Lawrence H. Merwin

Prospects of fused polycyclic nitroazines as thermally insensitive energetic materials

Abstract Novel chemical structures originally proposed as new thermally insensitive explosives were certain zero- to low-hydrogen-content, polynitro, polycyclic heteroaromatic compounds based on nitrogenous heterocycles. The proposed compounds were expected to be high-density materials with explosive yields in the RDX-to-HMX range, but with high melting points, good shock sensitivity, and significantly better thermal stabilities. Originally proposed candidates incorporated 3,6-dinitropyridazine as a structural feature. Based on the experimental results and on conclusions drawn from a careful consideration of principles of reactivity of this general class of compound—polynitroazines—important lessons were learned that are applicable to future choices of practical new energetic materials targets. A conclusion is drawn that the intractability of certain polynitroazine target compounds unavoidably arises from an extraordinary susceptibility to ubiquitous environmental contaminants such as water. The recognition of this structure–property relationship should have an important payoff toward future choices of target compounds.

NMR Investigation of the Thermolysis of Citric Acid

The thermolytic decomposition of citric acid in the presence of tin/lead solder has been investigated. The solid reaction products were first examined by solid-state 13C NMR. The samples were then dissolved in D2O, and 1H and 13C 1D and 2D (HMQC, TOCSY) spectra were obtained. Results indicate the presence of a series of compounds including 3-hydroxyglutaric, citraconic, itaconic and aconitic acids, and anhydrides. Solution- and solid-state NMR data are provided for citric acid and a number of metal and alkali metal citrate salts. Results of this work are related to the use of citric acid as a solder flux and to the elimination of chlorofluorocarbon cleaning processes in the electronics industry.

Aminonitroheterocyclic N-oxides -- A new class of insensitive energetic materials

The need continues for new powerful but insensitive explosive ingredients, which match the performance of RDX with the insensitivity of TATB. One approach has been to take the inherent stability of an aromatic heterocycle, combine this with the explosive insensitivity and thermal stability associated with alternating amino and nitro groups, and to supplement the performance of the molecule with an energy contribution from the N-oxide functionality. The synthesis, characterization and properties (both sensitivity and performance) of aminonitropyridine-1-oxides and aminonitropyrimidine-1,3-dioxides will be described.

Extended accordion polymers for optical modulation

Progress on second-order nonlinear optical polymers for high speed optical signal modulation is reported. New accordion polymers containing head-to-head backbone chromophores extended with a styryl-thienyl-vinyl linkage are described. The maximum absorption of the electronic transition (ground state yields excited state) for these polymers occurs at a wavelength of 494 nm. A corona-poled film of the ortho-xylyl bridged accordion polymer has a resonance-enhanced second- order nonlinear optical coefficient of 120 pm/V measured at 1.06 microns, and a glass transition temperature of about 187 degree(s)C. Along with linear polymer, polar cyclic dimers were formed during the polymerization. An extraction process was developed to remove the cyclic dimers from the polymer.