NEW FLUOROHYDRATE SYSTEMS FOR THE DEVELOPMENT OF INNOVATIVE SYNTHETIC AND PRODUCTION PROCESSES

Hydrofluoric acid (HF) is an essential chemical with applications across a wide range of industrial and technological sectors, from the glass and electronics industries to the synthesis of fine chemicals and functional polymers. However, its high toxicity and corrosiveness make it a highly hazardous and difficult-to-handle compound. In this context, translating HF chemistry into solid polymeric reagents represents a simple and effective strategy to improve the safety of synthetic protocols involving this acid. In this work, the reactivity of several organic mixtures containing HF (MIX·HF) toward silyl ether deprotection was evaluated under mild conditions. Deprotection of the bis(tert-butyldiphenylsilyl) ether of tyrosol was selected as the model reaction owing to the presence of both an alkyl and a phenolic silyl ether. The reaction kinetics and selectivity were shown to depend not only on the nature of the MIX·HF reagent but also on the chemical environment surrounding the protecting group, thus opening the possibility of performing orthogonal protection-deprotection strategies by simply selecting the appropriate combination of protecting group and MIX·HF reagent. Coordination of HF with polymer resins can be achieved through the preparation of core-shell systems in which the outer layer consists of polymer brushes designed to mimic the chemistry of MIX·HF reagents. The inert polystyrene core was synthesized via dispersion polymerization of styrene, and the effect of adding divinylbenzene (DVB) as a cross-linker on particle morphology was evaluated. Copolymerization of styrene with an inimer (initiator-monomer) enables the modification of the particles by growing polymer brushes covalently grafted onto their surface. Surface-initiated atom transfer radical polymerization (SI-ATRP) of HF-coordinating monomers from polystyrene particles functionalized with tertiary bromides resulted in rapid and poorly controlled polymerization, leading to the formation of a thick polymer shell surrounding the polystyrene cores. To overcome limitations of conventional dispersion polymerization, we envisioned the use of a reversible addition-fragmentation chain-transfer polymerization-induced self-assembly (RAFT-mediated PISA) process to obtain micron-sized functional polystyrene particles by dispersion polymerization without the need for additional stabilizers. The amount of a macromolecular chain-transfer agent (macroCTA) based on poly(4-vinylpyridine) bearing a trithiocarbonate end group (P4VP-CTPP) was optimized to obtain micrometric polystyrene particles in ethanol. Control experiments performed with P4VP lacking the trithiocarbonate chain end highlighted the importance of forming P4VP-b-PS to ensure stabilization of the growing micro-particles. A further advance concerns tolerance toward oxygen during surface-initiated reversible deactivation radical polymerizations (SI-RDRP), essential for scaling up polymer brush fabrication. Using surface-initiated photoinduced ATRP (SI-photoATRP) as a model, we demonstrated that careful adjustment of Cu-catalyst and “free” initiator concentrations can suppress oxygen inhibition, reduce edge effects, and yield thick, uniform brushes even under air-exposed conditions. Finally, the study introduces a new method for detaching polymer brushes from silicon or silica surfaces, an important step for chemical characterization. Conventional aqueous HF is widely used for this purpose, especially for degrafting challenging polymers such as POEGMA. We showed that selected MIX·HF reagents can completely detach POEGMA brushes from flat silicon substrates within one hour under sonication. This development highlights the promise of MIX·HF systems as safer, efficient alternatives for post-polymerization processing.