Polymerization-induced self-assembly via RAFT in emulsion: effect of Z-group on the nucleation step

Abstract

Polymerization-Induced Self-Assembly (PISA) has emerged as one of the most powerful and widely employed techniques for preparation of block copolymer and polymeric nanoparticles in dispersed systems. Its success relies on...

Synthesis of Poly(methacrylic acid)-block-Polystyrene Diblock Copolymers at High Solid Contents via RAFT Emulsion Polymerization

“…Very large particle radii of 85 nm and 96 nm were synthesized for 35 wt% and 40 wt% as measured by DLS, when replacing the propyl Z-group with a butyl Z-group. These results fit to the proposed mechanism from Zetterlund et al, which was also shown in Figure 8 for hydrophilic RAFT agents [53]. However, the very large deviation of Mn,exp from Mn,theo infers a not well-controlled polymerization.…”

“…In case of a hydrophilic RAFT agent, for example the CTA1 at very high solid concentrations of styrene (above 30 wt%), slow nucleation and polymerization occurs. The group of Zetterlund et al described that this phenomenon is caused by the Z-group induced RAFT exit [53]. The Z-group RAFT species is produced by the addition of a radical, entering a precursor particle and fragmentation afterwards to create a PMAA radical (pre-equilibrium of the RAFT mechanism, see Figure 9).…”

“…The hydrophilic RAFT species, in case only a few units of styrene were added, might exit the hydrophobic domains (shown in Figure 8) due to their different polarities. The loss of RAFT agent from the polymerization loci reduces the chain extension rate, thus, less amphiphilic chains will be created, which impact the colloidal stability negatively, leading to larger and fewer particles [53].…”

“…The hydrophilic RAFT species, in case only a few units of styrene were added, might exit the hydrophobic domains (shown in Figure 8) due to their different polarities. The loss of RAFT agent from the polymerization loci reduces the chain extension rate, thus, less amphiphilic chains will be created, which impact the colloidal stability negatively, leading to larger and fewer particles [53]. In previous publications, some authors have described the long inhibition period as well as no polymerization in a RAFT emulsion polymerization due to the exit of the radical R˙ from the particle (R group cleavage of the RAFT agent in the pre-equilibrium step of the RAFT mechanism), where it can terminate in the aqueous phase with another initiatorderived radical or after reentry with a growing chain in a particle [40,[54][55][56][57].…”

RAFT Emulsion Polymerization for (Multi)block Copolymer Synthesis: Overcoming the Constraints of Monomer Order

“…Implementation of RAFT polymerization in dispersed systems provides access to numerous types of polymeric nanoparticles of complex internal structure and morphology, [3][4] most notably via Polymerization-Induced Self-Assembly (PISA). [5][6][7] One of the most important features of RDRP and RAFT is the ability to prepare a wide range of block copolymers. 8 Such polymers are of interest for a multitude of reasons, which include potential applications in e.g.…”