Coupling of block base copolymers terminated by a lithium atom of the typical formula S-B-Li, in which S is a monovinylaromatic hydrocarbon block and B is a conjugated diene block, by the use of at least one difunctional deactivating coupling agent and at least one polyfunctional deactivating coupling agent in a molar ratio such that the linear polymer obtained by coupling represents 65 to 95% by