Thermoresponsive behavior of dual hydrophilic diblock copolymers prepared via organotellurium-mediated living radical polymerization

This study prepared dual thermoresponsive diblock copolymers (E₉₅N_n; n = 93 and 291) comprising poly(ethylene glycol) ethyl ether acrylate (PeDEGA; E) and poly(N-isopropylacrylamide) (PNIPAM; N) blocks with different lower critical solution temperatures (LCSTs). E₉₅N_n was prepared via organotellurium-mediated living radical polymerization through a one-pot synthesis method. Energy-dispersive X-ray spectroscopy revealed that tellurium residue at the polymer chain end was removed during purification via dialysis. The LCST of the PeDEGA was lower than that of PNIPAM. At temperatures below the LCST of PeDEGA, E₉₅N_n dissolved as a single polymer chain (the unimer state). When an aqueous solution of E₉₅N_n was heated, polymer micelles with a PeDEGA core and PNIPAM shells formed above the LCST of the PeDEGA. In pure water, 7–10 polymer micelles formed intermicellar aggregates. The polymer micelles encapsulated hydrophobic guest molecules into the hydrophobic core formed from the PeDEGA chains. Large intermicellar aggregates formed above the LCST of PNIPAM owing to hydrophobic interactions between the PNIPAM shells. It is expected that E₉₅N_n polymer micelles can be applied as drug carriers for thermoresponsive controlled drug release.