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The cobalt-mediated radical polymerization (CMRP) of 1-vinyl-3-ethylimidazolium bromide (VEtImBr) is described. Polymerizations were performed at 30 °C in solution either in dimethylformamide (DMF) or in methanol (MeOH) or in a mixture of both solvents, using a preformed alkyl–cobalt(III) adduct, CH3OC(CH3)2CH2–C(CH3)(CN)–(CH2–CHOAc)<4–Co(acac)2, as the mediating agent. Excellent control over molecular weights and dispersities (Mw/Mn∼ 1.05–1.06) was achieved in MeOH, with a linear increase of experimental molecular weights with the monomer conversion. Substituting methanol for DMF induced much faster polymerization process, even under quite high diluted conditions: for instance, about 80% monomer conversion was reached in 30 min in DMF, compared to 10 h in MeOH. However, size exclusion chromatography (SEC) traces of PVEtImBr samples synthesized in DMF revealed a side population in the high molecular weight region, presumably due to the occurrence of irreversible coupling reactions of a small proportion of growing chains. Well-defined diblock copolymers featuring both a poly(vinyl acetate) (PVAc) block and a PVEtImBr-based poly(ionic liquid) block, PVAc-b-PVEtImBr, were next obtained by sequential CMRP of VAc and VEtImBr. To this end, a PVAc-Co(acac)2was first prepared by CMRP and employed as a macroinitiator for the polymerization of VEtImBr either in methanol or in a mixture of DMF and MeOH (2/1: v/v) at 30 °C. Finally, cobalt-mediated radical coupling (CMRC) of the aforementioned PVAc-b-PVEtImBr diblock copolymers, using isoprene as a simple coupling agent, led to unprecedented and structurally well-defined PVAc-b-PVEtImBr-b-PVAc triblock copolymers. [ABSTRACT FROM AUTHOR]

The protonation constant pKa2of l-norvaline has been determined in aqueous solution at different ionic strengths and different temperatures, using the pH-metric technique. The thermodynamic quantities (ΔG°, ΔH°, and ΔS°) have been studied and discussed. Evaluation of the effect of organic solvent of the medium on the protonation processes was also reported and discussed. The organic solvents used were methanol, dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetone, and dioxane. The pKa2values for the ionization in a water (1) + dioxane (2) mixture [100 w2= 10 %, 20 %, 30 %, 40 %, and 50 %] have been determined at five different temperatures from T= (288.15 to 308.15) K. The thermodynamic quantities were calculated. [ABSTRACT FROM AUTHOR]