Retarded Anionic Polymerization: Copolymerization of Butadiene and Styrene in the Presence of Alkyllithium and n,s‐Dibutylmagnesium or Triisobutylaluminium Derivatives

Abstract

Summary: The influence of Lewis acid additives on the anionic butadiene polymerization using lithium as a counter ion in non‐polar solvent is investigated. A decrease of the polymerization rate was always observed. In the presence of n,s‐Bu2Mg the percentage of 1,2‐vinyl units increases with the [Mg]/[Li] ratio. This evolution can be explained by further complexation of lithium with free dialkylmagnesium modifying the nature of the propagating species and/or possible 1,4 to 1,2 isomerization during chain exchanges between lithium and magnesium derivatives. As a result of the transmetallation process, 0.5 to 1 supplementary chains are formed by magnesium depending on the [Mg]/[Li] ratio. In contrast, the iBu3Al/RLi system does not yield any modification of polybutadiene microstructure, which remains close to the one observed with s‐BuLi alone. The determination of the reactivity ratios in styrene‐butadiene copolymerization shows that tapered‐like copolymers are obtained in the presence of both n,s‐Bu2Mg and iBu3Al. However the magnesium derivative induces a lesser increase of styrene incorporation in the copolymer than the aluminium additive. The observed microstructure and reactivity ratios support that the monomer insertion proceeds directly into heterocomplexes.magnified image

Controlled Anionic Homo- and Copolymerization of Ethylene Oxide and Propylene Oxide by Monomer Activation

“…We have shown recently that the association of organoaluminic derivatives (AlR y X 3- y ) to alkali metal salts yield the formation of “ate” complexes which are active initiators both for the retarded anionic polymerization of styrenic monomers and dienes , and for the anionic polymerization of propylene oxide (POx). , For the oxirane, in contrast to ethylenic monomers, a slight excess of the aluminum derivative with respect to the alkali metal is needed to trigger the polymerization. This is explained by the necessary formation of a second complex between the aluminum derivative in excess and the monomer.…”

“…11 However, Esswein and Mo ¨ller showed that the addition of strong Lewis base, for example the phosphazene base tBu-P 4 , can strongly complex the Li + counterion and allows EO polymerization in THF. [12][13][14] We have shown recently that the association of organoaluminic derivatives (AlR y X 3-y ) to alkali metal salts yield the formation of "ate" complexes which are active initiators both for the retarded anionic polymerization of styrenic monomers and dienes 15,16 and for the anionic polymerization of propylene oxide (POx). 17,18 For the oxirane, in contrast to ethylenic monomers, a slight excess of the aluminum derivative with respect to the alkali metal is needed to trigger the polymerization.…”

Structure and characterization for conterminously linked polymer of short‐chain epoxy resin with triallyl isocyanurate and bismaleimide

“…Finally, it should be noted that some authors propose an 1,4‐3,4 isomerization to explain the regioselectivity changes observed in the course of an alkyl lithium mediated anionic polymerization of diene conducted in the presence of magnesium dialkyls 41, 42…”

Temperature Variation Enables the Design of Biobased Block Copolymers via One‐Step Anionic Copolymerization

“…For instance, polar modifiers and retarders have been investigated for the polybutadiene system [ 35 ] and for polyisoprene. [ 36–41 ] In brief, previous studies revealed an increase of the 1,2 addition instead of the 1,4 diene addition mode with increasing content of polar modifier. [ 42 ] The microstructures and the content of possible 1,2‐, 3,4‐ and 1,4‐ polymyrcene units ( Figure ) were determined by 1 H NMR spectroscopy.…”