Miktopolymer compositions

1. An elastomeric polymer composition comprising miktopolymers of the structure (A 2 -B) n —X-(A 1 ), where

a. A 1 and A 2 are each a polymer block of a monoalkenyl arene and B is a polymer block of one or more conjugated dienes or a hydrogenated polymer block of one or more conjugated dienes;

b. n is an integer from 2 to 30; and

c. X is the residue of a coupling agent;

and wherein:

i. τ is an asymmetry parameter of monoalkenyl arene associated with the A 1 and A 2 blocks according to the formula τ=NA 1 /(NA 1 +NA 2 ) where NA 1 is the number of monomer units in the A 1 monoalkenyl arene block and NA 2 is the number of monomer units in an A 2 monoalkenyl arene block;

ii. f is the volume fraction of monoalkenyl arene in said miktopolymer;

iii. τ has a value of 0.7 to 0.95;

iv. f has a value greater than or equal to 0.4; and

v. block A 1 has a peak molecular weight of between 10,000 and 300,000, where the ratio of the peak molecular weight of A 1 to A 2 is greater than or equal to 2.

2. The composition according to claim 1 , wherein said monoalkenyl arene for the A 1 and A 2 blocks is styrene and said conjugated diene for the B block is selected from the group consisting of isoprene, 1,3-butadiene and mixtures thereof.

3. The composition according to claim 2 , wherein at least 90% of the unsaturated bonds in the B blocks of the polymer are hydrogenated and the conjugated diene is 1,3-butadiene and wherein about 20 to about 80 mol percent of the condensed butadiene units in block B have 1,2-configuration.

4. The composition according to claim 2 , wherein the monoalkenyl arene content ranges from about 40 to about 75 weight percent of said miktopolymer.

5. The composition according to claim 1 , wherein said block A 1 has a peak molecular weight of between 10,000 and 300,000, said A 2 block has a peak molecular weight of between 5,000 and 30,000, and said block B has a peak molecular weight of between 10,000 and 150,000.

6. A composition according to claim 1 and comprising at least one component selected from the group consisting of fillers, reinforcements, polymer extending oils, tackifying resins, lubricants, stabilizers, styrene polymers, antioxidants, styrene/diene block copolymers and polyolefins.

7. A composition according to claim 1 , wherein the composition is catalytically hydrogenated and at least about 90 percent of the conjugated diene double bonds have been reduced and between 0 to about 10 percent of the arene double bonds have been reduced.

8. A process for preparing a miktopolymer of the structure (A 2 -B) n —X-(A 1 ), where

a. A 1 and A 2 are each a polymer block of a monoalkenyl arene and B is a polymer block of one or more conjugated dienes or a hydrogenated polymer block of one or more conjugated dienes;

b. n is an integer from 2 to 30;

c. X is the residue of a coupling agent;

d. τ is an asymmetry parameter of monoalkenyl arene associated with the A 1 and A 2 blocks according to the formula τ=NA 1 /(NA 1 +NA 2 ) where NA I is the number of monomer units in the A 1 monoalkenyl arene block and NA 2 is the number of monomer units in an A 2 monoalkenyl arene block;

e. f is the volume fraction of monoalkenyl arene in said miktopolymer;

said process comprising:

i. polymerizing a monoalkenyl arene in a first reactor in the presence of an inert hydrocarbon solvent and an organolithium initiator whereby a living polymer block A 2 terminated with a lithium ion is formed;

ii. adding a conjugated diene to the first reactor and continuing the polymerization of the conjugated diene whereby a living polymer block A 2 B terminated with a lithium ion is formed;

iii. polymerizing a monoalkenyl arene in a second reactor in the presence of an inert hydrocarbon solvent and an organolithium initiator whereby a living polymer block A 1 terminated with a lithium ion is formed; and

iv. combining the contents of the first reactor and second reactor, and then adding a coupling agent, wherein said miktopolymer is formed;

wherein the molecular weights of the A 1 and A 2 blocks and the amount of A 2 B blocks and A 1 blocks are controlled to achieve a value for τ of 0.7 to 0.95 and a value for f greater than or equal to 0.4.

9. The process according to claim 8 , wherein said mono alkenyl arene for the A 1 and A 2 blocks is styrene and said conjugated diene for the B block is selected from the group consisting of isoprene, 1,3-butadiene and mixtures thereof.

10. The process according to claim 9 , wherein said conjugated diene is 1,3-butadiene and wherein less than about 15 mol percent of the condensed butadiene units in block B have 1,2-configuration.

11. The process according to claim 10 , wherein the monoalkenyl arene content ranges from about 40 to about 75 weight percent for the miktopolymer.

12. The process according to claim 11 , wherein said block A 1 has a peak molecular weight of between 10,000 and 300,000, said A 2 block has a peak molecular weight of between 5,000 and 30,000, and said block B has a peak molecular weight of between 20,000 and 150,000.

13. A process according to claim 8 , wherein n is an integer from 4 to 10.

14. The process of claim 8 , wherein an article is formed in a process selected from the group consisting of injection molding, over molding, dipping, extrusion, roto molding, slush molding, fiber spinning, film making or foaming.

15. The process of claim 14 , wherein an article is selected from the group consisting of closures, synthetic corks, cap seals, tubing, food containers, beverage containers, interior automotive parts, window gaskets, elastic films, foamed products, gels, cushions, bicomponent fibers, monofilaments, adhesives, cosmetics and medical goods.

16. The process according to claim 8 , wherein the miktopolymer is catalytically hydrogenated and at least about 90 percent of the conjugated diene double bonds have been reduced and between 0 to about 10 percent of the arene double bonds have been reduced.