Molecular mobility in branched methacrylic copolymers with various concentrations of chromophore groups is studied by dielectric spectroscopy. At temperatures from -100 degrees C to 220 degrees C and in the frequency range 10(-1)-5.10(6) Hz three relaxation processes are detected. Molecular mechanisms of local beta and beta(1) processes and cooperative a process occurring in the glassy and in the rubbery state, respectively, are determined on the basis of the dielectric spectroscopy; molecular modeling results are consistent with experimental data. The mobility of azochromophore groups, which define nonlinear optical properties, begins at temperature 30 degrees C higher than that for alpha process. (C) 2016 Elsevier B.V. All rights reserved.