Study on the long-range chain degradation behavior of polylactic acid promoted by nanometer zinc oxide

Abstract

Polylactic acid (PLA) is known for its degradative properties. Since PLA possesses a long chain macromolecular structure, its degradation behavior and characteristics have been the focus of research. In the presence of Lewis acid, the carbonyl oxygen in the ester group of PLA molecular chain can coordinate with it and be activated, so as to break the ester group and cause PLA degradation. However, there is still a lack of research strategies on the evolution of the remote structure of PLA chains, and there were few studies on the long-range degradation of PLA molecular chain in the effect of Lewis acid. In this work, a statistical method, combined with molecular weight testing, was proposed to investigate the long-range degradation behavior of PLA molecular chains. Results showed that in the presence of nano-ZnO, the long-range degradation of PLA molecular chain in solution was initially carried out in the form of terminal group biting-back and exchanging within 4 hours, and the molecular chain with new terminal-group was still long enough after degradation, gradually shortened over time. PLA began to degrade obviously after 8 h reaction. This chain scission method can provide a reaction platform for some reactions such as long-chain branching, which can be utilized to prepare PLA with special molecular chain topology and explore the mechanism of PLA chain structure transformation.