Method for preparation of a polyester

Abstract

Disclosed in the present invention is a preparation method for a polyester, relating to the technical field of organic catalysis and polymeric materials. The preparation method in the present invention comprises: (1) using pyridine and saccharin in a ratio of 1:1 to prepare pyridine saccharin salt in tetrahydrofuran at 60° C. and separating the pyridine saccharin salt out in methanol and hexane. (2) Freeing out a small amount of pyridine from the pyridine saccharin salt in a heating state, catalyzing by the pyridine saccharin salt and pyridine a cyclic lactone or a carbonate to be ring-opened and polymerized to form the polyester; and the system has no other compound residues. (3) In the presence of an alcohol initiator, catalyzing by the pyridine saccharin salt the cyclic lactone to be ring-opened and polymerized to obtain the polyester. The catalytic system can efficiently synthesize a specific polylactone. Compared with a method for synthesizing a polyester by the use of a metal-containing catalyst in the prior art, the system has wide application. Moreover, the system is advantageous of no metal residue, narrow molecular weight distribution and no chain transesterification, and therefore has great commercial application potential in bio-pharmaceutical field and microelectronic field.

Claims

1. A method for preparing a polyester, comprising: conducting a ring-opening polymerization of a cyclic lactone monomer or a cyclic carbonate monomer in presence of an initiator alcohol and a catalyst to obtain a polyester, wherein the catalyst is a pyridine saccharin salt of Formula III prepared by a reaction between a saccharin of Formula I and a substituted pyridine ring of Formula II: ##STR00042## wherein, in Formula II, R.sup.1, R.sup.2, and R.sup.3 are selected from N,N-dimethylamino, pyrrolidinyl, hydrogen, unsubstituted C1-C10 alkyl groups, and C1-C10 alkyl groups substituted with one or more of the same or different substituent selected from a halogen atom, a hydroxyl group, a phenyl group, and a substituted phenyl group.

2. The method according to claim 1, wherein, in Formula II, when R.sup.1 is selected from one of N,N-dimethylamino, pyrrolidinyl, and hydrogen, R.sup.2 and R.sup.3 are independently selected from hydrogen, ethyl, isopropyl, tert-butyl, sec-butyl, and C1-C10 alkyl groups substituted with the same or different substituents selected from a halogen atom, a hydroxyl group, a phenyl group, and a substituted phenyl group; and when R.sup.3 is selected from one of N,N-dimethylamino, pyrrolidinyl, and hydrogen, R.sup.1 and R.sup.2 are independently selected from hydrogen, ethyl, isopropyl, t-butyl, sec-butyl, C1-C10 alkyl groups substituted with the same or different substituents selected from a halogen atom, a hydroxyl group, a phenyl group, and a substituted phenyl group.

3. The method according to claim 2, wherein the substituted pyridine ring of Formula II has a structural formula selected from No. 1-12: TABLE-US-00004 No. Structure 1 2 3 4 5 6 7 8 9 10 11 12

4. The method according to claim 1, wherein the pyridine saccharide salt of Formula III is prepared by recrystallization of the saccharin of Formula I and the substituted pyridine ring of Formula II in a tetrahydrofuran solution at 60° C.

5. The method according to claim 1, wherein the cyclic lactone monomer or the cyclic carbonate monomer is of Formula IV, Formula V, or Formula VI, wherein, in Formula IV, ##STR00055## A is [—(CR.sup.1R.sup.2)—].sub.n, n is an integer of 2-10; R.sup.1 and R.sup.2 are independently selected from H, C1-C5 alkyl groups, and C1 and C5 alkyl groups substituted with a halogen atom or a hydroxyl group, X is O or NH, wherein, in Formula V, ##STR00056## A and B are [—(CR.sup.1R.sup.2)—].sub.n, n is an integer of 0-10, and A and B are the same or different; and R.sup.1 and R.sup.2 are independently selected from H, C1-C5 alkyl groups, and C1 and C5 alkyl groups substituted with a halogen atom or a hydroxyl group, X is O or NH, and wherein, in Formula (VI) ##STR00057## R.sup.1 and R.sup.2 are independently from H, C1-C5 alkyl groups substituted with a halogen atom or a hydroxyl group.

