Iron Oxide-Based Multi-Compartment Colloids with Complex Structures

Dörmbach, Karla; Pich, Andrij (Thesis advisor); Simon, Ulrich (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2015)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2015

Abstract

This dissertation deals with the synthesis and characterization of iron oxide-based multi-compartment colloids combining the chemical and physical properties of inorganic nanoparticles with different polymers. All colloids are synthesized in solution by template-free bottom-up approaches. In the first part an insight into the intrigued world of hematite nanoparticles is given. During the synthesis in aqueous solution the morphology can be adjusted to range from spherical to spindle-type shapes. Analyses concerning chemical composition of different species as well as selected physical properties are performed. In the further chapters, these nanoparticles are used as templates for the formation of more complex structures.Next, the coating of spherical and ellipsoidal hematite colloids with silica using different coating methods is presented. The chapter opens with detailed investigations of standard silica coating procedures focusing especially on the role of adhesion promoters during the silica deposition in organic media. Subsequently, a silica coating process is presented where highly functional, water-soluble hyperbranched polyalkoxysiloxanes are used. In a surfactant-free water-based coating procedure, the resulting hematite core silica shell nanoparticles are decorated with reactive groups on the surface. Asymmetric multi-compartment lemon- and dumbbell-shaped colloids are the main topic of the following part. Some of the monomers used for the asymmetric polymer coating, are hydrophobic in nature, but also water-soluble, functional monomers, e.g. N vinylcaprolactam, are used making the polymer shell more hydrophilic, reactive and responsive. Furthermore, structures described are used to deposit silica selectively on the free edges of the ellipsoids to obtain dumbbells. Finally, different methods of encapsulation of magnetic nanoparticles into PVCL microgels are discussed. One approach describes the grafting of polymer from the spherical hematite nanoparticle surface resulting in core-shell nanocomposites. Loading of sub-10 nm FePt colloids by a solvent exchange method into microgels is the other subject here. For both hybrid material responsiveness to external stimuli is observed.