Bicontinuous cubic and related 3D-ordered thermotropic phases of rod-like mesogens could be spontaneously chiral, such as the triple-network I23 or the double-network Smectic-Q, or non-chiral, such as the double-network gyroid Ia-3d with Schoen’s minimal surface. With non-chiral mesogens, chirality  originates from the twist between stacked molecular rafts building the network segments [1,2]. The absence of net chirality of the gyroid is due to cancellation of the twists of the two antichiral networks related by glide planes [3]. But what happens when chiral mesogens, and particularly those with a chiral core [4], also form the gyroid phase? Will the phase show optical rotation and circular dichroism? If so will they be strong or marginal? How will the homogeneous molecular chirality be reconciled with the opposite intrinsic chiralities of the two networks? And what will happen in a racemic mixture? These questions will be discussed based on recent experimental evidence.

[1] X.B. Zeng, G. Ungar J. Mater. Chem. C 2020, 8, 5389.

[2] H.J. Lu et al. Angew. Chem. Int. Ed. 2018, 57, 2835.

[3] C. Dressel et al. Angew. Chem. Int. Ed., 2014, 53, 13115.

[4] Y. Wang et al. J. Am. Chem. Soc. 2013, doi 10.1021/jacs.3c06164