Phase segregated block copolymers with tunable properties

Abstract

Phase segregated block-copolymer based on repeating structural elements represented by formula I ##STR00001## wherein PHA represents at least one block based on one or more α-hydroxy acids, PDAS represents a central block based on a dialkylsiloxane, the PDAS block has a weight average molecular weight in the range of from 4000 to 10000, the blocks PHA have a weight average molecular weight in the range of from 2000 to 10 000, the phase segregated block copolymer has a weight average molecular weight of from 40 000 to 120 000.

Claims

1. A product comprising a stent, a suture, an orthodontic material, a bone screw, a nail, a catheter, a tube, an orthopedic brace, a splint, or a scaffold for tissue engineering, the product further comprising a phase segregated block-copolymer comprising repeating structural elements represented by formula I ##STR00010## wherein PHA represents at least one block comprising one or more α-hydroxy acids, PDAS represents a central block comprising a dialkylsiloxane, the PDAS block has a weight average molecular weight in the range of from 4,000 to 10,000, the blocks PHA have a weight average molecular weight in the range of from 1,500 to 10,000, the phase segregated block copolymer has a weight average molecular weight of from 40,000 to 120,000, and R is a residue of a diisocyanate.

2. The product in accordance with claim 1 wherein the α-hydroxy acids are represented by the formula ##STR00011## wherein R is a linear, branched, or cyclic aliphatic group having 1 to 30 carbon atoms, an aryl group comprising 6 to 30 carbon atoms which may comprise a fused ring, or an alkylaryl group having 7 to 40 carbon atoms.

3. The product in accordance with claim 1, wherein the α-hydroxy acid is selected from glycolic acid, lactic acid, malic acid, fumaric acid, citric acid, tartaric acid or from products obtained through diazotation of α-amino acids.

4. The product in accordance with claim 3 wherein the α-hydroxy acid is selected from malic acid, lactic acid or glycolic acid or mixtures thereof.

5. The product in accordance with claim 4 wherein the α-hydroxy acid is selected from lactic acid or glycolic acid or mixtures thereof.

6. The product in accordance with claim 1, wherein the alkyl groups of the dialkylsiloxane may be the same or different at each occurrence, and represent linear, branched or cyclic alkyl groups.

7. The product in accordance with claim 6 wherein the alkyl groups of the dialkylsiloxane are linear or branched alkyl groups having 1 to 12 carbon atoms.

8. The product of claim 7, wherein the phase segregated block-copolymer has a weight average molecular weight of from 50,000 to 90,000.

9. The product in accordance with claim 6 wherein the alkyl groups of the dialkylsiloxane are methyl groups.

10. The product of claim 9, wherein the phase segregated block-copolymer has a weight average molecular weight of from 50,000 to 90,000.

11. The product of claim 9, wherein the phase segregated block-copolymer has a weight average molecular weight of from 50,000 to 90,000, and wherein the copolymer is biodegradable.

12. The product of claim 9, wherein the phase segregated block-copolymer has a weight average molecular weight of from 50,000 to 90,000, wherein the copolymer is a shape memory copolymer.

13. The product of claim 6, wherein the phase segregated block-copolymer has a weight average molecular weight of from 50,000 to 90,000.

14. The product in accordance with claim 1, wherein the phase segregated block-copolymer is biodegradable.

15. The product in accordance with claim 1, wherein the phase segregated block-copolymer is a shape memory polymer.

16. The product in accordance with claim 1, wherein the product is a suture, an orthodontic material, a bone screw, a nail, a catheter, a tube, an orthopedic brace, a splint, or a scaffold for tissue engineering.

17. The product in accordance with claim 1, wherein the product is a shape recovery polymer stent.

18. The product of claim 1, wherein the phase segregated block-copolymer has a weight average molecular weight of from 50,000 to 90,000.

Description

EXAMPLES 1-4

(1) Pre-dried Poly(dimethylsiloxane), bis(hydroxyalkyl) terminated (Mw˜8500 g/mol, Mn 5600 g/mol, PDI 1.5, purchased from Sigma Aldrich) and lactide (98%, Aldrich) were charged in a clean pre-dried three-neck round-bottom flask (equipped with overhead KPG stirrer, reflux condenser) and dried in vacuo for 1 h. The reactor was flushed with Argon as an inert gas and was connected to Argon balloon during the reaction. Dry toluene (dried by Na in Ar atmosphere) was added as solvent and the reaction mixture was heated to 90° C. (using a silicon oil bath with a magnetic stirrer). Sn(Oct).sub.2 catalyst (1-0.5 mol-% of lactide) dissolved in 5 mL dry toluene was added drop wised and the reaction mixture was stirred for 20 h at 90° C. (after addition of glycolide 15 h more).

(2) 10-20 mL dry toluene was added for high viscous solutions. The temperature was decreased to 70° C. and 1,6-hexamethylene diisocyanate (HDI), dissolved in 5 mL dry toluene was added drop wised. The mixture was stirred for 2.5 h at 70° C. The temperature was elevated to 90° C. and pre-dried 1,4-Butanediol (BD) chain extender was added. The mixture was stirred for 2 h at 90° C. Oil bath was removed and the mixture was stirred over night at room temperature.

(3) Work-Up

(4) The polymer solution was diluted with the reaction solvent if it is too viscous, coagulated in 500 mL cold Ethanol, washed with technical grade Ethanol (3 times, 500 mL) and finally dried under reduced pressure to yield constant weight.

(5) The details of the experiments are shown in Table 1.

(6) TABLE-US-00001 TABLE 1 PDMS Macro- Lactide or Sn(Oct).sub.2 BD initiator Glycolide Solvent μL μL μL Ex. 1 PSLLU 7.4 g  7.2 g 20 mL 323 424 117 1:1 L-Lactide Toluene Ex. 2 PSLLU 7.4 g 10.8 g 30 mL 485 424 117 1:1.5 L-Lactide Toluene Ex. 3 PSLLU 7.4 g 14.4 g 40 mL 646 424 117 1:2 L-Lactide Toluene Ex. 4 PSLGU 7.4 g 5.76 g 20 mL 162 424 117 1:0.8:0.2 L-Lactide + Toluene 1.16 g 10 mL Glycolide DMAc (by (after 20 h Glycolide of reaction) addition)

(7) The molecular weight of the starting materials, the intermediate block polymers obtained before addition of the HDI and of the final products products as well as the polydispersity index are given in Table 2 was determined by GPC as described before. as can be seen the PDMS block had a Mw of 8500 g/mol, the PLA block of between 6900 and 9200 g/mol and the final products had molecular weights Mw of from 55900 to 79400 g/mol. A comparative product (Example 4) obtained from PDMS and HDI only (without lactide) had a Mw of 135 000 and a polydispersity index of 1.36.

(8) TABLE-US-00002 TABLE 2 PDMS content PLA content Example Mw PDI wt % Wt % 1 intermediate 15,500 1.33 49 49 1 final 79,400 1.55 48 49 2 intermediate 17,700 1.29 41 58 2 final 55,900 1.36 40 59 3 intermediate 17,200 1.08 34 64 3 final 58,600 1.34 33 66 4 intermediate — — — — 4 final 135,470 1.36 100 0

(9) The products in accordance with the invention showed good thermal stability and mechanical properties and were melt processible. They had an excellent property spectrum for implementation in temperature triggered cardiovascular implants, in particular for the manufacture of shape recovery polymer stents activatable at the human body temperature.