Block copolymer, resin composition, stretch conductor, electronic device, and pressure-sensitive adhesive film

A block copolymer mainly composed of a structural unit derived from an ethylenically unsaturated monomer, which has at least one mercapto group, a number average molecular weight of 5,000 to 500,000, wherein the block copolymer contains an organic iodine-based living radical polymerization initiator residue and has any structure of the following General Formulae (2) to (4), and the polymerization unit in the General Formulae (2) to (4) is a block structure that is a triblock structure of polymer block (A)-polymer block (B)-polymer block (A) or a star-shaped block structure of [polymer block (A)-polymer block (B)]qX,

• wherein q represents an integer of 2 or more and 6 or less,
• the glass transition temperature of the polymer block (A) is 20° C. or higher,
• the glass transition temperature of the polymer block (B) in the case of the triblock structure and the glass transition temperature of [polymer block (B)]qX in the case of the star-shaped block structure are lower than 20° C., and
• X represents an initiator residue and/or a coupling agent residue, or its derivatives,
• where the polymerization unit is a polymer unit mainly composed of a structural unit derived from an ethylenically unsaturated monomer independently for each branch from Y in the case of General Formula (4),
• Z1 each independently represents a divalent group selected from the group consisting of an ester group, a ketone group and an amide group, or a direct bond for each branch from Y,
• Q represents a monovalent molecular terminal group, and the molecular terminal group is a functional group, a hydrocarbon group which may have a functional group, or an iodine group independently for each branch from Y,
• Y represents a p-valent hydrocarbon group which may have a substituent,
• p represents an integer of 2 to 6,
• R2, R5 and R6 each independently represent a hydrogen atom or a monovalent hydrocarbon group which may have a substituent independently for each branch from Y in the case of General Formula (4),
• R3 and R7 each independently represent a hydrogen atom, a monovalent hydrocarbon group which may have a substituent or —COR8 independently for each branch from Y in the case of General Formula (4),
• R4 represents a monovalent hydrocarbon group which may have a substituent, —COR8, a cyano group or a nitro group,
• R2 and R3, R3 and R4, R2 and R4 and R6 and R7 each independently may be bonded to each other to form a ring independently for each branch from Y in the case of General Formula (4),
• R8 each independently represents a hydrogen atom, a hydroxy group, an alkoxy group, an amino group or a monovalent hydrocarbon group which may have a substituent,
• R11 represents a divalent hydrocarbon group, which may have a substituent,
• R12 represents a divalent hydrocarbon group selected from the group consisting of an alkylene group, an arylene group and an alkylene oxide group or a direct bond, and
• the hydrocarbon group may have a heterocycle, and each independently include at least one of a chain hydrocarbon group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group.