RAFT polymerisation of pH-responsive monomers and the impact of polymer architecture on microalgae flocculation Valentin Beyer 1 , Jonas Blockx 1,2 , Ayessa Pires Macielab 3 , Sakshi Tyagia 2 , Irem Demir- Yilmaz 3 , Cécile Formosa-Dague 3 , Koenraad Muylaert 2 , Wim Thielemans 1 1 Sustainable Materials Laboratory, Department of Chemical Engineering, KU Leuven, Belgium, 2 Laboratory for Aquatic Biology, KU Leuven, Belgium, 3 TBI, Université de Toulouse, France Microalgae are a promising CO 2 -fixing feedstock which is gaining growing attention for the production of biofuel, the extraction of valuable fatty acids, and other high value chemicals. Despite the great potential of cultivating microalgae, their production and especially the isolation of the biomass remains economically unsustainable due to the high energy cost for harvesting. Since microalgae carry an overall negative surface charge, sedimentation can be induced by addition of cationic flocculants, which is a common harvesting technique. The presented work will investigate the structural impact of polymeric flocculants by assessing different macromolecular architectures, namely linear and branched polymers. RAFT copolymerisation of commercially available 2-(dimethylamino) ethyl methacrylate (DMAEMA) and a dimethacrylate crosslinker is demonstrated to be a suitable technique for the synthesis of the target architectures with different compositions. The polymer library is thoroughly analysed in order to confirm their absolute structure, molecular weight and solution properties. Furthermore, the results of flocculation tests on fresh- and salt water algae under various conditions are presented and a relationship between polymer architecture and flocculation efficiency is assessed. The flocculation process is further investigated by atomic force microscopy.
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