The Study Of Chemical Sensing Material Based On Hyperbranched Poly (Phenylenen Sulfide)

Dendrimer and hyperbranched polymer (HPs) are highly branched polymers with typical topology. They possess a large number of internal cavities, and can carry many functional end groups. In contrast to linear polymer, the dendrimer and hyperbranched polymer permit higher polymerization unit density, good solubility, low viscosity, higher chemical reactivity, etc. Hyperbranched polymers, even though have irregular structures with random branched topology, still have similar unique physical and chemical properties, analogous figuration to dendrimers. Importantly, one of the advantages that HPs can be facilely produced by one-pot reaction could compensate the irregular three-dimensional architecture or structural defects of hyperbranched polymers. Hyperbranched poly (phenylene sulfide) (HPPS) is a stiff macromolecule with three-dimensional spherical structure. As a result of the existence of abundant branched chains and intramolecular cavities, it can dissolve in normal organic solvents at room temperature. HPPS was synthesized via one-pot reaction procedure, and served as a suitable scaffold for immobilizing Au NPs by use of cavities and S atoms. Because of aryl groups conjugated with sulfur atoms, it has stable fluorescence. Through the nucleophilic substitution and hydrolysis reaction, HPPS was further modified by probe molecules, and highly sensitive fluorescent chemosensor was achieved. The works were several following parts:1. The synthesis of hyperbranched poly (phenylene sulfide) (HPPS) and its fundamental propertiesIn NMP solvent system, by control polycondensation time, hyperbranched poly (phenylene sulfide) was synthesized via one-pot reaction procedure with 2,4-dichlorothiophenol as monomer and KOH, K2CO3 as alkali reaction auxiliary. HPPS can dissolve in normal organic solvents at room temperature, and its structure had been characterized by IR and 1H NMR spectroscopy and the results indicated that the HPPS was synthesized successfully. Thermogravimetry results demonstrated that, in contrast to linear poly (phenylene sulfide), the presence of abundant branching have no significant effect to its thermostability. Meantime, Size Exclusion Chromatography-Multi-Angle Laser Light Scattering (SEC-MALLS) was used for testing absolute molecular weight and molecular conformation determination of HPPS.2. Hyperbranched Poly (phenylene sulfide) (HPPS) as a stabilizer for gold nanoparticlesStable and monodisperse gold nanoparticles (Au NPs), protected by HPPS using its cavities and S atoms, were prepared by one-phase and two-phase synthetic routes. By measuring the prepared of Au NPs at that current time and three months later, the stability of Au NPs was studied by Uv-vis absorption spectrum. The synthetic approach and the amount of HPPS had significant impact on the stability of Au NPs. The stable Au NPs were measured by TEM. The formed Au NPs displayed a size of sub-5 nm and narrow distribution. The stabilization mechanism of HPPS-Au NPs was also discussed.3. Highly sensitive detection of Hg2+ by a reaction-based hyperbranched poly (phenylene sulfide) (HPPS) fluorescent polymer chemosensorHPPS, which has stable fluorescence, was used as the core. Through the nucleophilic substitution and hydrolysis reaction, peripheral Cl atoms of HPPS were modified by NH2 groups, and the HPPS-NH2 was achieved. The fluorescent sensor (HPPSNT) was fabricated by HPPS-NH2 azo N=N covalently bonded to small probe molecule Benzamide, N-[[[2-(phenylamino) ethyl] amino] thioxomethyl], which can react with Hg2+ sensitively and selectively, causing desulfurization and cyclization. The results showed that HPPSNT sensor exhibited excellent sensitivity towards Hg2+, and can selectively recognize Hg2+ over other metal ions, such as Al3+, Ba2+, Cd2+, Cu2+, Fe3+, Zn2+, Pb2+, Mg2+, K+, Ag+. In comparison with the conventional molecular-based fluorescent chemosensors, hyperbranched polymer-based chemosensors have shown enhanced sensitivity through the sensory signal amplification. It was found that the decreased absorption of fluorescent signal intensity was proportional to the mercury content concentration in a range of 2.5～100 nmol/L with a coefficient of correlation R of 0.9931, and a detection limit of 0.46 nmol/L. The mechanism of high sensitivity was discussed.