POLYBUTADIENE COMPOSITION, PRODUCTION METHOD THEREFOR, RUBBER COMPOSITION, TIRE, AND RUBBER BELT

A polybutadiene composition that is excellent in hardness of a rubber composition, in processability and extrusion dimensional stability, and in physical properties. The polybutadiene composition includes polybutadiene rubber and syndiotactic-1,2-polybutadiene, and the polybutadiene composition has an interfacial component between the polybutadiene rubber and the syndiotactic-1,2-polybutadiene, and the interfacial component has a thickness of 40 to 55 nm as measured by an atomic force microscope.