Synthesis, Characterization, and Energetic Properties of Nitrate Ester Acrylate Polymer.

An energetic nitrate ester acrylate monomer (4) was synthesized in a total yield of 68% and polymerized to form the energetic nitrate ester acrylate polymer (NEAP). Compound 4 is a liquid at room temperature with a melting point of -8.6 °C and NEAP is a solid with a glass-transition temperature of -8.8 °C. Intermediates leading to 4 and NEAP were characterized by high-resolution mass spectrometry, elemental analysis, Fourier transform infrared spectroscopy, and proton and carbon nuclear magnetic resonance spectroscopies (1H and 13C{1H} NMR). Both 4 and NEAP have electrostatic discharge, friction, and impact sensitivities comparable to those of trinitrotoluene, making NEAP a potential candidate for advanced energetic formulations.

Synthesis and Energetic Properties of N-Substituted 3,4- and 3,5-Dinitropyrazoles.

3,4- and 3,5-Dinitropyrazoles (DNPs) were substituted with acryl and allyl groups on the N1 nitrogen atom, resulting in three novel energetic materials. These compounds are all liquids at room temperature with melting points ranging from -60.2 to -38.6 °C and were fully characterized by high-resolution mass spectrometry, elemental analysis, proton and carbon nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. These materials were also tested for electrostatic discharge, friction, and impact sensitivities and then compared to DNP starting materials and to the explosive nitroglycerin (NG). These results indicate that the synthesized compounds are less sensitive to impact compared to NG and have higher thermal stabilities to decomposition.

[3+2] click chemistry approach to tetrazine containing polymers.

We report a [3+2] cycloaddition using 3,6-bis-propargyloxy-1,2,4,5-tetrazine and azides to synthesize energetic polymers containing 1,2,4,5-tetrazine within the scaffold. This work also includes [3+2] cycloaddition to crosslink azide containing glycidyl azide polymer (GAP). These reactions provide pathways for incorporation of 1,2,4,5-tetrazine into novel energetic materials using click-chemistry and provide an alternative polymer curing approach.

Molecular Interactions and Layer Stacking Dictate Covalent Organic Framework Effective Pore Size.

Interactions among ions, molecules, and confining solid surfaces are universally challenging and intriguing topics. Lacking a molecular-level understanding of such interactions in complex organic solvents perpetuates the intractable challenge of simultaneously achieving high permeance and selectivity in selectively permeable barriers. Two-dimensional covalent organic frameworks (COFs) have demonstrated ultrahigh permeance, high selectivity, and stability in organic solvents. Using reactive force field molecular dynamics modeling and direct experimental comparisons of an imine-linked carboxylated COF (C-COF), we demonstrate that unprecedented organic solvent nanofiltration separation performance can be accomplished by the well-aligned, highly crystalline pores. Furthermore, we show that the effective, as opposed to designed, pore size and solvated solute radii can change dramatically with the solvent environment, providing insights into complex molecular interactions and enabling future application-specific material design and synthesis.

Synthesis, Postsynthetic Modifications, and Applications of the First Quinoxaline-Based Covalent Organic Framework.

We report a new synthetic protocol for preparing highly ordered two-dimensional nanoporous covalent organic frameworks (2D-COFs) based on a quinoxaline backbone. The quinoxaline framework represents a new type of COF that enables postsynthetic modification by placing two different chemical functionalities within the nanopores including layer-to-layer cross-linking. We also demonstrate that membranes fabricated using this new 2D-COF perform highly selective separations resulting in dramatic performance enhancement post cross-linking.

Global Alignment of Solution-Based Single-Wall Carbon Nanotube Films via Machine-Vision Controlled Filtration.

Over the past decade, substantial progress has been made in the chemical control (chiral enrichment, length sorting, handedness selectivity, and filling substance) of single-wall carbon nanotubes (SWCNTs). Recently, it was shown that large, horizontally aligned films can be created out of postprocessed SWCNT solutions. Here, we use machine-vision automation and parallelization to simultaneously produce globally aligned SWCNT films using pressure-driven filtration. Feedback control enables filtration to occur with a constant flow rate that not only improves the nematic ordering of the SWCNT films but also provides the ability to align a wide range of SWCNT types and on a variety of nanoporous membranes using the same filtration parameters. Using polarized optical spectroscopic techniques, we show that under standard implementation, meniscus combing produces a two-dimensional radial SWCNT alignment on one side of the film. After we flatten the meniscus through silanization, spatially resolved nematicity maps on both sides of the SWCNT film reveal global alignment across the entire structure. From experiments changing ionic strength and membrane charging, we provide evidence that the SWCNT alignment mechanism stems from an interplay of intertube interactions and ordered membrane charging. This work opens up the possibility of creating globally aligned SWCNT film structures for a new generation of nanotube electronics and optical control elements.

A Highly Ordered Nanoporous, Two-Dimensional Covalent Organic Framework with Modifiable Pores, and Its Application in Water Purification and Ion Sieving.

The preparation of membranes with high selectivity based on specific chemical properties such as size and charge would impact the efficiency of the world's energy supply, the production of clean water, and many other separation technologies. We report a flexible synthetic protocol for preparing highly ordered two-dimensional nanoporous polymeric materials (termed covalent organic frameworks or COFs) that allow for placing virtually any function group within the nanopores. We demonstrate that membranes, fabricated with this new family of materials with carboxylated pore walls, are very water permeable, as well as highly charged and size selective.