Chemical mechanism prediction unravels multiple macromolecular outcomes from free-radical reactions

Abstract

Molecular-level reactions predominantly dictate all macro-level properties in the materials world. Understanding nano-level molecular reactions opens up the door to grasping how bottom-up building blocks lead to novel molecules and thus materials. Here, free radicals from the thermal decomposition of peroxide molecules were pursued to explore different plausible reactions with polyethylene oxide as a macromolecular polymer model. Many chemical compounds with different functional groups, such as acetals or hemiacetals, alkoxy ethers, geminal diols, aldehydes, ketenes and orthoesters, were detected. An important observation was chain scission due to tertiary radical formation that created oligomers with carboxylic end groups, a plausible sign of the deterioration of the final product's mechanical properties. Additionally, theoretical prediction enhanced our understanding of intermediate outcomes and revealed hydrogels with the potential to degrade in dilute acids due to vulnerable acetal, hemiacetal or orthoester functional groups, with profound effects on the macroscopic-level properties.