Modified conjugated diene polymer, and polymer composition containing said polymer

A modified conjugated diene polymer including a structural unit derived from a compound represented by formula (1) and a structural unit derived from a conjugated diene

• wherein in formula (1),
• α and β represent integers such that 1≤α≤5, 1≤β≤5 and 2≤α+β≤6 are satisfied,
• n represents 0 or 1,
• (i) when n is 0,
• R11, R12, R13, R16, R17 and R18 each independently represent a hydrocarbyl group, substituted amino group, hydroxy group or hydrocarbyloxy group,
• from among R11, R12, R13, R16, R17 and R18, at least two are substituted amino groups and at least one is a hydroxy group or hydrocarbyloxy group,
• two groups selected from among R11, R12, R13, R16, R17 and R18 are optionally bonded either directly or indirectly at positions where a hydrogen atom has been removed from each group,
• R15 represents an (α+β)-valent group resulting from removal of (α+β) hydrogen atoms from a hydrocarbon,
• (ii) when n is 1,
• R11, R12, R13, R16, R17 and R18 each independently represent a hydrocarbyl group, substituted amino group, hydroxy group or hydrocarbyloxy group,
• R14 represents:
• (a) a group resulting from removal of two hydrogen atoms from a hydrocarbon with an amino group or substituted amino group,
• (b) a group resulting from removal of two hydrogen atoms from a hydrocarbon with a substituent including a heteroatom other than a nitrogen atom, or
• (c) a hydrocarbylene group,
• when R14 is (a) a group resulting from removal of two hydrogen atoms from a hydrocarbon with an amino group or substituted amino group, from among R11, R12, R13, R16, R17 and R18, at least one is a substituted amino group and at least one is a hydroxy group or hydrocarbyloxy group,
• when R14 is (b) a group resulting from removal of two hydrogen atoms from a hydrocarbon with a substituent including a heteroatom other than a nitrogen atom, or (c) a hydrocarbylene group, from among R11, R12, R13, R16, R17 and R18, at least two are substituted amino groups and at least one is a hydroxy group or hydrocarbyloxy group,
• at least two groups from among R11, R12, R13, R14, R16, R17 and R18 are optionally bonded either directly or indirectly at positions where a hydrogen atom has been removed from each group, and
• R15 represents an (α+β)-valent group resulting from removal of (α+β) hydrogen atoms from a hydrocarbon,
• wherein the modified conjugated diene polymer has a molecular chain which is a conjugated diene polymer including a structural unit derived from the conjugated diene, and the structural unit derived from the compound represented by formula (1) is chemically bound to one or both ends of the molecular chain of the modified conjugated diene polymer or is chemically bound as a side chain on the molecular chain of the modified conjugated diene polymer.