Quantum-Chemical Study of the Effect of Triethylaluminum on the Chain-End Structure, Reactivity, and Microtacticity of Poly(N,N-dimethylacrylamide) with Lithium Counterion in Nonpolar Solvents

Abstract

Reactions of chain growth in the anionic polymerization of N,N-dimethylacrylamide (DMAAm) with lithium counterion in the presence of triethylaluminum (Et3Al) were studied using quantum-chemical DFT methods. The active sites were simulated by chain fragments consisting of two DMAAm units, the lithium counterion being coordinated to carbonyl oxygen atoms of both ultimate and penultimate units. For all local minima and transition states zero-point vibration energies and free energies, ΔG, at 200 K were calculated. It was shown that in the absence of Et3Al iso-addition of the monomer to the model chain end is the most favorable, while in the presence of two Et3Al molecules syndio- and iso-additions of DMAAm are equally probable. In the presence of one Et3Al molecule, an unambiguous prediction of the prevailing stereomode of DMAAm addition is impossible because different stereomodes are preferred at the BHLYP/SVP (syndio-addition via 1LA-DAS mechanism) and BHLYP/aug-cc-pVTZ//BHLYP/SVP (iso-addition via 1LA-AM mechanism) levels. Thus, on the basis of the performed DFT calculations, it is possible to predict the possibility to influence the microtacticity of poly(N,N-dimethylacrylamide), varying the [Al]/[Li] ratio: the polymer should be predominantly isotactic at [Al]/[Li] = 0 and atactic at [Al]/[Li] ≥ 2.

Indirect GC‐MS Method via Alcoholysis Reaction for Rapid Detection of Organoaluminum Compounds and its Impurities: A Case Study of Triethylaluminium

“…Among those organoaluminum compounds, triethylaluminium (TEAL) can be widely used not only as the catalyst component but also as energetic materials in fuel or propellant. As the catalyst component, TEAL is used for olefin polymerization, and also for the synthesis of alpha olefin, alpha fatty alcohol and intermediates [6][7][8][9][10][11][12][13][14][15]. For example, Groppo et al conducted a systematic investigation on the effect of TEAL on the Cr(VI)/SiO 2 catalyst during the olefin polymerization reaction and explaining the faster polymerization initiation rate [16].…”

“…Among those organoaluminum compounds, triethylaluminium (TEAL) can be widely used not only as the catalyst component but also as energetic materials in fuel or propellant. As the catalyst component, TEAL is used for olefin polymerization, and also for the synthesis of alpha olefin, alpha fatty alcohol and intermediates [6–15]. For example, Groppo et al.…”