The Study of Organic-Inorganic Clay and Quantum Dots Nanocomposites on Physical Properties

• Main Authors: Fu, Huai-Kuang, 傅懷廣
• Other Authors: Chang, Feng-Chih
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/32220963794264167942

博士 === 國立交通大學 === 應用化學系所 === 97 === Polymer nanocomposites are commonly defined as the combination of a polymer matrix and additives that have at least one dimension in nanometer range. The additives can be one-dimensional (example include nanotubes and fibers), two- dimensional (which include layered minerals like clay), or three-dimensional (include spherical particles and quantum dots). Nanoscale-filled polymeric systems offer the prospect of greatly improving many of the properties of the polymer matrix. The dissertation was focused on four major subjects: the study of the inorganic additives of polymer nanocomposites on physical properties. 1.Studies on Thermal Properties of PS Nanocomposites for the Effect of Intercalated Agent with Side Groups Polystyrene layered silicate nanocomposites were prepared from three new organically modified clays by emulsion polymerization method. These nanocomposites were exfoliated up to 3 wt % content of pristine clay relative to the amount of polystyrene (PS). The intercalated agents, C20, C20-4VB, and C20-POSS intercalated into the galleries result in improved compatibility between hydrophobic polymer and hydrophilic clay and facilitate the well dispersion of exfolicated clay in the polymer matrix. Results from X-ray diffraction, TEM and Fourier transform infrared spectroscopy indicate that these intercalated agents are indeed intercalated into the clay galleries successfully and these clay platelets are exfoliated in resultant nanocomposites. Thermal analyses of polystyrene-layered silicate nanocomposites compared with virgin PS indicate that the onset degradation temperature ca. 25 °C increased and the maximum reduction in coefficient of thermal expansion (CTE) is ca. 40 % for the C20-POSS/clay nanocomposite. In addition, the glass transition temperatures of all these nanocomposites are higher than the virgin PS. 2.Properties Enhancement of PS Nanocomposites through the POSS surfactants The polyhedral oligomeric silisesquioxnae (POSS)-clay hybrids of polystyrene are prepared by two organically modified clays using POSS-NH2 and C20-POSS as intercalated agents. X-ray diffraction (XRD) studies show that the formation of these POSS/clay/PS nanocomposites in all cases with the disappearance of the peaks corresponding to the basal spacing of MMT. Transmission electronic spectroscopy (TEM) was used to investigate the morphology of these nanocomposites and indicates that these nanocomposites are comprised of a random dispersion of exfoliated throughout the PS matrix. Incorporation of these exfoliated clay platelets into the PS matrix led to effectively increase in glass transition temperature (Tg), thermal decomposition temperature (Td) and the maximum reduction in coefficient of thermal expansion (CTE) is ca. 40 % for the C20-POSS/clay nanocomposite. 3.Effect of the organically modified Nanoclay on Low-Surface-Energy Materials of Polybenzoxazine Novel low surface free energy materials of polybenzoxazine/organically modified silicate nanocomposites have been prepared and characterized. The CPC (cetylpyridinium chloride)/clay10%/Poly(3-phenyl-3,4-dihydro-2H-1,3-benzoxazine) (PP-a) possesses an extremently low surface free energy (12.7 mJ/m2) after 4 hrs curing at 200 ℃, even lower than that of poly(tetrafluoroethylene) (22.0 mJ/m2) calculated on the basis of the three-liguid geometric method. X-ray photoelectron spectroscopy (XPS) shows higher silicon content on the surface of nanocomposites than average composition, implying that the clay is more preferentially enriched on the outermost layer. In addition, the glass transition temperature (Tg) of the polybenzoxazine (PP-a) in the nanocomposite is 22.6 ℃ higher and its thermal decomposition temperature is also higher than the pure PP-a. This finding provides a simple way to prepare lower surface energy and high thermal stability material. 4.Preparation of the Stimuli-Responsive ZnS/PNIPAM Hollow Spheres Novel quantum dots ZnS/poly(N-isopropylacrylamide) (PNIPAM) hybrid hollow spheres were obtained by localizing free radical polymerization of NIPAM and crosslinker (MBA) at the peripheral of PCL nanoparticles, followed by biodegradation of PCL with an enzyme of the Lipase PS. The formation of ZnS/PNIPAM hollow spherical structures and the thermo-sensitive reversible properties were systematically investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. The ZnS/PNIPAM hollow spheres possess the photoluminescence properties and a swelling and de-swelling at about 32 oC, which agrees well with the slight red-shift in photoluminescence spectra.