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theses

Boron-containing polymers have received tremendous attention over the past decades due to the diverse potential applications, including their use as polymer-supported catalysts, in drug delivery, optoelectronic materials, and sensors for anions. The ability of the empty pB-orbital in tri-coordinate boranes to delocalize π–electrons and to form Lewis acid-base complexes is widely applied in Lewis acid catalysis, supramolecular assembly, and the development of luminescent materials. Here we focus on the incorporation of tri-coordinate borane moieties into the side chains of polystyrene (PS) and its derivatives for catalysis applications. An alternative strategy to incorporate boron into polymeric systems is the replacement of a C-C unit for an isosteric B-N unit. Nowadays, the study of carbon-boron-nitrogen (CBN) heterocycles has become one of the most popular topics in organic and materials chemistry. Numerous BN-embedded aromatic compounds have been synthesized. Thus, in a second direction of this thesis, we targeted new azaborine-substituted polymers, with the goal of expanding the diversity and functionality of polystyrene via BN for CC substitution.

We designed a new class of polymers that feature bulkier groups in the ortho-position to boron to stabilize the borane moiety. The attachment of the tailored triarylborane moieties to the polyolefin backbone provides access to new polymer-supported Lewis acids with improved stability and recyclability that we applied in the catalytic hydrosilylation of unsaturated organic substrates. In addition, we discovered that both the model compounds and copolymers are strongly luminescent, and display thermally activated delayed fluorescence (TADF), a phenomenon that is attracting much current interest.
To expand the diversity and functionality of polystyrenes via BN for CC substitution, we successfully prepared a series of new isomeric azaborine-substituted polymers with high molecular weights via standard free-radical polymerization. Furthermore, we investigated the effects of the position of the vinyl group relative to the BN moiety on the polymerization reactivity and physical properties of the respective polymers. The results revealed that the reactivity and physical properties strongly depends on the substitution pattern. Lastly, the ring opening metathesis polymerization of BN Dewar isomers was accomplished with Grubbs 2nd generation catalyst. The synthesized polymer features four-membered BN-heterocycles alternating with vinylene groups in the main chain.

ETD_11118

Ph.D.

Includes bibliographical references

ETD doctoral

doi:10.7282/t3-tzjd-bq56

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