Search results for "Thermal"

Properties of new asymmetrically quaternized dicationic ammonium based room-temperature ionic liquids with ether functionality

2013

Eleven asymmetrically quaternized dicationic ammonium-based room-temperature ionic liquids (DRTILs) with bis(trifluoromethanesulfonyl)imide (TFSI) were synthesized and characterized, along with 11 analogous dibromide precursors. Two-step synthesis was used to diquaternize tetramethyl-1,3-propanediamine and 2-(dimethylamino)-ethyl ether amines with a variety of alkyl and ether functionalized side chain groups (R1 ≠ R2). Each salt contain 1 to 3 ether groups located either in a linkage or in a side chain moieties. Structural and thermoanalytical properties, water content, and viscosity have been characterized using, for example, NMR, mass spectrometry (MS), X-ray diffraction, and thermal anal…

Determination of the adiabatic compressibility of bovine serum albumen in concentrated solution by a new ultrasonic method

2000

Abstract New data are presented for the adiabatic compressibility of bovine serum albumen (BSA) over the temperature range 2–85°C and at pH 5, 6, 7 and 8. The relative impact of intrinsic and hydration contributions to the observed compressibility for BSA is estimated and shown to agree very well with general values for globular protein and with previous results for BSA. The compressibility manifests a maximum value in the regions where BSA is most stable, exhibiting a parabolic dependence on temperature with lowest values where it is least stable. These data are obtained with a novel technique that employs a commercial, low cost and automated pulse echo apparatus for the measurement of the…

Solid-state NMR characterization of the structure and thermal stability of hybrid organic-inorganic compounds based on a HLaNb2O7 Dion-Jacobson layer…

2016

Dion-Jacobson phases, like MLaNb2O7, are an interesting class of ion-exchangeable layered perovskites possessing electronic and photocatalytic properties. Their protonated and organo-modified homologues, in particular, have already been indicated as promising catalysts. However, the structural analysis of these highly tailorable materials is still incomplete, and both the intercalation process and thermal stability of the included organic moieties are far from being completely understood. In this study, we present a thorough solid-state NMR characterization of HLaNb2O7·xH2O intercalated with different amounts of octylamine, or with decylamine. Samples were analyzed as prepared, and after th…

Synthesis and crystal structure of Na1+xV4P4O17(OH) (x ≈ 1.44)

1990

Abstract Hydrothermal synthesis starting from Na0.46VOPO4 · 1.58H2O leads to a new mixed-valence sodium vanadium phosphate: Na2.44V4P4O17(OH) (orthorhombic, space group Pnma; Z = 4; a = 13.723(5) A, b = 6.314(2) A, c = 16.139(4) A; R = 0.032 for 2659 reflections). In this phase, the interconnection of three complex types of infinite chains, built from VO6 octahedra and PO4 tetrahedra, sometimes edgeshared, defines tunnels partly occupied by a portion of the sodium atoms.

A Co2O2 metallacycle exclusively supported by l-valine

2008

Abstract [Co2(OH)2( l -valine)4]·2.5H2O has been prepared under hydrothermal conditions and constitutes the first example of a [Co2O2] core supported exclusively by aminoacids. This synthetic dimetallic model for redox active metalloenzymes is one of the few binary aminoacid compounds of biologically relevant metal ions that has been structurally characterized, showing the possibilities of this synthetic approach for preparation of models in bioinorganic chemistry.

Influence of Thermal Annealing on the Thermodynamic and Mass-Transfer Kinetic Properties of d- and l-Phenylalanine Anilide on Imprinted Polymeric Sta…

1999

An investigation of the material, chromatographic, thermodynamic, and kinetic properties of thermally treated (i.e., annealed) polymeric stationary phases imprinted with l-phenylalanine anilide (l-PA) was carried out. The imprinting procedure of the solid phase used in this study was the same as for the untreated imprinted stationary phase studied previously. However, after polymerization, these new stationary phases were treated at elevated temperatures (50, 120, 140, and 160 °C) for 24 h. The treatment at 120 and 140 °C led to a larger decrease in the retention of l-PA than that of d-PA. The polymer treated at 160 °C could no longer resolve the d,l-PA racemate. The heat treatments were ac…

Effect of extrusion and photoxidation on polyethylene/clay nanocomposites

2009

Polyethylene (a 1:1 blend of m-LLDPE and z-LLDPE) double layer silicate clay nanocomposites were prepared by melt extrusion using a twin screw extruder. Maleic anhydride grafted polyethylene (PEgMA) was used as a compatibiliser to enhance the dispersion of two organically modified monmorilonite clays (OMMT): Closite 15A (CL15) and nanofill SE 3000 (NF), and natural montmorillonite (NaMMT). The clay dispersion and morphology obtained in the extruded nanocomposite samples were fully characterised both after processing and during photo-oxidation by a number of complementary analytical techniques. The effects of the compatibiliser, the organoclay modifier (quartenary alkyl ammonium surfactant) …

Rigid biobased polycarbonates with good processability based on a spirocyclic diol derived from citric acid

2020

Introducing biobased polymers from renewable sources for use as high-performance thermoplastics with high demands on mechanical rigidity, transparency, thermal stability, as well as good processability, is a significant challenge. In the present work we have designed and prepared a rigid biobased bis-spirocylic diol by di-cycloketalization of a bicyclic diketone (cis-bicyclo[3.3.0]octane-3,7-dione, obtained from citric acid) using trimethylolpropane. This spiro-diol monomer has two reactive primary hydroxyl groups and the synthesis from inexpensive biobased starting materials is straightforward and readily upscalable, involving no chromatographic purification. In order to explore the useful…

Synthesis of Precision Poly(1,3-adamantylene alkylene)s via Acyclic Diene Metathesis Polycondensation

2019

[Image: see text] Fully saturated, aliphatic polymers containing adamantane moieties evenly distributed along the polymer backbone are of great interest due to their exceptional thermal stability, yet more synthetic strategies toward these polymers would be desirable. Herein, we report for the first time the synthesis of poly(1,3-adamantylene alkylene)s based on α,ω-dienes containing bulky 1,3-adamantylene defects precisely located on every 11th, 17th, 19th, and 21st chain carbon via acyclic diene metathesis polycondensation. All saturated polymers revealed excellent thermal stabilities (452–456 °C) that were significantly higher compared to those of structurally similar polyolefins with al…

1990