Patent ID: 8829133

Claim:
An ABA triblock copolymer comprising: an A-block having, in a constitutional unit thereof, a monomer represented by the following general formula (1) or a monomer represented by the following general formula (2); and a B-block having, in a constitutional unit thereof, a hydrophilic monomer having a radical polymerizable unsaturated bond, where R 1 is a hydrogen atom or a methyl group; R 2 is a C5-C18 alkylene group; M is a hydrogen atom or a monovalent metal atom; and X 1 is —NH— or an oxygen atom in the general formula (1), and where R 11 is a hydrogen atom or a methyl group; R 12 is a C5-C18 alkylene group; R 13 and R 14 are each independently a hydrogen atom, a methyl group, or an ethyl group; and X 11 is —NH— or an oxygen atom in the general formula (2), wherein the hydrophilic monomer is a monomer represented by the general formula (3): where R 21 is a hydrogen atom or a methyl group; and R 22 and R 23 are each independently a hydrogen atom, a methyl group, or an ethyl group in the general formula (3), and wherein an average polymerization degree of the A-block [P(A)] and an average polymerization degree of the B-block [P(B)] satisfy the following formulae (I) and (II): 3< P ( A )<10 Formula (I) 20< P ( B )/ P ( A )<300 Formula (II).