Surface stress effects on the bending direction and twisting chirality of lamellar crystals of chiral polymer

Expression of chirality in the highly ordered assembly structures of various types of natural and synthetic materials is still a mystery. Although surface stresses have been known to widely exist in polymer lamellae, how they affect the twisting chirality is yet an unsolved issue. Here we report inversion of the lamellar twisting chirality of microbial poly(R-3-hydroxybutyrate) copolymers from left-handed to right-handed via copolymeriza-tion or blending, with the molecular chirality and the structures in the crystalline core unchanged. We interpret the observed inversion of twisting chirality and the complicated lamellar curvature with a continuum model based on surface elasticity theory. Quantitative simulations reveal that the distribution of the anisotropic surface stresses and the surface elasticity property of the lamellae significantly affect the morphological chirality of lamellar twisting. For different chiral polymers, the same bending direction may correlate to the opposite twisting chirality.