Mechanism of Controlled/“Living” Radical Polymerization of Styrene in the Presence of Nitroxyl Radicals. Kinetics and Simulations

Abstract

The polymerization of styrene in the presence of a stable radical, TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy), has been simulated using a Predici simulations package. On the basis of the experimental data, a kinetic model for the TEMPO-mediated polymerization of styrene is proposed. In order to simulate the experimental data properly, it was necessary to include thermal self-initiation, transfer, and irreversible decomposition of intermediate alkoxyamines in addition to the reversible cleavage of the TEMPO-polymeric radical adduct. This model, combined with the values of the rate constants of propagation (k p), termination (k t), transfer (k trm), and alkoxyamines decomposition (k decomp), was then employed to estimate the kinetic and thermodynamic parameters for the exchange between dormant and active species. The equilibrium constant, K, was estimated to be approximately 10-11 mol·L-1, the deactivation rate constant, k d = 8 × 107 mol-1·L·s-1, and the activation rate constant, k a = 8 × 10-4 s-1, for bulk styrene polymerization at 120 °C.

Styrene-vinylferrocene random and block copolymers by TEMPO-mediated radical polymerization

“…According to Matyjaszewski et al 27) and Fukuda et al 28) thermal initiation is essential for the TEMPO-system. Although vinylferrocene polymerizes thermally, the homopolymerization of vinylferrocene did not show the features of a controlled radical polymerization.…”

Exploring the Full Potential of Reversible Deactivation Radical Polymerization Using Pareto-Optimal Fronts

“…The basic kinetic scheme of the second studied RDRP, i.e., NMP [17,35], is shown in Figure 1 (right panel). NMP is one of the first discovered RDRP systems, due to the pioneering work of Rizzardo et al [36].…”

Synthesis of Narrow Molecular Weight Distribution Norbornene-Lactone Functionalized Polymers by Nitroxide-Mediated Polymerization: Candidates for 193-nm Photoresist Materials

“…At higher conversions, the plots tend to plateau. The reason for the plateau could be attributed to the chain transfer side reactions to the solvent and monomers, which become more prevalent at higher conversions [63]. However, it should be noted that the styrenic comonomer tended to be incorporated preferentially into each of the copolymers, and the preferential incorporation could have led to irreversible termination reactions at a higher conversion, as the controlling co-monomer concentration would be steadily depleted or removed completely.…”

“…The newly created chains are probably still able to polymerize in a controlled manner, but with a significant fraction of new chains at low molecular weight, this would result in a lower than expected � and a broader molecular weight distribution. Greszta et al demonstrated that the combination of chain transfer to monomer and alkoxyamine decomposition were the main reasons for lower � and higher � � ⁄ at high conversions in the polymerization of styrene with TEMPO nitroxide [63].…”