Melting Point Measurements Research Articles

Synthesis and characterization of novel polyimide from bis‐(3‐aminophenyl)‐4‐(trifluoromethyl)phenyl phosphine oxide

AbstractA novel diamine, bis‐(3‐aminophenyl)‐4‐(trifluoromethyl)phenyl phosphine oxide (mDA3FPPO), containing phosphine oxide and fluorine moieties was prepared via the Grignard reaction from an intermediate, 4‐(trifluoromethyl)phenyl diphenyl phosphine oxide, that was synthesized from diphenylphosphinic chloride and 4‐(trifluoromethyl)bromobenzene, followed by nitration and reduction. The monomer was characterized by Fourier transform infrared (FTIR), 1H NMR, 31P NMR, 19F NMR spectroscopies; elemental analysis; melting point measurements; and titration and was used to prepare polyimides with a number of dianhydrides such as pyromellitic dianhydride (PMDA), 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl)ethyliden]‐bis‐1,3‐isobenzofuranedione (6FDA), 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), and 4,4′‐oxydiphthalic dianhydride (ODPA). Polyimides were synthesized via a conventional two‐step route; preparation of polyamic acids, followed by solution imidization, and the molecular weight were controlled to 20,000 g/mol. Resulting polyimides were characterized by FTIR, NMR, DSC, and intrinsic viscosity measurements. Refractive‐index, dielectric constant, and adhesive properties were also determined. The properties of polyimides were compared with those of polyimides prepared from 1,1‐bis‐(4‐aminophenyl)‐1‐phenyl‐2,2,2‐trifluoroethane (3FDAm) and bis‐(3‐aminophenyl) phenyl phosphine oxide (mDAPPO). The polyimides prepared from mDA3FPPO provided high glass‐transition temperatures (248–311 °C), good thermal stability, excellent solubility, low birefringence (0.0030–0.0036), low dielectric constants (2.9–3.1), and excellent adhesive properties with Cu foils (107 g/mm). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3335–3347, 2001

EPR study on γ-irradiated single crystals of a non-linear optical material: 3-methoxy-4-hydroxy benzaldehyde

Abstract Single crystals of non-linear optical (NLO) material 3-methoxy-4-hydroxy benzaldehyde (MHBA) were grown following slow evaporation method. The grown crystals were characterised by the measurement of unit cell dimensions single crystal X-ray diffraction, density, melting point and X-ray powder diffraction pattern. Hardness study for the grown crystals was carried out. The grown crystals were γ-irradiated to produce free radicals and were analysed by electron paramagnetic resonance (EPR) technique.

Low-valent chemistry of cobalt amide. Synthesis and structural characterization of cobalt(II) amido, aryloxide, and thiolate compounds.

The binuclear cobalt(II) amide complex [(CoL2)2-(TMEDA)] (1) [L = N(Si(t)BuMe2)(2-C5H3N-6-Me); TMEDA = Me2NCH2CH2NMe2] has been synthesized by the reaction of anhydrous CoCl2 with 2 equiv of [Li(L)(TMEDA)]. X-ray crystallography revealed that complex 1 consists of two [CoL2] units linked by one TMEDA ligand molecule, which binds in an unusual N,N'-bridging mode. Protolysis of 1 with the bulky phenol Ar(Me)OH (Ar(Me) = 2,6-(t)Bu2-4-MeC6H2) and thiophenol ArSH (Ar = 2,4,6-(t)Bu3C6H2) gives the neutral monomeric cobalt(II) bis(aryloxide) [Co(OAr(Me))2(TMEDA)] (2) and dithiolate [Co(SAr)2(TMEDA)] (3), respectively. Complexes 1-3 have been characterized by mass spectrometry, microanalysis, magnetic moment, and melting-point measurements, in addition to X-ray crystallography.

The Melting Properties of Tuyere Slags with and without Flux Injection into the Blast Furnace.

