分子印迹手性分离过程的热力学研究

Thermodynamic Study on Chiral Separation Process Using Molecular Imprinting

以丙烯酰胺为功能单体, 以二甲基丙烯酸乙二醇酯为交联剂, 在模板分子 N-叔丁氧羰酰-L-色氨酸(N-Boc-L-Trp)和 N-叔丁氧羰酰-L-酪氨酸(N-Boc-L-Tyr)的存在下, 分别采用光引发聚合和热引发聚合制备了 N-Boc-L-Trp 和N-Boc-L-Tyr 的分子印迹聚合物(MIPs), 进行分子印迹手性分离过程的热力学研究. 测定了分离过程的熵变、焓变和自由能变化. 结果显示, 在流动相中添加异丙醇或甲醇等强氢键竞争性溶剂时, 熵变对分离起到了主要作用, 而且分离过程中的溶剂化对分离的影响也非常大. 分子印迹聚合物对印迹分子和非印迹分子进行分子识别的主要作用是印迹聚合物与印迹分子匹配的三维空间结构.

Two kinds of enantio-selective molecularly imprinted polymers (MIP) of N-tert-butoxycarbonyl-L-tryptophan (N-Boc-L-Trp) and N-tert-butoxycarbonyl-L-tyramine (N-Boc-L-Tyr), were synthesized by photo-induced and thermal-induced polymerization, respectively, in which acrylamide (functional monomer) and ethylene glycol dimethacrylate were co-polymerized in the presence of N-Boc-L-Trp and N-Boc-L-Tyr. Thermodynamic studies on chiral separation process using molecular imprinting were then carried out when the above two MIPs were employed as the stationary phase in liquid chromatography. Changes of entropy, enthalpy and Gibbs free energy in the process of imprinted-separation were analyzed. The results showed that not only the change of entropy played an important role in the separation, but also the solvation effect of the solutes and stationary phase, when a strong hydrogen-bond competitive solvent, such as isopropyl alcohol, alcohol or methanol, was supplemented into the mobile phase. Further studies showed that the molecular recognition of imprinted molecules and their enantiomorphs mainly depended on how well the geometric cavity structures of MEP suited the structure of the imprinted molecules.