This Ph.D. thesis aims to study the assembly of gold nanoparticles (AuNPs) within stimuli-responsive polymer brushes that are grafted from planar surfaces. The apparent color of such brush/AuNP hybrids depends on the particle loading and vicinity. Thus, controlling the particle assembly inside the polymer brush matrix allows tuning the color of brush/AuNP hybrids to optimize them for sensor applications. As discussed in this Ph.D. thesis, the particle assembly in polymer brush matrices is influenced by many parameters such as brush thickness, brush grafting density, polymer chemistry, as well as particle surface functionalization, size, and shape. Surface-grafted poly((N,N-dimethylamino ethyl)methacrylate) (PDMAEMA) and poly(N-isopropylacrylamide) (PNIPAM) brushes were prepared by atom transfer radical polymerization (ATRP) and loaded with AuNPs by a dipping process. Both polymers exhibit a lower critical solution temperature (LCST), above which the polymer chains undergo reversible shrinking. In this Ph.D thesis, X-ray and neutron reflectivity, UV/vis spectroscopy, scanning electron microscopy and ellipsometry are combined to study the AuNP assembly and optical properties of the prepared brush/AuNP hybrids. The uptake and penetration of AuNPs could be increased after decreasing the grafting density of the surface-anchored polymers. At high grafting density, the AuNPs penetrated more effectively when PNIPAM was used as the brush matrix. Color changes of PNIPAM/AuNP hybrids could be induced by either varying the temperature or increasing the salinity; the structure of PNIPAM/AuNP and the apparent color strongly depended on the type of salt. The assembly of AuNPs could be controlled by immobilizing two different particle types into the PNIPAM brush matrices, namely citrate-coated AuNPs and AuNPs stabilized with 12-mercaptododecanoic acid ligands, into PNIPAM brushes. The color change associated with the thermoinduced collapse of the PNIPAM brushes depended on the particle type. Finally, surface-bound grafting density gradients and gradients in quaternization degree were employed to determine the dominating factors that govern the assembly of anisotropic gold nanorods in PDMAEMA brushes.
|Advisor:||von Klitzing, Regine|
|School:||Technische Universitaet Berlin (Germany)|
|Source:||DAI-C 81/1(E), Dissertation Abstracts International|
|Subjects:||Electrical engineering, Materials science, Nanotechnology, Condensed matter physics|
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