Method for preparing polylactone by ring opening

Abstract

Disclosed is a method for preparing polylactone by ring opening, belonging to the technical fields of organic catalysis and polymer materials. The invention proposes a new catalytic mechanism, wherein an organic alcohol is used as an initiator to initiate ring opening polymerization of a cyclic monomer under the catalysis of an organic catalyst to obtain a polylactone; and the catalyst is a pyridinium salt. The present invention has the advantages of non-toxic reaction, simple conditions and controllable process; further, the invention can obtain a narrow molecular weight distribution in the absence of solution polymerization, and can effectively inhibit the occurrence of the transesterification compared with the catalysis of 4-(N,N-dimethylamino)pyridine.

Claims

1. A method for preparing polylactone carrying out a ring opening polymerization of a cyclic monomer in the presence of an organic catalyst and an organic alcohol as an initiator to obtain a polylactone, wherein the organic catalyst is a pyridinium salt shown as formula I: ##STR00027## wherein: when R.sup.5 is hydrogen, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently selected from hydrogen, methyl, ethyl, isopropyl, and C1-C4 alkyls substituted by one or more substituents selected from hydroxyl, phenyl, and cyano; X is one selected from fluorine, chlorine, bromine, iodine, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, trichloromethanesulfonic acid, trifluoroacetic acid, trichloroacetic acid, and benzenesulfonic acid; when R.sup.5 is selected from N,N-dimethylamino, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently selected from hydrogen, methyl, ethyl, isopropyl, tert-butyl, sec-butyl, and C1-C10 alkyls substituted by one or more substituents selected from hydroxyl, phenyl, and cyano, with the proviso that R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are not simultaneously hydrogen; X is one selected from fluoro, chloro, bromo, iodo, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, trichloromethanesulfonic acid, trifluoroacetic acid, trichloroacetic acid and benzenesulfonic acid; and when R.sup.5 is selected from N-pyrrolidinyl, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently selected from hydrogen, methyl, ethyl, isopropyl, tert-butyl, sec-butyl, and C1-C10 alkyls substituted by one or more substituents selected from hydroxyl, phenyl, and cyano; X is one selected from fluoro, chloro, bromo, iodo, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, trichloromethanesulfonic acid, trifluoroacetic acid, trichloroacetic acid and benzenesulfonic acid.

2. The preparation method of claim 1, wherein the organic catalyst is selected from ##STR00028## ##STR00029## ##STR00030## ##STR00031##

3. The preparation method of claim 1, wherein R in the initiator organic alcohol ROH is an alkyl or a phenyl group, and the alkyl is a linear, branched or cyclic chain having 1 to 22 carbon atoms.

4. The preparation method of claim 3, wherein the organic alcohol is methanol, ethanol, pentaerythritol, butynol, phenylpropanol, or benzyl alcohol.

5. The preparation method of claim 1, wherein the cyclic monomer is one of lactones of formula (II), carbonates of formula (III), and lactides of formula (IV), ##STR00032## wherein, in formula (II), A is [—(CR.sup.1R.sup.2)—].sub.n, n is an integer from 2 to 10; R.sup.1 and R.sup.2 are independently selected from H, unsubstituted C1-C5 alkyls, and C1-C5 alkyls substituted with a halogen or a hydroxyl group; wherein, in formula (III), A and B are [—(CR.sup.1R.sup.2)—], n is an integer from 1 to 10, and A and B are the same or different; R.sup.1 and R.sup.2 are independently selected from H, C1-C5 alkyls, and C1-C5 substituted with a halogen atom or a hydroxyl group; Wherein, in formula (IV), A is [—(CR.sup.1R.sup.2)—].sub.n, n is an integer from 1 to 10; R.sup.1 and R.sup.2 are independently selected from H, C1-C5 alkyls, and C1-C5 alkyls substituted with a halogen atom or a hydroxyl group.

6. The preparation method of claim 5, wherein the lactone cyclic monomer is butyrolactone, valerolactone, or caprolactone; the carbonate cyclic monomer is trimethylene carbonate, dimethyl carbonate and diethyl carbonate; and the lactide cyclic monomer is glycolide or lactide.

7. The preparation method of claim 1, wherein a molar ratio of the cyclic monomer, the organic catalyst, and the organic alcohol is (30:1:1)-(120:1:1).

8. The preparation method of claim 1, wherein further comprising adding a terminator to the reaction mixture, and precipitating a polymer in a precipitation solvent that is methanol, diethyl ether, n-hexane, or n-pentane.

9. The preparation method of claim 1, wherein the ring opening polymerization is carried out at a temperature of 30-140° C. for 1-48 hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1: .sup.1H NMR of polylactic acid prepared with 4-(N, N-dimethylamino) pyridine hydrochloride catalyst;

(3) FIG. 2: .sup.1H NMR of polytrimethylene carbonate prepared with 4-(N, N-dimethylamino) pyridine hydrochloride catalyst; and

(4) FIG. 3: a spectrum of polylactic acid prepared by 4-(N, N-dimethylamino) pyridine hydrochloride catalyst in a volume exclusion chromatography.

DETAILED DESCRIPTION OF THE INVENTION

(5) 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 embodiments 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.

