Samenvatting

In this research, acrylate crosslinked PEG-b-PS polymersomes were synthesized and extensively tested. Polymersomes are nanovesicles that are self-assembled from amphiphilic block copolymers. Like liposomes, they can contain aqueous solutions in the core, which makes them interesting in the field of nanomedicine. They can also act as nanoreactors by encapsulating enzymes and they can act as catalysts by covalently binding catalysts to the polymersome. A major restriction of the use of polymersomes as nanoreactor or catalyst is their stability in organic solvents. Polymersome membranes can be crosslinked to give them stability in organic solvents. The goal of this research was to develop a crosslinking method for PEG-b-PS polymersomes based on acrylate crosslinking. Hereto, an acrylate functionalized PEG-b-PS polymer was synthesized using RAFT-polymerization and a substitution reaction. This polymer was able to form polymersomes. The crosslinkable polymersomes were crosslinked by adding UV-initiator Irgacure 2959 before self-assembly and curing using UV light. At least 0.5 equivalents of UV-initiator are needed to crosslink the vesicles. A crosslinkable polymer with the thiocarbonyl thio group for RAFT-polymerization removed did not form polymersomes. The crosslinked polymersomes were tested for their stability in the organic solvents THF, ethanol, DCM and toluene. They showed excellent stability in these solvents for up to a month, although the crosslinked polymersomes in DCM and toluene turned to disc-shapes after the addition of the solvent. Crosslinked polymersomes can retain 10% non-crosslinkable polymer, as evidenced by fluorescence spectrometry. Possibly, up to 30% non-crosslinkable polymer can be retained in the crosslinked membrane. At 40% non crosslinkable polymer, the polymersomes begin to form holes in the membrane after addition to organic solvent. From 60% non-crosslinkable polymer onward, the structure starts to degrade. Freeze-drying of crosslinked polymersomes without lyoprotectant is possible, but the vesicles only retain their shape when put back in organic solvent. Shape transformation of crosslinkable polymersomes to stomatocytes was attempted in multiple ways, though these attempts did not succeed.