Design Of Chiral Functional Polymers And Properties Of Enantioselective Recognition

Chiral Functional polymers based on Ï€-conjugated chain backbone structures have attracted much interest during the past decade. These chiral conjugated polymers can be systematically modified by introduction of the different chiral functional groups based on steric and electronic properity at well-defined molecular lever. They can be used to prepare nonlinear optical materials, supramolecular sensors and circularly polarized luminescence materials, etc. Meanwhile, the study of chiral polymers can help people understand the eath or origin of chirality in biological sysyems and other important scientific issues.In this dissertation, the studies focused on the design, synthesis and application as circularly polarized luminescence materials and chemosensors of chiral conjugate polymers.1.(R,R)-salen/salan-based polymer fluorescence sensors for Zn2+detection(R,R)-salen-based polymer fluorescence sensor P1could be synthesized by the polymerization of5,5’-(isoquinoline-5,8-diylbis(ethyne-2,1-diyl))-bis(3-tert-butyl-2-hydroxybenzaldehyde)(M1) with (R,R)-1,2-diaminocyclohexane (M2) via nucleophilic addition-elimination reaction, and (R,R)-salan-based polymer sensor P2could be obtained by the reduction reaction of P1with NaBH4. The fluorescence response behaviors of two chiral polymers P1and P2on Zn2+were investigated by fluorescence spectra. The fluorescence intensities of P1and P2can exhibit gradual enhancement upon addition of Zn2+. Compared with other cations, such as Na+, K+Mg2+, Ca2+, Fe3+, Co2+, Ni2+, Cu2+, Ag+, Cd2+, Cr3+and Pb2+, Zn2+can lead to the pronounced fluorescence enhancement as high as22.8-fold for P1and3.75-fold for P2, respectively. The results show that PI and P2incorporating (R,R)-salen/salan moieties as receptors in the polymer main chain backbone can exhibit high sensitivity and selectivity for Zn2+detection.2. Salen-Based Chiral Fluorescence Polymer Sensor for Enantioselective Recognition of a-Hydroxyl Carboxylic Acids(R,R)-Salen-based chiral polymer P3was synthesized by the polymerization of5,5’-((2,5-dibutoxy-1,4-phenylene)bis(ethyne-2,1-diyl))bis(2-hydroxy-3-(piperidin-1-ylmethyl) benzaldehyde (M1) with (1R,2R)-cyclohexane-1,2-diamine (M2) via nucleophilic addition-elimination reaction, and (R,R)-salan-based polymer P4could be obtained by the reduction reaction of P3with NaBH4.(R,R)-Salen-based chiral polymer P3can exhibit greater fluorescence enhancement response towards (L)-a-hydroxyl carboxylic acids, and the value of enantiomeric fluorescence difference ratio (ef) can reach as high as8.41for mandelic acid,6.55for lactic acid, respectively. On the contrary,(R,R)-Salan-based chiral polymer P4shows obvious fluorescence quenching response towards a-hydroxyl carboxylic acids. Most importantly,(R,R)-Salen-based polymer P3can display bright blue fluorescence color change in the presence of (L)-α-hydroxyl carboxylic acids under a commercially available UV lamp, which can be clearly observed by the naked eyes.3. A Chiral Ionic Polymer for Direct Visual Enantioselective Recognition of a-Amino acid AnionA novel chiral ionic polymer exhibits high fluorescence enantioselectivity towards a-amino acid anions, and its solution appears bright green upon addition of (L)-a-amino acid anions, which can be clearly observed by the naked eye for direct visual enantioselective recognition.4. Chiral Sensing for Induced Circularly Polarized Luminescence by Using an Eu(III)-containing Polymer and D-or L-Proline An Eu(III)-containing water soluable polymer can exhibit intense induced circularly polarized luminescence (CPL) in the presence of proline. In addition, the optical anisotropy factor (glum) of polymer for5D0â†'7F1/7F2transition was much higher than single model molecule, which reveals the amplification effect of CPL arising from conjugated polymer structure. This research work could provide a new strategy to develop higher glum, value of CPL-active polymer materials.