Formation of Helical Phases in Achiral Block Copolymers by Simple Addition of Small Chiral Additives

Helical superstructures were induced in poly(ethylene oxide)-b-poly(tert-butyl acrylate) (PEO-b-PtBA) achiral diblock copolymers (BCPs) through the simple addition of pure enantiomers of tartaric acid. Hydrogen bond interactions between tartaric acid and poly(ethylene oxide) (PEO) block not only enhance the phase segregation strength of the PEO-based block copolymer but also transfer the chiral information from the additive into the achiral backbone to induce the conformational chirality. The helical phase was formed after thermal annealing with a pitch of similar to 25 nm and confirmed by transmission electron microscopy (TEM) and TEM tomography. The handedness of helices can be easily selected by choice of the corresponding enantioisomer of tartaric acid.