Formation mechanism of hydroxylamine-nitrate-based electrically controlled solid propellant: A DFT analysis

Infrared spectroscopic analysis was conducted to determine the formation mechanism of hydroxylamine nitrate (HAN)-based electrically controlled solid propellant (ECSP). Results indicated that chemical crosslinking occurs between HB and PVA by forming a borate ester bond, while physical crosslinking arises from hydrogen bonding among PVA, HAN, HB, and H 2 O. The analysis was carried out from chemical and physical crosslinking perspectives, employing various Density Functional Theory (DFT) analytical methods. These methods included reaction barrier calculations, Electrostatic Potential (ESP) analysis, hydrogen bond binding energy calculations, Atoms-in-molecules (AIM) analysis, Electron Density Difference (EDD) analysis, and charge transfer calculations. Results indicate that chemical crosslinking mainly occurs through a generalized acid–base reaction between boric acid (HB) and polyvinyl alcohol (PVA), with an activation barrier of 55.303 kJ/mol. Physical crosslinking is governed by hydrogen bonding between PVA and the small molecules HB, NO 3 − , NH 3 OH + , and H 2 O. Moderate hydrogen bonds are formed with HB (−7.909 kcal/mol) and H 2 O (−6.559 kcal/mol), while stronger hydrogen bonds are established with NO 3 − (−11.677 kcal/mol) and NH 3 OH + (−21.563 kcal/mol). EDD analysis reveals enhanced electron density at the PVA–molecule interfaces, and charge-transfer calculations confirm partial charge delocalization, thereby corroborating the presence of hydrogen-bond interactions.