Chiral Recognition of Poly(Lactic Acid) Stereocomplex

Chiral recognition is a very important concept for structural formation of sterocomplex (SC) of right and left handed helices. A well known system is Poly(Lactic acid) SC. Recently, re-investigation of X-ray fiber diffraction proposed that there is no chiral recognition in PLA SC. In this work, solid-state NMR spectroscopy can be used to study both chain-packing and folding structure of PLA SC by ¹³C isotope labeling and Double quantum (DQ) spectroscopy. ¹³C CPMAS NMR spectra supported by isotope labeling technique provides stoichiometry of L:D in the SC phase in varied mixing ratio in the blends. DQ spectroscopy provides detailed packing structure as well as chain-folding structure. Uniqueness of interemolecular packing (chiral recognition) in SC will be highlighted.