Indirect Methods Using End-Capping of Living Polymeric Anions

3 Indirect Methods using End-Capping of Living Polymeric Anions 

Anionic deactivation processes can also be used to introduce quantitatively into a polymer chain terminal functions which can be utilized for the synthesis of macromonomers. 

Styryl carbanions readily react with carbon dioxide 31) to yield carboxy end groups. These terminal groups are also introduced by reaction with anhydrides 19) whereas the use of oxirane 23) leads to the formation of hydroxy end groups esters and nitriles are used to introduce carbonyl functions at the chain end. These reactions can be carried out at low temperature in THF solution and proceed quantitatively if no deactivation by protons occurs. 

Diene carbanions exhibit a reactivity similar to that of styryl carbanions. Carban-ionic sites of lower reactivity can be functionalized under certain conditions32). Living polymers with alkoxide end groups exhibit the same reactivity as alcoholates with respect to proton-donating substances and activated organic halides. Protonation yields terminal hydroxy groups which are often used in the two-step macromonomer synthesis. 

Polyethylene oxide)macromonomers have thus been synthesized by two-step processes. Poly(oxyethylene)mo nomethyl ethers with widely varying molecular weights are commercially available. They are obtained by anionic polymerization of oxirane initiated by monofunctional alkoxides261 such as potassium 2-methoxyethanol. 

---