Anionic polymerization of N,N-dimethylacrylamide with thienyllithium and synthesis of block co-polymers of isobutylene and N,N-dimethylacrylamide by site transformation of chain ends

Abstract

The anionic polymerization of N,N-dimethylacrylamide (DMAAm) was carried out in THF with a binary initiator system prepared from thienyllithium and the Lewis acids triethylaluminium (Et 3 Al), diethylzinc (Et 2 Zn) or triethylborane (Et 3 B). Polymerizations proceeded in a homogeneous manner and gave polymers having controlled molecular weights. However, in presence of alkoxides the polymerization resulted in polymers insoluble in THF, even when using Et 3 Al. A synthetic route for the synthesis of polyisobutylene-b-PDMAAm was developed by combining living carbocationic and anionic polymerizations. Thiophene end-capped polyisobutylene (PIB-T), prepared by cationic polymerization, was metalated with n-butyllithium in THF at −40 • C. The resulting stable macrocarbanion (PIB-T − , Li + ), in conjunction with Lewis acids, was used to initiate the living anionic polymerization of DMAAm, resulting in a new amphiphilic block co-polymer PIB-b-PDMAAm. The molecular structure was characterized by size exclusion and adsorption chromatography and NMR, and the micellisation in aqueous solution was characterized by fluorometry and dynamic light scattering.

Polymeric micelles: authoritative aspects for drug delivery

“…Polyacrylamide derivatives Polyisobutylene-b-poly(N,N-dimethylacrylamide) [94] Polyacrylamide hydrophobically modified with dihexylacrylamide [95] [105]. Cao and others prepared polystyrene-poly(methacrylic acid) (PS-PMA) block copolymer micelles by directly adding the polymer to 80:20 v/v dioxane:water followed by a stepwise dialysis to pure aqueous buffer [106].…”

New Dual Initiators To Combine Quasiliving Carbocationic Polymerization and Atom Transfer Radical Polymerization

“…To create block copolymers from monomers that cannot be polymerized by the same mechanism, one may couple existing prepolymers or combine different controlled/living polymerization methods using either site (mechanism) transformation or a dual initiator approach. Site transformation has been employed to convert the growing chain ends of a cationically derived polymer into an initiating site for several different types of polymerization processes including atom transfer radical polymerization (ATRP), − reversible addition−fragmentation chain transfer (RAFT) polymerization, , anionic olefin polymerization, − and anionic ring-opening polymerization. , Dual initiators contain initiating sites for two different polymerization processes within the same molecule. Only a few dual initiators have been reported in which one site is a cationic polymerization initiator.…”

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

“…Recently, to control the polymerization of DMAAm, new effective anionic initiating systems were developed, consisting of organometallic compounds of alkali and alkaline earth metals modified by electron acceptor Lewis acids (LA), such as Et 3 B, , Et 2 Zn, ,,, and Et 3 Al . It has been found that in the presence of Lewis acids soluble and highly syndiotactic or heterotactic , polymers are formed with predictable molecular weight and narrow molecular weight distribution ,, even at 30 °C…”