Modification of polyampholytic poly(dehydroalanine) : strategies and utilization in hybrid nanomaterials applied as smart dispersants, sensors and in photocatalysis

This thesis describes strategies towards the preparation of tailor-made polyampholytes based on polydehydroalanine (PDha). PDha, carrying amino and carboxylic moieties in each repeat unit, is characterized by a high charge density, stimuli-responsive behavior, tunable charge and the interaction with ions, small molecules and nanoparticles. Therefore, it is a promising water-soluble material to be implemented in hybrid materials and was applied as a smart dispersant, sensor or in photocatalysis. Within this thesis, PDha was modified via different synthetic routes and a straight-forward strategy was developed to obtain graft copolymers through the post-polymerization modification in water. This allowed the attachment of various side chains to tune the resulting polymer properties and solution behavior. In this regard, amphiphilic as well as double hydrophilic PDha-based graft copolymers were obtained. The amphiphilic polyampholytes were used as reversible, pH-responsive dispersants for carbon nanotubes. PDha-based graft copolymers containing hydrophilic poly(ethylene glycol) side chains were found to be suitable templates for the preparation of Au and Ag nanoparticles, as well as their nanoalloys. Here, the tunable overall charge of the PDha backbone was exploited to determine the resulting alloy composition. The attachment of N-isopropyl acryl amide gave triple stimuli-responsive polyampholytes (pH, T and metal ions). The interplay of these triggers was investigated and the polymer was used as a sensor for heavy metal cations. At last, a novel application field for polyampholytes was explored and double acidic graft copolymers (sulfonic and phosphonic acid side chains) were used as soft matrices for the light-driven hydrogen evolution from water. Therefore, various photocatalytically active components were hosted and linked by the polymeric matrix. The prepared multi-component hybrid materials showed an enhanced photocatalytic activity and high turnover numbers.



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