A laboratory study concerning the melting properties of tuyere slags has been conducted. The meltingpoint measurements of various specimens, consisting of coke ash, coal ash and fluxes (BOF slag, burnt lime and burnt dolomite), corresponding to the tuyere slags formed in front of the tuyeres with or without flux injection, have been performed in a high-temperature microscope. Theoretical estimations of melting points have been made based on the chemical composition of the tuyere slag specimens. The results have shown that injection of fluxes has quite a positive effect on the melting properties of the tuyere slag. The melting point of the tuyere slag decreases and the temperature interval between softening and complete melting of the tuyere slag becomes narrower. Compared to the injection of burnt lime and burnt dolomite, the injection of BOF slag will result in still better tuyere slag properties in terms of lower flow point and narrower temperature interval between softening and melting. The differences in melting behaviour in the tuyere slag specimens indicate that injection of BOF slag will also give the tuyere slag a lower viscosity compared to injection of burnt lime or burnt dolomite at the same levels of slag basicity B2.

Rheology and Thermotropic Properties of Bis-Urea-Based Organogels in Various Primary Alcohols

The thermotropic and viscoelastic properties and the structure of thermoreversible organogels composed of enantiomerically pure trans-1,2-bis(3-dodecylureido)cyclohexane (1) and primary alcohols, i.e., propanol, butanol, hexanol, and octanol, have been investigated by melting-point measurements, differential scanning calorimetry (DSC), rheology, and electron microscopy. The electron microscopic studies revealed that gelation of these solvents occurred through the formation of an entangled network by 1. In all solvents, the gels behave as viscoelastic solids, with G‘ ≫ G‘ ‘ at frequencies >0.01 Hz (time scales <100 s) and values of G‘ up to 500 kPa (50 mM in propanol). The thixotropic character of the gels, however, indicates that the network structure is dynamic at larger time scales. Although the structure of the gels in these solvents is not significantly different, both the thermal stability and the strength of the gels depend on the solvent, and they increase in the order octanol < hexanol < butanol <...

Study of congruent-melting composition of langasite and its effects on crystal quality

Congruent-melting composition of langasite (La 3Ga 5SiO 14) was studied by a combination of melting-point measurement, crystal growth and compositional characterizations. The melting points of sintered samples with various compositions within the solid solution range determined by X-ray diffraction (XRD) around the stoichiometric composition were measured by differential thermal analysis (DTA). Upon the growth of single crystals from the compositions with the highest melting point, the compositions of various parts of the crystals and residual melts were investigated by X-ray fluorescence spectrum (XFS). The congruent-melting composition was determined to be the composition from which a minimum deviation of composition of both the crystal and the residual melt was obtained.

Synthesis of model diamide, diester and esteramide adducts and studies on their chlorine tolerance

The stability of various aromatic adducts containing diamide, diester and esteramide linkages towards chlorine gives an insight into the development of improved polymer structures which may be useful as reverse osmosis membranes. Model aromatic compounds were prepared by benzoylation of various diamines ( o-, m- and p-phenylene diamines), diols (hydroquinone, resorcinol and bisphenol-A) and m- and p-aminophenols. These adducts were subjected to chlorine treatments of increasing severity and their susceptibility to attack was monitored by melting point and NMR measurements. The diesters showed the highest chlorine resistance while the esteramides showed similar susceptibility as the diamides. The chlorine resistance of the diamides and esteramides was strongly influenced by the substitution ( o-, m-, p-) pattern, with the o-phenylene diamine-based adduct showing as high chlorine resistance as the diesters.

Structure in the condensed state and amphiphilic properties of novel copolymers having alkyl chains and phosphatidylcholine analogous groups

N-Stearylacrylamide (SAAm), N-oleylacrylamide (OAAm), and N-laurylacrylamide (LAAm) were synthesized. They were characterized by 1H-NMR, 13C-NMR, FT-IR, melting point measurements, and elemental analysis. The copolymerizations of SAAm, OAAm, and LAAm with 2-[(3-(acrylamido)propyl)dimethylammonio]ethyl 2′-isopropyl phosphate were carried out, and a series of amphiphilic poly(acrylamide)s (1a,b, 2, and 3a,b) were obtained. These copolymers showed polyelectrolyte behavior in their viscous properties in polar solvents. X-ray diffraction analysis indicated that the copolymers 1a,b formed similar stacked bilayers with hydrophilic groups and hydrophobic parts. The polymorphic phase transition of these copolymers was also observed by DSC. In addition, the monolayers as well as LB films of these amphiphilic copolymers were prepared on the surface of water and their π–A isotherms were investigated at different temperatures. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1293–1302, 1999

