Structural Evolution and Self-assembly in Polymer Nanocomposites in Confined Geometry.

[摘要] Polymer nanocomposites (PNCs) are prepared by incorporating nanoparticles within a polymer host. The properties of PNCs are determined, in part, by the functionalities (e.g. electronic, optical, mechanical) of the nanoparticles and of the polymer host. Designing PNCs, however, is challenging due to uncontrolled enthalpic and entropic interactions that generally lead to micro and macrophase separation between the nanoparticles and the polymer; this negatively impacts the properties of the PNC. The goals of this thesis are the design of the structure and properties of thin film polymer nanocomposites in thin film geometry. Specifically, the research involved: (1) using thermodynamic principles to design and to fabricate thin film homopolymer/metallic nanoparticle PNCs; (2) investigating the dynamics of structural evolution of di-block copolymer (BCP)/metallic nanoparticle PNCs. In order to control the structure of PNCs, particularly the nanoparticle distribution, polymer chains were grafted onto the surface of the nanoparticles. Prudent choices of the grafted chain lengths, grafting densities and nanoparticle radii enabled significant control of the nanoparticle distribution within the PNC. A morphological phase diagram, which describes regimes of miscibility, in terms of the molecular characteristics of the mixture, was developed for polystyrene/polystyrene-coated gold nanoparticle (PS/PS-Au) mixtures. This information enabled the design and fabrication of PS/PS-Au PNCs with unusual optical absorption (surface plasmon) and dielectric properties. The refractive indices of the thin film PNCs were tailored by manipulating the nanoparticle concentration and distribution, and the film thickness. In the second part of this thesis, it was shown how defects, specifically dislocations, had a significant impact on the nanoparticle distribution throughout thin film BCP hosts. When the nanoparticles are small compared to the average phase separated domains of the BCP, they reside preferentially within the domains. However, when the nanoparticles were comparable to the domain size they preferentially resided within the defect structures. This was shown to have a significant effect on the time-dependent evolution of surface nano-architecture of the BCP thin films.

[发布机构] University of Michigan

[效力级别] Materials Science and Engineering

[关键词] Structure Formation of Thin Film Polymer Nanocomposites;Materials Science and Engineering;Engineering;Materials Science and Engineering