(6) The structures of catalysts used in the examples are shown in the following table:

(7) TABLE-US-00002 No. Structure 16 0 3 5 7 12 14 10

Example 1

(8) In a 3 ml polymerization tube, L-lactide (0.4147 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 16) (0.0152 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 140° C. for 1.5 h. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.3855 g of a white solid with a conversion of 96.0%, a number average molecular weight M.sub.n of 4300 g/mol and a dispersity PDI of 1.03.

Example 2

(9) In a 3 ml polymerization tube, L-lactide (1.660 g, 11.52 mmol, 120 equiv), a catalyst (compound shown as No. 16) (0.0152 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 140° C. for 7 h. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 1.403 g of a white solid with a conversion of 84.7%, a number average molecular weight M.sub.n of 13610 g/mol and a dispersity PDI of 1.04.

Example 3

(10) In a 3 ml polymerization tube, trimethylene carbonate (0.2937 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 16) (0.0152 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 60° C. for 24 h. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.2620 g of transparent oil with a conversion of 91.0%, a number average molecular weight M.sub.n of 2850 g/mol and a dispersity PDI of 1.04.

Example 4

(11) In a 3 ml polymerization tube, trimethylene carbonate (1.1761 g, 11.52 mmol, 120 equiv), a catalyst (compound shown as No. 16) (0.0152 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 60° C. for 70 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.9875 g of transparent oil with a conversion of 83.4%, a number average molecular weight M.sub.n of 10300 g/mol, and a dispersity PDI of 1.05.

Example 5

(12) In a 3 ml polymerization tube, D-lactide (0.4147 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 3) (0.0195 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 140° C. for 1.5 h. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.3042 g of a white solid with a conversion of 73.4%, a number average molecular weight M.sub.n of 3270 g/mol and a dispersity PDI of 1.07.

Example 6

(13) In a 3 ml polymerization tube, L, D-lactide (0.4147 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 3) (0.0195 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 140° C. for 1.5 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.2998 g of a white solid with a conversion of 72.3%, a number average molecular weight M.sub.n of 3200 g/mol and a dispersity PDI of 1.07.

Example 7

(14) In a 3 ml polymerization tube, glycolide (0.3343 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 5) (0.0208 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 100° C. for 4 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.3067 g of a white solid with a conversion of 91.7%, a number average molecular weight M.sub.n of 3300 g/mol and a dispersity PDI of 1.02.

Example 8

(15) In a 3 ml polymerization tube, butyrolactone (0.2479 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 5) (0.0208 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 90° C. for 24 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.2250 g of a white solid with a conversion of 90.8%, a number average molecular weight M.sub.n of 2440 g/mol and a dispersity PDI of 1.05.

Example 9

(16) In a 3 ml polymerization tube, butyrolactone (0.2479 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 7) (0.0298 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 60° C. for 30 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.1912 g of a white solid with a conversion of 77.1%, a number average molecular weight M.sub.n of 2090 g/mol and a dispersity PDI of 1.06.

Example 10

(17) In a 3 ml polymerization tube, valerolactone (0.2883 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 7) (0.0298 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 90° C. for 20 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.2422 g of a white solid with a conversion of 84.0%, a number average molecular weight M.sub.n of 2600 g/mol and a dispersity PDI of 1.04.

Example 11

(18) In a 3 ml polymerization tube, valerolactone (0.2883 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 12) (0.0294, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 90° C. for 20 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.2621 g of a white solid with a conversion of 90.9%, a number average molecular weight M.sub.n of 2730 g/mol and a dispersity PDI of 1.05.

Example 12

(19) In a 3 ml polymerization tube, caprolactone (0.3287 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 12) (0.0294 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 90° C. for 24 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.2790 g of a white solid with a conversion of 84.9%, a number average molecular weight M.sub.n of 3010 g/mol and a dispersity PDI of 1.06.

Example 13

(20) In a 3 ml polymerization tube, caprolactone (0.3287 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 14) (0.0469 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 90° C. for 28 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.2867 g of a white solid with a conversion of 87.2%, a number average molecular weight M.sub.n of 2980 g/mol and a dispersity PDI of 1.05.

Example 14

(21) In a 3 ml polymerization tube, glycolide (0.3343 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 14) (0.0469 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 100° C. for 36 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.2980 g of a white solid with a conversion of 89.1%, a number average molecular weight M.sub.n of 3380 g/mol and a dispersity PDI of 1.03.

Example 15

(22) In a 3 ml polymerization tube, glycolide (0.3343 g, 2.88 mmol, 30 equiv), a catalyst (compound shown as No. 10) (0.0234 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 100° C. for 36 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.2850 g of a white solid with a conversion of 85.2%, a number average molecular weight M.sub.n of 3072 g/mol and a dispersity PDI of 1.07.

Example 16

(23) In a 3 ml polymerization tube, L-lactide (0.8294 g, 5.76 mmol, 60 equiv), a catalyst (compound shown as No. 16) (0.0152 g, 0.096 mmol, 1.0 equiv), and benzyl alcohol (10 μL, 0.096 mmol, 1.0 equiv) were added and stirred mechanically at 140° C. for 3 hours. At the end of the reaction, the reaction was stopped and the resulting crude product was slowly dropped into cold methanol, followed by precipitation by centrifugation to obtain a polymer, which was filtered and dried to constant weight to give 0.7090 g of a white solid with a conversion of 85.5%, a number average molecular weight M.sub.n of 7490 g/mol and a dispersity PDI of 1.06.