Pelras Théophile, Knolle Wolfgang, Naumov Sergej, Heymann Katja, Daikos Olesya, Scherzer Tom
Leibniz-Institut für Oberflächenmodifizierung (IOM), Permoserstraße 15, D-04318 Leipzig, Germany.
Photochem Photobiol Sci. 2017 May 17;16(5):649-662. doi: 10.1039/c6pp00444j.
The potential of tetrachlorinated and tetrabrominated bisphenol A diacrylates and dimethacrylates for self-initiation of a radical photopolymerization was investigated. The kinetics of the photopolymerization of an acrylic model varnish containing halogenated monomers was studied by real-time FTIR spectroscopy, whereas the formation of reactive species and secondary products was elucidated by laser flash photolysis and product analysis by GC-MS after steady-state photolysis. The interpretation of the experimental data and the analysis of possible reaction pathways were assisted by quantum chemical calculations. It was shown that all halogenated monomers lead to a significant acceleration of the photopolymerization kinetics at a minimum concentration of 5 wt%. Steady-state and laser flash photolysis measurements as well as quantum chemical calculations showed that brominated and chlorinated samples do not follow the same pathway to generate radical species. Whereas chlorinated (meth)acrylates may cleave only at the C-O bonds of the carboxyl groups resulting in acrolein and oxyl radicals for initiation, brominated monomers may cleave either at the C-O bonds or at the C-Br bonds delivering aryl and bromine radicals. The quantum yields for the photolysis of the halogenated monomers were found to be in the order of 0.1 for acrylates and 0.2 for methacrylates (with an estimated error of 25%), independently of the attached Br and Cl halogens. Finally, the trihalogenated bisphenol A di(meth)acrylate radicals and the acrolein radicals were found to show the highest efficiencies for the reaction with another acrylic double bond leading to the formation of a polymer network.
研究了四氯化双酚A二丙烯酸酯和四溴化双酚A二丙烯酸酯及二甲基丙烯酸酯引发自由基光聚合反应的潜力。通过实时傅里叶变换红外光谱研究了含卤代单体的丙烯酸模型清漆的光聚合动力学，同时通过激光闪光光解阐明了活性物种的形成，并在稳态光解后通过气相色谱 - 质谱联用仪进行产物分析。借助量子化学计算对实验数据进行解释并分析可能的反应途径。结果表明，所有卤代单体在最低浓度为5 wt%时均能显著加速光聚合动力学。稳态和激光闪光光解测量以及量子化学计算表明，溴化和氯化样品产生自由基物种的途径不同。氯化（甲基）丙烯酸酯可能仅在羧基的C - O键处裂解，生成丙烯醛和氧自由基用于引发，而溴化单体可能在C - O键或C - Br键处裂解，产生芳基和溴自由基。发现卤代单体的光解量子产率，丙烯酸酯约为0.1，甲基丙烯酸酯约为0.2（估计误差为25%），与所连接的Br和Cl卤素无关。最后，发现三卤化双酚A二（甲基）丙烯酸酯自由基和丙烯醛自由基与另一个丙烯酸双键反应形成聚合物网络的效率最高。
