Synthesis And Anion Recognition Properties Of Chiral Polymer

Development of anion-sensors is of particular interest because of their significance in biological and environmental sciences. In comparison to small molecular receptors, the polymeric fluorescent counterparts offer several potential advantages, such as fluorescence efficiency enhancement and possible cooperative effects of multiple recognition sites. Besides, as a unique feature, such polymeric sensory materials allow facile fabrication of detecting devices and development of the multifunctional sensors. Thus, the polymer-based sensors have been drawing much attention in chemosensor research field.Our previous work demonstrated that N-naphthaldimine derivatives of chiral α-phenylethylamine exhibited dramatic and reversible variations in the absorption, emission and circular dichroism (CD) spectra upon acid/base stimulus, which mainly attributed to the conformational transition. In this thesis we designed a new functional monomer (VNP) and prepared the corresponding non-conjugated polymer (PVNP) bearing optically active naphthaldimine chromophores in the side chain via RAFT method to explore its potential as a new class of chemosensors with chiroptical channel. The results showed that the sensory system binds hydrogen sulfate anion with specific selectivity relative to other anions including F-, Cl-, Br-, H2PO4-, CH3CO2-, and NO3-. Interestingly, it exhibited pronounced absorbance, fluorescence and circular dichroism responses upon HSO4-complexation in "turn-on" fashion. A remarkable colorless-to-pale yellow color change was easily observed by naked eyes. The HSO4-induced CD signal can be totally reversed with addition of base and eventually recovered the initial state, leading to a reproducible molecular switch with two distinguished "on" and "off" states. The reversible and reproducible chemical switching could be used to construct an "INHIBIT" logic gate. The selective HSO4-recognition mechanis is based on the hydrogen bonding interaction between host and guset molecules, which supported by the1H NMR titration of VNP and the density functional theory (DFT) calculation.The copolymerization of VNP with2-hydroxyethyl methacrylate (HEMA) produced the desired product. The thin films of poly(HEMA-co-VNP) casted on quartz plate also showed remarkable "turn-on" fluorescent response toward HSO4 ions in both organic and aqueous samples without the concentration quenching of fluophores. The results indicate that the polymer film sensor is very useful in practical applications for HSO4detection such as physiological treatment. Such polymeric materials might find potential use in nuclear waste remediation applications requiring the selective removal of hydrogen sulfate from nitrate-rich waste mixture.