Abstract
This work explores new ways of preparing reactive polymer-based nanoparticles prepared through polymerisation-induced self-assembly (PISA). PISA is an emerging and advantageous method to prepare well-defined diblock copolymer nanoparticles but the literature up until now has only demonstrated few examples of incorporating reactive functional groups. This work centres on the 2,3,4,5,6-pentafluorobenzyl (PFB) moiety - an underexplored reactive functionality - in the monomer 2,3,4,5,6-pentafluorobenzyl methacrylate (PFBMA). In order to explore the reactivity of the PFB group the monomer was reacted with sodium azide to give, in quantitative conversion, the 4-azido-2,3,5,6-tetrafluorobenzyl-functional species, a previously unreported compound. This species was further transformed into amine, amide, 1,2,3-triazole and amidine. Next, PFBMA was used in PISA formulations with poly[poly(ethylene glycol) methyl ether methacrylate] (pPEGMA) as macromolecular chain transfer agent. pPEGMApPFBMA nano-objects presented spheres, worms, or vesicles morphologies with examples of worms samples forming free-standing gels that underwent a reversible degelation and morphological transition to spheres upon heating. This work demonstrated that PFBMA is as versatile as the commonly used benzyl methacrylate. Significantly, however, the use of PFBMA allowed the inclusion of reactive functionality into the nanoparticle cores. This is novel as most literature-known examples of reactive PISA particles feature corona-reactive species. Herein, the reactivity of the PFB group towards nucleophilic aromatic substitution with thiols was exploited and several key advantages of the novel reactive PISA particles are highlighted: (i) the use of 1,8-octanedithiol to cross-link the cores prevented particles disintegration in non-selective solvents and resulted in the loss of the thermo-responsive behaviour; (ii) using polar thiols, particles underwent a order-disorder sphere-to-unimer transition, loosing their well defined character; (iii) large thiols resulted in size increase or order-order sphere-to-worm transition including gelation of worms. This latter case represents the first example of a chemically triggered morphological transition following an increase of the packing parameter. It is anticipated that the understanding gained in this work will contribute to the future development of reactive “universal nanoparticle precursors” that can be easily modified into functional nanoparticles with predictable size, shape, and behaviour on demand.