Homogeneous radical polymerization of 2‐hydroxyethyl methacrylate mediated by cyclometalated cationic Ruthenium(II) complexes with PF₆⁻ and Cl⁻ in protic media

Abstract

Cationic coordinatively saturated complexes of ruthenium(II), [Ru(o-C 6 H 4 -2-py)(phen)(MeCN) 2 ] þ , bearing different counterions of PF 6 À and Cl À have been used in the radical polymerization of 2-hydroxyethyl methacrylate in protic media and acetone under homogeneous conditions. Exchange of PF 6 À by Cl À increases the solubility of the complex in water.Both complexes led to the fast polymerization under mild conditions, but control was achieved only in methanol and acetone and was better for the complex with Cl À . The polymerization accelerated in aqueous media and proceeded to a high conversion even with a monomer/catalyst ¼ 2000/1, but without control. Polymerization mediated by complex bearing Cl À was slower in protic solvents but faster in acetone and always resulted in lower molecular weight polymers. Thus, the nature of the anion strongly affected the catalytic activity of the complexes and may serve as way of fine-tuning the catalytic properties.

Synthesis of Poly(2-Acrylamido-2-Methylpropane Sulfonic Acid) and its Block Copolymers with Methyl Methacrylate and 2-Hydroxyethyl Methacrylate by Quasiliving Radical Polymerization Catalyzed by a Cyclometalated Ruthenium(II) Complex

“…As can be seen in Figure 3, the Mn increased with conversion and a narrow molecular weight distribution is obtained (in the range of 1.22-1.55). A discrepancy was observed between the theoretical (Mn-t) and experimental Mn values due to the difference in the hydrodynamic volume between PAMPS, which is hydrophilic, and the hydrophobic calibration standard (PMMA) [21,33,35]. On the other hand, the polymerization of AMPS in DMF catalyzed by [Ru(o-C 6 H 4 -2-py) (phen)(MeCN) 2 ]PF 6 was slightly slower-reaching a conversion of 61% in 8 h and 74% in 10 h-than the aforementioned systems.…”

“…As shown in Figure 2, the study of the reaction kinetics in water:DMF showed a slow initiation, with an induction period of around 2 h and a considerable increase in viscosity from the fourth hour. This can be attributed to low efficiency of the initiator caused by the decrease of the solubility of EBiB in aqueous media or the spontaneous polymerization capacity of this type of acid monomer in aqueous solutions [21,31,32]. With regard to the spontaneous polymerization of AMPS in the presence of water, the dependence of the initial polymerization rate on the neutralization degree was reported.…”

“…A significant increase is observed in molecular weight in copolymers with 12 and 25% mol PAMPS from 37.050 to 78.520 and from 42.400 to 68.000, respectively, with a reduction in the Ð with respect to the PAMPS macroinitiator, indicating the efficient formation of the copolymer. Furthermore, the curves of the copolymers were monodispersed and symmetrical, attributed to the absence of impurities or dead chains of the macroinitiator [21,43]. It is worth noting that the copolymers presented bimodal curves when they originated from a PAMPS macroinitiator synthesized in a reaction of less than 16 h, due to the propagation of the MMA monomer with unreacted AMPS monomer [11].…”

“…Ruthenium catalysts in ATRP have been described as more tolerant to several functional groups with good solubility in protic and aprotic solvents, which permit quasiliving polymerization in polar media [21][22][23]. In particular, series of cationic 18-electron coordinatively saturated cyclometalated ruthenium(II) complexes have been successfully applied in homopolymerizations and copolymerizations of hydrophobic and hydrophilic monomers [21,[24][25][26]. The use of cyclometalated ruthenium(II) complexes can eliminate the undesired copper-promoted side reactions.…”

A new initiating system based on [(SiMes)Ru(PPh3)(Ind)Cl2] combined with azo-bis-isobutyronitrile in the polymerization and copolymerization of styrene and methyl methacrylate

“…Under biphasic conditions (aqueous/organic), these cationic systems led to the radical polymerization of methyl methacrylate and styrene, in which the resulting polymers had narrow molecular weight distributions. Cationic complexes of ruthenium (II), such as [Ru(o-C 6 H 4-2 -py)(phen)(MeCN) 2 ] + , bearing different counter ions of and Cl − were used by Diaz et al [ 23 ] in the radical polymerization of 2-hydroxyethyl methacrylate in protic solvents and acetone, under homogeneous conditions. The exchange of by Cl − led to an increase in the solubility of the complex in water.…”