End group effect on poly(L-lactic acid) crystal*

Following translational symmetry in crystal growth is one of the most fundamental laws in crystallization. Numerous polymer crystals with broken translational symmetry however have been observed, including helicoidal, tubular, and spherical crystals. Herein we report a new group of single crystals that has broken translational symmetry. Scrolled α-form poly(L-lactic acid) (PLLA) crystals are grown via solution crystallization. PLLA is end-functionalized with different types of end groups study the end-group effect on the crystallization process. The single crystal gradually scrolled into a hollow cylindrical structure along a specific axis of crystals. Selected area electron diffraction shows the scrolling axis of single crystals is along the fastest crystal growth direction. The bending of original 2D lamellae of single crystals is attributed to the unbalance surface stress of the lamellae. The end groups’ effect on crystal morphology is discussed in the solution crystallization regime.