Self-Assembled Superhelical Structure of Poly(N-vinylcarbazole)-Based Donor-Acceptor Polymer at the Air-Water Interface

Preparation of helical polymers designed for mimicking biological helices and developing supramolecular helical assemblies with a controlled helix sense still remains a major challenge. A previously unknown superhelical structure constructed by achiral random copolymer poly(N-vinylcarbazole) (PVK) with pendant azobenzene chromophores and terminal nitro moieties (PVK-AZO-NO2) at the air/water interface was systematically investigated by CD spectroscopy, AFM, and TEM. The compression of the interfacial films may induce the helices to. coil up and form large superhelices with the opposite handedness in a manner analogous to forming the supercoiled tertiary structure of DNA. The structure model for the self-assembly of PVK-AZO-NO2 into suprahelical structures at the air/water interface was also proposed.