Monovinylarene/conjugated diene copolymers having lower glass transition temperatures

1. A monovinylarene/conjugated diene block copolymer, comprising:

a random (conjugated diene x /monovinylarene y ) m block, wherein x is about 2.5 wt % to about 10 wt %, y is from about 90 wt % to about 97.5 wt %, and x+y is about 97.5 wt % to 100 wt %; and

a (conjugated diene) n block;

wherein n is from about 20 wt % to about 30 wt %, m is from about 70 wt % to about 80 wt %, and m+n is from about 90 wt % to 100 wt %.

2. The monovinylarene/conjugated diene block copolymer of claim 1 , wherein x is about 5 wt % to about 10 wt %.

3. The monovinylarene/conjugated diene block copolymer of claim 1 , wherein y is about 90 wt % to about 95 wt %.

4. The monovinylarene/conjugated diene block copolymer of claim 1 , wherein n is about 25 wt % and m is about 75 wt %.

5. The monovinylarene/conjugated diene block copolymer of claim 1 , wherein the T g is at least about 10° C. less than the T g of a reference polymer differing only in x being about 0 wt % and y being about 100 wt %.

6. The monovinylarene/conjugated diene block copolymer of claim 5 , wherein the T g is at least about 20° C. less than the T g of the reference polymer.

7. The monovinylarene/conjugated diene block copolymer of claim 6 , wherein the T g is at least about 30° C. less than the T g of the reference polymer.

8. The monovinylarene/conjugated diene block copolymer of claim 1 , further comprising a monovinylarene/conjugated diene block.

9. The monovinylarene/conjugated diene block copolymer of claim 1 , further comprising a monovinylarene block.

10. An article, comprising the monovinylarene/conjugated diene block copolymer of claim 1 .

11. The article of claim 10 , wherein the article is a shrink film.

12. A method of preparing a monovinylarene/conjugated diene block copolymer comprising:

(a) charging a monovinylarene monomer, a conjugated diene monomer, an initiator, and a randomizer, allowing polymerizing to occur, to produce a random (conjugated diene x /monovinylarene y ) m block; wherein x is about 2.5 wt % to about 10 wt %, y is from about 90 wt % to about 97.5 wt %, and x+y is about 97.5 wt % to 100 wt %, and m is from about 70 wt % to about 80 wt %;

(b) charging a monovinylarene monomer, a conjugated diene monomer, and an initiator, allowing polymerization to occur, to produce a monovinylarene/conjugated diene block;

(c) charging a conjugated diene monomer, and allowing polymerization to occur, to produce a (conjugated diene) n block, wherein n is from about 20 wt % to about 30 wt % and m+n is from about 90 wt % to 100 wt %; and

(d) charging the reaction mixture with a coupling agent, to form monovinylarene/conjugated diene block copolymer.

13. A monovinylarene/conjugated diene block copolymer, produced according to the method of claim 12 .

14. A method of preparing a monovinylarene/conjugated diene block copolymer comprising:

(a) charging an initiator and a monovinylarene monomer and allowing polymerization to occur, to produce a monovinylarene block;

(b) charging a randomizer, an initiator, and a conjugated diene/monovinylarene monomer mixture and allowing polymerization to occur, to produce a random (conjugated diene x /monovinylarene y ) m block, wherein x is about 2.5 wt % to about 10 wt %, y is from about 90 wt % to about 97.5 wt %, x+y is about 97.5 wt % to 100 wt %, and m is from about 70 wt % to about 80 wt %;

(c) charging a conjugated diene monomer and allowing polymerization to occur, to produce a conjugated diene block;

(d) charging a randomizer, an initiator, and a conjugated diene/monovinylarene monomer mixture and allowing polymerization to occur, to produce a random (conjugated diene x /monovinylarene y ) m1 block, wherein x 1 is about 2.5 wt % to about 10 wt %, y 1 is from about 90 wt % to about 97.5 wt %. x 1 +y 1 is about 97.5 wt % to 100 wt %, and m 1 is from about 70 wt % to about 80 wt %;

(e) charging a conjugated diene monomer and allowing polymerization to occur, to produce a conjugated diene block; and

(f) charging the reaction mixture with a coupling agent, to form monovinylarene/conjugated diene block copolymer.

