Synthesis and characterization of polyamides containing s-triazine rings in the main chain

Polyamides were synthesized from diacids containing a s-triazine ring and two aromatic diamines, namely 4,4′-diaminodiphenyl ether (ODA) and 4,4′-diaminodiphenylmethane (MDA), by direct polycondensation using the phosphorylation reaction. Polymers thus obtained were characterized by viscosity measurement, IR spectroscopy, thermogravimetry, X-ray diffraction, and solubility tests. These polyamides had inherent viscosities in the range of 0.51–0.77 dL/g, and were amorphous in nature. All the polymers were readily soluble in various organic solvents and did not lose weight below 270°C in air.     

Infrared spectral analysis during the thermal decomposition of pure and irradiated crystalline NH4ClO4

Variable temperature /303–553 K/ IR spectroscopic studies are made during thermal decomposition of pure and -treated ammonium perchlorate /AP/. Decomposition is enhanced by radiation or in the presence of an additive /Gd₂O₃/. Intensity of the stretching /1100 cm^–1/ and bending /625 cm^–1/ frequencies of ClO ₄ ^– decrease on heating the KBr matrix even below 360 K. Above this temperature, a broad band develops over 480–510 cm^–1 in the pure and -treated AP which is attributed to ClO ₃ ^– /₄/.     

Synthesis of Cadmium Selenide thin films at low-temperature by simple Chemical route and their Characterization

Crystalline CdSe thin film has been deposited using appropriate precursor solution containing cadmium sulfate octahydrate, tartaric acid, potassium hydroxide, ammonia and sodium selenosulfate. The effect of parameters such as bath composition, deposition temperature, pH of the solution, speed of the rotation and the specificity of complexing agent on growth process is studied. The ‘as-deposited’ CdSe thin film was found to be red in color, specularly reflective and well adherent to the glass substrate. The crystalline phase of the deposited sample was hexagonal wurtzite-type. The analysis of optical absorption data shows energy band gap energy (E_g) 2.01 eV. The morphological study and compositional analysis of film sample have been discussed. The electrical resistivity of CdSe thin film was found to the order of 10⁶ Ω cm.     

Effects of different additives on the thermal decomposition of ammonium perchlorate

IR spectral investigations on ammonium perchlorate (AP) in the presence of varying amounts of ammonium permanganate (APm) and 2% by weight of different rare earth oxide additives were made over the temperature range 25–290°. Heating and spectral scanning were done simultaneously and the peak intensity was presumed to be proportional to the amount of undecomposed AP. Presence of 10% APm lowered the temperature of AP decomposition from 200 to 110° and increased the rate by several folds. Mixed oxide produced as a result of deflagration of APm are considered catalyzing the process. In the presence of rare earth oxides additives, the NH ₄ ⁺ stretching peak intensity decreased considerably, the extent followed the trend Gd₂O₃ > MnO₂ > Nd₂O₃ > Pr₂O₃ > Dy₂O₃ > Y₂O₃ > La₂O₃ > virgin AP. An electron transfer mechanism is envisaged to explain the results.     

Synthesis and properties of polyurethanes containing s-triazine rings in the main chain

Eight new diisocyanate monomers containing s-triazine ring have been prepared from the parent diacids via the Curtius rearrangement of the corresponding diacyl azides. The parent diacids were synthesised by the reaction of p- and m-hydroxybenzoic acid with 6-methoxy-2,4-dichloro-s-triazine, 6-phenoxy-2,4-dichloro-s-triazine, 6-phenyl-2,4-dichloro-s-triazine, and 2-diphenylamino-4,6-dichloro-s-triazine respectively. Polyurethanes have been synthesised by solution polymerization of these diisocyanates with ethylene glycol in N,N-dimethylacetamide (DMAC). The resulting polymers were characterized by IR spectroscopy, viscosity measurement, solubility tests, and softening points.     

