Conjugated diene-based polymer, conjugated diene-based polymer composition, and method for producing conjugated diene-based polymer

A conjugated diene-based polymer comprising an aromatic vinyl unit based on an aromatic vinyl compound and a conjugated diene unit based on a conjugated diene compound, wherein

• the conjugated diene-based polymer is modified with a compound containing a heteroatom and has an SP value of 16.80 MPa1/2 to 17.10 MPa1/2,
• an amount of vinyl bonds of the conjugated diene-based polymer is 45 mol % to 80 mol %, where 100 mol % is the content of the conjugated diene unit,
• a glass transition temperature of the conjugated diene-based polymer is −70° C. to −30° C.,
• the compound containing a heteroatom is selected from the group consisting of acrylamide compounds, vinylsilane compounds, alkoxysilane compounds, polysiloxane compounds, silane sulfide compounds, sulfanylsilane compounds, cyanate compounds and polyimine compounds,
• wherein the vinylsilane compound is selected from the group consisting of bis(dimethylamino)methylvinylsilane, bis(diethylamino)methylvinylsilane, bis(n-propylamino)methylvinylsilane, bis(di(n-butyl)amino)methylvinylsilane, bis(dimethylamino)ethylvinylsilane, bis(diethylamino)ethylvinylsilane, bis(dipropylamino)ethylvinylsilane and bis(dibutylamino)ethylvinylsilane.