Abstract: The present invention provides a coupled polymer, which is prepared by reacting a living alkali metal-terminated polymer with a particular coupling agent. The coupling agent has the formula ##STR1## where R1, R3 are independently selected from the group consisting of aliphatic alkyl and alkenyl, and hydrogen, and R.sub.2 is alkylene, alkenylene, divalent cycloalkylene, divalent arenyl, or a C.sub.1-17 divalent hydrocarbyl containing ether or ketone group. By means of the particular coupling agent, the coupling efficiency is relatively high, and no harmful materials will be generated to corrode the pipes. The coupled polymer obtained has a coupling number of less than 3, and good rubbery physical properties, transparency, and wear resistance.

Abstract: The rubber for high-performance tire tread of the invention basically includes: (a) about 10%.about.50% weight percentage low molecular weight coupled copolymer of aromatic vinyl compound and conjugated diene or conjugated diene monopolymer, having a molecular weight of 5.times.10.sup.4 .about.35.times.10.sup.4, (b) about 10%.about.60% weight percentage middle molecular weight uncoupled copolymer of aromatic vinyl compound and conjugated diene, having a molecular weight of 10.times.10.sup.4 .about.80.times.10.sup.4, and (c) 5.about.60% weight percentage high molecular weight coupled copolymer of aromatic vinyl compound and conjugated diene, having a molecular weight of 45.times.10.sup.4 .about.200.times.10.sup.4.