Scrolled Poly(L-lactic acid) Single Crystals via Chain End-Induced Symmetry-Breaking

Single crystals that do not obey translational symmetry have been reported in various material systems. In polymers, twisted crystals are typically formed in banded spherulites, while a class of non-flat polymer single crystals (PSCs) has been observed. Herein, we report the formation of scrolled single crystals of biodegradable polymer poly(L-lactic acid) (PLLA). While classical 2-dimensional single crystals formed in solution-crystallized PLLA are flat, we show that PLLA crystals bend into scrolls in low molar mass PLLA. The formation of these unique scrolled PLLA single crystals depends on polymer chain ends and the polymer molecular weight. This work, therefore, demonstrates a new mechanism to break translational symmetry in PSC growth.