Details

Autor(en) / Beteiligte

• Meier, Michael Andreas Robert

Titel

Facing current challenges in (supra-)macromolecular science: A high-throughput approach

Erscheinungsjahr

2006

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Current challenges in polymer science focus on the control of polymer architecture, molecular weight, end-group and other parameters. Scientists have realized that the synthesis of such complex and well-defined macromolecules possess major challenges as well as opportunities since novel chemical, physical and biological properties of the studied materials might be obtained in a controllable fashion. The advances made in the preparation of macromolecules due to the invention of controlled and living polymerization techniques in combination with specific organic reactions for end-group modifications or the preparation of functional monomers offer the synthetic chemist the right tools to address these challenges. However, this enormous parameter space is difficult to tackle and requires the combination of the synthetic techniques with a detailed structure and property characterization. Therefore, combinatorial and parallel approaches in combination with efficient screening methods seem to be the perfect solution to investigate this parameter space. This thesis describes several aspects of combinatorial, parallel and automated approaches in polymer science covering the necessary development of new detailed characterization techniques as well as the synthesis of novel macromolecules with defined architectures and their property evaluation. In particular, automated and parallel approaches in three different fields of research were addressed, namely: high-throughput screening by MALDI-TOFMS, micellar systems of biocompatible block copolymers and supramolecular metal-containing polymers. The first part describes the development and evaluation of a new sample preparation technique for MALDI-TOFMS that allowed the integration of MALDI-TOFMS as a high-throughput screening technique into the workflow of combinatorial materials research (CMR). Therefore, a novel multiple-layer sample preparation technique for synthetic polymers was invented and evaluated revealing improved analytic results. Subsequently, this technique could be automated and integrated into synthetic robots in order to provide a new screening technique for polymer libraries. In a final step of automation and miniaturization this sample preparation technique could be transferred to ink jet printing technology opening the way for ultra high-throughput approaches. Moreover, two application examples of the developed techniques are discussed, namely the investigation of a library of poly(2-oxazoline)s and the online monitoring of reversible addition fragmentation transfer (RAFT) polymerizations of methyl methacrylate (MMA). In general, this multiple-layer spotting technique provided significantly improved analytical results for a large variety of synthetic polymers, could be automated in straightforward fashions, saved valuable sample preparation time and was therefore very well suited for screening approaches in CMR. The second part describes the synthesis and characterization of block copolymers of poly(ethylene glycol) and poly(epsilon-caprolactone). In particular, linear and star-shaped block copolymers were prepared and characterized in detail. Their micellar properties were investigated utilizing self-developed high-throughput screening assays revealing structure-property relations concerning the guest encapsulation behavior for the linear block copolymers. Moreover, the star-shaped block copolymers showed an interesting reversed unimolecular micellar behavior and were able to encapsulate and phase transfer a large variety of different guest molecules. This encapsulation behavior could be correlated to the macromolecular structure and it was for instance observed that the maximum loading of guest molecules within a reversed unimolecular micelle was independent of the chain length of the poly(epsilon-caprolactone) comprising the corona of these micelles. Moreover, the guest transport of both micellar systems could be confirmed by analytical ultracentrifugation experiments. Finally, the star-shaped block copolymers could be used as templates for the synthesis of defined palladium nanoparticles, which could successfully be applied as catalysts for C-C coupling reactions. The last part of this thesis describes the synthesis and detailed characterization of metal-containing supramolecular polymers based on terpyridine ligands. The investigations were started due to the need of improved characterization methods for these polymers. A MALDI-TOFMS model study revealed the relative binding strength of the terpyridine ligand for a large variety of different transition metal ions that are frequently used in these supramolecular polymers, whereas a size exclusion chromatography (SEC) study resulted in optimized chromatographic conditions for ruthenium-containing polymers. Especially the SEC study was crucial for the success of a subsequently performed parallel optimization of the reaction conditions of RuCl(3) with a defined low molecular weight bis-terpyridine ligand where it was applied as the major screening technique. These investigations led to the development of a new type of supramolecular ABA triblock copolymer based on a simple polycondensation strategy that revealed amphiphilic behavior and formed micelles in water. Finally, the investigation of a star-shaped supramolecular polymer by means of parallel high-throughput techniques led to the accelerated development of a new sensoric system for transition metal ions. This system is based on the encapsulation of fluorophores within a terpyridine end-group modified star-shaped polymer and quenching of the fluorescence due to metal complex formation. The described results clearly demonstrate that automated and parallel approaches in polymer science provide one possible solution to efficiently address current challenges in materials science. Generally, the study of the three different topics by these techniques led to a better understanding of the investigated subjects within a reduced time frame and revealed the effectiveness of the chosen approaches. In conclusion, the results obtained during the study of these subjects significantly extended the scientific knowledge in all three sub disciplines. Moreover, the addressed new application possibilities of the prepared macromolecular architectures as well as the developed screening techniques are not only useful for the combinatorial researcher but also provide significant advantages for the whole scientific community.