6. The method according to claim 5, wherein the cyclic monomer of Formula (IV) is ##STR00058## β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, macrocyclic undecanolactone, β-propiolactam, ε-caprolactam, or chlorocaprolactone.

7. The method according to claim 5, wherein the cyclic monomer of Formula (V) ##STR00059## is glycolide, lactide, bromoglycolide, 3,6-dimethyl morpholine-2,5-dione, tetranolide, decanolide, macrocyclic decanolide, ο-carboxyanhydride, or N-carboxyanhydride.

8. The method according to claim 5, wherein the cyclic monomer is trimethylene carbonate, hydroxytrimethylene carbonate, or chlorotrimethylene carbonate.

9. The method according to claim 1, wherein the initiator alcohol is methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, benzyl alcohol, phenylethyl alcohol, ethylene glycol, triethyleneglycol or pentaerythritol.

10. The preparation method according to claim 1, wherein the ring-opening polymerization is carried out at 90-150° C., and further comprises dissolving a reaction product in a good solvent to form a solution; and adding a solvent into the solution to precipitate the polyester, wherein the good solvent is dichloromethane, chloroform, toluene, benzene, acetone, or tetrahydrofuran, and the solvent is methanol, ethanol, or water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Examples of the present invention will be described in detail with reference to the accompanying drawings, in which

(2) FIG. 1: .sup.1H NMR spectrum of polylactic acid prepared by using 4-(N,N-dimethylamino) pyridine saccharin salt as a catalyst;

(3) FIG. 2: the chromatogram of size exclusion chromatography of polylactic acid prepared by using 4-(N,N-dimethylamino) pyridine saccharin salt as a catalyst;

(4) FIG. 3: .sup.1H NMR spectrum of polypentalactone prepared by using 4-(N,N-dimethylamino) pyridine saccharin salt as a catalyst;

(5) FIG. 4: the chromatogram of size exclusion chromatography of polypentalactone prepared by using 4-(N,N-dimethylamino) pyridine saccharin salt as a catalyst;

DETAILED DESCRIPTION OF THE INVENTION

(6) The invention is further illustrated by the following examples, which are intended to illustrate and not to limit the invention. Those skilled in the art will appreciate that the examples do not limit the invention in any way, and that suitable modifications and data changes may be made thereto without departing from the spirit and scope of the invention.

(7) The structure of the catalyst pyridine saccharin salt used in the examples is as shown in formula III:

(8) ##STR00041##

Example 1

(9) In a 10 mL polymerization tube, butyrolactone (0.3856 g, 2.88 mmol), benzyl alcohol (10 μL, 0.096 mmol), and compound No. 13 (0.029 g, 0.096 mmol) were added and the reaction was magnetically stirred for 2 h at 90° C. After the reaction was finished, the obtained crude product was dissolved in a minimum amount of dichloromethane, and then the mixture was added into a cold methanol solution to separate out polymers. 0.23 g of a white solid was obtained by centrifugation and then transferred to a vacuum oven for drying. The structure of the polymer was identified by .sup.1H NMR and .sup.13C NMR, and the molecular weight and dispersity of the polymer were determined by GPC. After the determination, the conversion of the polymer was 90.6%, the number average molecular weight Mn was 2600 g mol.sup.−1 and the Mn/Mw was 1.36. To the compound No. 13 in a 250 ml reaction flask were added compound No. 1 (12.27 mmol, 1.5 g) and saccharin (12.27 mmol, 1.5 g) and the resultant mixture was stirred in a tetrahydrofuran (THF) solution overnight at 60° C. The solvent was removed under vacuum to give the crude product to which methanol (10 ml) and hexane (20 ml) were added for recrystallization to give white crystals over a period of time at room temperature, which were filtered and dried for later use.

