Mild-Temperature Mn₂(CO)₁₀-Photomediated Controlled Radical Polymerization of Vinylidene Fluoride and Synthesis of Well-Defined Poly(vinylidene fluoride) Block Copolymers

By contrast to typical high-temperature (100–250 °C) telo-/polymerizations of gaseous fluorinated monomers, carried out in high-pressure metal reactors, the visible light, Mn₂(CO)₁₀-photomediated initiation of vinylidene fluoride (bp = −83 °C) polymerization occurs readily from a variety of alkyl, semifluorinated, and perfluorinated halides at 40 °C, in low-pressure glass tubes and in a variety of solvents, including water and alkyl carbonates. Perfluorinated alkyl iodide initiators also induce a controlled radical polymerization via iodine degenerative transfer (IDT). While IDT proceeds with accumulation of the less reactive P_<i>m</i>-CF₂-CH₂-I vs the P_<i>n</i>-CH₂-CF₂-I chain ends, Mn₂(CO)₁₀ enables their subsequent quantitative activation toward the synthesis of well-defined poly­(vinylidene fluoride) block copolymers with a variety of other monomers

Metal and Ligand Effects of Photoactive Transition Metal Carbonyls in the Iodine Degenerative Transfer Controlled Radical Polymerization and Block Copolymerization of Vinylidene Fluoride

The metal and ligand effect of a series of transition metal carbonyls in conjunction with alkyl and perfluoroalkyl halides was investigated in the initiation and control of the visible light, radical photopolymerizations of vinylidene fluoride (VDF) and respectively, in the synthesis of PVDF block copolymers. No polymerization was observed for CpMn­(CO)_3, CpCo­(CO)₂, Cp₂Fe₂(CO)_4, Cp*₂Cr₂(CO)_4, Mo­(CO)₆, Fe­(CO)_5, Cr­(CO)₆, Co₂(CO)₈, Co₄(CO)₁₂, Fe₃(CO)₁₂, Ru₃(CO)₁₂, (PPh₃)₂Ni­(CO)₂, Cp₂Ti­(CO)₂, and Au­(CO)­Cl. A free radical polymerization, and respectively an iodine degenerative transfer, controlled radical polymerization was obtained for Mn₂(CO)₁₀ ∼ Re₂(CO)₁₀ ≫ Cp₂Mo₂(CO)₆ ≫ Cp₂W₂(CO)₆ with CH₃(CH₂)₅–Br, CH₃(CH₂)₅–I, CH₃–I, CCl₃–Cl, CCl₃–Br, Br–(CF₂)₆–Br, and respectively with CF₃(CF₂)₃–I and I–(CF₂)_4,6–I. Furthermore, while Fe­(CO)₅, Cp*Cr₂(CO)₄ and Co₄(CO)₁₂ led to ∼ CF₂–I bond insertion, Re₂(CO)₁₀, Mn₂(CO)₁₀, Cp₂W₂(CO)₆, Cp₂Mo₂(CO)₆ and Cp₂Fe₂(CO)₄ provided quantitative radical activation of both PVDF–CH₂–CF₂–I and PVDF–CF₂–CH₂–I chain ends, and were employed in the synthesis of well-defined ABA triblock PVDF copolymers with vinyl acetate, <i>tert</i>-butyl acrylate, methyl methacrylate, isoprene, styrene, and acrylonitrile

Stabilization of Graphene Sheets by a Structured Benzene/Hexafluorobenzene Mixed Solvent

Applications requiring pristine graphene derived from graphite demand a solution stabilization method that utilizes an easily removable media. Using a combination of molecular dynamics simulations and experimental techniques, we investigate the solublization/suspension of pristine graphene sheets by an equimolar mixture of benzene and hexafluorobenzene (C₆H₆/C₆F₆) that is known to form an ordered structure solidifying at 23.7 °C. Our simulations show that the graphene surface templates the self-assembly of the mixture into periodic layers extending up to 30 Å from both sides of the graphene sheet. The solvent structuring is driven by quadrupolar interactions and consists of stacks of alternating C₆H₆/C₆F₆ molecules rising from the surface of the graphene. These stacks result in density oscillations with a period of about 3.4 Å. The high affinity of the 1:1 C₆H₆/C₆F₆ mixture with graphene is consistent with observed hysteresis in Wilhelmy plate measurements using highly ordered pyrolytic graphite (HOPG). AFM, SEM, and TEM techniques verify the state of the suspended material after sonication. As an example of the utility of this mixture, graphene suspensions are freeze-dried at room temperature to produce a sponge-like morphology that reflects the structure of the graphene sheets in solution