Copolymer, ink including copolymer, and ink-stored container

An ink comprising:

• water;
• a coloring material;
• and
• a copolymer,
• wherein the copolymer is a copolymer including:
• a structural unit represented by General Formula (1) below;
• and
• a structural unit represented by General Formula (2) below,
• where, in General Formula (1), R1 is a hydrogen atom or a methyl group, L1 is an alkylene group having 2 or greater carbon atoms but 5 or less carbon atoms, and X is a hydrogen atom or a cation,
• where, in General Formula (2), R2 is a hydrogen atom or a methyl group and L2 is an alkylene group having 2 or greater carbon atoms but 18 or less carbon atoms.

An ink-stored container comprising:

• an ink;
• and
• a container storing the ink,
• wherein the ink includes:
• water;
• a coloring material;
• and
• a copolymer,
• wherein the copolymer is a copolymer including:
• a structural unit represented by General Formula (1) below;
• and
• a structural unit represented by General Formula (2) below,
• where, in General Formula (1), R1 is a hydrogen atom or a methyl group, L1 is an alkylene group having 2 or greater carbon atoms but 5 or less carbon atoms, and X is a hydrogen atom or a cation,
• where, in General Formula (2), R2 is a hydrogen atom or a methyl group and L2 is an alkylene group having 2 or greater carbon atoms but 18 or less carbon atoms.