Controlled Anionic Graft Polymerization of Ethylene Oxide Directly from Poly(N-isopropylacrylamide)

A study was conducted to demonstrate controlled anionic graft polymerization of ethylene oxide (EO) directly from poly(n-isopropylacrylamide) (PNIPAM). PNIPAM having an apparent number-averagemolecular weight of 43 kg/mol and a polydispersity index (PDI) of 1.13, as determined by size-exclusion chromatography (SEC), was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization. It was prepared using 3- benzylsulfanylthiocarbonylsulfanylpropionic acid (BPATT) as the chain transfer agent. The reactor was sealed by a stopcock and polymerization was conducted at 45 °C for 48 hours after the cryo-condensation of a predetermined amount of EO. Acetone, tetrahydrofuran (THF), and diethyl ether were used as received for RAFT polymerization and end-group removal, while THF was dried successively by Na and Na/K alloy for anionic graft polymerization. Acetone was evaporated and the residual solution of PNIPAM was dialyzed in cellulose membrane against distilled water for 3 days after quenching with rapid cooling.