Weak polyelectrolytes for the reversible binding of metal cations : applications in separation membranes and solution nanostructures

In this thesis, pathways towards membranes bearing various polyelectrolytes or polyzwitterions were investigated. In the first three parts polymerisation, coupling and quarternisation reactions aiming towards membranes containing polydehydroalanine (PDha), betains based on poly (2-vinylpyridine) (P2VP) or poly(2-acrylamidogylycolic acid) (PAGA) were explored, respectively. Moreover, the solution self-assembly and additional physical properties were investigated for block copolymers containing P2VP and PAGA. In the fourth and final part, the obtained membranes are characterised in detail and compared regarding their performance to react on external stimuli in terms of water flux and adsorption of charged species. Despite problems regarding the synthesis or quarternisation of the necessary polymers, membranes could be obtained containing all of the targeted polyelectrolytes or precursors thereof. Most difficulties were faced regarding the synthesis of amphiphilic poly (styrene co isoprene) block poly (tert -butoxycarbonylamino-methylacrylate) (P(S co I) b PtBAMA) diblock terpolymers. Isoprene as comonomer prevented a sequential polymerisation via ATRP while tBAMA was found to be inaccessible for RAFT polymerisation. Instead of an approach using sequential polymerisation, chain coupling was attempted via hetero Diels-Alder reaction. An approach based on the self-assembly of amphiphilic diblock terpolymers containing styrene, isoprene and 2-vinylpyridine allowed the successful manufacture of membranes that could moreover be quarternised yielding the desired polyzwitterion-functionalised membranes. Additionally, the surface functionalisation of track-etched membranes with poly(N-acetyl dehydroalanine) PNADha and PAGA was investigated using scanning electron microscopy, contact angle and permeability measurements as well as the adsorption of methylene blue.


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