AbstractThe polymorphic behaviour of polymers\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \rlap{--} (OOC} - {\rm (CH}_{\rm 2} {\rm )}_{{\rm n - 2}} - {\rm COO} - {\rm C}_{\rm 6} {\rm H}_{\rm 4} - {\rm C(CH}_{\rm 3} {\rm ) = CH} - {\rm C}_{\rm 6} {\rm H}_{\rm 4} {\rm \rlap{--} )}_{\rm X} $\end{document}(n = 8, 10) has been investigated. They show thermotropic, mesophasic properties with a nematic structure. Both polymers exhibit a multiple solid state polymorphism which is a function of the temperature and of their thermal history.