RESUMO
We report for the first time a reversible addition-fragmentation chain transfer polymerisation-induced self-assembly (RAFT-PISA) formulation in ionic liquid (IL) that yields worm gels. A series of poly(2-hydroxyethyl methacrylate)-b-poly(benzyl methacrylate) (PHEMA-b-PBzMA) block copolymer nanoparticles were synthesised via RAFT dispersion polymerisation of benzyl methacrylate in the hydrophilic IL 1-ethyl-3-methyl imidazolium dicyanamide, [EMIM][DCA]. This RAFT-PISA formulation can be controlled to afford spherical, worm-like and vesicular nano-objects, with free-standing gels being obtained over a broad range of PBzMA core-forming degrees of polymerisation (DPs). High monomer conversions (≥96%) were obtained within 2 hours for all PISA syntheses as determined by 1H NMR spectroscopy, and good control over molar mass was confirmed by gel permeation chromatography (GPC). Nanoparticle morphologies were identified using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), and further detailed characterisation was conducted to monitor rheological, electrochemical and thermal characteristics of the nanoparticle dispersions to assess their potential in future electronic applications. Most importantly, this new PISA formulation in IL facilitates the in situ formation of worm ionogel electrolyte materials at copolymer concentrations >4% w/w via efficient and convenient synthesis routes without the need for organic co-solvents or post-polymerisation processing/purification. Moreover, we demonstrate that the worm ionogels developed in this work exhibit comparable electrochemical properties and thermal stability to that of the IL alone, showcasing their potential as gel electrolytes.
RESUMO
Silicon-oxygen and silicon-nitrogen heterodehydrocoupling catalyzed by the commercially available cyclopentadienyl dicarbonyl iron dimer [CpFe(CO)2]2 (1) under photochemical conditions is reported. Reactions between alcohols and PhSiH3 with catalytic 1 under visible-light irradiation produced silyl ethers quantitively. Reactions between either secondary or tertiary silanes and alcohols also produced silyl ethers, however, these reactions were marked by their longer reaction times and lower conversions. Reactions of either primary or secondary amines and silanes with catalytic 1 demonstrated mixed efficiency, featuring conversions of 20-100%. Mechanistic study indicates that an iron silyl compound is unimportant in the bond-formation step and argues for either a nucleophilic alkoxide or amide intermediate. Most important, mechanistic study reveals that the most immediate hurdle in the catalysis is the poor activation of 1, demonstrating the necessity to fully activate the catalyst to realize the potential of iron in this reactivity.
RESUMO
Density Functional Theory (DFT) calculations using a consistent methodology accounting for solvation, dispersion and thermal effects have been used to study C-H activation of the simple directing group substrate 2-phenylpyridine (a-H). The computational model uses acetate (-OAc) and benzene to represent the carboxylate and arene co-ligands coordinated at a Ru organometallic complex. A variety of different mechanisms ranging from cationic to neutral, ion-paired, arene free, two substrates bound, and solvent (MeCN) coordinated have been explored. Computed results indicate that the cationic pathways from "B+", [(C6H6)Ru(OAc)(a-H)]+, and "D+ (η6)", [(η6-a-H)Ru(OAc)(a-H)]+, involve the lowest overall barriers to C-H activation. Consideration of solvent coordination leads to a complex variety of isomers and conformers. Here a neutral pathway with either one or two acetonitriles coordinated to the Ru centre give very low barriers to C-H activation.