Functions and Preparation of Polymer LB Films having Chiral Discrimination

轴向手性双萘发色团（BN）可以作为N -烷基丙烯酰胺的共聚单体加入到聚合物Langmuir-Blodgett （LB）薄膜中，形成稳定的单层和LB多层膜。通过测量表面压力-面积等温线，研究了(S)-2-甲氧基-1,1′-二萘-2′-甲基丙烯酸酯（(S)-MeBn）或(S)-2-羟基-1,1′-二萘-2′-甲基丙烯酸酯（(S)-HOBM）与n -癸基（DA）、十二烷基（DDA）或十四烷基丙烯酰胺（TDA）的共聚物的扩散行为。等温线结果表明，当BN的摩尔分数小于约20 mol%时，共聚物尤其是DDA共聚物在纯水表面形成稳定的缩合单体，轴手性双萘发色团在水中分布均匀，具有自己的表面积。通过Langmuir-Blodgett沉积技术（y型沉积），可以将共聚物单分子膜依次转移到固体载体上。在LB薄膜上观察到由正第一和负第二棉花效应组成的强CD（圆二色）光谱，支持手性二萘发色团的(S)构型。用电化学电位法研究了手性共聚物LB膜对旋光性1-苯乙胺（PEA）的对映选择性反应。用共聚物单层修饰的电极在加入PEA时引起了非常敏感的电位变化。(S)- hobn共聚物单层电极对R-和S- pea具有明显的手性分辨，而(S)- mebn共聚物电极对R-和S- pea无明显的手性分辨。可以清楚地揭示手性分子识别的机理。

Axially chiral binaphthalene chromophores (BN) can be incorporated into polymer Langmuir-Blodgett (LB) films as a comonomer of N -alkylacrylamides which have an excellent ability to form stable monolayrs and LB multilayrs. The spreading behavior of the copolymers of (S)-2-methoxy-1,1'-binaphthalene-2'-yl methacrylate ((S)-MeBn) or (S)-2-hydroxy-1,1'-binaphthalene-2'-yl methacrylate ((S)-HOBM) with N-decyl (DA), dodecyl (DDA), or tetradecyl acrylamide (TDA) was investigated by a measurement of the surface pressure-area isotherms. The isotherms show that the copolymers, especially DDA copolymers, form a stable condensed monolayr on pure water and the axially chiral binaphthalene chromophore is dispersed uniformly having its own surface area on water when the mole fraction of BN is less than ca. 20 mol%. The copolymer monolayrs could be transferred onto solid supports successively by the Langmuir-Blodgett technique (Y-type deposition). The strong CD (circular dichroism) spectra consisting of positive first and negative second Cotton effects were observed for the LB films, supporting the (S)-configuration of the chiral binaphthyl chromophore. The enantioselective response of the chiral copolymer LB films to optically active 1-phenylethylamine (PEA) was investigated by an electrochemical potentiometric method. The electrodes modified with the copolymer monolayrs induced a very sensitive potential change on addition of PEA.The electrode with (S)-HOBN copolymer monolayrs showed a large chiral discrimination to distinguish between R- and S-PEA, whereas the (S)-MeBN copolymers showed no discrimination. The mechanism for the chiral molecular recognition can be shown clearly.