Computational mechanistic studies on persulfate assisted p‐phenylenediamine polymerization

Abstract

p‐Phenylenediamine (p‐PDA) is a monomer of many important polymers such as kevlar, twaron, poly‐p‐PDA. Most of the noticed polymers formation is initiated by a free‐radical, but their polymerization mechanism is not elucidated computationally. The proposed study helps to fully understand the frequently utilized initiator/oxidant, potassium persulfate (K2S2O8) role in the aromatic diamines polymerization, which support experimental protocols, and a polymer scope. The formation of the poly‐p‐PDA is studied with the density functional theory (DFT) B3LYP‐D3 functional using experimental polymerization parameters (0°C and aqueous media). K2S2O8 initiated free‐radical polymerization of p‐PDA is studied in detail, taking into account sulfate free‐radical (SO4−)·, SFR, persulfate anion (S2O8)2−, PA and K2S2O8 cluster, PP. The reaction mechanism is calculated as the conversion of p‐PDA to free‐radical, the p‐PDA free‐radical attack to the next p‐PDA (dimerization), ammonia extrusion from the dimer adduct, the dimer adduct conversion to the free‐radical (completion of p‐PDA polymerization cycle) for the polymer chain elongation. Calculations show that the dimerization step is the rate‐limiting step with a 29.2 kcal/mol energy barrier when SFR initiates polymerization. In contrast, the PA‐assisted dimerization energy barrier is only 12.7 kcal/mol. PP supported polymerization is calculated to have very shallow energy barriers completing the polymerization cycle, i.e., dimerization (TS2K, ∆G‡ = 11.6 kcal/mol) and ammonia extrusion (TS3K, ∆G‡ = 6.7 kcal/mol).

Computational exploration of the copper(I)‐catalyzed conversion of hydrazones to dihalogenated vinyldiazene derivatives

“…15 Despite the economical and efficient transformations of 2Cl-VD synthon into versatile heterocyclic organic compounds, as stated above, the 2Cl-VD synthesis reaction mechanism has so far not been investigated theoretically, even though calculations are frequently applied to scrutinize reaction mechanisms. [18][19][20][21][22][23][24][25] TMEDA and other related diamine species have been frequently exploited previously as ligands for stabilizing copper complexes. 26,27 Lumb et al studied copper (I) and some diamine (N,N 0 -di-tert-butylethylenediamine, p-(N,N-dimethylamino)pyridine, etc.)…”

Ionic Liquid-Mediated Urea Pyrolysis to Cyanuric Acid: Experimental Protocol and Mechanistic Insights

“…Theoretical studies were applied to understand reaction mechanisms and direct experimentalists to design an efficient catalyst, eventually developing a cost-effective procedure. , Despite the industrial importance of the reaction (Scheme ), only a few computational studies were performed on the catalyst-free urea pyrolysis . Parallel to experimental optimizations, we theoretically studied the urea pyrolysis mechanism.…”