Production of d-iditol from d-sorbose by Rhodotolura rubra RY10 isolated from miso paste

The yeast strain RY10 that can convert d-sorbose to d-iditol was isolated from miso paste and identified as Rhodotolura rubra. The cells grown on d-fructose were found to have relatively high conversion potential. Addition of ethanol to the reaction mixture significantly accelerated the conversion rate of d-sorbose to d-iditol. During the conversion reaction, ethanol was added to the reaction mixture at 48 h intervals to maintain the concentration of ethanol at 1.0%. The final conversion ratios were 82.7%, 95.0%, 93.7%, and 78.0% using washed cells when the concentration d-sorbose were 1.0%, 2.0%, 3.0% and 5.0%, respectively. The product produced from d-sorbose was identified as d-iditol by high performance liquid chromatography analysis, infrared spectrum, optical rotation and melting point measurements.

Melting-Point Measurements at High Static Pressures from Laser Heating Methods: Application to Uranium

Two experimental approaches dealing with the determination of melting at high static pressures are described and analyzed. With the sample squeezed inside a diamond anvil cell, high temperatures up to the solid–liquid transition are obtained using Nd:YAG laser heating. Two methods have been investigated. In the first technique, the heating is accomplished with a pulsed laser and the brief radiation variations (t<10 ms) emitted from the sample are recorded with two high-speed infrared detectors. The melting location is defined by a plateau or changes of slope of the signals, and the temperatures are calculated by assuming a constant value of emissivity factor at the end of the transition over the studied pressure range. The second system employs a continuous laser and a two-dimensional CCD detector to measure temperatures using multispectral pyrometry. Melting is detected from criteria related either to textural change in the sample involving interference contrast under a laser illumination or to the specific variations of temperature and emissivity as a function of laser power. Thermal radiation is fitted to Planck's law with temperature and emissivity as the free parameters. Advantages and drawbacks are presented from results obtained on pure uranium.

Effect of the Substitution Pattern of Diaminoanthraquinone on Some Physical Properties

Two diaminoanthraquinones have been deposited under vacuum: 1,4-DAAQ and 2,6-DAAQ. They have been characterized by infrared (IR) absorption and nuclear magnetic resonance (NMR) to check that the products did not decompose during the deposition process. They have also been characterized by visible and near-ultraviolet absorption, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) and their purities have been checked by melting point measurements. The IR and NMR spectra of the films were identical to those of the reference powder spectra, which shows that the structure of the molecules is preserved. The presence of a hydrogen bond in 1,4-DAAQ is clearly put in evidence by the IR, NMR, XPS, and optical absorption measurements. Whereas 2,6-DAAQ thin films are crystallized, 1,4-DAAQ thin films are amorphous. The optical properties of 1,4-DAAQ thin films are modified by the presence of a silver thin film, whereas those of 2,6-DAAQ are not.

Studies on syntheses and properties of novel polyamides containing phosphatidylcholine analogous moieties by interfacial polycondensation

Polyamides (4a-b and 5a-b) were synthesized from interfacial polycondensation of novel diamine containing phosphatidylcholine analogous moiety, hexamethylene diamine with adipoyl chloride, or sebacoyl chloride in the interface of water and carbon tetrachloride at room temperature. The characterizations of synthesized diamine and polyamides were carried out with FT-NMR, or IR spectral method, elemental analysis, and melting point measurements, respectively. These polyamides obtained are insoluble in any normal solvents. From the results of X-ray diffraction analysis and POM observation, it was revealed that the polyamide 4b was prepared with high molecular weight, while polyamide 4a obtained seemed to have low molecular weight. For copolymers 5a and 5b, X-ray reflections from only adipoyl or sebacoyl chloride parts were observed as in crystalline state. In addition, thermal properties were also studied by DSC and transmitted light intensity measurements. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3065–3074, 1997

