The Study On Hyperbranched Polyphenylene Sulfide Stabilized Silver Nanoparticles

Dendrimer and hyperbranched polymer are both highly branched polymers with a large number of internal cavities. In contrast to linear polymer, the dendrimer and hyperbranched polymer possess some advanced properties such as higher polymerization unit density, good solubility, low viscosity, higher chemical activity, etc. Even though the hyperbranched polymer has irregular structures with random branched topology, it can be facilely produced by one-pot reaction, which brings the meaning to study hyperbranched polymers, especially its application. Hyperbranched poly（phenylene sulfide）（HPPS） is a stiff macromolecule with three-dimensional spherical structure. Due to the abundant branched chains and intramolecular cavities, HPPS can usually dissolve in normal organic solvents at room temperature. HPPS was synthesized via one-pot reaction procedure, and served as a suitable scaffold for immobilizing Ag NPs by being hosted within cavities and coordinating with sulphur atoms. HPPS have a large of external terminal groups and abundant interior cavities, which could supply certain spaces for the growth of nano metallic particles. When nano metallic particles stabilized by HPPS were applied as catalyst or antibacterial agent, the effective contact area becomes a significant factor for catalytic efficiency and antimicrobial activity because the shape, sizes and superficial area of nano metallic particles were closely related with its formation mechanism. So study on the effect of HPs’ s space structure upon the formation mechanism of nano metallic particles would contribute to quantitative research of catalytic efficiency and antimicrobial activity. The work was divided into the several following parts.1. Hyperbranched Poly（phenylene sulfide）（HPPS） as a stabilizer for Ag nanoparticles and the basic property of Ag nanoparticleIn NMP solvent system, by polycondensation time control, hyperbranched poly（phenylene sulfide） was synthesized via one-pot reaction procedure with 2,4-dichlorothiophenol as monomer and KOH, K₂CO₃ as alkali. Because HPPS could dissolve in normal organic solvents at room temperature, stable and monodisperse Ag NPs protected by HPPS with its cavities and S atoms, were prepared by two-phase synthetic routes. The stability of Ag NPs was studied by Uv-vis absorption spectrum. The result revealed that the synthetic approach and the amount of HPPS had significant impact on the stability of Ag NPs. The shape and size of Ag NPs were measured by TEM with the result of sizes of 9.55 ± 2.00 nm and a narrow distribution.2. Formation Mechanism of Hyperbranched Polyphenylene Sulfide Stabilized Silver NanoparticlesThe formation mechanisms of silver nanoparticles using Hyperbranched polyphenylene sulfide（HPPS） as the stabilizer, Ag NO₃ as precursor and sodium borohydride as reducing agent were investigated based on time-resolved in situ experiments. By analyzing the variation of the maximum absorption wavelength（λ max）, it indicated that the growth process were divided into three stages. At the beginning, there was no apparent maximum absorption peak before Na BH₄ was added to the system. In the mid, Ag nanoparticles gradually grew with time after Na BH₄ was added to the system and the growth phase of silver nanoparticles was prolonged with the increasing of HPPS molecular weight. Finally, the sizes of silver nanoparticles maintained stable due to the internal cavity of HPPS when the λmax were invariable at around 4min. In addition, the λmax also kept stable when the mass ratio of Ag NO₃（g）/ HPPS（g） changed from 2.55×10^-3 to 4.25×10^-3.