Rubber composition and pneumatic tire using same

A rubber composition comprising a diene rubber including at least one styrene-butadiene copolymer and a reinforcing filler, wherein a styrene-butadiene copolymer component including the at least one styrene-butadiene copolymer has the characteristics of (1) to (4):

• (1) a content of bonded styrene is from 5 to 50 wt. %;
• (2) when a decomposed component Si including one styrene-derived unit and a decomposed component S1V1 including one styrene-derived unit and one 1,2-bonded butadiene-derived unit are measured by gel permeation chromatography as decomposed components obtained by ozone decomposition, a total content of styrene of the decomposed component S1 and the decomposed component S1V1 is less than 80 wt. % of the amount of bonded styrene, and a total content of styrene of the decomposed component S1V1 is less than 10 wt. % of the amount of bonded styrene;
• (3) when the decomposed components obtained by ozone decomposition are measured by a liquid chromatography-mass spectrometer, an integrated intensity of a decomposed component S1V2 including one styrene-derived unit and two 1,2-bonded butadiene-derived units is not less than 15% of an integrated intensity of all the decomposed components including styrene-derived units;
• and
• (4) a vinyl content of a butadiene portion is not less than 20% and less than 50%;
• wherein the decomposed component S1 is represented by following general formula (I):
• the decomposed component S1V1 is represented by at least one selected from following general formulae (II) and (III):
• and
• the decomposed component S1V2 is represented by at least one selected from following general formulae (IV) through (VI):