An amphiphilic pentablock copolymer that is temperature- and pH-sensitive and has superior and sustained gel strength, includes (a) a hydrophilic triblock copolymer that is temperature-sensitive and that is a copolymer of a poly(ethylene glycol)-based compound and a biodegradable polymer that is one or more polymer selected from the group consisting of polylactide, polyglycolide, polycaprolactone, poly(caprolactone-lactide) random copolymer, poly(caprolactone-glycolide) random copolymer, poly(lactide-glycolide) random copolymer, and mixtures thereof coupled with (b) a polyurethane-based oligomer (PU) that is pH sensitive and that includes a diisocyanate compound represented by a Formula as follows: OCN—(CH2)n—NCO, where n is an integer of 4 to 10, polymerized with a diol compound having a tertiary amine on a main chain thereof that is one or more of 1,3-bis{1-(2-hydroxyethyl) -4-pyridyl}propane and 1,4-bis(2-hydroxyethyl)piperazine, and is represented by Formulae as follows:where R and R′ are alkyl groups of 1 to 8 carbon atoms, respectively.
