Aba triblock polymer, composition, surface treatment agent, article, and method for manufacturing article

An ABA triblock polymer, comprising an A block and a B block, wherein:

• the A block is a random polymer including a constituent unit derived from a reactive group-containing polymerizable monomer and a constituent unit derived from a reactive group-free polymerizable monomer,
• the B block contains a polyalkylene oxide chain or a divalent organopolysiloxane residue in a main chain,
• the constituent unit derived from a reactive group-free polymerizable monomer in the A block contains a constituent unit derived from a hydrophobic group-containing polymerizable monomer in a case in which the B block contains a polyalkylene oxide chain in a main chain,
• the constituent unit derived from a reactive group-free polymerizable monomer in the A block contains a constituent unit derived from a hydrophilic group-containing polymerizable monomer in a case in which the B block contains a divalent organopolysiloxane residue in a main chain,
• the reactive group is at least one group selected from the group consisting of a reactive silyl group, an isocyanato group, a phosphoric acid ester group, a carboxy group, a carbodiimide group, an oxazoline group, and an epoxy group,
• the hydrophobic group is at least one group selected from the group consisting of a linear alkyl group having from 12 to 30 carbon atoms and a divalent organopolysiloxane residue, and
• the hydrophilic group is at least one group selected from the group consisting of a hydroxyl group and a polyalkylene oxide chain.