Tapes of the thermotropic, comb-like, polymer poly(p-phenylene-2,5-didodecyloxyterephthalate) were investigated by dynamic mechanical thermal analysis in tension. This polymer, in which the main chains form layers, exhibits three different low-temperature structures, characterized by the amount of side-chain ordering. The influence of the structure as well as the degree of orientation on the dynamic modulus of films was measured. The results show that the temperature-dependent modulus of oriented films is largely determined by the successive side-chain relaxations and disorderings. The main differences in modulus between the structures arise because of the beta relaxation around -35-degrees-C; they level off at higher temperatures on passing the respective side-chain disordering transitions.