gradient NMR as a function of time after sample preparation. Pentane and propane display tortuous diffusion behavior in TFE/PDD copolymer (65% PDD) which means the apparent diffusion constant of these molecules slows as a function of the time, milliseconds to seconds, over which diffusion is observed in the pulse field gradient NMR experiment. High-permeability polymers are known to have changes in permeability as a result of aging and conditioning. These changes occur over a period of hours, days, and weeks so the determination of apparent diffusion constants was repeated on the same sample over this time scale. Pentane or propane was added to a freshly cast film of the copolymer and then sealed in an NMR tube. The first measurement of apparent diffusion constants was made within 24 h and then repeated a few weeks later and then a year later. Diffusion became more rapid after a few weeks which was ascribed to conditioning by the penetrant. More rapid diffusion at short times or small length scales indicates the introduction of high free volume regions, and the more rapid diffusion at longer lengths scales indicates improved connectivity between these regions. After a year, diffusion at short time scales corresponding to short length scales slowed. This was interpreted as resulting from the densification of smaller high free volume regions. Over longer length scales diffusion remained relatively constant which was interpreted as little change in the connectivity of high free volume regions. Diffusion as seen in the pulse field gradient experiment was compared for two copolymer compositions: 65% PDD and 87% PDD. Diffusion in 87% PDD copolymer is faster and no evidence of tortuosity is observed, both of which are consistent with a larger proportion of high free volume regions.

Molecular structure of [CpRu(PPh3)2(tht)]BF4, tht=tetrahydrothiophene

The title compound [CpRu(PPh3)2(tht)]BF4,1, tht=tetrahydrothiophene, is obtained by the reaction of CpRu(PPh3)2Cl, tht and AgBF4 in CH2Cl2 solution. Yellow crystals of [CpRu(PPh3)2(tht)]BF4 were grown by the slow diffusion of pentane into a CH2Cl2 solution of1 and have been studied by X-ray crystallography: space group is P21/n,a=9.507(2),b=18.336(3),c=22.372(6) A, β=94.28(2)°,V=3889(1) A3,Z=4. The tht ligand binds to the Ru atom through the sulfur atom at a distance of 2.395(2) A. The tht ring is in the puckered configuration.

Molecular and crystal structure of Cp2Mo(mto), mto=monothiooxalate

Compoundl, Cp2Mo(mto) is obtained by the reaction of Cp2MoCl2 with methanol solutions of potassium dithiooxalate in air. Red platelike crystals of Cp2Mo(mto) were grown by the slow diffusion of pentane into a CH2Cl2 solution ofl and have been studied by X-ray crystallography: space group, P21/n,a=7.578(1),b=10.551(2),c=14.090(3) A, β=94.38(2)°,V=1123.1(4) A3,Z=4. The mto ligand chelates to the Mo atom through one oxygen atom and the sulfur atom. The two Cp rings form dihedral angles of 24° with the least-squares plane of the mto ligand. The Mo−O and Mo−S bond distances are 2.193(5) and 2.449(2) A, respectively.

Ein einfacher Weg zur Herstellung von Alkylpalladium‐Verbindungen durch PdO‐Bindungs‐Spaltung in kationischen Bis(ether‐phosphan)palladium(II)1‐Komplexen mit Grignard‐Reagenzien

