Method for catalyzing ring-opening copolymerization of cyclic anhydride and oxetane based on iodine-based charge transfer compound

Abstract

The invention discloses a novel metal-free iodine-based binary catalyst system, belongs to the technical field of organic catalysis and high polymer materials, and is characterized in that an iodine-based charge transfer compound composed of I2, tetrabutylammonium acetate (TBAAc) and other quaternary ammonium salts catalyzes and oxidizes heterobutane and cyclic anhydride for controlled alternate ring opening copolymerization. In addition, the method has been effectively applied to ring-opening copolymerization by combining an epoxide and a cyclic anhydride. The catalyst system in the preparation method disclosed by the invention has the advantages of low cost, easiness in obtaining, low potential toxicity and biodegradability, and has a great practical application value.

Description

Technical Field

[0001] The present invention belongs to the technical fields of organocatalysis and polymer materials, and particularly relates to a method for catalytic ring-opening copolymerization of cyclic anhydrides and oxetanes. Technical Background

[0002] As important polymer materials, polyesters and polycarbonates are widely used in fields such as packaging, plastics, fibers, and films. Aliphatic polyesters or polycarbonates can be biodegradable, and due to their different main-chain and side-chain structures, they exhibit a variety of material properties. Given the hydrolyzable nature of the ester functional group, polyesters (especially aliphatic polyesters) as potential alternatives to non-degradable polyolefin materials to address the urgent global plastic waste problem have attracted great research interest. There are mainly three routes for the synthesis of polyesters or polycarbonates: (1) polycondensation of diols and diacids; (2) ring-opening polymerization (ROP) of cyclic esters; (3) ring-opening copolymerization (ROCOP) of cyclic anhydrides and cyclic ethers. In contrast, the copolymerization of epoxides with cyclic anhydrides not only has the advantages of atom economy and controllability but also has rich renewable monomer sources and mild preparation conditions, and is suitable for the development of highly configurable polycarbonate and polyester materials, which are characterized by their chain growth mechanism and wide tunability through potential combinations of various cyclic anhydrides and cyclic ethers. Since the pioneering work of Finoue et al., this polymerization method has attracted extensive attention in the ROCOP of propylene oxide and phthalic anhydride (PA). Epoxides are the most commonly used cyclic ethers for copolymerization with cyclic anhydrides, resulting in polyesters with a C2 linker between adjacent ester moieties. It has been reported that compared with poly(vinyl succinate) with a C2 linker, the aliphatic polyester poly(propylene succinate) with a C3 linker shows higher biodegradability. In addition to the conventional synthesis route through polycondensation, ROCOP of oxetanes as cyclic anhydrides and quaternary ethers is a suitable alternative method for obtaining such polyesters with a C3 linker. However, there has been little research on this method, which may be because compared with epoxides, oxetanes have lower reactivity due to their lower ring strain, and the preparation method of oxetanes is more complex than that of epoxides.

[0003] The ring-opening copolymerization (ROCOP) of oxetane with cyclic anhydrides was developed by Endo and his colleagues in 1999. They achieved the ring-opening copolymerization of trimethylene oxide (TO) and cyclic anhydrides using a bisphenol titanium complex as a catalyst. Although this was considered a groundbreaking achievement, polyether structures due to homopolymerization were observed in the obtained copolymers. In 2002, Nishi Kubo et al. reported that near-perfect alternating copolymers of oxetane and cyclic anhydrides were obtained using a quaternary ammonium salt as a catalyst and initiator; however, the catalytic reactivity was relatively low. Since then, the research on the ROCOP of oxetane and cyclic anhydrides has been relatively dormant for nearly two decades until a recent breakthrough. In 2021, Buchard and his colleagues reported the study of xylose-derived oxetane and cyclic anhydrides using a transition metal salen complex as a catalyst. Subsequently, Williams et al. synthesized an interesting ABB-type poly(ester-alt-ether) structure using the ROCOP of Zr(IV)-functionalized oxetane (B) and cyclic anhydride (A). Most metal-based catalysts have problems such as complex ligands, high synthesis costs, high environmental risks, and metal residues, which seriously affect their applications in fields such as microelectronics, food packaging, and biomedical materials. Although non-metal catalysts have also developed greatly in recent years and solved the problem of metal residues, their prices are still very high, and the high cost limits their industrial application value. Therefore, it is of great significance to develop a ring-opening alternating copolymerization catalyst that is green, non-toxic, inexpensive, has good monomer universality, and high polymerization activity. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a catalyst combination that is green, non-toxic, inexpensive, has good monomer universality, and high polymerization activity in view of the current technical situation of preparing polyesters by ring-opening alternating copolymerization. The polyester prepared with this catalyst combination has the advantages of regular structure, controllable molecular weight, and narrow molecular weight distribution.

