Modified high-Cis polybutadiene polymer, related methods and rubber compositions

A modified high-cis polybutadiene polymer having

• polymer chains bonded to a residue of a functionalizing compound having formula (I) as follows
• where X is a group reactive with the living end polymer chains and is selected from the group consisting of cyano, epoxy, ketone, aldehyde, ester, and acid anhydrides,
• R1 is selected from hydrocarbylene of C1-C20, wherein each of the foregoing optionally contain one unsaturated carbon-carbon bond,
• each R′ is selected from alkoxy of C1-C20, and
• R″ is selected from alkyl of C1-C20 or aryl of C6-C20,
• wherein each polymer chain is bonded to the residue of the functionalizing compound through the X group, and the modified high-cis polybutadiene polymer has
• a cis 1,4-bond content of 92-98%,
• an initial Mooney viscosity ML1+4 at 100° C. of 20-100, and
• an aged Mooney viscosity ML1+4 at 100° C. of no more than 120, wherein the aged Mooney viscosity is determined after aging at 100° C. for 2 days.