Crystallization of molecular bottlebrush crystallization: symmetry breaking via polymer chain overcrowding

One of the fundamental laws in crystallization is translational symmetry, which accounts for the profound shapes observed in natural mineral crystals and snowflakes. The translational symmetry, however, is broken in a class of polymer crystals defined as shape-symmetry incommensurate crystals (SSICs) which include helical, helicoidal, scrolled, tubular crystals, and the newly discovered crystalsomes. In this talk, we discuss the crystallization behavior of crystalline molecular bottlebrush (mBB) polymers. Spherical hollow crystalline shells are formed via solution crystallization. The unique structure is named as mBB crystalsome (mBBC), highlighting its similarity to the classical molecular vesicles and previously reported crystalsomes. The spherical morphology of mBBCs suggests the spontaneous translational symmetry breaking during crystal growth. Fluorescence resonance energy transfer (FRET) experiments demonstrated that the mBBC formation is driven by local chain overcrowding-induced asymmetrical lamella bending.