Reactive Polymorphic Nanoparticles: Preparation via Polymerization‐Induced Self‐Assembly and Postsynthesis Thiol–para‐Fluoro Core Modification

The use of 2,3,4,5,6‐pentafluorobenzyl methacrylate (PFBMA) as a core‐forming monomer in ethanolic reversible addition–fragmentation chain transfer dispersion polymerization formulations is presented. Poly[poly(ethylene glycol) methyl ether methacrylate] (pPEGMA) macromolecular chain transfer agents were chain‐extended with PFBMA leading to nanoparticle formation via polymerization‐induced self‐assembly (PISA). pPEGMA‐pPFBMA particles exhibited the full range of morphologies (spheres, worms, and vesicles), including pure and mixed phases. Worm phases formed gels that underwent a thermo‐reversible degelation and morphological transition to spheres (or spheres and vesicles) upon heating. Postsynthesis, the pPFBMA cores were modified through thiol–para‐fluoro substitution reactions in ethanol using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene as the base. For monothiols, conversions were 64% (1‐octanethiol) and 94% (benzyl mercaptan). Spherical and worm‐shaped nano‐objects were core cross‐linked using 1,8‐octanedithiol, which prevented their dissociation in nonselective solvents. For a temperature‐responsive worm sample, cross‐linking additionally resulted in the loss of the temperature‐triggered morphological transition. The use of the reactive monomer PFBMA in PISA formulations presents a simple method to prepare well‐defined nano‐objects similar to those produced with nonreactive monomers (e.g., benzyl methacrylate) and to retain morphologies independent of solvent and temperature. Polymer nanoparticles with tuneable morphologies, temperature‐responsiveness, and reactive cores are prepared through reversible addition–fragmentation chain transfer dispersion polymerization and polymerization‐induced self‐assembly based on 2,3,4,5,6‐pentafluorobenzyl methacrylate. Para‐fluoro substitution with a dithiol successfully cross‐linked nanoparticles, resulting in temperature‐independent morphology retention in nonselective solvents.