Example 2

(10) In a 10 mL polymerization tube, valerolactone (0.288 g, 2.88 mmol), benzyl alcohol (10 μL, 0.096 mmol), and compound No. 14 (0.0375 g, 0.096 mmol) were added and the reaction was magnetically stirred for 1 h at 90° C. After the reaction was finished, the obtained crude product was dissolved in a minimum amount of dichloromethane, and then the mixture was added into a cold methanol solution to separate out polymers. 0.21 g of a white solid was obtained by centrifugation and then transferred to a vacuum oven for drying. The structure of the polymer was identified by .sup.1H NMR and .sup.13C NMR, and the molecular weight and dispersity of the polymer were determined by GPC. After the determination, the conversion of the polymer was 92.8%, the number average molecular weight Mn was 2900 g mol.sup.−1 and the Mn/Mw was 1.21. To the compound No. 14 in a 250 ml reaction flask were added compound No. 2 (12.27 mmol, 1.5 g) and saccharin (12.27 mmol, 1.5 g) and the resultant mixture was stirred in a tetrahydrofuran (THF) solution overnight at 60° C. The solvent was removed under vacuum to give the crude product to which methanol (10 ml) and hexane (20 ml) were added for recrystallization to give white crystals over a period of time at room temperature, which were filtered and dried for later use.

Example 3

(11) In a 10 mL polymerization tube, caprolactone (0.328 g, 2.88 mmol), benzyl alcohol (10 μL, 0.096 mmol), and compound No. 16 (0.038 g, 0.096 mmol) were added and the reaction was magnetically stirred for 1 h at 100° C. After the reaction was finished, the obtained crude product was dissolved in a minimum amount of dichloromethane, and then the mixture was added into a cold methanol solution to separate out polymers. 0.23 g of a white solid was obtained by centrifugation and then transferred to a vacuum oven for drying. The structure of the polymer was identified by .sup.1H NMR and .sup.13C NMR, and the molecular weight and dispersity of the polymer were determined by GPC. After the determination, the conversion of the polymer was 98.7%, the number average molecular weight Mn was 3500 g mol.sup.−1 and the Mn/Mw was 1.37. To the compound No. 16 in a 250 ml reaction flask were added compound No. 4 (12.27 mmol, 1.5 g) and saccharin (12.27 mmol, 1.5 g) and the resultant mixture was stirred in a tetrahydrofuran (THF) solution overnight at 60° C. The solvent was removed under vacuum to give the crude product to which methanol (10 ml) and hexane (20 ml) were added for recrystallization to give white crystals over a period of time at room temperature, which were filtered and dried for later use.

Example 4

(12) In a 10 mL polymerization tube, glycolide (0.6682 g, 5.76 mmol), benzyl alcohol (10 μL, 0.096 mmol), and compound No. 18 (0.032 g, 0.096 mmol) were added and the reaction was magnetically stirred for 3 h at 140° C. After the reaction was finished, the obtained crude product was dissolved in a minimum amount of dichloromethane, and then the mixture was added into a cold methanol solution to separate out polymers. 0.47 g of a white solid was obtained by centrifugation and then transferred to a vacuum oven for drying. The structure of the polymer was identified by .sup.1H NMR and .sup.13C NMR, and the molecular weight and dispersity of the polymer were determined by GPC. After the determination, the conversion of the polymer was 92.9%, the number average molecular weight Mn was 6600 g mol.sup.−1 and the Mn/Mw was 1.24. To the compound No. 18 in a 250 ml reaction flask were added compound No. 6 (12.27 mmol, 1.5 g) and saccharin (12.27 mmol, 1.5 g) and the resultant mixture was stirred in a tetrahydrofuran (THF) solution overnight at 60° C. The solvent was removed under vacuum to give the crude product to which methanol (10 ml) and hexane (20 ml) were added for recrystallization to give white crystals over a period of time at room temperature, which were filtered and dried for later use.

