In order to investigate such discrepancies further, we conducted CoGEF calculations for the 4 model polymers 2 -5 representing typical substructures as observed in cellulose, novolaks, polystyrene or polysulfones. In the case of our polystyrene model 3, we observed homolytic bond scission (Figure ) between one of the methyl groups and the backbone chain (B3LYP/6-31G(d), B3LYP-D3BJ) and a rearrangement reaction that recombines the network structure (PBE1PBE, M06-D3). In the case of BP86-D3, we observed first homolytic bond breakage and a radical rebound reaction that forms also the rearrangement product in a step-wise fashion. This directly reflects experimental evidence that homolytic bond scission is predominant, however, the radicals generated are short lived and can recombine. Of course, in a more realistic larger polymer model the radical reactions after bond cleavage would not be limited to this interaction but could easily show a large diversity.