On the anionic polymerization of dialkylaminoisoprenes, 4. Experimental observation of the unusual polymerization kinetics

Abstract

SUMMARY The anionic polymerization of 5-(N,N-dialkylamino)isoprenes with set-butyllithium was investigated in different solvents under various conditions. The homopolymerization can be described as a 2"d order reaction with respect to the monomer concentration, indicating that two monomer units are involved in the rate determining reaction. A mechanistic proposal to explain this unusual behaviour is based on the structure of amino-functional lithium organic compounds.

Novel Bowl-Shaped Morphology of Crew-Cut Aggregates from Amphiphilic Block Copolymers of Styrene and 5-(N,N-Diethylamino)isoprene

“…The polymerization reaction was carried out in benzene, using sec -butyllithium as the initiator. The 5-( N , N -diethylamino)isoprene monomer was synthesized and purified as described elsewhere . Styrene and benzene were distilled over calcium hydride under nitrogen and dried over di- n -butylmagnesium (1.0 M solution in heptane).…”

Synthesis of Amine-Functionalized Diene-Based Polymers as Novel Gene Delivery Vectors

“…This can be explained by the chelation of the lithium to the amino group on the active chain end. 10 Unlike polybutadiene and polyisoprene in polar solvents, where the negative charge is mostly localized on the γ-carbon (Figure 3a), 18 for the aminefunctionalized polymers the negative charge is mainly localized on the R-carbon due to the chelation (Figure 3b). Because of this chelation, a high 4,1-microstructure was obtained.…”

“…Having synthesized and purified the desired monomers, the anionic polymerization studies were carried out. While there are several examples in the literature describing the anionic polymerization of similar monomers, one common theme is that the conversion from monomer to polymer is not quantitative. − The reason is not well understood. A better understanding of the reaction mechanism is critical for preparing block copolymers by sequential monomer addition.…”

“…No polymer was obtained when the reaction was carried out in THF, while butadiene and isoprene form polymers with high vinyl microstructure content when the polymerization reactions are carried out in polar solvents such as THF or with TMEDA added to the reaction. This can be explained by the chelation of the lithium to the amino group on the active chain end . Unlike polybutadiene and polyisoprene in polar solvents, where the negative charge is mostly localized on the γ-carbon (Figure a), for the amine-functionalized polymers the negative charge is mainly localized on the α-carbon due to the chelation (Figure b).…”