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聚对苯撑苯并二噁唑(PBO)纤维对光较为敏感,在紫外光照射下会发生降解.本文研究了该纤维的单体2-苯基苯并噁唑(PO)的初级光化学反应机理.当PO分子吸收一个光子而跃迁到第一激发态后,克服25.59kJ·mol-1能垒而越过过渡态,此时噁唑环打开,且两个苯环形成大约90°的二面角而得到产物,该产物可进一步与空气中的水发生次级反应.计算结果表明在第一激发态上噁唑开环反应很容易,但在基态势能面并没有发现噁唑的开环路径.分子中的原子(AIM)的计算结果与上述分析过程相吻合.
Poly (p-phenylenebenzobisoxazole) (PBO) fibers are sensitive to light and degrade under UV irradiation.In this paper, the primary photochemical reactions of 2-phenylbenzoxazole (PO) Mechanism. When the PO molecule absorbs one photon and transitions to the first excited state, it crosses the transition state overcoming the energy barrier of 25.59 kJ · mol -1, at which point the oxazole ring opens and the two benzene rings form two sides of about 90 ° And the product can be further reacted with water in air. The calculated results show that oxazole ring-opening reaction is very easy in the first excited state, but no open-loop path of oxazole is found in the ground state potential energy surface The calculation of the atom (AIM) in the molecule is consistent with the above analysis.