Zune, C. Dubois, P. Jérôme, R. Kříž, J. Dybal, J. Lochmann, L. Janata, M. Vlček, P. Werkhoven, T. M. Lugtenburg, J. Study of the Propagation Center in the Anionic Polymerization of (Meth)acrylic Monomers:  NMR and MO LCAO Study of the Interaction of Di-<i>tert</i>-butyl 2-Lithio-2,4,4-trimethylglutarate and the Living Poly(<i>tert</i>-butyl methacrylate) Oligomers with Lithium 2-(2-Methoxyethoxy)ethoxide in Tetrahydrofuran Interactions of lithium 2-(2-methoxyethoxy)ethoxide (LiOEEM) with the model dimer di-<i>tert</i>-butyl 2-lithio-2,4,4-trimethylglutarate (<b>A</b>) and the living poly(<i>tert</i>-butyl methacrylate) oligomers (<b>B</b>) were studied in tetrahydrofuran-<i>d</i><sub>8</sub> at 203−273 K using <sup>1</sup>H, <sup>13</sup>C, <sup>7</sup>Li, and <sup>6</sup>Li, 1D and 2D, NMR and ab initio SCF 3-21G and MNDO quantum chemical calculations. LiOEEM is shown to have a strong tendency to self-aggregation, producing dimeric, trimeric, and tetrameric aggregates and competing with its mixed aggregation (or complexation) with <b>A </b>and, in particular, <b>B</b>. When dissolved in THF, LiOEEM as well as its mixtures with <b>A </b>form metastable systems which relax in several days at 258 K into equilibrium. Interaction of LiOEEM with <b>A </b>leads to a system of mixed aggregates LiOEEM<b><sub>1</sub></b><b>A</b><b><sub>1</sub></b>, LiOEEM<b><sub>3</sub></b><b>A</b><b><sub>1</sub></b>, and possibly LiOEEM<b><sub>2</sub></b><b>A</b><b><sub>1</sub></b> along with the original components, in relative populations depending on the LiOEEM/<b>A</b> molar ratio, temperature, time, and probably other factors of preparation. Probable structures of these complexes are proposed, and the nature of the prevalent bonding is suggested. Experimental results indicate that LiOEEM is unable to convert <b>A </b>completely at moderate excess (up to 4/1 mol/mol). Interaction of LiOEEM with <b>B </b>leads to quite analogous complexes but with even lower yields. There appear to be traces of uncomplexed <b>B </b>even at the LiOEEM/B ratio of 10 mol/mol. This is suggested to produce at least two different kinds of active growth centers in the corresponding ligated anionic polymerization of <i>tert-</i>butyl methacrylate and, consequently, the observed bimodality of the polymeric product. The difference with respect to methyl methacrylate, where LiOEEM ensures an almost ideal living polymerization, is suggested to be due to the steric hindrance of efficient complexation exerted by the <i>tert-</i>butyl group. THF;form metastable systems;MNDO quantum chemical calculations;NMR;tert;butyl methacrylate;SCF;model dimer di;aggregates LiOEEM 1;MO LCAO Study 1998-04-17
    https://acs.figshare.com/articles/journal_contribution/Study_of_the_Propagation_Center_in_the_Anionic_Polymerization_of_Meth_acrylic_Monomers_NMR_and_MO_LCAO_Study_of_the_Interaction_of_Di-_i_tert_i_-butyl_2-Lithio-2_4_4-trimethylglutarate_and_the_Living_Poly_i_tert_i_-butyl_methacrylate_Oligomers_with_Lithiu/3732555
10.1021/ma971368s.s001