PLA branching with anhydrides and tri-functional aziridine

Branched PLA was prepared by melt blending with tri-functional aziridine (T-Az) and pyromellitic dianhydride (PMDA). $^{1}$HNMR, gel permeation chromatography (GPC) and rheology were used to characterize the topological structures of branched PLA. Fast reaction between PLA carboxyl end group and T-Az resulted in 3-arm stars and increased the molecular weight. However, the 3-arm stars did not show strain hardening behavior under extensional flow. After modifying PLA hydroxyl end group with PMDA, PLA can react with T-Az on both chain ends and form long chain branched structure, which showed strain hardening in extension. It was found that that only 10{\%} of the PLA hydroxyl end groups reacted with PMDA.