May Trifluoromethylation and Polymerization of Styrene Occur from a Perfluorinated Persistent Radical (PPFR)?

The radical polymerization of styrene (St) initiated by a trifluoromethyl radical generated from a perfluorinated highly branched persistent radical (PPFR) is presented with an isolated yield above 70 %. The release of ^. CF₃ radical occurred from a temperature above 85 °C. Deeper ¹ H and ¹⁹ F NMR spectroscopies of the resulting fluorinated polystyrenes (CF₃ -PSts) evidenced the presence of both CF₃ end-group of the PSt chain and the trifluoromethylation of the phenyl ring (in meta-position mainly). [PPFR]₀ /[St]₀ initial molar ratios of 3:1, 3:10 and 3:100 led to various molar masses ranging from 1750 to 5400 g mol^-1 in 70-86 % yields. MALDI-TOF spectrometry of such CF₃ -PSts highlighted polymeric distributions which evidenced differences between m/z fragments of 104 and 172 corresponding to styrene and trifluoromethyl styrene units, respectively. Such CF₃ -PSt polymers were also compared to conventional PSts produced from the radical polymerization of St initiated by a peroxydicarbonate initiator. A mechanism of the polymerization is presented showing the formation of a trifluoromethyl styrene first, followed by its radical (co)polymerization with styrene. The thermal properties (thermal stability and glass transition temperature, T_g ) of these polymers were also compared and revealed a much better thermal stability of the CF₃ -PSt (10 % weight loss at 356-376 °C) and a T_g of around 70 °C.

Site-Specific C(sp3 )-H Aminations of Imidates and Amidines Enabled by Covalently Tethered Distonic Radical Anions

The utilization of N-centered radicals to synthesize nitrogen-containing compounds has attracted considerable attention recently, due to their powerful reactivities and the concomitant construction of C-N bonds. However, the generation and control of N-centered radicals remain particularly challenging. We report a tethering strategy using SOMO-HOMO-converted distonic radical anions for the site-specific aminations of imidates and amidines with aid of the non-covalent interaction. This reaction features a remarkably broad substrate scope and also enables the late-stage functionalization of bioactive molecules. Furthermore, the reaction mechanism is thoroughly investigated through kinetic studies, Raman spectroscopy, electron paramagnetic resonance spectroscopy, and density functional theory calculations, revealing that the aminations likely involve direct homolytic cleavage of N-H bonds and subsequently controllable 1,5 or 1,6 hydrogen atom transfer.

Influence of the Molar Mass on Long-Chain Branching of Polypropylene

Long-chain branching (LCB) with peroxydicarbonates (PODIC) is known as a suitable post-reactor process to introduce strain-hardening behaviour and an increase of melt strength to a linear polypropylene (PP). This opens up new possibilities for processing and therefore application. Especially in the case of adding value to PP post-consumer waste, LCB is a promising approach. LCB takes place by a combination of chain scission and recombination after radical activation of the PP macromolecule. However, chemical modification of post-consumer waste is challenging because of the inhomogeneous composition and the manifold number of PP grades. The influence of the molar mass of the linear PP precursor on this reaction was studied with different PP grades ranging from extrusion grade to injection moulding grade. To exclude side effects, all PP grades had similar polydispersity indices. A PP with higher molar mass undergoes significant chain scission during the LCB process compared to a PP with low molar mass for injection moulding. Therefore, the two grades differ significantly in their branching number, which influences their behaviour in elongational flow.

Towards new strategies for the synthesis of functional vinylidene fluoride-based copolymers with tunable wettability

–COOH functionalized poly(vinylidene fluoride) prepared using water-based non-fluorinated solvents displays tunable wettability suitable for potential application in coating, oil recovery and water purification.