The crystal structure of a block copolymer, constituted by the periodic alternation of three thienyl- and two phenyl fragments separated by azomethine residues, has been determined and refined on powder X-ray diffraction data. Polymers of this kind are particularly interesting because of some evidences of electronic confinement, i.e. possible realization of multiple-quantum-dot sequences have been detected. Although the quality of the measured profile was poor, a molecular model is proposed giving a satisfactory agreement with the observed data.