Rubber composition and tire having tread thereof

A rubber composition comprised of

• (A) 100 parts by weight of at least one diene-based elastomer selected from homopolymers of conjugated dienes, copolymers of conjugated dienes and copolymers of conjugated dienes with vinyl aromatic compounds selected from at least one of styrene and alpha-methylstyrene;
• (B) about 30 to about 100 phr of reinforcing filler composed of (i) a functionalized carbon black composite containing integral silica on the surface thereof or (ii) about 30 to about 100 phr of said functionalized carbon black composite and about 10 to about 80 phr of at least one of classical rubber reinforcing carbon black and precipitated silica, wherein said functionalized carbon black composite is exclusive of carbon blacks created by reacting a carbon black with an organic silane and is formed by (1) co-fuming carbon black and silica at an elevated temperature in a manner to provide composite of carbon black with integral, discrete silica domains primarily on the surface thereof followed by (2) reacting said carbon black composite with a trialkoxy silane of the formula (OR)3SiR1 wherein R is selected from at least one of methyl, ethyl and propyl radicals and R1 is selected from at least one of hexyl, octyl, dodecyl, hexadecyl and octadecyl radicals;
• wherein said silica domains of said carbon black composite and said precipitated silica contain silanol groups on the surface thereof;
• wherein said carbon black of said carbon black composite and said classical carbon black contain hydroxyl groups on the surface thereof;
• and wherein the silicon to carbon ratio of said carbon black composite is in a range of about 0.1/1 to about 0.9/1, and
• (C) at least one coupling agent having a moiety reactive with the said silanol groups and said hydroxyl groups and another moiety interactive with at least one of said diene-based elastomers.