Energetic polymeric networks prepared via a solvent- and catalyst-free thermal cycloaddition of azide-bearing polymers with alkynes and hydroxyl-isocyanate addition reactions

Abstract

Polymeric networks were prepared through a 1,3-dipolar cycloaddition of azide-bearing polymers with a variety of compounds having two or three terminal alkynes without solvents and catalysts. Dipolarophiles with an α-carbonyl underwent a very rapid Huisgen reaction within a few minutes to afford networks that were side-linked with triazole moieties. The reactivities of dipolarophiles were estimated by using frontier molecular orbital energies. To avoid the formation of defects in elastically ineffective networks, all polymer chain-ends were linked with urethane moieties, and very small quantities of azides were reacted with the dipolarophiles to link the pendent groups with the triazoles. Because the crosslinking densities of the energetic networks were inversely proportional to the reactivity of the dipolarophiles to the azides, the less reactive alkynes provided better mechanical properties to the networks prepared using the Huisgen cycloaddition reaction compared to the more reactive alkynes. b ; Fax: +82 2 942 0108; Tel: +82 2 940 5583This journal is

Fabrication of polyurethane binders grafted with functional reactive plasticizers by a catalyst‐free click reaction

“…In terms of catalyst‐free click reactivity, propiolate species that neighbor alkyne groups have become kinetically comparable to metal catalysts . As shown in the rheological measurements, the kinetic difference could be associated with a methylene spacer between the EWG and alkyne group.…”

“…Anomalously, a conspicuous increase in viscosity from 111 to 1135 cP was observed for the BCHMP/PGT mixture. The rheological profile of propiolate species was predictably in accordance with the relevant study of the catalyst‐free click reaction . The elevated viscosity of this binary mixture proved the in situ covalent coupling of NRP with the PGT prepolymer in the absence of catalyst.…”

Reactive Energetic Plasticizers Utilizing Cu-Free Azide-alkyne 1,3-dipolar Cycloaddition for In-Situ Preparation of Poly(THF-<em>co</em>-GAP)-Based Polyurethane Energetic Binders

“…To chemically link the REPs with PGT-based PU binders during PU reaction, the catalystfree Huisgen 1,3-DPCA of an organic azide and alkyne was considered to be a proper reaction due to its ideal compatibility and specificity (byproduct-free) towards those hydroxyl-telechelic azido energetic binders cured by isocyanate agents [18][19][20]. Nevertheless, the reactivity of 1,3-DPCA reaction should be controlled to manipulate the fabrication process for a propellant or PBX formulation [20]. For example, Min and coworkers studied the Cu-free 1,3-DPCA reactivity of propiolate (HC≡C-COOR) and propargyl (HC≡C-CH2-OCOR) species by checking the gel time when mixed with GAP.…”

“…The REPs consisted of a gem-dinitro energetic group as the energy resource and a terminal alkyne functional group with Huisgen 1,3-dipolar cycloaddition (1, reactivity. The 1,3-DPCA reaction is a powerful and appealing synthetic tool for linking two compounds [18][19][20].…”

In‐situ Robust Polymeric Networks Prepared via Facile Uncatalyzed Huisgen Cycloaddition of Alkyne‐terminated Polyurethane with Terminal Azides

“…We reported previously a few works on the preparation of polymeric networks crosslinked via triazole moieties formed via CF-AAC of polymers bearing azides at backbones or chain-ends with various terminal alkynes in the absence of any solvents [15,17,30]. We also prepared solid composite propellants based on these triazole-crosslinked networks, followed by characterizing the mechanical, burning and adhesion properties [8].…”