Preparing isotactic stereoblock poly(lactic acid)

• US 6,538,101 B2
• Filed: 09/21/2001
• Issued: 03/25/2003
• Est. Priority Date: 10/24/2000
• Status: Expired due to Fees

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Inventors: Ovitt, Tina M., Coates, Geoffrey W.
• Primary Examiner(s): HAMPTON HIGHTOWER, PATRICIA
• Application Number:
  US09/957,666
• Publication Number:
  US 20020055612A1
• Time in Patent Office: 550 Days
• Field of Search: 528/354, 528/357, 528/355, 528/359, 528/361, 528/363
• US Class Current: 528/354
• CPC Class Codes: C08G 63/06 derived from hydroxycarboxylic acids
• CPC Class Codes: C08G 63/08 Lactones or lactides
• CPC Class Codes: C08G 63/823 for the preparation of polylactones or polylactides

Abstract

A stereospecific poly(lactic acid) is isotactic poly(lactic acid) having a number average molecular weight ranging from 10,000 to 200,000 grams per mole, with, on average, an equal number of poly (R) and poly (S) blocks where each block contains an average of 5 to 50 monomer units. Product was prepared by polymerizing rac-lactide in the presence of racemic catalyst consisting of:

and the corresponding S-enantiomer or in the presence of racemic catalyst consisting of:

and the corresponding S-enantiomer, wherein R is C₁-C₄ alkyl which is straight chain or branched.

Claims

1. Isotactic stereoblock poly(lactic acid) having a number average molecular weight ranging from 10,000 to 200,000 grams per mole with, on average, an equal number of poly (R) and poly (S) blocks of equal average number of monomer units where each block contains an average of 9 to 50 monomer units.

2. The isotactic stereoblock poly(lactic acid) of claim 1 having a M_n of 22,600 grams per mole, with an average of 11 monomer units in each block.

3. The isotactic stereoblock poly(lactic acid) of claim 1 having a M_n of 29,560 grams per mole, with an average of 10 monomer units in each block.

4. A method for preparing the isotactic stereoblock poly(lactic acid) of claim 1 which comprises polymerizing rac-lactide in the presence of a racemic catalyst consisting of:

and the corresponding S-enantiomer, where R is C₁-C₄ alkyl which is straight chain or branched.

5. The method of claim 4 which is for preparing isotactic stereoblock poly (lactic acid) having a M_n of 22,600 moles per gram with, on average, an equal number of poly (R) and poly (S) block where each block contains an average of 11 monomer units, where R in the catalyst is isopropyl.

6. A method of preparing the isotactic stereoblock poly(lactic) acid of claim 1 which comprises polymerizing rac-lactide in the presence of racemic catalyst consisting of:

and the corresponding S-enantiomer, where R is C₁-C₄ alkyl which is straight chain or branched.

7. The method of claim 6 which is for preparing isotactic stereoblock poly (lactic acid) having a M_n of 29,560 grams per mole, with, on average, an equal number of poly (R) and poly (S) blocks where each block contains an average of 10 monomer units, where R in the catalyst is isopropyl.

8. The isotactic stereoblock poly (lactic acid) of claim 1 with, on average, an equal number of poly (R) and poly (S) blocks where each block contains an average of 10 to 50 monomer units.

9. The method of claim 5 where the polymerization is performed at a temperature ranging from 50 to 100°

C.

10. The method of claim 7 where the polymerization is performed at a temperature ranging from 50 to 100°

C.