Modified conjugated diene-based polymer and rubber composition including the same

A modified conjugated diene-based polymer having:

• a unimodal molecular weight distribution curve measured by gel permeation chromatography (GPC),
• molecular weight distribution (PDI;
• MWD) of less than 1.7,
• a Si content of 100 ppm or more based on a total weight of the modified conjugated diene-based polymer,
• the modified conjugated diene-based polymer comprising a repeating unit derived from an aromatic vinyl monomer in an amount of 15 wt % or more and less than 30 wt % based on the total weight of the modified conjugated diene-based polymer, and
• wherein the Si content is measured by an inductively coupled plasma analysis method,
• wherein the modified conjugated diene-based polymer is prepared by:
• (S1) polymerizing a conjugated diene-based monomer, or an aromatic vinyl-based monomer and a conjugated diene-based monomer, in a hydrocarbon solvent including an organometallic compound to prepare an active polymer;
• and
• (S2) reacting the active polymer prepared in (S1) with a modifier,
• wherein the active polymer is coupled with an organometal,
• the step (S1) is continuously performed in two or more polymerization reactors, and
• a polymerization conversion ratio in a first polymerization reactor is 50% or less.