Achiral structure of B4 phase in a Bent-Core Liquid Crystal

Bent-core smectic layers have a tendency to exhibit spontaneous saddle-splay curvature, driven by the intra-layer structural mismatch. In the chiral B4 phase, the tendency for twist in the orientation of neighboring molecules coupled with the saddle-splay curvature lead to the formation of helical nanofilaments with either clockwise or anticlockwise twist. In addition to the helical nanofilament structure, we observe another microscopic structure in P12OPIMB, which is achiral, with no helical twist. This coffee-bean-like microstructure is dominated by saddle-splay curvature, like the dark conglomerate phase, but appears to have three dimensional order. The origin of these structures will be discussed.