Molecular Structural Basis in Polymer Melt-Crystallization

There are long-standing debates in crystallization mechanism and chain folding structure of long polymer chains from the melt. In this talk we present local chain trajectory of Poly(L-lactic Acid) (PLLA) in extreme conditions, thermodynamically stable crystals formed at a very high temperature from the melt and the glass (cold-crystallization),  and a rapidly quenched glass by applying ¹³C-¹³C double quantum spectroscopy. The results indicate that i) polymer chains adopt adjacent folding structure even in a glassy state, and ii) adjacent re-entry number in the cold and melt-grown crystals is the same with that in the glass. The newly obtained molecular view in the glassy state proves that chain folding occurs in the pre-stage of crystallization and subsequent crystallization do not induce additional chain folding.