Electrochemical oxidation of l-cysteine catalyzed by 10-ethylphenothiazine

Abstract The electrochemical oxidation of l -cysteine catalyzed by 10-ethylphenothiazine at a glassy carbon electrode in 0.1 M NaClO4 ethanol + water (1:1, v/v) solution has been studied. Cystine was the oxidation product which has been verified by melting-point measurement and thin layer chromatography. The rate constant for the catalytic reaction was evaluated as (1.59 ± 0.05) × 103 M−1 s−1 by chronoamperometry. The 10-ethylphenothiazine cation radical produced by electrochemical oxidation of neutral 10-ethylphenothiazine is stable in either acidic or neutral solutions of KCl, NH4Cl and NaClO4. Experimental conditions, which maximize the current efficiency of this electrochemical oxidation, such as pH value and the concentration of the catalyst, were also investigated and discussed in this paper.

A novel class of phenol–pyridine co-crystals for second harmonic generation

To test the approach of combining both ionic and hydrogen-bonding interactions for the design of non-linear optical (NLO) materials, a number of phenol–pyridine co-crystals have been synthesized and their NLO properties investigated. The co-crystals are characterized by second harmonic generation measurements as well as the more conventional methods of melting point measurements, infrared and nuclear magnetic resonance spectroscopy. To investigate whether the phenol co-crystals are organic salts, the 2-methoxy-4-nitrophenol–4-(dimethylamino)pyridine (2:1) co-crystal 6 and the 2-methoxy-4-nitrophenol–4-pyrrolidinylpyridine–water (1:1:1) co-crystal 8 are further characterized by X-ray single-crystal diffraction. Crystal structure analyses reveal that both 6 and 8 are ionic co-crystals (or organic salts) composed of a phenoxide anion, a pyridinium cation and a neutral molecule. In the two co-crystals, the phenoxide, pyridinium and neutral molecules are held together by ionic attractions as well as hydrogen-bonding interactions. Both 6 and 8 crystallize in non-centrosymmetric structures [Pna2 1 (orthorhombic), a=6.880(4), b=38.40(1), c=8.454(3) A, Z=4, D c =1.369 g cm -3 and R=0.051 for 6 and Cc (monoclinic), a=7.302(3), b=23.518(2), c=9.940(1) A, β=107.12(2)°, Z=4, D c =1.365 g cm -3 and R=0.036 for 8]. In addition to X-ray structure determination, it is possible to predict whether phenol–pyridine co-crystals are organic salts based on the ΔpK a [pK a (pyridine)-pK a (phenol)] and stoichiometric ratio of the co-crystals. Preliminary results suggest that this type of co-crystals, particularly for the ionic co-crystals, may have a higher chance of forming non-centrosymmetric structures than the normal achiral organic compounds.

Synthesis and Characterizations of Copolymers Containing Both Phosphatidylcholine Analogues and Poly(Ethylene Glycol) in the Side Chains

Abstract New phospholipid analogous polymers were prepared by radical copolymerizations of 2-(methacryloyloxy)ethyl-2-(trimethylammonio)-ethyl phosphate and poly(ethylene glycol)monomethylether methacrylates (PEGMM) at room temperature, using (NH4)2S2O8 as the initiator and pure water as the solvent. The copolymers obtained were characterized based on their IR, 1H-, and 13C-NMR spectral data and melting point measurements. The molecular weights of these copolymers decrease as the length of the PEGMM side chain increases. These new polymers, which contain phosphatidylcholine analogous groups in their side chains, show viscosity properties similar to typical polyelectrolytes.

TRIMETHYLTIN CHLORIDE AND PSEUDOHALIDE COMPLEXES OF TRYPTOPHAN

Abstract Organotin chloride and pseudohalide complexes of tryptophan of the type Me3SnX. Tryp (Me = methyl, X = Cl, SCN, N3, CN and NCO; Tryp = tryptophan) were prepared by the addition reactions of tryptophan with trimethyltin chloride and the appropriate pseudohalide prepared in situ. The complexes were characterized by elemental analyses, spectroscopic (IR, NMR) studies, melting point and conductance measurements. Melting point and conductance measurements show them to be stable and non-electrolytes in DMSO. The spectroscopic data indicate that tryptophan coordinates with tin covalently through its carboxylate group as an asymmetric bidentate ligand. It is suggested that the complexes have an octahedral geometry.

