Thermal-stimulated depolarization current (TSDC) experiments were performed on a series of tyrosine-derived polyarylates with different number of methylene groups in the backbone. The low temperature TSDC spectra (80-240 K) were analyzed at two different degrees of hydration to assess the effects of small amounts of loosely and tightly bound water in the observed complex beta band. Higher temperature TSDC spectra (250-350 K) provided the alpha relaxation peaks associated with the glass transition temperature. The direct signal analysis (DSA) method allowed the deconvolution of the peaks into elementary processes and the determination of their mean relaxation parameters. The variations in the low and high temperature polarization with the number of backbone methylene groups were interpreted as a combination of flexibility and entanglement phenomena. The dielectric manifestation of the disentanglement effects was observed for the case of the longest polymer.