【摘要】 光潜碱(或光产碱剂)在光照下可以分解并释放出碱,后者可用于碱催化的反应,即可将碱催化的热反应转变为光热反应。本文以a-溴代苯乙酮分别与1,8-二氮杂双环[5.4.0]十一-7-烯(DBU)、4-甲基吡啶和3-甲基吡啶合成了三种季铵盐,再通过阴离子交换合成了以四苯基硼为配对阴离子的三种具有光化学活性的叔胺型光潜碱。采用核磁共振仪、实时红外吸收光谱(RT-IR)和紫外-可见吸收光谱(UV-Vis)等表征了合成产物的结构、跟踪了光潜碱的光化学以及光分解过程。UV-Vis表明紫外光照后三种光潜碱的吸收光谱都发生了明显变化,并在260-320 nm产生了新的紫外吸收谱带,而两种甲基吡啶的光潜碱在λmax=450nm处的吸收峰消失;RT-IR显示三种光潜碱的苯甲酰基吸收在紫外光照后消失,但产生新的C=O吸收峰,DBU光潜碱的苯甲酰基吸收在紫外光照10s后消失,而甲基吡啶光潜碱的消失要慢一些。用DBU光潜碱进行了光催化多硫醇-甲基丙烯酸羟乙酯(HEMA)的光聚合反应,RT-IR跟踪实验表明,C=C双键反应速率快,在光照300s后完全转化,而巯基在光照300s后转化率才达到66.4%;对比DBU催化多硫醇与HEMA的迈克尔加成反应,证明DBU光潜碱的光催化多硫醇HEMA光主要是通过巯-烯聚合反应。更多还原

【Abstract】 When irradiated with light, photobase generator decomposes and releases the base, which can be used for alkali catalyzed reaction. A series of quaternary ammonium photobase generators were synthesized from 2-bromoacetophenone, 1,8-Diazabicyclo [5.4.0] undec-7-ene(DBU), 4-methylpyridine and 3-methylpyridine with tetraphenylborate as the anion. The chemical structure, photochemical and photolyzing processes were analyzed by NMR, real time FT-IR(RT-IR) and UV-Vis spectroscopy. It is found that after irradiation with UV light the absorption spectra of the three photobase generaters changed significantly, and a new absorption band emerged between 260nm and 320nm. The absorption peaks around 450nm for the two methyl pyridine photobase generators disappeared after photo-irradiation. It has been found by RT-IR that the adsorption of the benzoyl group of the three photobase generators disappeared under the UV light irradiation while a new adsorption peak of carbonyl group emerged. For the DBU-type photobase generator, the adsorption peak of the benzoyl group disappeared after UV-light irradiation for 10s, while for the methyl pyridines photobase generators the disappearance takes much longer time. The photo-polymerization reaction of polythiol with β-hydroxyethyl methacrylate(HEMA) was carried out with DBU-type photobase generator as the catalyst. It is found by RT-IR that the reaction by C=C double bound is faster than by thiols as the conversion of C=C double bound and-SH group is 100% and 66.4%, respectively, after UV-irradiation for 300s. The Michael addition reaction between polythiol and HEMA catalyzed by DBU was also carried out as a comparison. The photochemical reaction between polythiol and HEMA catalyzed by DBU-type photobase generator was mainly through the thiol-ene reaction.更多还原