Krys Pawel, Fantin Marco, Mendonça Patrícia V, Abreu Carlos M R, Guliashvili Tamaz, Rosa Jaquelino, Santos Lino O, Serra Arménio C, Matyjaszewski Krzysztof, Coelho Jorge F J
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States.
CEMMPRE, Department of Chemical Engineering, University of Coimbra, 3030-790 Coimbra, Portugal.
Polym Chem. 2017 Nov 14;8(42):6506-6519. doi: 10.1039/C7PY01319A. Epub 2017 Sep 22.
The mechanism of atom transfer radical polymerization (ATRP) mediated by sodium dithionite (NaSO), with CuBr/MeTREN as catalyst (MeTREN: tris[2-(dimethylamino)ethyl]amine)) in ethanol/water mixtures, was investigated experimentally and by kinetic simulations. A kinetic model was proposed and the rate coefficients of the relevant reactions were measured. The kinetic model was validated by the agreement between experimental and simulated results. The results indicated that the polymerization followed the SARA ATRP mechanism, with a SO radical anion derived from NaSO, acting as both supplemental activator (SA) of alkyl halides and reducing agent (RA) for Cu/L to regenerate the main activator Cu/L. This is similar to the reversible-deactivation radical polymerization (RDRP) procedure conducted in the presence of Cu. The electron transfer from SO, to either CuBr/MeTREN or R-Br initiator, appears to follow an outer sphere electron transfer (OSET) process. The developed kinetic model was used to study the influence of targeted degree of polymerization, concentration of CuBr/MeTREN and solubility of NaSO on the level of polymerization control. The presence of small amounts of water in the polymerization mixtures slightly increased the reactivity of the Cu/L complex, but markedly increased the reactivity of sulfites.
研究了连二亚硫酸钠（Na₂S₂O₄）介导、以CuBr/MeTREN为催化剂（MeTREN：三[2-(二甲基氨基)乙基]胺））在乙醇/水混合体系中进行的原子转移自由基聚合（ATRP）的机理，通过实验和动力学模拟展开研究。提出了动力学模型并测定了相关反应的速率系数。通过实验结果与模拟结果的一致性验证了该动力学模型。结果表明，聚合反应遵循SARA ATRP机理，由Na₂S₂O₄衍生的SO₃·-自由基阴离子既作为卤代烃的补充活化剂（SA），又作为Cu⁺/L的还原剂（RA）以使主要活化剂Cu⁺/L再生。这类似于在Cu存在下进行的可逆失活自由基聚合（RDRP）过程。SO₃²⁻向CuBr/MeTREN或R-Br引发剂的电子转移似乎遵循外层电子转移（OSET）过程。所建立的动力学模型用于研究目标聚合度、CuBr/MeTREN浓度和Na₂S₂O₄溶解度对聚合控制水平的影响。聚合混合物中少量水的存在略微提高了Cu⁺/L配合物的反应活性，但显著提高了亚硫酸盐的反应活性。
