Universal Behaviors for Chirality Effect on Self-Assembly of Block Copolymers

Here, we aim to investigate the universal behaviors of the chirality effect on the self-assembly of chiral block copolymers (BCPs*). A new type of BCP*, poly(cyclohexylglycolide) (PCG)-containing block copolymer (BCP) (i.e., poly(benzyl methacrylate)-b-poly(D-cyclohexylglycolide) (PBnMA-PDCG)), are designed and synthesized for self-assembly. Exclusive handedness of PCG polymer chain in the enantiomeric BCPs* can be found due to intramolecular chiral interaction of chiral entities as evidenced by coupling of carbonyl group (C=O) in vibrational circular dichroism (VCD) spectra. By taking advantage of intermolecular chiral interaction, the self-assembly of the PCG-containing BCP* gives the formation of helical phase (H*), suggesting the chirality effect on BCP self-assembly. Most interestingly, with the high twisting power, the metastability of forming H* can be significantly affected, resulting in the tendency to give H* with higher thermodynamic stability. The observed phase behaviors of the PCG-containing BCP*s are in line with theoretical prediction based on chiral orientational self-consistent field theory at which the chiral PCG behaves like mesogenic liquid crystal as evidenced by the mirror-imaged VCD signals of C-O-C vibration.