Conductive composition and production method therefor, and water-soluble polymer and production method therefor

A water-soluble polymer represented by formula (3):

• wherein R8 denotes a linear or branched alkyl group with 6 to 20 carbon atoms, R9 denotes a hydrophilic group, R10 denotes a hydrogen atom or a methyl group, Y2 denotes a single bond, —C(═O)—O— or —O—, and p2 denotes an average number of repetitions and is a number of more than 1 and not more than 50.

A method for producing a water-soluble polymer (B) comprising a water-soluble polymer (B1) represented by formula (1), the method comprising a polymerization step of polymerizing a water-soluble vinyl monomer in a solvent (C2) satisfying condition 1 in the presence of a polymerization initiator having a terminal hydrophobic group:

• Condition 1:
• a chain transfer constant of methyl acrylate to the solvent (C2) at 50° C. is 0.001 or less.
• wherein R1 denotes a linear or branched alkyl group with 6 to 20 carbon atoms, R2 denotes a hydrophilic group, R3 denotes a hydrogen atom or a methyl group, Y1 denotes a single bond, —S—, —S(═O)—, —C(═O)—O— or —O—, and p1 denotes an average number of repetitions and is a number of from 1 to 50.