十八烷基-L-苯丙氨酸齐聚物在有机溶剂中的自组装

由L-苯丙氨酸和二(三氯甲基)碳酸酯反应得到的L-苯丙氨酸-N-羧基-环内酸酐(L-Phe-NCA), 在十八胺的引发下开环聚合得到十八烷基-L-苯丙氨酸齐聚物(简称L-Phe-R18). ¹H NMR (300 MHz)和FT-IR表征了产物结构, 是平均聚合度为5的齐聚物. L-Phe-R18能在多种有机溶剂中发生聚集和自组装, 并进而在这些有机溶剂中形成热可逆的物理凝胶. 其中, 该齐聚物能在氯苯、二苯醚、甲苯等溶剂中形成透明凝胶. 也能在苯、硝基苯、醋酸丁酯等溶剂中形成非透明凝胶. L-Phe-R18在这些有机溶剂中的最低凝胶化浓度(MGC)在w＝0.3%～1%之间. X射线衍射(XRD)数据和场发射扫描电镜(FE-SEM)以及分子模拟表征了L-Phe-R18聚集体的微观形态和可能的聚集方式. 认为L-Phe-R18在有机溶剂中通过分子间氢键、π-π堆积等非共价键相互作用聚集、组装成厚度约为20 nm左右的带状纤维, 溶剂分子以毛细力存在于相互缠绕的纤维网络结构中, 使体系形成稳定的凝胶.

Self-assembly of Octadecyl-L-phenylalanine Oligomer in Organic Solvents

L-Phenylalanine-N-carboxyanhydride (L-Phe-NCA) was synthesized from bis(trichloromethyl)-carbonate and L-phenylalanine. Octadecyl-L-phenylalanine oligomer was obtained by the ring-opening reaction of L-Phe-NCA using octadecylamine as initiator. The average polymerization degree of the oligomer is 5 determined by ¹H NMR. The oligomer can aggregate and self-assemble to form thermal reversible physical gels in some organic solvents. It can form transparent gels in chlorobenzene, toluene and diphenyl ether and but non-transparent gels in the solvents such as benzene, nitrobenzene and butyl acrylate. The minimum gelation concentration of the oligomer in these organic solvents is in the range of w＝0.3%～1%. The morphology and structures of oligomer aggregated in the media were characterized by XRD, FE-SEM and molecular simulation. The results indicated that hydrogen bonding and π-π stack were main driving forces for the self-assembly of oligomer. The aggregates of oligomer were tape-like with thickness of approximate 20 nm. The solvent molecules were immobilized by capillary force in the entangling network.