Hyperbranched Polyester For Preparation Of Nanomaterials

This study investigated the application of hyperbranched polyester (HBP) for modifying and preparing nanomaterials, including using the functional HBP to modify ultrafine zinc oxide, to synthesize and characterize silver single nanocrystals with HBP as template, and preparing photocurable conductive adhesive with nano and micro sized silver powers as conductive fillers and HBP as binder. The main results are outlined as follows:1. Nano- and micro scale zinc oxide particles were modified with HBP containing -COOH groups. Stable and transparent suspension solutions of ZnO in ammonia aqueous were prepared by the presence of HBP. The stability of the suspension solution was effected by mole ratio of -COOH/ZnO. When -COOH /ZnO = 1/8, the transparent and suspension solutions was maintained over 72h. When acetone or butane acetate was used as solvent instead of ammonia aqueous, ZnO particles were precipitated from the suspension solution. The HBP modified ZnO powders were studied by FT-IR, X-ray photoelectron spectroscopy (XPS), elemental analyses and transmission eletron microscopy (TEM). In the IR spectra, new vibration absorption appeared at 1591 cm"1. XPS, elemental analyses and TEM data indicated that the HBP was bonded onto surface of ZnO powders, and as a result, the aggregation of ZnO powders was depressed.2. Hyperbranched polyester-encapsulated crystals of silver nanoparticles with size in 3-19 nm, averaged at 7.7±0.5nm, were prepared by the photoreduction of silver ions with the assistance of aliphatic phosphate surfactant and HBP terminated by-OH and -COOH groups with ultraviolet irradiation. The silver nanoparticles were characterized by transmission electron microscopy, selected area electron diffraction, UV-vis spectra, X-ray diffraction, X-ray photoelectron spectra and FT-IR spectroscopy. Controlled and comparing experiments showed that non-aggregated silver nanoparticles could not be synthesized without the using of either hyperbranched polyester or aliphatic phosphate surfactant, indicating the importance of HBP and phosphate surfactant in stabilizing silver nanoparticles during the photoreduction.3. To more efficiently preparing well defined and uniform silver single nanocrystal, a new method was studied by combining photo with chemical reduction of silver ions with the assistance of aliphatic phosphate surfactant and HBP. The obtained silver nanoparticles encapsulated with HBP sized in 3-11 nm, averaged at 7.4+ 0.5nm. Though HBPs terminated with -COOH and -OH groups played a crucial role as template, the combination of HBPs with phosphate surfactant, were necessary for the synthesis of narrow distributed, nanosize single crystalline silver particles with high efficiency.4. Using GMA-HBP and silver powers and nanoparticles, UV curable conductive adhesives with surface resistance about lO0"^ were prepared. Diluents (hydroyethyl acrylate, HEA, and acrylic acid, AA), conductive fillers: micro-sized silver power and nanoparticles, and tow UV curable resins: epoxy and GMA-HBP, were studied. It was found that silver nanoparticles was not an effective conductive filler as comparing with micro-sized Ag powder; HBP was useful when combining with acrylic epoxy resin as the binder.