2D and 3D assembly of block copolymer coated nanoparticles
- 2D und 3D Anordnung von Blockcopolymer beschichteten Nanopartikeln
Leffler, Vanessa Bianca; Förster, Stephan (Thesis advisor); Richtering, Walter (Thesis advisor)
Aachen (2020, 2021)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2020
Nanocomposite made from inorganic nanoparticles and polymers combine the best of both worlds. They have the excellent properties of functional nanoparticles and the easy processing of polymers. Furthermore, by using e.g. a diblock copolymer it is possible to achieve highly ordered nanostructures as the polymer acts as a kind of template for the assembly of the nanoparticles. These well defined nanocomposites are excellent candidates for next generation materials such as solar cells and scintillator materials. The preparation of these highly ordered nanocomposites poses several challenges: the nanoparticles need to be very well defined; the thermodynamic immiscibility of the nanoparticle and the polymer needs to be overcome and the interparticle distance as well as the location of the nanoparticle within the polymer matrix need to be controlled very precisely. In this thesis, the nucleation and growth kinetics of iron oxide nanoparticles are investigated via in situ small and wide angle X ray scattering to enable the synthesis of tailor made, well defined nanoparticles. These are then coated with diblock copolymer synthesized in an anionic polymerization. By using this approach, the main challenges in the preparation of highly ordered nanocomposites are overcome very effectively. The structures of the prepared nanocomposite monolayers and bulk films are investigated using highly sophisticated methods like transmission electron microscopy and small angle X ray scattering. The formation of the iron oxide nanoparticles shows a mechanism with three main phases including the formation of amorphous clusters and subsequently crystalline nuclei like particles, which then start to grow. The block copolymer coated nanoparticles form highly ordered structures in 2D as well as in 3D. The most crucial parameters for the formation of the nanostructures are the nanoparticle/ domain size ratio, the grafting density and the block ratio of the polymer. For the monolayers a stronger influence of the grafting density is observed while the block ratio has a more pronounced effect for the bulk films. Furthermore, the influence of the high curvature of the nanoparticles is much more pronounced in the bulk films as here even the incorporation of very small volume fractions of nanoparticles leads to a considerable change in structure towards morphologies with a higher interfacial curvature.