Tuning of polymer nanoparticle morphology via polymerization-induced self-assembly

Polymeric nanoparticles have attracted great attention in a variety of areas such as the field of nanomedicine, microelectronics and catalysis. The traditional focus has been on spherical particles, because this geometry is the most accessible from a synthesis perspective. Polymerization-induced self-assembly (PISA), which is most commonly based on reversible deactivation radical polymerization (RDRP), has emerged as a very useful method for synthesis of a wide range of morphologies beyond spherical particles. PISA enables synthesis of higher order morphologies such as worms and vesicles, as well as other more exotic morphologies. The basis of PISA is in situ formation of an amphiphilic diblock copolymer which self-assembles during the polymerization, thus giving rise to particle formation. This thesis mainly focuses on PISA implemented as dispersion polymerization involving stimuli responsive polymers via reversible addition-fragmentation transfer (RAFT) polymerization. The basic notion is that the physical and chemical properties of the macroRAFT agent (the first block) changes in responsive to external triggers. It is demonstrated that manipulation of extrinsic parameters such as the solution pH, ionic strength or CO2 pressure can be used to tune the particle morphology. This thesis also demonstrates a novel approach for implementation of PISA via conventional “non-living” radical polymerization based on addition-fragmentation chain transfer (AFCT) polymerization. This way of synthesising diblock copolymer and self-assemble to (nano)particles is entirely different from a living polymerization. Diblock copolymers of fixed length are generated throughout the polymerization (unlike in RDPR, where the chain length increases with conversion) and accumulate continuously during the polymerization. Spheres, worms and vesicles can be accessed by altering the length of the solvophobic block. This approach may have the potential to significantly expand the scope of PISA for synthesis of sulfur-free (nano)particles with different morphologies. This body of work spans the range of current research in the growing PISA field. The innovative approaches of tuning particle morphology provide interesting perspective for stimulus-responsive PISA. The successful implementation of AFCT in PISA broadens the chemical nature of synthesising copolymers in heterogeneous system, paving the way towards new applications of PISA-derived nanoparticles