A GAP Replacement: Improved Synthesis of 3-Azidooxetane and Its Homopolymer Based on Sulfonic Acid Esters of Oxetan-3-ol.

In the field of energetic binders, only hydroxy-terminated glycidyl azide polymer (GAP) has found widespread application and prevailed in the market. However, oxiranes such as glycidyl azide (GA) allow two ring-opening modes during polymerization and thus lead to polymers of different termination causing inhomogeneous curing results. An elegant solution is the polymerization of 3-azidooxetane as only terminating primary hydroxyl groups are formed. Beyond this, poly(3-azidooxetane) and GAP are equal in other aspects due to the similar repetition unit. Since literature methods for the preparation of 3-azidooxetane either employed toxic solvents, gave low yields or impurified product, or could not be reproduced, a new synthesis method was developed to afford pure material and satisfying yields. The syntheses of toluene- and methanesulfonic acid esters of oxetan-3-ol as precursors were also significantly improved in comparison to the literature and their molecular structures elucidated by single-crystal X-ray diffraction. The aforementioned compounds and poly(3-azidooxetane) were intensively studied by vibrational and multinuclear NMR spectroscopy (1H, 13C, 14N), differential scanning calorimetry, and elemental analysis. The key compound, 3-azidooxetane, was compared to glycidyl azide regarding performance using the EXPLO5 V6.04 thermochemical code and their sensitivity toward external stimuli like shock and friction assessed according to BAM standard procedures.