<p>A significant challenge in developing block copolymer photonic crystals is constructing low-symmetric ordered phases, which are essential for achieving a complete photonic band gap. Here, we propose a promising strategy to create low-symmetric ordered morphologies by incorporating shape-anisotropic rod-like side chains into block copolymers. Using dissipative particle dynamics simulations, we demonstrate that block copolymers with longer rod-like side chains can self-assemble into a hexagonally packed columnar phase characterized by a low-symmetric rectangular cross-section. Photonic band structure calculations reveal that this low-symmetric columnar phase can exhibit a complete photonic band gap, with the gap size dependent on the aspect ratio of the rectangular cross-sections of the columns. Our findings suggest an effective approach to constructing low-symmetric photonic crystals through the self-assembly of block copolymers with shape-anisotropic segments.</p>