No abstract

Ruthenium(II) complexes of Schiff base derived from cycloalkylamines (cycloalkyl ¼ cyclopentyl (1a), cyclohexyl (1b), cycloheptyl (1c), and cyclooctyl) (1d) were synthesized: [RuCl(CyPen-Salen)(PPh 3) 2 ] (2a), [RuCl(CyHex-Salen)(PPh 3) 2 ] (2b), [RuCl(CyHep-Salen)(PPh 3) 2 ] (2c), and [RuCl(CyOct-Salen)(PPh 3) 2 ] (2d). The Schiff base-Ru II complexes 2a-d were characterized by elemental analysis, FTIR, UV-Vis, 1 H-, 13 C and 31 P NMR, and cyclic voltammetry. The complexes 2a-d were evaluated as catalytic precursors for ROMP of norbornene (NBE) and for ATRP of methyl methacrylate (MMA). The syntheses of polynorbornene (polyNBE) via ROMP with complexes 2a-d as pre-catalysts were evaluated under different reaction conditions ([HCl]/[Ru], [EDA]/[Ru], [NBE]/[Ru], and temperature). The highest yields of polyNBE were obtained with [NBE]/[HCl]/[Ru] ¼ 5000/25/1 M ratio in the presence of 5 mL of EDA for 60 min at 50 C. MMA polymerization via ATRP was conducted using the complexes 2a-d in the presence of ethyla-bromoisobutyrate (EBiB) as initiator. The catalytic tests were evaluated as a function of the reaction time using the initial molar ratio of [MMA]/[EBiB]/[Ru] ¼ 1000/2/1 at 85 C. The linear correlation of ln([MMA] 0 /[MMA]) and time indicates that the concentration of radicals remains constant during the polymerization and that the ATRP of MMA mediated by 2a-d proceeds in a controlled manner. Molecular weights increased linearly with conversion, however, the experimental molecular weights were higher than the theoretical ones.

Atom-Transfer Radical Copolymerization (ATRP) of methyl methacrylate (MMA) and ethyl methacrylate (EMA) under different reaction conditions was conducted using Grubbs 1 st (1) and 2 nd (2) generation catalysts. Initially, the study focused on the reactivity of the catalysts in ATRP of EMA individually, then the syntheses of poly(MMA-co-EMA) were also conducted in different mixtures of monomers ([MMA]/[EMA] = 100/200 and [MMA]/[EMA] = 200/100). Conversion and semilogarithmic kinetic plots as a function of time were related to the different catalysts and reaction conditions. The values of M n and PDI also changed when different catalysts were used in the presence of Al(OiPr) 3 , and more controlled polymerizations were achieved using 1. In the syntheses of poly(MMA)-co-(EMA), conversion of 60% was reached for both catalysts at different [MMA]/[EMA] ratios for 16 h; however, for shorter time, 4 h, better conversion values were obtained using 1 as catalyst for both [MMA]/[EMA] = 100/200 or 200/100.