The present invention relates to butadiene/isoprene/monovinyl aromatic monomer heptablock copolymers having the following symmetric structure: Z-XZ-X-Y-X-XZ-Z wherein Z represents a polymer block of monovinyl aromatic monomer, X and Y, being different from each other, represent polymer blocks of butadiene or isoprene, XZ represents a tapered copolymer block of monovinyl aromatic monomer and butadiene or isoprene, and wherein the content of the recurring units derived from monovinyl aromatic monomer is 10 to 50 percent by weight, the content of the recurring units derived from butadiene is 10-75 percent by weight and the content of the recurring units derived from isoprene is 10-75 percent by weight, all based on the weight of the block copolymer, and methods for the preparation thereof.