Additive for chemical mechanical polishing, method for producing the same, and polishing liquid composition

A method for producing an additive for a chemical mechanical polishing liquid, the additive containing a polymer, comprising;

• producing the polymer by a living radical polymerization method,
• wherein the polymer contains a structural unit derived from a vinyl monomer having a -(LO)n-R group,
• a total content of a structural unit derived from a monomer containing one or more functional groups selected from the group consisting of a carboxylic acid group, a phosphoric acid group, a phosphonic acid group, a sulfuric acid group, a sulfonic acid group, and salts thereof is 0 to 0.6 mass % in the polymer, and
• a dispersity (PDI) of the polymer, which is represented by weight average molecular weight (Mw)/number average molecular weight (Mn), is 2.0 or less,
• wherein L represents an alkylene group having 4 or less carbon atoms, n represents an arbitrary integer of 3 to 150, and R represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 4 carbon atoms.