The effect on the mesophase behaviour of the substitution of mesogenic bibenzoate groups by non-mesogenic terephthalate units is studied. Time-resolved synchrotron X-ray and DSC experiments indicate that copolymers with an amount of terephthalate units as high as 29 mol% exhibit liquid crystalline properties, and a smectic mesophase is obtained on cooling, which further experiences a transformation into a three-dimensional crystal. The two transitions are rather sharp and well defined, in contrast to other similar copolymers.