N12A-T023 TITLE: Coupled Molecular Design and Synthesis of High Density Energetic Materials

TECHNOLOGY AREAS: Materials/Processes, Weapons

OBJECTIVE: This effort will exploit the use of theoretical molecular design, organic synthesis manipulation, and quantum chemical modeling to provide energetic materials which meet existing munitions performance while achieving IM compliance. The investigator will establish and verify the molecular design, the form and nature of the crystalline packing and the interactions with matrix materials in a composite system. Scientifically, this program will establish the foundation upon which the molecular design, the nature of crystal packing and the interactions with matrix materials in composite systems are combined to design energetic ingredients resistant to thermal or shock loading conditions. The program will provide a potential replacement of one or more of today�s energetic ingredients solving the requirement for an insensitive high performance energetic material for combat safe military applications.

DESCRIPTION: This program will team molecular dynamics and organic synthesis chemists, materials scientists and theoreticians. While the fundamental challenge of this topic is directed toward the synthesis of new insensitive energetic ingredients, it can only be achieved through a fundamental understanding of the underlying molecular and crystalline structural properties. The program will provide modeling of new ingredients with the appropriate structural criteria solving long standing issues of sensitivity and performance. This program addresses the fundamental chemistry and physics underpinning the energetic ingredient conflict: Significant enhancements in delivered energy in compact volumes while remaining resistant to catastrophic failure in extremely stressful environments. Solving these conflicting requirements will save lives making this initiative critical to Navy and Marine Corps operations.

PHASE I: Models will be developed based on the six (6) empirical observations below which will provide the foundation upon which proposed research efforts can be measured. Models developed provide theoretical results for materials which can then be synthesized in laboratories before being handed off to private industry for full scale development.
1. Increase Hydrogen Bonding; Impart high levels of hydrogen bonding to the molecules to increase the heat capacity of the compounds. This should allow the materials to dissipate the heat in a manner other than breaking bonds and consequently detonating.
2. Delocalize Electron Density in Nitro Groups; Design compounds in which the electron density is spread from the nitro groups to surrounding groups. This increases bond order between the nitro group and the atom to which it is bound; the resulting charge distribution should render the molecule more stable.
3. Utilize Coulombic Attractions to Stabilize the Ground-State Structure; Stabilize the ground-state geometry by designing structures whose sigma or pi framework have alternating positive and negative charges.
4. Reduce the Number of Nitro Groups; Impart stability to these molecules, by including energetic oxygen functionality in groups other than nitro groups, such as N-Oxides.
5. Avoid High Acidity; High acidity reduces the formulation compatibility of an explosive; measures to avoid high acidity such as using imidazole rings and aminating to block hydrogen should be explored.
6. Maximize Crystal Packing Planarity; Design compounds with linear planar two dimensional atomic arrangements to minimize slip plane resistance to shock and shear ignition mechanisms.

PHASE II: The energetic materials modeled and synthesized during phase one will be scale-up to the one-pound laboratory batch process. Process optimization and cost reduction steps will be sought and integrated into a final date package or Standard Operating Process (SOP) that can be provided to venders for large scale production. Testing will be conducted on the material to determine the energy content and evaluate the physical and mechanical properties.

PHASE III: A final down selection to the most optimum and IM compliant ingredient will be scaled to 5 � 10 pound batch or continuous process. The material will undergo initial formulation and processing in pint to 1 gallon mixes to determine IM and performance properties. Collaboration with a government lab is encouraged. The material will be tested for the following properties:
1. Down select to best material for 5-10 pound process validation.
2. Formulate pint to 1 gallon mixes of energetic material to determine compatibility and processing requirements.
3. Measure heat content via bomb calorimeter.
4. Determine the physical and mechanical properties.
5. Conduct preliminary IM testing on energetic material.
6. Conduct preliminary energetic qualification.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: N/A

REFERENCES:
1. J. Akhavan, "The Chemistry of Explosive, 3rd Edition", RSC Publishing, 2011.

2. R. Meyer, J Kohler, A. Hombury, "Explosives, 5th Edition", Wiley-VCH, 2002.

3. Philip E. Eaton 1 *, Mao-Xi Zhang 1, Richard Gilardi 2, Nat Gelber 3, Sury Iyer 3, Rao Surapaneni 3, Prop., Explos., Pyrotech, 27, 1, 2002.

4. A.T. Nielsen, S. Barbara, Caged Polynitramine Compound, U.S. Patent 5,693,794, 1997-12-02

5. Subbiah Venkatachalam, Gopalakrishnan Santhosh, Kovoor Ninan Ninan Prop., Explos., Pyrotech, 29, 178, 2004.

6. L. Zhang, S.V. Zybin, A.C.T. van Duin, and W.A. Goddard III, "Modeling High Rate Impact Sensitivity of Perfect RDX and HMX Crystals by ReaxFF Reactive Dynamics", J. Energetic Materials, 28(1), 92-127, (2010).

7. S.V. Zybin, W.A. Goddard III, P. Xu, A.C.T. van Duin, and A.P. Thompson, "Physical mechanism of anisotropic sensitivity in pentaerythritol tetranitrate from compressive-shear reaction dynamics simulations", Appl. Phys. Lett., 96, 081918, (2010).

8. L. Zhang, S.V. Zybin, A.C.T. van Duin, S. Dasgupta, W.A. Goddard III, and E.M. Kober, "Carbon Cluster Formation during Thermal Decomposition of Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine and 1,3,5-Triamino-2,4,6-trinitrobenzene High Explosives from ReaxFF Reactive Molecular Dynamics Simulations", J. Phys. Chem. B, 113 (40), 10619-10640, (2009).

KEYWORDS: Insensitive Munitions;Hydrogen Bonding; Nitro Groups;Crystal Packing Planarity; Molecular Design Modeling; Ammonium Perchlorate

Questions may also be submitted through DoD SBIR/STTR SITIS website.