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Über dieses Buch

This doctoral thesis explains the synthesis and characterization of novel, smart hybrid nanomaterials. Bastian Ebeling combines in this work synthetic polymers with inorganic nanoparticles from silica or gold.

The first chapters offer a comprehensive introduction to basics of polymer science and the applied methodologies. In following chapters, the author describes in detail how he systematically tailored the polymers using reversible addition-fragmentation chain transfer polymerization (RAFT) for combination with inorganic nanoparticles.

This work also unravels mechanistic, thermodynamic, and structural aspects of all building blocks and reaction steps. The method described here is simple to perform and opens up pathways to new sets of nanohybrid materials with potential applications as sensors, in energy conversion, or catalysis. Readers will find a unique picture of the step-by step formation of new complex nanomaterials. It offers polymer scientists a systematic guide to the formation and synthesis of a new class of responsive nanomaterials.

Inhaltsverzeichnis

Frontmatter

Introductory Part

Frontmatter

Chapter 1. Introduction and background

Abstract
This first chapter gives a theoretical introduction to the subjects of this thesis. After the general introduction, which also contains the main objectives for the performed work, the current state of research of the underlying field and the basics for the easy understanding of the results in the main part are outlined in the section “Theoretical background”. The key topics here are polymers, in particular RAFT polymerization, the very special properties of pNIPAm, and the relevant concepts of nanosciences, including the general pathways for the surface functionalization of nanomaterials with polymers.
Bastian Ebeling

Experimental

Frontmatter

Chapter 2. Instrumentation

Abstract
In this instrumental chapter, detailed information on all instruments used for synthesis and characterization experiments are given and the general experimental methods are explicated. This includes the acquirement of cloud points using the custom high-pressure set-up. Readers who are mainly interested in the results and the discussion can safely jump directly to Chapter 4 and only refer to this and the next chapter as a reference for experimental details.
Bastian Ebeling

Chapter 3. Substances

Abstract
In this chapter, all substances used in this thesis are listed along with the necessary spectroscopic results. If the substances have been synthesized within this work, the experimental protocols and polymerization data are given in a detailed way that allows for their reproduction. Readers who are mainly interested in the results and the discussion can safely jump directly to Chapter 4 and only refer to this and the previous chapter as a reference for experimental details.
Bastian Ebeling

Results

Frontmatter

Chapter 4. Analysis of microscopic images

Abstract
This chapter is dedicated to two microscopic techniques which work on the nanometer scale: transmission electron microscopy (TEM) and atomic force microscopy (AFM). Micrographs obtained with these techniques play a pivotal role for several further discussions in this work. In order to gather the information in one place, make it easier to find, and to not interrupt the flow of the remaining text, the general workflows to acquire and process the images and extract the desired data and information from them are explained here. Additionally, the explanations for typical features visible in several unrelated micrographs in the rest of the thesis are given.
Bastian Ebeling

Chapter 5. Building-block design

Abstract
This chapter deals with the design and the detailed characterization of the building blocks which were used for the phase-behaviour or functionalization experiments in the ensuing chapters. These building blocks are gold nanoparticles from different synthesis protocols, special RAFT agents, and different types of polymers of NIPAm prepared via RAFT polymerization.
Bastian Ebeling

Chapter 6. High-pressure phase behavior of aqueous pNIPAm solutions

Abstract
This chapter is dedicated to the study of the special responsive behavior of aqueous solutions of the pNIPAm samples prepared in the preceding chapter upon exertion of high pressures. After a detailed literature study on the current state of research regarding the high-pressure experiments and the outline of the experimental set-up, the effect of different parameters on the phase-behavior is examined systematically. Especially the addition of ethanol as a cononsolvent provides new insight into this kind of system. By the later combination with nanoparticles, the polymer’s special responsive features can be passed on to the resulting smart nanohybrids.
Bastian Ebeling

Chapter 7. Nanocomposites via Polymerization from Silica

Abstract
This chapter shows how the previously synthesized special RAFT agents can be immobilized on the surface of different types of silica substrates via methoxysilyl moieties located at the end of their stabilizing Z-groups. In subsequent surface-confined RAFT polymerizations, which give rise to particular polymer–silica nanocomposites according to a grafting-from approach, these adaptively designed RAFT agents can play to their special strengths: The doubly anchored RAFT agent leads to polymer loops on the surface of fumed silica through a polymerization mechanism in which the propagating radicals as well as the mediating groups remain attached to the surface. By the use of a RAFT agent with an anchor group only capable of forming a single covalent bond (rather than three as for a conventional RAFT agent in a control experiment), the crosslinking of colloidally dispersed carrier particles of silica during the immobilization process can successfully be prevented.
Bastian Ebeling

Chapter 8. Nanohybrids of Gold Particles

Abstract
In this chapter, it is outlined how the different types of previously synthesized gold nanoparticles can be functionalized with non-polymeric ligands of different types for stabilization and introduction of functional groups, especially hydroxyl and azido moieties, to which RAFT agents with complementary functionalities could then be coupled. In the second part, it is shown how the gold nanoparticles can be coated with NIPAm polymers bearing trithiocarbonate groups, which act as anchor units for the gold surface. When polymers with multiple trithiocarbonate groups incorporated along their backbone are used for the functionalization of gold nanoparticles, they are found to be wrapped around the gold nanoparticles with several gold–trithiocarbonate junctions, without crosslinking individual nanoparticles. These structures constitute a novel type of nanohybrid.
Bastian Ebeling

Chapter 9. Future perspectives

Abstract
In this chapter, selected experiments are presented which are seminal for more detailed systematic examinations. Also, possible future studies building upon concepts presented in this work are discussed.
Bastian Ebeling

Chapter 10. Conclusions

Abstract
With a view back to the initially stated goals for the presented work, some general conclusions are drawn from the results of this thesis.
Bastian Ebeling

Backmatter

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