DTHFP is used as modifier for the organolithium catalyst to increase the level of 1,2-microstructure (vinyl structure) in the polyene. DTHFP is bidentate coordinating ether that dramatically affects organolithium structures and reactivities. DTHFP is especially useful in controlling the structure of polymers produced from anionic polymerization of dienes (butadiene, isoprene), styrene-diene copolymers, hydrogenated styrene-butadiene block copolymers and liquid polybutadienes. It can be applied to SSBR, SEBS, TPES, etc.