Kim Dongkwan, Scranton Alec B, Stansbury Jeffrey W
University of Colorado-Denver, School of Dental Medicine, Department of Craniofacial Biology, PO Box 6511/Mail Stop 8310, Aurora, Colorado 80045.
J Polym Sci A Polym Chem. 2009 Mar 1;47(5):1429-1439. doi: 10.1002/pola.23252.
We investigated the formation of ground state donor/acceptor complexes between xanthene dyes (rose Bengal (RB) and fluorescein (FL)) and a diphenyl iodonium salt (DPI) which is dissolved in 2-hydroxyethyl methacrylate (HEMA) monomer. To characterize the association constant of the complex, we have suggested a new analysis model based upon the Benesi-Hildebrand model. Because the assumption of the original Benesi-Hildebrand model is that the absorption bands are due only to the presence of the complex and that the absorption by the free component is negligible; the model cannot be applied to our systems, which is a dye-based initiator system. For each dye, the molar absorptivity of the ground state complex was evaluated as a function of wavelength and this analysis confirmed the validity of the modified Benesi-Hildebrand model. In addition, we observed the RB/DPI photoinitiator system failed to produce a perceptible polymerization rate but the FL/DPI photoinitiator system provided very high rates of polymerization. Based upon the association constant for these complexes, we concluded that the observed kinetic differences arise from the different association constant values of the ground state dye-acceptor complex, resulting in back electron transfer reaction.
我们研究了呫吨染料（孟加拉玫瑰红（RB）和荧光素（FL））与溶解在甲基丙烯酸2-羟乙酯（HEMA）单体中的二苯基碘鎓盐（DPI）之间基态供体/受体复合物的形成。为了表征复合物的缔合常数，我们基于贝内西-希尔德布兰德模型提出了一种新的分析模型。由于原始贝内西-希尔德布兰德模型的假设是吸收带仅归因于复合物的存在且游离组分的吸收可忽略不计；该模型不能应用于我们的体系，即基于染料的引发剂体系。对于每种染料，评估了基态复合物的摩尔吸光系数随波长的变化，该分析证实了修正的贝内西-希尔德布兰德模型的有效性。此外，我们观察到RB/DPI光引发剂体系未能产生可察觉的聚合速率，但FL/DPI光引发剂体系提供了非常高的聚合速率。基于这些复合物的缔合常数，我们得出结论，观察到的动力学差异源于基态染料-受体复合物不同的缔合常数，导致了反向电子转移反应。
