Block copolymers and method for making same
The present invention is a novel block copolymer containing a controlled distribution copolymer block of a conjugated diene and a mono alkenyl arene, where the controlled distribution copolymer block has terminal regions that are rich in conjugated diene units and a center region that is rich in mono alkenyl arene units. Also disclosed is a method for manufacture of the block copolymer.
1. A functionalized, selectively hydrogenated block copolymer having the general configuration A-B, A-B-A, (A-B) n , (A-B-A) n X, (A-B) n X or mixtures thereof, where n is an integer from 2 to about 30, and X is coupling agent residue wherein:
a. prior to hydrogenation each A block is a mono alkenyl arene polymer block and each B block is a controlled distribution copolymer block of at least one conjugated diene and at least one mono alkenyl arene;
b. subsequent to hydrogenation about 0–10% of the arene double bonds have been reduced, and at least about 90% of the conjugated diene double bonds have been reduced;
c. each A block has a number average molecular weight between about 3,000 and about 60,000 and each B block has a number average molecular weight between about 30,000 and about 300,000;
d. each B block comprises terminal regions adjacent to the A block that are rich in conjugated diene units and one or more regions not adjacent to the A block that are rich in mono alkenyl arene units;
e. the total amount of mono alkenyl arene in the hydrogenated block copolymer is about 20 percent weight to about 80 percent weight;
f. the weight percent of mono alkenyl arene in each B block is between about 10 percent and about 75 percent;
g. the styrene blockiness index of the B block is less than about 40 percent; and
h. at least one of the mono alkenyl arene polymer blocks has a sulfonic acid or sulfonate functional group.
2. The hydrogenated block copolymer of claim 1 wherein the block copolymer has from about one (1) sulfonic acid or sulfonate group per molecule of the block copolymer to about (1) sulfonic acid or sulfonate group per aromatic ring of the block copolymer.
3. The hydrogenated block copolymer of claim 2 wherein the block copolynier has from about three (3) sulfonic acid or sulfonate groups per molecule of the block copolymer to about one (1) sulfonic acid or sulfonate group per two (2) aromatic rings of the block copolymer.
4. The hydrogenated block copolymer of claim 3 wherein the mono alkenyl arene is styrene and the conjugated diene is selected from the group consisting of isoprene and butadiene.
5. The hydrogenated block copolyrner of claim 4 wherein the conjugated diene is butadiene, and wherein about 20 to about 80 mol percent of the condensed butadiene units in block B have 1,2-configuration prior to hydrogenation.
6. The hydrogenated block copolymer of claim 5 wherein the weight percentage of styrene in the B block is between about 10 percent and about 40 percent, and the styrene blockiness index of the block B is less than about 10 percent, the styrene blockiness index being the proportion of styrene units in the block B having two styrene neighbors on the polymer chain.