Three films of poly(methyl methacrylate) (PMMA) (samples X, Y, and Z) were prepared by compression molding of purified polymers as polymers having different tacticities. They were exhaustively characterized by H-1 NMR spectroscopy so as to be able to evaluate the differences in content of the repeating stereosequences:... mmrm... (termini of isotactic sequences);.... rrrmr (breaking off syndiotactic sequences; pure heterotactic... mrmr... moistures; and atactic parts. By applying the so-called thermal step method, the behavior in space charge showed a priority charge injection from both electrodes and some polarization at the cathode. Some strong differences between the samples were evidenced and they accurately agree with the variations in the above repeating stereosequences for the samples. The results allow to define every stereosequence as specific trap of the distinct sorts of space charge, namely injection from the anode or the cathode and polarization. These attributions are common with those proposed for poly(vinyl chloride) (PVC) and poly(propylene) (PP) in earlier work. Conversely, whether the priority charge is of injection or polarization type, depends markedly on the type of polymer. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 633-639, 2009