Monomer- and polymer radicals of vinyl compounds: EPR and DFT studies of geometric and electronic structures in the adsorbed state
作者:Anders Lund、Marek Danilczuk
DOI:10.1016/j.saa.2012.08.054
日期:2012.12
paramagnetic resonance (EPR) spectroscopy was applied to study the paramagnetic species formed from styrene, 1,1-diphenylethylene, α-methylstyrene, β-methylstyrene and methylmethacrylate adsorbed on amorphous silica gel after γ-irradiation at 77K. Radicals formed by the hydrogen atom addition at the vinyl group of the monomers were observed in all samples. The hydrogen atoms were shown to originate to
应用电子顺磁共振(EPR)光谱研究了在77Kγ辐射下吸附在无定形硅胶上的苯乙烯,1,1-二苯基乙烯,α-甲基苯乙烯,β-甲基苯乙烯和甲基丙烯酸甲酯形成的顺磁物质。在所有样品中均观察到通过在单体的乙烯基上加氢原子而形成的自由基。通过使用具有氘代硅烷醇基团的硅胶,显示出氢原子在很大程度上源自吸附剂。对于包含甲基丙烯酸甲酯(MMA)的样品,在升高的温度下观察到分配给自由基的EPR光谱。采用DFT量子化学方法计算了吸附配合物的结构,各自的超细分裂常数和吸附能。对MMA分子与MMA自由基之间的反应以及传播自由基的结构进行了建模。计算出的所有自由基的超细分裂常数证实了实验光谱的归属。