Example 5

(13) In a 10 mL polymerization tube, lactide (1.2441 g, 8.64 mmol), benzyl alcohol (10 μL, 0.096 mmol), and compound No. 19 (0.036 g, 0.096 mmol) were added and the reaction was magnetically stirred for 5 h at 140° C. After the reaction was finished, the obtained crude product was dissolved in a minimum amount of dichloromethane, and then the mixture was added into a cold methanol solution to separate out polymers. 0.87 g of a white solid was obtained by centrifugation and then transferred to a vacuum oven for drying. The structure of the polymer was identified by .sup.1H NMR and .sup.13C NMR, and the molecular weight and dispersity of the polymer were determined by GPC. After the determination, the conversion of the polymer was 93.4%, the number average molecular weight Mn was 12100 g mol.sup.−1 and the Mn/Mw was 1.36. To the compound No. 19 in a 250 ml reaction flask were added compound No. 7 (12.27 mmol, 1.5 g) and saccharin (12.27 mmol, 1.5 g) and the resultant mixture was stirred in a tetrahydrofuran (THF) solution overnight at 60° C. The solvent was removed under vacuum to give the crude product to which methanol (10 ml) and hexane (20 ml) were added for recrystallization to give white crystals over a period of time at room temperature, which were filtered and dried for later use.

Example 6

(14) In a 10 mL polymerization tube, bromoglycolide (0.794 g, 2.88 mmol), benzyl alcohol (10 μL, 0.096 mmol), and compound No. 21 (0.029 g, 0.096 mmol) were added and the reaction was magnetically stirred for 3 h at 140° C. After the reaction was finished, the obtained crude product was dissolved in a minimum amount of dichloromethane, and then the mixture was added into a cold methanol solution to separate out polymers. 0.56 g of a white solid was obtained by centrifugation and then transferred to a vacuum oven for drying. The structure of the polymer was identified by .sup.1H NMR and .sup.13C NMR, and the molecular weight and dispersity of the polymer were determined by GPC. After the determination, the conversion of the polymer was 93.4%, the number average molecular weight Mn was 7700 g mol.sup.−1 and the Mn/Mw was 1.25. To the compound No. 21 in a 250 ml reaction flask were added compound No. 9 (12.27 mmol, 1.5 g) and saccharin (12.27 mmol, 1.5 g) and the resultant mixture was stirred in a tetrahydrofuran (THF) solution overnight at 60° C. The solvent was removed under vacuum to give the crude product to which methanol (10 ml) and hexane (20 ml) were added for recrystallization to give white crystals over a period of time at room temperature, which were filtered and dried for later use.

Example 7

(15) In a 10 mL polymerization tube, tetranolide (0.4953 g, 2.88 mmol), benzyl alcohol (10 μL, 0.096 mmol), and compound No. 22 (0.025 g, 0.096 mmol) were added and the reaction was magnetically stirred for 10 h at 150° C. After the reaction was finished, the obtained crude product was dissolved in a minimum amount of dichloromethane, and then the mixture was added into a cold methanol solution to separate out polymers. 0.35 g of a white solid was obtained by centrifugation and then transferred to a vacuum oven for drying. The structure of the polymer was identified by .sup.1H NMR and .sup.13C NMR, and the molecular weight and dispersity of the polymer were determined by GPC. After the determination, the conversion of the polymer was 95.4%, the number average molecular weight Mn was 5100 g mol.sup.−1 and the Mn/Mw was 1.28. To the compound No. 22 in a 250 ml reaction flask were added compound No. 10 (12.27 mmol, 1.5 g) and saccharin (12.27 mmol, 1.5 g) and the resultant mixture was stirred in a tetrahydrofuran (THF) solution overnight at 60° C. The solvent was removed under vacuum to give the crude product to which methanol (10 ml) and hexane (20 ml) were added for recrystallization to give white crystals over a period of time at room temperature, which were filtered and dried for later use.

