Chemical Physics Letters, Vol.680, 78-82, 2017
DFT studies of the effectiveness of p-substituted diphenyl amine antioxidants in styrene-butadiene rubber through their Cu(II) coordination ability
Structures of a series of diphenyl amine (DPA) antioxidants and of their complexes with Cu2+ were optimized at B3LYP level of theory. DPAs may be divided into two groups according to their molar antioxidant effectiveness (AEM). The effectiveness of high-AEM DPA antioxidants at 130 degrees C rises with decreasing spin densities at Cu atoms and with the increasing electron density Laplacian at Cu-N bond critical points in the (2)[DPA...Cu](2+) complexes similarly as in the case of p-phenylene diamine antioxidants. No such trends are observed at 25 degrees C and for low- AEM DPA antioxidants. (C) 2017 Elsevier B.V. All rights reserved.