Browsing by Author "Häkkinen, Satu"

Preparation of polymer nanoparticles has become of great interest to polymer scientists due to their wide range of applications. Block copolymer nano-objects have been studied for decades, however new production methods are still needed to achieve better commercial viability and thus a wider use of the materials. Polymerization-induced self-assembly (PISA) is a new approach to preparing block copolymer nanoparticles, in which the polymerization of the second block and the self-assembly of the particles are achieved in one step. The method exploits the growing insolubility of the propagating chain to induce the self-assembly already during the polymerization, yielding nano-objects of various morphologies. The approach has gained significant attention in the last few years, and its popularity is expected to grow in the future. This thesis presents the fundamentals of PISA, while offering insight into both the benefits and challenges of the method. The focus of the work is on aqueous emulsion RAFT PISA formulations. Additionally, a new method for the preparation of poly(ethylene glycol)-block-poly(N-vinylcaprolactam) nanoparticles through PISA was developed. The synthesis exploited the lower critical solution temperature behaviour of poly(N-vinylcaprolactam) by conducting the polymerization of said block above its phase transition temperature in water. The polymerizations were carried out as RAFT reactions in emulsion and the resulting particles were characterized by dynamic light scattering. The method yielded particles of 200 nm in diameter that dissolved in water upon cooling to room temperature. Moreover, the purified and dried polymers were analysed using size-exclusion chromatography, NMR spectroscopy and turbidimetry. Preliminary tests showed that the stable particles can be physically crosslinked with salicylic acid to prevent dissolution upon cooling.