丙烯酸酯/液晶复合体系的光聚合动力学

采用光差示扫描量热分析，研究了以2, 4, 6-三甲基苯甲酰基-二苯基氧化膦(TPO)为光引发剂、丙烯酸异辛酯(EHA)和三羟甲基丙烷三甲基丙烯酸酯(TMPTA)为单体、液晶为P0616A的丙烯酸酯/液晶复合体系在-40~80℃的光聚合动力学。研究表明：丙烯酸酯/液晶复合体系光聚合的自动加速现象非常显著，聚合反应速率和表观动力学常数在聚合过程中均存在最大值。随着反应温度的提高，体系的最终转化率、最大聚合反应速率(Rpmax)均明显提高，当反应温度高于20℃后，其增长均趋于平缓。随着体系中液晶含量的增加，体系的Rpmax呈下降趋势，体系的聚合反应转化率随时间的增长速率较慢，但是最终转化率差别不大，均接近80%。随着UV光强的增高，体系的Rpmax和最终转化率均明显提高, 体系的阈值光强约为4 mw/cm2。而随着体系平均官能度的增加，体系的Rpmax和最终转化率则呈下降的趋势。

Kinetics of Photopolymerization for the Acrylate/Liquid Crystal Mixture

Photo differential scanning calorimetry (P-DSC) was used to characterize the photopolymerization kinetics for the mixture of 2-ethylhexyl acrylate (EHA), trimethylolpropane trimethacrylate (TMPTA) and nematic liquid crystal (P0616A) with 2, 4, 6-trimethylbenzoyldiphenyl phosphine oxide (TPO) as photoiniator at different reaction temperature ranged from -40oC to 80oC. The results revealed that the auto-acceleration of photopolymerization is more obvious than the traditional free radical polymerization, and there are maxima in photopolymerization rate and apparent kinetic constant. The final conversion and the maximum photopolymerization rate increase with the reaction temperature. After the reaction temperature rises to 20oC, the above increases are slight. Rpmax decreases with increasing the content of liquid crystals, and the conversion increases slowly with time. But the final conversions have a slight difference for the acrylate/liquid crystal mixture with different LC content, and all of them close to 80%. With increasing the UV intensity, both of Rpmax and the final conversion increase obviously. The threshold value of UV intensity is 4 mW/cm2. However, Rpmax and the final conversion tend to decrease with increasing the average functionality of monomers.