Thermal-stimulated polarization and depolarization experiments without blocking electrodes are performed on tyrosine-derived polyarylates with different backbone lengths. The experiments on the different samples are carried out using the same thermal history throughout the entire characterization process. The high-temperature current rise caused by the conductivity of the samples is studied with a simple model that utilizes an approximation of the Williams-Landel-Ferry (WLF) relaxation time. The conductivity data is well reproduced except for temperatures well below the glass-transition temperature and for small currents. The glass-transition peak is modeled with a phenomenological expression valid near T-g, which is able to describe the glass relaxation with a minimum number of parameters. The conduction and the glass-transition relaxation are studied versus the structural changes for the different samples. It is found that the conductivity and the glass-transition temperature shift to lower temperatures as the methylene groups in the backbone increase. Furthermore, if the experimental data is presented as a function of the reduced temperature, the shape of the glass-transition relaxation for the different samples is independent of the polymer backbone length.