Abstract
A thermal and X-ray investigation is reported of a main-chain polyester consisting of two p-oxybenzoate diads alternatively spaced by a pentamethylene and an heptamethylene segment. Evidences are provided for the existence of an enantiotropic smectic C phase and a monotropic nematic phase. Cooling from the mesophase allows for the lock-in of the smectic C structure in the glassy state.