Making glassy semicrystalline polylactic acid ductile

We borrow the insights that explain the molecular mechanism for the brittle-to-ductile transition in polymeric glasses [1] to study the mechanics of semicrystalline polymers. Polyesters such as polylactic acid (PLA) and poly(ethylene terephthalate) (PET) are known to be brittle in their fully crystalline form. PLA is brittle in its amorphous state because of the rapid physical aging that cannot be avoided. Such poor mechanical properties are the bottleneck preventing the wider application of PLA to replace the petroleum-based polymers including PET. We demonstrate a strategy to make PLA tough and heat resistant with zero shrinkage at 100 ^oC along with a molecular picture detailing the structure-property relationship.