Method For Producing Polydienes With Reduced Cold Flow

A process for preparing a polydiene having increased viscosity and reduced cold flow that includes polymerizing a conjugated diene monomer in the presence of a lanthanide-containing compound to form an intermediate polymer, and then adding a non-organometallic trimellitate ester compound as a coupling agent to raise the viscosity of the intermediate polymer. The coupling agent is added to the intermediate polymer mixture in an amount of about 0.01 to about 0.15 parts per hundred monomer (phm) of the starting monomer amount.