Example 8

(16) In a 10 mL polymerization tube, ο-carboxyanhydride (0.4147 g, 5.76 mmol), benzyl alcohol (10 μL, 0.096 mmol), and compound No. 18 (0.036 g, 0.096 mmol) were added and the reaction was magnetically stirred for 5 h at 130° C. After the reaction was finished, the obtained crude product was dissolved in a minimum amount of dichloromethane, and then the mixture was added into a cold methanol solution to separate out polymers. 0.29 g of a white solid was obtained by centrifugation and then transferred to a vacuum oven for drying. The structure of the polymer was identified by 41 NMR and .sup.13C NMR, and the molecular weight and dispersity of the polymer were determined by GPC. After the determination, the conversion of the polymer was 96.3%, the number average molecular weight Mn was 4300 g mol.sup.−1 and the Mn/Mw was 1.27. To the compound No. 18 in a 250 ml reaction flask were added compound No. 6 (12.27 mmol, 1.5 g) and saccharin (12.27 mmol, 1.5 g) and the resultant mixture was stirred in a tetrahydrofuran (THF) solution overnight at 60° C. The solvent was removed under vacuum to give the crude product to which methanol (10 ml) and hexane (20 ml) were added for recrystallization to give white crystals over a period of time at room temperature, which were filtered and dried for later use.

Example 9

(17) In a 10 mL polymerization tube, lactide (0.4147 g, 2.88 mmol), benzyl alcohol (10 μL, 0.096 mmol), and compound No. 13 (0.029 g, 0.096 mmol) were added and the reaction was magnetically stirred for 4 h at 120° C. After the reaction was finished, the obtained crude product was dissolved in a minimum amount of dichloromethane, and then the mixture was added into a cold methanol solution to separate out polymers. 0.28 g of a white solid was obtained by centrifugation and then transferred to a vacuum oven for drying. The structure of the polymer was identified by .sup.1H NMR and .sup.13C NMR, and the molecular weight and dispersity of the polymer were determined by GPC. After the determination, the conversion of the polymer was 98.4%, the number average molecular weight Mn was 4400 g mol.sup.−1 and the Mn/Mw was 1.13. To the compound No. 13 in a 250 ml reaction flask were added compound No. 1 (12.27 mmol, 1.5 g) and saccharin (12.27 mmol, 1.5 g) and the resultant mixture was stirred in a tetrahydrofuran (THF) solution overnight at 60° C. The solvent was removed under vacuum to give the crude product to which methanol (10 ml) and hexane (20 ml) were added for recrystallization to give white crystals over a period of time at room temperature, which were filtered and dried for later use.

Example 10

(18) In a 10 mL polymerization tube, lactide (0.4147 g, 2.88 mmol), benzyl alcohol (10 μL, 0.096 mmol), and compound No. 13 (0.029 g, 0.096 mmol) were added and the reaction was magnetically stirred for 2 h at 150° C. After the reaction was finished, the obtained crude product was dissolved in a minimum amount of dichloromethane, and then the mixture was added into a cold methanol solution to separate out polymers. 0.29 g of a white solid was obtained by centrifugation and then transferred to a vacuum oven for drying. The structure of the polymer was identified by .sup.1H NMR and .sup.13C NMR, and the molecular weight and dispersity of the polymer were determined by GPC. After the determination, the conversion of the polymer was 96.4%, the number average molecular weight Mn was 4400 g mol.sup.−1 and the Mn/Mw was 1.29. To the compound No. 13 in a 250 ml reaction flask were added compound No. 1 (12.27 mmol, 1.5 g) and saccharin (12.27 mmol, 1.5 g) and the resultant mixture was stirred in a tetrahydrofuran (THF) solution overnight at 60° C. The solvent was removed under vacuum to give the crude product to which methanol (10 ml) and hexane (20 ml) were added for recrystallization to give white crystals over a period of time at room temperature, which were filtered and dried for later use.