Fig. 1

PBDT structural motifs along with experimental and simulated XRD results. a X-ray diffraction pattern for 20 wt% PBDT aqueous solution. The main diffractions are labeled A, B, C, D, E, and F and the helix tilt angle is θ. b The simulated X-ray diffraction pattern based on the HELIX software package (see also Supplementary Figure 1). The layer lines 1, 2, and 3 in the simulated results clearly mimic the experimental results. c The chemical repeat unit of PBDT includes one set of –SO₃⁻ groups (two sulfonate groups from one biphenyl unit) and two –NHCO– groups, each of which are mutually connected by one benzene ring. d The second PDBT strand is shifted 8.4 Å (B = P/4) away from the first strand along the helix axis. Numerous intermolecular interactions between chains (notably hydrogen bonding, dipole–dipole, and/or ion–dipole interactions between –SO₃⁻ and –NHCO– groups—shown as green dashed lines) and the rotation of each subunit contribute to the double helical conformation. e PBDT double helices self-assemble into an aligned (nematic) morphology in aqueous solution. The purple dots refer to Na⁺ counterions. The red dots are water molecules. f Elucidation of interchain bonding and molecular packing for PBDT with the double helical conformation. The helical parameters used for the X-ray simulation are also listed (P = 33.6 Å, h = 5.6 Å, a = 4 Å, Azimuthal shift = 180°)