text: The strength and directionality of halogen bonds are a key tool in the discipline of crystal engineering, which attempts to shape crystal structures through close control of intermolecular interactions.  Halogen bonds can stabilize copolymers or induce mesomorphism in otherwise isotropic liquids.  Indeed, halogen bond-induced liquid crystalline phases are known in both alkoxystilbazoles and silsesquioxanes (pictured).   Alternatively, the steric sensitivity of halogen bonds can cause bulky molecules to crystallize into porous structures; in one notable case, halogen bonds between iodine and aromatic π-orbitals caused molecules to crystallize into a pattern that was nearly 40% void.