Molecular Structural Basis for Stereocomplex Formation of Polylactide Enantiomers in Dilute Solution

Poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) alternatively pack with each other and form stereo-complex crystals (SCs). The crystal habits of SCs formed in the dilute solution highly depend on the molecular weight (< M-w >). In this study, we investigated chain-folding (CF) structure for C-13 labeled PLLA (l-PLLA) chains in SCs with PDLAs that have either high or low < M-w > s by employing an advanced Double Quantum (DO) NMR It was found that the ensemble average of the successive adjacent re-entry number < n > for the l-PLLA chains drastically change depending on < M-w > s of the counter PDLA chains in the SCs. It was concluded that the CF structures of l-PLLA depending on < M-w > s of PDLA determine the crystal habits of SCs.