Abstract：
Liquid crystal monomers (LCMs) are a new class of emerging pollutants with high octanol-water partition coefficients; however, their transformation behavior and associated risk to environments with high organic matter content has rarely been reported. In this study, we investigated the photodegradation kinetics, mechanism, and toxicity variation of 23 LCMs on leaf wax models (e.g., organic solvents methanol and n-hexane). The order of the photolysis rates of these LCMs were biphenylethyne LCMs > phenylbenzoate LCMs > diphenyl/terphenyl LCMs under simulated sunlight, while the phenylcyclohexane LCMs were resistant to photodegradation. The phenylbenzoate and biphenylethyne LCMs mainly undergo direct photolysis, while the diphenyl/terphenyl LCMs mainly undergo self-sensitized photolysis. The main photolysis pathways are the cleavage of ester bonds for phenylbenzoate LCMs, the addition, oxidation and cleavage of alkynyl groups for biphenylethyne LCMs, and the cleavage/oxidation of chains attached to phenyls and the benzene ring opening for diphenyl/terphenyls LCMs. Most photolysis products remained toxic to aquatic organisms to some degree. Additionally, two quantitative structure-activity relationship models for predicting kobs of LCMs in methanol and n-hexane were developed, and employed to predict kobs of 93 LCMs to fill the kobs data gap in systems mimicking leaf surfaces. These results can be helpful for evaluating the fate and risk of LCMs in environments with high content of organic phase.
摘要：
液晶单体(LCM)是一类新的新兴污染物,具有高的辛醇-水分配系数;然而,它们的转化行为和对高有机质含量环境的相关风险很少报道。在这项研究中,我们研究了光降解动力学，机制，和23个LCM在叶蜡模型上的毒性变化(例如，有机溶剂甲醇和正己烷)。在模拟阳光下，这些LCMs的光解速率顺序为联苯乙炔LCMs>苯甲酸苯酯LCMs>二苯基/三联苯LCMs，而苯基环己烷LCM对光降解具有抗性。苯甲酸苯酯和联苯乙炔LCMs主要进行直接光解，而二苯基/三联苯LCM主要进行自敏化光解。主要的光解途径是苯甲酸苯酯LCMs的酯键断裂，加法,联苯乙炔LCM的炔基氧化和裂解，以及与苯基连接的链的裂解/氧化和二苯基/三联苯LCM的苯环打开。大多数光解产物在某种程度上对水生生物仍然有毒。此外,建立了两种定量构效关系模型，用于预测LCMs在甲醇和正己烷中的kobs，并用于预测93个LCM的kobs，以填补模仿叶片表面的系统中的kobs数据空白。这些结果有助于评估LCM在高有机相含量环境中的命运和风险。
