Silica reinforced rubber composition containing a multi-functional group functionalized elastomer and tire with tread

1. A rubber composition comprised of:

(A) at least one conjugated diene-based elastomer comprising at least one of a high vinyl and low vinyl polybutadiene;

(B) filler reinforcement for said rubber composition comprised of a combination of precipitated silica and rubber reinforcing carbon black, together with silica coupling agent having a moiety reactive with silanol groups on said precipitated silica and another different moiety interactive with said diene-based elastomers,

wherein at least one conjugated diene-based elastomer is an end-chain functionalized diene-based elastomer, wherein the end-chain functionalized conjugated diene-based elastomer is a reaction product, absent an intermediary, of a diene elastomer terminated with an alkoxyorganosilane polysulfide comprised of the general formula:

(R 1 O) 3 —Si—R 2 —S x —R 2 —Si—(OR 1 ) 3

wherein R1 represents the same or different aliphatic hydrocarbon radicals containing from 1 to 12 carbon atoms, R2 represents an aliphatic hydrocarbon containing from 1 to 8 carbon atoms and x represents a value of from 1 to and including 8 such that the polysulfide has an average of from about 2 to about 2.6 connecting sulfur atoms in its polysulfidic bridge; and

wherein the multi-functional groups are exclusive of alkoxyorganomercaptosilanes and alkoxyaminosilanes.

2. The rubber composition of claim 1 comprised of

(A) 100 phr of conjugated diene-based elastomers comprised of:

(1) about 10 to about 90 phr of a diene-based elastomer containing at least one end-chain multi-functional group of comprised of an alkoxyorganosilane polysulfide of claim 1 , and

(2) about 90 to about 10 phr of at least one additional diene-based elastomer; and

(B) about 40 to about 200 phr of the rubber reinforcing filler.

3. The rubber composition of claim 2 wherein, for said end-chain multi-functionalized elastomer, said end-chain group is a bis(3-trialkoxysilylalkyl) polysulfide.

4. The rubber composition of claim 3 wherein, for said end-chain multi-functional elastomer, at least one of said R 1 radicals of said bis(3-trialkoxysilylalkyl) polysulfide is an ethyl radical.

5. The rubber composition of claim 4 wherein, for said end-chain multi-functional elastomer, said alkoxyorganosilane polysulfide is a bis(3-triethoxysilylpropyl) polysulfide.

6. The rubber composition of claim 1 wherein, for said end-chain multi-functional elastomer, at least one of said R 1 radicals of said alkoxyorganosilane polysulfide is an ethyl radical.

7. The rubber composition of claim 1 wherein, for said end-chain multi-functional elastomer, said conjugated diene-based elastomer containing at least one of said end-chain polyfunctional groups is comprised of at least one of polymers of at least one of isoprene and 1,3-butadiene monomers and of styrene with at least one of isoprene and 1,3-butadiene monomers.

8. The rubber composition of claim 1 , wherein said elastomers are comprised of a mixture of end-chain functionalized and non-functionalized elastomers wherein at least 50 percent of said elastomers of said mixture are said end-chain functionalized elastomer.

9. The rubber composition of claim 1 further comprising, based on parts by weight per 100 parts by weight of rubber (phr):

(A) 100 phr of conjugated diene-based elastomers comprised of;

(1) about 10 to about 90 phr of at least one of diene-based elastomer containing at least one end-chain multi-functional group comprised of an alkoxyorganosilane polysulfide of claim 1 , and

(2) about 90 to about 10 phr of at least one additional diene-based elastomer exclusive of styrene containing elastomers, and

(B) about 40 to about 200 phr of rubber reinforcing filler comprised of a combination of precipitated silica and rubber reinforcing carbon black, together with silica coupling agent having a moiety reactive with silanol groups on said precipitated silica and another different moiety interactive with said diene-based elastomers.

10. The rubber composition of claim 1 wherein said end-chain multi-functional elastomer is comprised of a plurality of elastomer chains terminated by the same multi-functional group.

11. The rubber composition of claim 1 wherein said rubber composition is a sulfur cured rubber composition.

12. A tire having a component comprised of the rubber composition of claim 1 wherein said rubber composition is a sulfur cured rubber composition.

13. The tire of claim 12 wherein said component is a tire tread.