Catalytic Regulation of Oligomers in Polycaprolactone

Abstract

l Tetraphenyltin catalyst improved the performance of PCL l The obtained PCL showed the Mn 80000, PDI 1.36, and 4.251 wt.% oligomers l The formation and contents of oligomers in PCL was revealed l Coordination inserting an anhydride bond was the main mechanism for inhibiting the formation of oligomers There is a lack of effective approaches that produce polycaprolactone (PCL) materials with a high molecular weight, narrow polymer dispersity index (PDI), and fewer formations of oligomers. The immigration of the remained oligomers predominantly causes poor PCL quality and induces odor release. This study investigates the effects of different catalysts and loadings on the PCL performance along with the formation of oligomers in detail. The results show that tetraphenyltin is an effective catalyst to promote propagation and produce high-performance PCL that possesses the highest Mn (80000), narrowest PDI (1.36), and the lowest content of oligomers (4.251 wt.%). Density functional theory (DFT) studies combining with characterizing key intermediates verified that an anhydride bond was formed close to the end hydroxyl group in the PCL chain because of the particular mechanism. This unusual chemical structure effectively suppresses the “back-biting” behavior, which is helpful for lowering the content of oligomers. This study provides a scalable synthetic approach to creating high-performance polymers.