Enhanced Polyacrylamide Degradation via OH Radical-Initiated Single-Electron Transfer

Jun Zhang; Ming Hao; Depeng Zhang; Xuesong Zhang; Shijun Guo; Bo Wang; Junping Xiao; Yang Gao; Xiaoan Li

doi:10.1021/acsomega.3c05548

Enhanced Polyacrylamide Degradation via OH Radical-Initiated Single-Electron Transfer

ACS Omega. 2023 Nov 29;8(49):46589-46597. doi: 10.1021/acsomega.3c05548. eCollection 2023 Dec 12.

Authors

Jun Zhang^{1

2}, Ming Hao^{1

3}, Depeng Zhang⁴, Xuesong Zhang¹, Shijun Guo⁵, Bo Wang⁶, Junping Xiao⁷, Yang Gao^{8

9}, Xiaoan Li⁸

Affiliations

¹ The Key Laboratory of Enhanced Oil and Gas Recovery of Educational Ministry, Northeast Petroleum University, Daqing 163318, Heilongjiang, China.
² Liaohe Operation Service Company of Liaohe Oilfield Company, Panjin, Liaoning 124100, China.
³ Post-doctoral Working Station of Liaohe Oil Field, Panjin 124010, Liaoning, China.
⁴ Normal School, Shenyang University, Shenyang 110044, China.
⁵ College of Chemical Engineering, Daqing Normal University, Daqing 163712, Heilongjiang, China.
⁶ College of Science, Northeast Electric Power University, No. 169 Changchun Road, Jilin City 132012, P. R. China.
⁷ College of Physics and Electronic Information, Baicheng Normal University, Baicheng, Jilin 137000, China.
⁸ NHC Key Laboratory of Nuclear Technology Medical Transformation, Mianyang Central Hospital, School of Medicine, University of Electronic Science and Technology of China, Mianyang, Sichuan 621099, China.
⁹ Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, China.

Abstract

Hydroxyl (OH) radicals, as common radicals in aqueous environments, play an important role in inducing the degradation reactions of polymers. However, understanding the fundamental mechanisms of radical-induced degradation of polymers at the atomic level remains a formidable challenge. In this study, we employ density functional theory to investigate the geometric and electronic structural properties of polyacrylamide (PAM) in (-CH₂CHCONH₂-)_n (n = 2-6) complexes. Additionally, we explore the degradation mechanism of the n = 4 complex induced by the OH radical. The results indicate that there are three sites for the initial reaction (R1 and R2 are at the ends and R3 is in the middle). The OH radical removes a H atom from the PAM main chain and simultaneously triggers a single-electron-transfer process on the same chain. This process significantly reduces the dissociation energy barrier of the C-C bond in the PAM chain, from ∼90 to ∼20 kcal/mol. Specifically, when the induced reaction occurs at the end of the chain, a series of broken bonds will appear only along the main chain. While it happens in the middle, the broken bonds will exist simultaneously along both the main and side chains. Our results reveal the importance of OH radicals in polymer dissociation, particularly in PAM, and emphasize the degradation mechanism of SET.