Effect of Sonication on Crystal Properties

Ultrasonic irradiation resulting in acoustic cavitation was employed during the partial crystallization of diphenyl oxide and dimethyl phenyl carbinol from their respective crude melts. The crystals obtained showed improved purity and better olefactory values for both compounds. This was confirmed by melting point measurements and image analysis of the crystals thus obtained. The beneficial effect of ultrasonic irradiation on the resultant properties is explained on the basis of the theory of acoustic cavitation.

Chemico-Physical Characterization of Quinizarin Thin Films Deposited by Evaporation

Quinizarin (1,4-DHAQ) thin films deposited under vacuum were investigated by IR absorption, X-ray diffraction, nuclear magnetic resonance (NMR), optical absorption, electron spectroscopy for chemical analysis elemental analysis (XPS), and scanning electron microscopy and melting point measurements. It was found that amorphous quinizarin thin films are obtained. IR absorption spectra, ion mass spectroscopy, and NMR spectra show that there is no decomposition during the deposition of the film, the quinizarin powder being sublimated under vacuum from a tantalum boat sustained at T = 418 K. In addition, elemental analysis and melting point measurements demonstrate that the deposition process is also a purifying process of the quinizarin. SEM microphotographs show that continuous, smooth thin films may be obtained when they are deposited at a sufficiently slow rate. XPS analysis shows that, after decomposition of the peak spectra, the O 1s peak is composed of two different components corresponding to the oxygen bonded in the carbonyl and the hydroxyl groups. In the case of the C 1s peak, the main component corresponds to the carbon of the cycle, while it was not possible to discriminate between the carbonyl and hydroxyl bonds, perhaps because of the hydrogen bond between these two groups. The presence of an absorption band around 480 nm in the optical absorption confirms the hydrogen bond between the hydroxyl and carboxyl in the 1,4-DHAQ. Optical absorption of an Ag/DHAQ structure shows that a complex may be obtained by annealing.

Temperatures in the Earth's core from melting-point measurements of iron at high static pressures

THE temperature distribution in the Earth's core places important constraints on the Earth's internal heat budget and on models of the geodynamo. The solid inner core crystallizes from a liquid outer core, consisting mainly of iron alloyed with a lighter element, at a depth of about 5,100 km (corresponding to a pressure of about 3.3 Mbar). Thus, the most reliable means of determining the temperature gradient in the core is to estimate the melting temperature of iron and iron-rich compounds at the pressure of the inner core boundary. Current estimates range from about 4,000 to 8,000 K; but these estimates, obtained from shock compression1–3, theory (discussed in ref. 4) and extrapolation of static pressure data2,3,5, are poorly constrained. Here I present melting-point measurements on iron and iron–oxygen compounds at static pressures of up to Mbar. Extrapolation of these results to 3.3 Mbar yields a temperature at the inner-core boundary of 4,850±200 K. A weak change in optical absorption observed above 2,000 K may correspond to the solid–solid phase transition found in shock experiments at 2 Mbar (ref. 1).

Phase separation in a blend of poly(hydroxybutyrate) with poly(hydroxybutyrate- co-hydroxyvalerate)

Blends containing poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate- co-3-hydroxyvalerate) with 18.4% hydroxyvalerate units in various proportions have been studied using differential scanning calorimetry (d.s.c.) and optical and electron microscopy. D.s.c. measurements of melting points and peak areas from crystallized samples show that two-phase crystallization occurs for blend compositions containing 60–70% or more of copolymer, depending on crystallization temperature. The precise composition of the crystal phases obtained is thought to be governed primarily by kinetic factors. Phase separation in the melt was also investigated using d.s.c. by comparing the crystallization behaviour of nucleated and non-nucleated melts subjected to various thermal treatments. A region of liquid-liquid phase separation was identified, indicating partial miscibility between the two blend components. Morphological evidence confirmed the existence of different crystalline phases for the blends of highest copolymer content.