LAUSR

We explore the processing-structure-property relationship using poly(lactic acid) (PLA) and poly(ethylene terephthalate) (PET). Specifically, we show both pre-extension and pre-shear of amorphous PLA and PET above their glass transition temperatures Tg , carried out in the affine deformation limit, can induce a specific type of cold crystallization during annealing, i.e., nano-confined crystallization (NCC) where crystal sizes are limited to a nanoscopic scale in all dimensions so as to render the processed PLA and PET optically transparent. The new polymer structure after pre-melt deformation can show considerably enhanced mechanical properties. For example, pre-melt stretching produces geometric condensation of the chain network. This structural alternation can profoundly change the mechanical characteristics, e.g., turning brittle PLA ductile. In contrast, after pre-shear of amorphous PLA above Tg , the NCC containing PLA remains brittle, showing the importance to have geometric condensation from processing. Both AFM imaging and SAXS measurements have been carried to verify that pre-melt deformation of PLA and PET indeed results in NCC from annealing that permits the strain-induced cold crystallization to take place on the length scale of the mesh size of the deformed chain network. This article is protected by copyright. All rights reserved.