A double helical structure formed from an amorphous, achiral ABC triblock terpolymer

We present the experimental visualization of the three-dimensional (3D) helical morphology of a polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock terpolymer (SBM) using transmission electron microtomography. Our results uncovered a left-handed (and to a similar degree, right-handed) double helical structure composed of polybutadiene (PB) helical microdomains around polystyrene (PS) cores. The addition of short polystyrene chains into the PS cores by solution blending was found to be essential to control the pitch of the helix. We further discovered that the self-assembly in thin films of the present helical structure forms a thickness-independent stable alignment of the helical fibers arrayed in a honeycomb board perpendicular to the film plane.