Nucleophilic initiation of a chain-growth process in which the propagating species is an anion defines anionic polymerization. Typical initiators are organolithium reagents, alkali metal aromatic radical anions, or alkoxides; the monomer is an electron-deficient alkene, a strained heterocycle, or a related unsaturated electrophile. In the living limit, termination and transfer are absent, so the number-average molecular weight is set by the monomer-to-initiator ratio and the chain end remains available for further monomer addition or end-capping [1]. Ring-opening anionic polymerization of β-lactam sugar monomers produces poly-amido-saccharides, showing that the same ionic mechanism applies to cyclic amides [2]. Living anionic polymerization of phosphaalkenes likewise affords homopolymers and block copolymers with controlled chain length from a P=C monomer [3]. Architectural complexity—stars, combs, and cyclic polymers—arises from multifunctional initiation or from coupling of living carbanionic ends [1]. The concept is distinct from cationic polymerization (positively charged active centers) and from radical polymerization (neutral odd-electron chain ends).
- anionic polymerization
- living polymerization
- nucleophilic initiation
- chain-end control
Advanced Polymer Synthesis and Characterization • Organic Chemistry • Chemistry • Physical Sciences
References
- Nikos Hadjichristidis; Marinos Pitsikalis; Stergios Pispas; Hermis Iatrou; Polymers with Complex Architecture by Living Anionic Polymerization. Chem. Rev. 2001, 101, 3747-3792, 10.1021/cr9901337.
- Eric L. Dane; Mark W. Grinstaff; Poly-amido-saccharides: Synthesis via Anionic Polymerization of a β-Lactam Sugar Monomer. J. Am. Chem. Soc. 2012, 134, 16255-16264, 10.1021/ja305900r.
- Kevin J. T. Noonan; Derek P. Gates; Ambient‐Temperature Living Anionic Polymerization of Phosphaalkenes: Homopolymers and Block Copolymers with Controlled Chain Lengths. Angew. Chem. Int. Ed. Engl. 2006, 45, 7271-7274, 10.1002/anie.200602955.