A block copolymer having the general formula as formula (1): mediator-P2-P1-X, formula (1), and the chemical structural formula is formula (2), in which the mediator in formula (1) and formula (2) is a regulator, which is a conjugated seven-membered ring structure, P1 is a first polymer which may be a conjugated or non-conjugated olefin monomer, R1 is the functional group of P1, n is the number of the monomer of P1, which is a positive integer and the range is 10˜1,500. P2 is a second polymer, m is the number of the monomer of P2, which is a positive integer and the range is 10˜1,500, and X is the end-functional group of the block copolymer.