A DFT mechanistic study on the N‐acyloxyamine‐initiated controlled degradation of polypropylene

Abstract

AbstractN‐acyloxyamine is an excellent radical initiator for the controlled degradation of polypropylene (PP). Irgatec CR 76 (CR‐76) is one of the most important N‐acyloxyamines for the controlled degradation processes. The experiments show that 2 wt% CR‐76 caused a degradation and lowering of Mw to over 50% and of Mn in 10%–15%. The density functional theory (DFT) calculated results indicate that the NO bond cleavage of enol‐CR‐76 is the easiest to generate nitrogen (N˙) and ˙CH2COO radicals. In the controlled degradation process of PP, compared with the generated nitrogen (N˙), nitroxyl (NO˙), and nitrogen peroxide (NOO˙) radicals, the produced small molecule radicals such as CH3COO˙, (CH3)2CH˙, and (CH3)2CHCH2˙ radicals show better activity in the hydrogen abstraction process of PP. In addition, the NO˙, NOO˙, and ROO˙ (R = (CH3)2CH) radicals were proposed to be of importance in the radical coupling and β‐scission of PP˙ radical after the hydrogen abstraction in the controlled degradation of PP. This provide new insights into the controlled degradation of PP. Furthermore, thereby some theoretical guidance could be provided into the design of new N‐acyloxyamine radical initiator for the controlled degradation of polymers.