balance of −121, compared to −325 for HTPB. Other properties, such as safety and stability, material density, glass transition temperature (T g ), heat of formation, and the fact that each GAP repeat unit releases 1.5 nitrogen molecules render this polymer ideal as a binder in energetic compositions. [6] GAP and its close relative polyglycidyl nitrate (polyGLYN) [7] are currently commercially available, yet they are being used only in rather limited niche applications. Other energetic polymers, such as poly-3-nitratomethyl-3-methyl-oxetane (polyNIMMO) and poly-3-azidomethyl-3-methyl oxetane (polyAMMO), still have not reached commercial maturity. [8] A revival of the quest for energetic binders is expected to follow emerging 3D printing technology. This new additive manufacturing technique brings the promise of on-demand manufacturing of energetic devices from their ingredients with macroscopic, mesoscopic, and microscopic control over structure, morphology, composition, and thus device performance. Early examples, mostly focusing on production techniques of known materials are already reported in the literature. [9] For these new production techniques, there is a new need for suitable energetic binders that will not only fulfill the requirements from traditional energetic binders but will also be better suited for generating printable compositions by lowering the content of solid fillers.Here, we report on the preparation and characterization of novel mono-and bifunctional polymerizable energetic vinylimidazolium perchlorate monomers that are suitable for 3D printing of energetic polymers using light-induced radical polymerization techniques such as stereo lithography (SLA) and digital light processing (DLP). Results and DiscussionEnergetic bifunctional divinyl vinylimidazolium perchlorate salts 1a-3a were prepared according to Scheme 1a. Excess 1-vinylimidazole (VI) was reacted with 1,ω-dibromo-n-alkane, ω = 2, 3, and 5, in refluxing toluene, yielding divinyl dibromide derivatives 1-3, respectively. Ion exchange was achieved by mixing saturated aqueous solutions of LiClO 4 and the divinyl vinylimidazolium dibromide, yielding the corresponding divinyl diperchlorate salts 1a-3a as colorless solids. Monofunctional room-temperature ionic liquid, rt-IL, methyl vinyl imidazolium perchlorate, 4a, was prepared according to Scheme 1b. Dimethyl sulfate was slowly added to vinylimidazole at room temperature yielding methyl vinyl imidazolium methyl sulfate, 4, as a colorless solid. Ion exchange was achieved by mixing Energetic MaterialsNovel, simple-to-make energetic mono-and bisvinylimidazolium perchlorate monomers are prepared and characterized. These energetic monomers offer the possibility to 3D print energetic polymers that may allow decreasing the content of the energetic filler in energetic devices without compromising their energetic properties. The new printable materials are suited for photocuring-based additive manufacturing (AM), techniques, offering not only a large degree of control over the mechanical and en...

Polymers, made of energetic ionic liquid building blocks, are used as the fuel-binder part in propellant compositions. These compositions exhibit desired mechanical and energetic properties and may serve as a photoactive feed for 3D printable propellants. Quaternary vinyl imidazolium energetic salts, having perchlorate and nitrate counter ions, are used as monomers in fuel-binder polymers, while ammonium perchlorate is used as the heterogeneous oxidizer in the composition. The vinyl groups on the heterocyclic cations provide covalent interconnecting sites for the construction of the polymer backbone and binding sites for in-chain plasticizers, enabling control over mechanical and initiation sensitivity properties in the cured composite product. The advantageous oxygen balance and heat of formation values of these ionic liquid monomers, along with their ability to photo-polymerize, allow both the effective dispersion and reduced ratios of the heterogeneous oxidizer content without compromising the energetic properties of the resultant propellant. An intermolecular interaction between the heterocyclic imidazolium units was identified, which enables noncovalent reinforcement and may explain some of the observed properties of the compositions. Pressure-independent burn rates were achieved in compositions containing 2-ethoxyethyl acrylate plasticizer, thus avoiding the need for additional additives, stratification, and geometrical constraints on the burning bulk.