Ab Initio Study of the Penultimate Effect for the ATRP Activation Step Using Propylene, Methyl Acrylate, and Methyl Methacrylate Monomers

Abstract

High-level ab initio molecular orbital calculations are used to study the magnitude and origin of the penultimate unit effect in atom transfer radical polymerization (ATRP) of dimers involving the co-monomers methyl acrylate (MA), methyl methacrylate (MMA) and propylene (P). The penultimate unit effects depend on the nature of the terminal unit and the halogen and can be significant, with the MMA unit in particular altering the equilibrium constant for the bond dissociation equilibrium by as much as 2 orders of magnitude.Specifically, the ratio of the equilibrium constants (K) for the bond dissociation reactions of H-M 2 -M 1 -Cl at 298 K, relative to the equilibrium constant (K 0 ) of the corresponding unimer

Effect of Pressure on Activation–Deactivation Equilibrium Constants for ATRP of Methyl Methacrylate

“…Indeed, with 2,2′‐bipyridine as the ligand, k act has been determined to be eight times lower for methyl α‐bromo‐ iso ‐butyrate than for H‐MMA‐MMA–Br 15. The values estimated for K ATRP with H‐MMA–Br and H‐MMA‐MMA–Br species provide evidence for a significantly increased k act with the MMA‐MMA dimeric compound 16…”

Mechanism of supplemental activator and reducing agent atom transfer radical polymerization mediated by inorganic sulfites: experimental measurements and kinetic simulations

“…21 It should be noted that for kinetic modelling the same activation parameter k a1 = k a1p = (6.3 ± 0.9) × 10 3 M −1 s −1 was used for the activation of the MBrP and PMA–Br chain-end (Scheme 2, reactions (7) and (8), respectively), due to similarity in structure and reactivity. 56 …”

Predicting the Limit of Control in the ATRP Process: Results from Kinetic Simulations

“…The results suggest that the alkyl halide reduction potential should be in the range between À1 and À0.8 V (vs. SCE), rather than around À0.3, as the equilibrium constant calculated with the latter value is far from the (recalculated) experimental value. It should be noted, however, that the penultimate effect can have a significant impact on the ATRP equilibrium and a comparison between slightly different alkyl halide structures (i.e., MMA-Br and EBiB) might not be completely correct, [51,52] although the difference in E RX between these two alkyl halides was insignificant in the ab initio calculations [47] and should not affect the conclusions drawn here to any larger extent. …”