Radiation effects on thermal decomposition of ammonium perchlorate

Thermal decomposition of -irradiated (dose: 0–3.6 MGy) ammonium perchlorate was followed. The dynamic heating (range: 100–220 °C) and IR spectral measurements were carried out simultaneously. Temperature and dose brought a lowering in peak intensity of NH ₄ ⁺ and C10 ₄ ^– ions. Radiolytic products C10₃ and NH₃ are considered to initiate the decomposition process.     

Studies on gamma radiolysis of microcrystalline ammonium perchlorate

Gamma radiation induced decomposition of ammonium perchlorate (AP), pelletized in a KCl/KBr matrix has been followed IR spectrophotometrically. AP absorption peaks decreased in intensity as the -dose increased progressively. Irradiation of powdered AP produces ClO ₃ ^– ; its yield increases, attains a maximum and decreases beyond a dose of 0.5 MGy. The result is similar but much slower in the case of -irradiated pellets of pure AP.     

Electrochemical Fluorescence Switching from a Patternable Poly(1,3,4‐oxadiazole) Thin Film

A highly soluble poly(1,3,4‐oxadiazole) (POD) substituted with long alkyl chains was examined for electrochemical fluorescence switching. The high solubility of the polymers enabled a simple fabrication of an electrochemical cell, which showed reversible fluorescence switching between dark (n‐doping) and bright (neutral) states with a maximum on/off ratio of 2.5 and a cyclability longer than 1 000 cycles. Photochemical cleavage of the oxadiazole in POD allowed photo‐patterning of the POD film upon exposure to UV source. The patterned POD films displayed patterned image reversibly under a step potential of +1.8/−1.8 V.

     

TG/DTA studies on gamma-irradiated ammonium perchlorate and its mixtures with KCl/KBr

While normal ammonium perchlorate (AP) decomposes in two stages (at 315 and 375 °C), its 20% weight loss occurred even at 160 °C when it had absorbed 1.0 MGy dose. Increased crystal size caused further changes in the TG/DTA curves. Characteristics: the above weight loss approached 85% for 20 times larger particles. AP mixed with KCl/KBr in 11 ratio showed formation of potassium perchlorate on heating and the quantity increased progressively when the AP was pre-treated by irradiation.

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Zusammenfassung Während sich normales Ammoniumperchlorat (AP) in zwei Schritten zersetzt (bei 315 und 375 °C), tritt nach vorher absorbierter Dosis von 1.0 MGy ein 20%-iger Massenverlust schon bei 160 °C auf. Eine erhöhte Kristallgröße verursacht weitere Veränderungen an TG- und DTA-Kurven: bei 20 mal größeren Partikeln erreicht der obengenannte Massenverlust 85%. Nach Vermischen von AP mit KCl/KBr im Verhältnis 11 wird bei Erhitzen Kaliumperchlorat gebildet, wobei die Ausbeute nach einer Vorbehandlung des AP durch Bestrahlung progressiv anwächst.

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315 375° , 1,0 MGy 20% 160 °. /. 85% 20 . , - 11, , .

     

Studies on CL-20: The most powerful high energy material

CL-20 is an attractive HEM having density (>2 g cm^-3) and velocity of detonation (9400 m s^-1) superior to HMX (1.9 g cm^-3 and 9100 m s^-1). During this study, CL-20 was synthesized to establish viability of efficient synthesis method. The compound synthesized at HEMRL was characterized by FTIR, ¹H NMR and elemental analysis. Thermal studies (dynamic DSC and isothermal TG) were undertaken to determine kinetic parameters and understand the decomposition patterns. An attempt is made to explain the mechanism of decomposition of CL-20 on the basis of the data obtained by the authors and findings of other researchers. The activation energy values obtained during this work by adopting various approaches are close to the values reported for N-NO₂ bond cleavage suggesting that it is global rate determining process rather than the collapse of cage structure. Mass spectra also provides evidences in this regard. Monitoring of decomposition products at high temperature supports these findings and brings out that NO₂ initiates secondary decomposition processes because of entrapment in cage structure. This revised version was published online in August 2006 with corrections to the Cover Date.