MODIFIED CONJUGATED DIENE POLYMER AND METHOD FOR PRODUCING SAME, POLYMER COMPOSITION, CROSSLINKED POLYMER, AND TIRE

There is obtained a rubber composition which can improve low fuel consumption performance, workability, and abrasion resistance at the same time in uses of automobile tires and the like. A modified conjugated diene polymer is produced by a method comprising: a polymerization step of polymerizing a conjugated diene compound or polymerizing a conjugated diene compound and an aromatic vinyl compound to obtain a conjugated diene polymer having an active end in the presence of a metal amide compound obtained by mixing an alkali metal compound or an alkaline earth metal compound with a secondary amine compound and a first modification step of reacting the active end with the following compound (C1): (C1) a compound having a functional group (a) that interacts with silica, having one or more linear structures where three or more groups or atoms in total derived from at least either of a methylene group and a divalent atom are linearly connected, and capable of binding to a plurality of the active ends.