Thermal Decomposition Mechanism of a Series of Poly(Methylalkyldiallylammonium Chloride): A Combined Quantum Chemical and Experimental Study

A series of poly(methylalkyldiallylammonium chloride) homopolymers were innovatively investigated, and their thermal decomposition behavior was summarized. Quantum chemical calculations determined the bond breakage order under thermal conditions, and possible decomposition pathways were proposed for each polymer. Experimental validation was carried out using TG‐DSC‐MS and FTIR techniques. According to the TG‐DSC curves, all the homopolymers exhibited two distinct stages of thermal decomposition. The activation energies ( E a ) associated with each bond cleavage were calculated using the B3LYP/6‐31G* method. Simulation results revealed that the C─N bond within the five‐membered ring is the most prone to rupture, with the computed E a values being 260.58, 262.08, and 261.78 kJ·mol −1 for PMPDAAC, PMADAAC, and PMHDAAC, respectively. These findings confirmed that the hypothesis proposing the initial breakage of the C─N bond was supported by both TG‐DSC‐MS and FTIR spectroscopic analyses. For PMPDAAC, the dominant gas products evolved during its two thermal decomposition stages were CH 3 NH 2 , C 3 H 4 , CH 3 Cl, and C 3 H 8 . In the case of PMADAAC, the main gaseous species generated across its two decomposition steps were CH 3 NH 2 , C 3 H 4 , CH 3 Cl, as well as C 3 H 4 , C 3 H 8 . For PMHDAAC, the major gas products identified in its two decomposition stages included CH 3 NH 2 , C 3 H 4 , C 3 H 8 , CH 3 Cl, along with C 3 H 4 , C 3 H 8 .