Synthesis of End-Functionalized Polymers by Means of Living Anionic Polymerization. 8. Reactions of Living Anionic Polymers with α,ω-Dihaloalkanes

Abstract

In order to prepare well-defined polymers with halogen end groups, anionic living polymers of isoprene and styrene were allowed to react with excess amounts of α,ω-dihaloalkanes in THF at −78 °C. The monosubstitution reactions of 1,3-dichloropropane with these anionic living polymers proceeded cleanly to afford quantitatively the polymers with chlorine end groups that possessed controllable molecular weights and narrow molecular weight distributions. On the other hand, the reactions of the anionic living polymers with either α,ω-dibromoalkanes or α,ω-diiodoalkanes proceeded competitively with side reactions leading to dimer formation of the starting living polymers. Thus, the bromine- and iodine-terminated polymers were obtained in 12−93% yields along with undesirable dimers. As side reaction candidates, we speculated on metal−halogen interchange and/or single electron transfer pathways followed by coupling reactions between the reaction intermediates generated by both pathways. By end-capping the polystyryl anion with 1,1-diphenylethylene, one could almost suppress the dimer formation, and the end-functionalized polystyrenes with bromine and iodine were successfully obtained in more than 95% yield.

Synthesis of Functionalized Polymers by Means of Living Anionic Polymerization, 2. Synthesis of Well-Defined Chain-End and in-Chain Functionalized Polymers with 1,3-Butadienyl Groups

“…[16] The dark red color of the living functionalized polystyrene faded gradually, indicating that the reaction proceeded smoothly. The desired polymer was isolated in A90% yield by HPLC fractionation to remove unreacted end-functionalized polystyrene with 4-bromobutyl group used in excess in the reaction.…”

Recent developments in anionic polymerization

“…At a time when the recently discovered controlled radical polymerization [2*] is viewed as a much less demanding process, anionic polymerization still remains an important method, well-suited to kinetic studies [3*], the synthesis of polymers of predictable molecular weight (MW) with a narrow molecular weight distribution (MWD), tailoring of block copolymers [4,5*,6-9], design of nonlinear molecular architectures [10**, 11] and telechelic polymers [12][13][14][15][16][17], and stereoregular polymerization [18,19]. Major progress in mechanistic studies and macromolecular engineering reported in the past year(s) is to be found in the very challenging field of the anionic polymerization of (meth)acrylic monomers.…”

Anionic Polymerization: Recent Advances

“…In fact, these reactions have been utilized as the classical approach to the synthesis of chain-end-functionalized polymers. In this case, some of the functional groups were protected prior to the post-polymerization reactions, such that well-defined, chain-end-functionalized PSs and PIs with COOH, OH, SH, NH 2 , (CH 2 ) n X, perfluoroalkyl, d-glucose, aziridinyl, 4-vinylphenyl, 1,1-diphenylethenyl, and 1,3-butadienyl (>95%) could be successfully obtained [175][176][177][178][179][180][181]. Unfortunately, however, many of these reactions were inadequately characterized or optimized for general utility.…”