Studies On Design, Synthesis And Photophysical Properties Of Water-Soluble Fluorescent Polymer Materials

Since the first fluorescent material composed of polymer as a substrate was reported, fluorescent polymers have attracted much attention and recently various new materials have been prepared. Water-soluble fluorescent polymers show much more potential application compared with organic molecules. In this dissertation, the development of new fluorescent polymers materials is reviewed. To overcome the defects of organic molecules that are insoluble in water, five types of water-soluble copolymers bearing coumarin, fluorescein and 1, 8-naphthalimide were designed and synthesized.In this paper, the modified coumarin, fluorescein and 1, 8-naphthalimide as chromophores were attached successfully on several avirulent, low-cost, biocompatible and water soluble polymers through two different methods, respectively. The synthesized monomer and fluorescent polymers were characterized by the methods of nuclear magnetic resonance (¹H NMR), mass spectrography (MS), fourier transform infrared spectroscopy (FT-IR), ultra-violet-visible spectra (UV-Vis) and differential scanning calorimetry (DSC), respectively. And the fluorescence behaviors of polymers were investigated in detail.(1) A novel water-soluble fluorescent material was prepared via ring-opening reaction between 4-methyl-7-(2, 3-expoxypropoxy) coumarin (MEC) and poly(vinyl alcohol) (PVA) (via its epoxy derivate). The fluorescent behaviors of this material (PVA-MEC) in solution, solid and film were studied in detail. The results showed that the fluorescence of PVA-MEC arose from isolated dye molecules and had a good film forming ability. The effects of acid/base environments on PVA-MEC were also studied and the results showed that it was less affected by environment than 7-HMC. In addition, the temperature dependences of fluorescence of PVA-MEC were investigated in detail. The fluorescent polymer showed excellent linear response between fluorescence intensity and temperature. These observations suggest that PVA-MEC is an excellent fluorescent macromolecular material with a convenient method of preparation and had a good water-soluble ability. (2) An acrylic monomer bearing xanthene group, acryloyl-fluorescein (Ac-Flu) was synthesized from fluorescein and acryloyl chloride. The photophysical behaviors of Ac-Flu and its copolymer were explored by recording the fluorescence spectra in solution, solid state and film in detail. In addition, the ability of the copolymer to detect different metal cations in aqueous solution was investigated. The results showed that poly(Ac-Flu-co-AM) had a good linear response between the logarithm of concentration of Fe³ against the relative fluorescence intensity for Fe³⁺ concentration. The results suggest that this copolymer may offer potential as a reusable polymer sensor for Fe³⁺ ion in aqueous solution.(3) An acrylic monomer bearing couamrin moiety, 7-hydroxy-4-methyl-8-(4'-acryloylpiperazin-1'-yl) methylcoumarin (Ac-HMPC) was synthesized from 7-hydroxy-4-methyl-8-(4'-piperazin-1'-yl)methyl coumarin (HMPC) and acryloyl chloride (Ac). The main photophysical properties of the fluorescent copolymer poly(Ac-HMPC-co-AM) were determined viewing its sensor for protons and metal cations. The fluorescent polymer displayed "on-off"switching in its fluorescence intensity over a wide pH scale. In addition, it was found the fluorescence enhancement of poly(Ac-HMPC-co-AM) in the presence of Ni²⁺ ion. The results suggest that copolymer may offer potential as a reusable polymer for sensor protons and Ni²⁺ ion in aqueous solution.(4) A monomer 7-hydroxy-4-methyl-8-(4'-allyloxypiperazin-1'-yl)methyl-coumarin with blue fluorescence was synthesized. Then it was copolymerized with N-vinylpyrrolidone to obtain a water-soluble fluorescent copolymer poly(Al-HMPC-co-VP). The fluorescence characterstics of the polymer as a function of pH sensor were investigated in aqueous solution. It was found that the polymer displayed sensitive fluorescence signal amplification over a wide pH scale, which was ascribed to a photoinduced electron transfer from the peperazine receptor to the coumarin fluorophore. In addition, The influence of metal cations on the fluorescence intensity of poly(Al-HMPC-co-VP) were also studied. Obvious fluorescence enhancement was the photophysical response of the polymer to the presence of Ni ion. The results suggest that copolymer may offer potential as a reusable polymer for sensor protons and Ni²⁺ ion in aqueous solution.(5) A novel water-soluble colored polymer, based on 1, 8-naphthalimide, was synthesized through a series of easy reactions with high yields. It emitted green fluorescence both in an aqueous solution and in a solid state. Fluorescence characteristics of the polymer as a function of pH were investigated in aqueous solutions. The presence of metal cations (Zn²⁺, Co²⁺, Cr³⁺, Ni²⁺ and Cu²⁺) could enhance the fluorescence intensity of an aqueous solution of this polymer. It was sensitive to present in the studied system. The results suggest that this newly synthesized compound could work as a polymeric sensor responding to water polluted by Zn²⁺.In conclusion, the paper offered us a design of synthetic method that is simple, convenient and practical for the preparation of multifuctional fluorescent polymers, particularly fluorescent polymers sensors.