黄酮/叔胺引发三丙二醇二丙烯酸酯的光聚合反应

采用实时红外光谱(RTIR)研究了黄酮(FL)为紫外光光敏剂, 不同氢给体(如叔胺)为助引发剂时三丙二醇二丙烯酸酯(TPGDA)的光聚合反应. 结果表明, FL分子中的大π共轭体系使其UV吸收峰的摩尔消光系数(ε_max)远远高于商业化光敏剂二苯甲酮(BP). 当FL与不同助引发剂配合使用时, TPGDA光聚合动力学有较大差异, 其中叔胺体系助引发剂能够与激发态FL发生有效的电子/质子转移过程, 产生胺烷基自由基活性种引发TPGDA的光聚合反应, 所得固化膜的最终双键转化率(DC_f)为93%~97%, 接近完全固化; 而芝麻素(SM)及胡椒环(BDO)作为助引发剂时TPGDA的聚合速率则很低, 固化膜的DC_f仅为32%~38%. 当光敏剂质量分数为1.0%, 4-N,N'-二甲氨基苯甲酸乙酯(EDAB)质量分数为1.0%时, FL/EDAB引发TPGDA的聚合动力学与商业化BP/EDAB的相同, 所得固化膜的DC_f均为97%.

Flavone/Tertiary Amine as Free Radical Photoinitiator for UV Photopolymerization of Tripropylene Glycol Diacrylate(TPGDA)†

The polymerization kinetics of tripropylene glycol diacrylate(TPGDA) was monitored by real time near infrared(RTIR) with favone(FL) as photosensitizer and different hydrogen donor as coinitiator. The commercial photosensitizer benzophenone(BP) was used as control. The results showed that the molar extinction coefficient(ε_max) of FL was much higher than that of BP. When FL was used in combination with tertiary amine hydrogen donor ethyl 4-N,N'-dimethylaminobenzoate(EDAB), the rate of polymerization(R_p) and final double bond conversion(DC_f) could reach 0.58 s^-1 and 97%, respectively, which was very close to that of commercial BP/EDAB system. However, using sesamin(SM) and benzodioxole(BDO) as coinitiator for FL, the R_p and DC_f were both very low, which indicated that the excited FL and tertiary amine could generate aminoalkyl free radical species via electron/proton transfer process and initiate the efficient photopolymerization of TPGDA. More importantly, when the co-polymerizable tertiary amines such as EBERYL P115 and dimethy-laminoethyl methacrylate(DMEM) are used, the natural component characteristics of FL make it a promising photoinitiator in biomedical and food-packaging fields.