Hydrocarbyl esters of N-cyclopropyl-N-hydrocarbylcarbamic acids as coupling agents for conjugated diene polymerizations

A process of treating a living alkali metal terminated conjugated diene polymer, wherein said conjugated diene polymer is a homopolymer or copolymer of a conjugated diene or of a conjugated diene with a comonomer containing a vinylidene group, which comprises contacting said living alkali metal-terminated conjugated diene polymer with an effective coupling amount of a hydrocarbyl ester of N-cyclopropyl-N-hydrocarbylcarbamic acid, thereby resulting in a coupled conjugated diene polymer of increased molecular weight.