A Simple Method for the Preparation of Alkylpalladium Compounds by PdO Bond Cleavage in Cationic Bis(etherphosphane)palladium(II) Complexes with Grignard ReagentsHerrn Professor Heinrich Nöth zum 65. Geburtstag gewidmet. The bis(chelate) complexes [Pd(P∩O)2][ClO4]2 (3a – e) react with methylmagnesium chloride with a concomitant cleavage of two weak PdO bonds to give the methyl complexes trans1‐ClPd(P∼O)2(CH3) (4a – e) (P ∼ O; η1‐P1‐coordinated; P∩O: η21‐O, P1‐chelated; Scheme 1). Diffusion of pentane into the reaction mixture of 4a–e in the presence of the formed magnesium salts yields the cationic complexes trans‐[Ch3Pd(P∼O)1‐(P∩O)][ClO4] (6a, c). The reaction of 3a–e with benzylmagnesium chloride affords the cationic benzyl complexes cis‐[PhCh2Pd(P∼O)(P∩O)][ClO4] (8a–e) in which only one PdO bond has been cleaved. In the presence of carbon monoxide 4a–e adn 6a, c are transformed into the corresponding acyl complexes CH3C(O)Pd(P∼O)2Cl (5a–e and [CH3C(O)Pd‐(P∼O)(P∩O)][ClO4] (7a, c). Whereas at 183 K variable‐temperature 31P{1H}1‐NMR measurements of 6a, c, 7a, c indicate a non‐rigid behavior of the two differently bound ether‐phosphanes, the dynamic process is frozen out for 8a–e. By a lineshape analysis of the spectra the thermodynamic parameters ΔG≢, ΔH≢, and ΔS≢ are obtained. According to a crystal structure analysis 3d and 6c crystallize in the monoclinic space group P21/c with Z4.

Structures of two polymorphs of cis-TaBr4(PhPMe2)2

The title compound, tetrabromobis- (dimethyl(phenyl)phosphine)tantalum(IV), (TaBr4- (CsH~ ~P):), Mr -- 77689, is polymorphic. Monoclinic (1), P2~/c, a=8.493 (8), b=30.369(9), c= 8.898 (5) A, /3 = 99.22 (2) °, V = 2265.5 A 3, Z = 4, Dx = 2.28 g cm -3, A(Mo Ka) = 0-71073 A, ~ = 119-2 cm- l, F(000) = 1444, room temperature, R = 0.0514 for 2065 observed reflections. Orthorhombic (2), P2~2,2~, a-- 14.38(1), b-- 19.17(1), c-- 828 (2) A, V = 2282 1 A 3, Z = 4, Dx = 228 g cm-3, A(Mo Ka) = 0.71073 A, ~ = 119.2 cm-1, F(000) -- 1444, room temperature, R=0.0455 for 1448 observed reflections. The structures of the two forms (1) and (2) consist of octahedrally coordinated Ta atoms with comparable values of interatomic dis- tances, and differ mainly in the angles between the average planes of the phenyl groups: 10.1 and 42.6 °, respectively. The crystals were obtained by reduction of TaBr5 with either one or two equivalents of sodium amalgam in toluene and in the presence of the phosphorus ligand. Experimental. All compounds are air sensitive; mani- pulations were performed under argon with anhydrous and deoxygenated solvents. Sodium amal- gam (95mg, 9-4ml) was added to TaBr5 (Alfa Inorganics) (825 mg) in 30 ml toluene and PhPMe2 (Aldrich) (0.75 ml) at room temperature. Stirring was maintained for 2 h, and after filtration and concen- tration, diffusion of pentane at room temperature offered 450 mg (35%) of brown-red needles of cis- TaBr4(PhPMe2)2, (1). A comparable reduction applied to TaBr5 (0.723 g) in 20ml toluene and PhPMe2 (0.60 ml) with one equivalent of sodium amalgam gave, after 3~ h reaction time, an olive- green filtrate. Concentration induced formation of crystals of different shapes, corresponding mainly to cis-TaBra(PhPMe2)2, (2), while (1) appears as a minor compound. Analysis: Calc. for C16H22BraP2Ta: C: 24.74 H: 2.83 P: 7-97 Br: 41.16. Found: C: 24.40 H: 2.82 P: 7.15 Br: 38.58. The monocrystals were introduced under argon into sealed Lindemann capillaries and mounted on an Enraf-Nonius automatic diffractometer. The basic information about data collection and struc- tural refinement is shown in Table 1. Cell param- eters from setting angles of 25 reflections (2 ° _< 0 __