15. A monovinylarene/conjugated diene block copolymer, produced according to the method of claim 14 .

16. A method of fabricating an article, comprising:

forming a monovinylarene/conjugated diene block copolymer into the article, wherein the monovinylarene/conjugated diene block copolymer comprises (i) a random (conjugated diene x /monovinylarene y ) m block, wherein x is about 2.5 wt % to about 10 wt %, y is from about 90 wt % to about 97.5 wt %, and x+y is about 97.5 wt % to 100 wt %; and (ii) a (conjugated diene) n block; wherein n is from about 20 wt % to about 30 wt %, m is from about 70 wt % to about 80 wt %, and m+n is from about 90 wt % to 100 wt %.

17. The method of claim 16 , wherein forming comprises sheet extrusion, thermoforming, injection molding, blow molding, film blowing, or film casting.

18. A monovinylarene/conjugated diene block copolymer, comprising the structure:

(B/S)-B-CA,

wherein (B/S) is a random monovinylarene/conjugated diene block; B is a conjugated diene block; CA is a coupling agent residue; and —is a covalent linkage between blocks, and

wherein the monovinylarene/conjugated diene block copolymer further comprises a second structure selected from the group consisting of (a) a (B/S) block covalently linked to the (B/S) block of the (B/S)-B-CA structure, (b) a (B/S)-(B/S)-B structure covalently linked to the (B/S) block of the (B/S)-B-CA structure, (c) a (B/S)-B structure covalently linked to the (B/S) block of the (B/S)-B-CA structure, and (d) an S-(B/S)-B- structure covalently linked to the (B/S) block of the (B/S)-B-CA structure, wherein S is a monovinylarene block.

19. The monovinylarene/conjugated diene block copolymer of claim 18 , wherein the second structure is a (B/S) block covalently linked to the (B/S) block of the (B/S)-B-CA structure.

20. The monovinylarene/conjugated diene block copolymer of claim 18 , wherein the second structure is a (B/S)-(B/S)-B structure covalently linked to the (B/S) block of the (B/S)-B-CA structure.

21. The monovinylarene/conjugated diene block copolymer of claim 18 , wherein the second structure is a (B/S)-B structure covalently linked to the (B/S) block of the (B/S)-B-CA structure.

22. The monovinylarene/conjugated diene block copolymer of claim 18 , wherein the second structure is a S-(B/S)-B- structure covalently linked to the (B/S) block of the (B/S)-B-CA structure, wherein S is a monovinylarene block.

23. A monovinylarene/conjugated diene block copolymer, comprising the structure:

<B/S>2-<B/S>3-<B/S>4-<B/S>5-CA,

wherein <B/S> is a tapered monovinylarene/conjugated diene block; <B/S>2 has a conjugated diene content from about 2.5 wt % to about 10 wt %, <B/S>3, <B/S>4, and <B/S>5 have a conjugated diene content from about 30 wt % to about 70 wt %, and CA is a coupling agent residue.

24. The monovinylarene/conjugated diene block copolymer of claim 23 , further comprising a <B/S>1 block covalently linked to the <B/S>2 block of the <B/S>2-<B/S>3-<B/S>4-<B/S>5-CA structure, wherein <B/S>1 has a conjugated diene content from about 2.5 wt % to about 10 wt %.

25. A monovinylarene/conjugated diene block copolymer, comprising the structure:

(B/S)1-(B/S)2-<B/S>3-<B/S>4-<B/S>5-CA,

wherein (B/S) is a random monovinylarene/conjugated diene block; <B/S> is a tapered monovinylarene/conjugated diene block; CA is a coupling agent residue; —is a covalent linkage between blocks; (B/S)1 and (B/S)2 each have a conjugated diene content from about 2.5 wt % to about 10 wt %; and <B/S>3, <B/S>4, and <B/S>5 each have a conjugated diene content from about 30 wt % to about 70 wt %.

26. A monovinylarene/conjugated diene block copolymer, comprising the structure:

(B/S)1-(B/S)2-(B/S)3-(B/S)4-(B/S)5-CA,

wherein (B/S) is a random monovinylarene/conjugated diene block; CA is a coupling agent residue; —is a covalent linkage between blocks; (B/S)1 and (B/S)2 each have a conjugated diene content from about 2.5 wt % to about 10 wt %; and (B/S)3, (B/S)4, and (B/S)5 each have a conjugated diene content from about 30 wt % to about 70 wt %.