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The kinetics of gelation in the Activators Regenerated by Electron Transfer Atom Transfer Radical Polymerization (ARGET ATRP) of styrene, using a bifunctional initiator and no crosslinking agents are investigated. By applying the method of moments, we develop a system of differential equations that accounts for the formation of polymer rings. The kinetic rate constants of this model are optimized on the experimentally determined kinetics, varying the reaction temperature and ethanol fraction. Subsequently, we explore how variations in the amounts of catalyst, initiator, and reducing agents affect the simulated equilibria of ARGET ATRP, the emergence of gelation, and the swelling properties of the resulting networks. These findings suggest that favoring ring formation enhances the gelation phenomenon, supporting the hypothesis that the networks formed under the reported reaction conditions are olympic gels. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate the direct preparation of dihalo-γ-lactams featuring two distinct halogens from dichloroamides using a novel atom exchange radical cyclization (AERC) procedure. This method integrates the established atom transfer radical cyclization (ATRC) with halogen exchange in solution. The technique operates under mild conditions and requires small amounts of metallic copper, serving as both a supplemental activator and reducing agent. [ABSTRACT FROM AUTHOR]

Use of iron-based catalysts in atom transfer radical polymerization (ATRP) is very interesting because of the abundance of the metal and its biocompatibility. Although the mechanism of action is not well understood yet, iron halide salts are usually used as catalysts, often in the presence of nitrogen or phosphorous ligands (L). In this study, electrochemically mediated ATRP (eATRP) of methyl methacrylate (MMA) catalyzed by FeCl3, both in the absence and presence of additional ligands, was investigated in dimethylformamide. The electrochemical behavior of FeCl3 and FeCl3/L was deeply investigated showing the speciation of Fe(III) and Fe(II) and the role played by added ligands. It is shown that amine ligands form stable iron complexes, whereas phosphines act as reducing agents. eATRP of MMA catalyzed by FeCl3 was investigated in different conditions. In particular, the effects of temperature, catalyst concentration, catalyst-to-initiator ratio, halide ion excess and added ligands were investigated. In general, polymerization was moderately fast but difficult to control. Surprisingly, the best results were obtained with FeCl3 without any other ligand. Electrogenerated Fe(II) effectively activates the dormant chains but deactivation of the propagating radicals by Fe(III) species is less efficient, resulting in dispersity > 1.5, unless a high concentration of FeCl3 is used. [ABSTRACT FROM AUTHOR]

"Activator regenerated by electron transfer" "atom transfer radical polymerization" (ARGET ATRP) process catalyzed by CuCl2/tris(2-pyridylmethyl)amine (TPMA) (1/1) in ethyl acetate/ethanol (EtOAc/EtOH) for the polymerization of styrene from ethyl 2,2-dichloropropanoate (EDCP) is described. The (re)generation of the activating CuI complex is accomplished by Na2CO3 without the addition of any explicit reducing agent. Differently from the analogous process operating in the presence of ascorbic acid/carbonate as the reducing system, branching is not present and control over polymerization is improved. The activation mechanism should follow a composite route, where both EtOH and TPMA contribute to the regeneration of the catalyst. The oxidation of TPMA is suggested by the absence of the ligand in the final reaction mixture and by the reduction of CuII even in t-BuOAc/t-BuOH, notwithstanding the very poor ability of t-BuOH as a reducing agent. Oxidative degradation of TPMA causes a progressive malfunctioning of the redox catalyst. Consequently, the polymerization rate, after a prompt start, becomes slower and slower, fixing conversions at around 50% (4.5 h). This means a gradual decrease of the free radical concentration, which develops unfavorable conditions for the reductive coupling (termination) between the bifunctional growing chains, preserving a controlled growth of the polymer. [ABSTRACT FROM AUTHOR]