Versatile Approach for the Synthesis of Sequence-Defined Monodisperse 18- and 20-mer Oligoacrylates

Linear monodisperse 18- and 20-mer acrylates are obtained via consecutive synthesis of two sequence-defined acrylate 9- and 10-mers, followed by disulfide coupling utilizing reversible addition–fragmentation chain transfer (RAFT) end group chemistry. The sequence-defined oligoacrylates are accessed via consecutive single (SUMI) and multiple (MUMI) unit monomer insertions through RAFT polymerization, using the extensive acrylate monomer library as functional building blocks. Aminolysis of the trithiocarbonate macroRAFT end group and in situ oxidation of the thiols to form a disulfide bridge lead to the formation of 18- and 20-mer acrylates. In this approach, one or multiple acrylate building blocks can be inserted in each step by chain extension to form a stable carbon–carbon backbone. Isolation of the targeted monodisperse oligomers, from the statistical mixtures obtained at first, is performed by flash column chromatography with high efficiency. It is shown that the SUMI and MUMI strategy, when combined with flash column chromatography separation, is highly efficient and allows to construct monodisperse materials of very considerable length starting from cheap and very versatile building blocks

Visible Light-Mediated Polymerization-Induced Self-Assembly Using Continuous Flow Reactors

We present the synthesis of polymeric nanoparticles of targeted morphology in a continuous process via visible light-mediated aqueous RAFT polymerization-induced self-assembly (PISA). A trithiocarbonate-derived poly­(ethylene glycol) (PEG) macroRAFT was activated in the presence of hydroxypropyl methacrylate (HPMA) at 37 °C under blue light irradiation (460 nm), leading to the formation of PEG-<i>b</i>-P­(HPMA) nanoparticles. The method is attractive in its simplicityspheres, worms, and vesicles can easily be obtained in a continuous fashion with higher control in comparison to conventional batch procedures. This allows for more accurate production of particle morphologies and scalable synthesis of these nano-objects. The versatility of this process was demonstrated by the <i>in situ</i> encapsulation of an active compound

Reversible Surface Engineering via Nitrone-Mediated Radical Coupling

Efficient and simple polymer conjugation reactions are critical for introducing functionalities on surfaces. For polymer surface grafting, postpolymerization modifications are often required, which can impose a significant synthetic hurdle. Here, we report two strategies that allow for reversible surface engineering via nitrone-mediated radical coupling (NMRC). Macroradicals stemming from the activation of polymers generated by copper-mediated radical polymerization are grafted via radical trapping with a surface-immobilized nitrone or a solution-borne nitrone. Since the product of NMRC coupling features an alkoxyamine linker, the grafting reactions can be reversed or chain insertions can be performed via nitroxide-mediated polymerization (NMP). Poly­(<i>n</i>-butyl acrylate) (<i>M</i>_n = 1570 g·mol^–1, <i>D̵</i> = 1.12) with a bromine terminus was reversibly grafted to planar silicon substrates or silica nanoparticles as successfully evidenced via X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry, and grazing angle attenuated total reflection Fourier-transform infrared spectroscopy (GAATR-FTIR). NMP chain insertions of styrene are evidenced via GAATR-FTIR. On silica nanoparticles, an NMRC grafting density of close to 0.21 chains per nm² was determined by dynamic light scattering and thermogravimetric analysis. Concomitantly, a simple way to decorate particles with nitroxide radicals with precise control over the radical concentration is introduced. Silica microparticles and zinc oxide, barium titanate, and silicon nanoparticles were successfully functionalized