[0005] The second technical problem to be solved by the present invention is to provide a ring-opening alternating copolymerization method based on the above catalyst combination.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A novel metal-free iodine-based binary catalyst system is used, and an iodine-based charge transfer complex composed of I2 and quaternary ammonium salts such as tetrabutylammonium acetate (TBAAc) catalyzes the polymerization reaction of cyclic anhydride and oxetane monomers.

[0007] The molecular formula of the quaternary ammonium salt is divided into two parts. The cation part is nBu4 or nPr4, and the anion part is as shown in formula (I) 1-8:

[0008]

[0009] The cyclic anhydride is as shown in Formula (II) 9-13:

[0010]

[0011] The copolymerization reaction preferably occurs under bulk conditions.

[0012] The molar ratio of the I2 to the quaternary ammonium salt is 0.5:1 - 2:1, preferably 2:1.

[0013] The molar ratio of the cyclic anhydride to the oxetane is 1:1 - 1:10, preferably 1:1.

[0014] The molar ratio of the quaternary ammonium salt to the cyclic anhydride is 0.125:100 - 5:100, preferably 1:100.

[0015] The reaction temperature is 65 - 105 °C, preferably 85 °C.

[0016] The reaction time is 3 - 72 h, preferably 12 - 48 h.

[0017] Beneficial Effects

[0018] The object of the present invention is to provide a novel metal-free iodine-based binary catalyst system. An iodine-based charge transfer complex composed of I2 and a quaternary ammonium salt such as tetrabutylammonium acetate (TBAAc) catalyzes the controlled alternating ring-opening copolymerization of oxetane and cyclic anhydride. In addition, this method has been effectively applied to the ring-opening copolymerization by combining epoxides and cyclic anhydrides. The catalyst system in the preparation method of the present invention has the advantages of being inexpensive and easily available, having low potential toxicity and being biodegradable, and has great practical application value. Description of the Drawings

[0019] The embodiments of the present invention will be described in detail in conjunction with the accompanying drawings, where

[0020] Figure 1 : 1H NMR spectrum of Example 9 (PA-alt-TO) 1 1H NMR spectrum

[0021] Figure 2 : Spectrum in the size exclusion chromatography analysis of Example 9 (PA-alt-TO);

[0022] Figure 3 : 1H NMR spectrum of Example 4 (I)-4nBu4 quaternary ammonium salt 1 1H NMR spectrum

[0023] Figure 4 : 1H NMR spectrum of Example 6 (I)-8nBu4 quaternary ammonium salt 1 1H NMR spectrum

[0024] Figure 5: Mass spectrum of the quaternary ammonium salt of Example 5 (I)-5nBu4

[0025] Figure 6 : Mass spectrum of the quaternary ammonium salt of Example 3 (I)-3nBu4

[0026] Figure 7 : F spectrum of the quaternary ammonium salt of Example 5 (I)-5nBu4 Detailed implementation manners

[0027] In the following examples, unless otherwise specified, the experimental methods are all conventional methods; the reagents and materials, unless otherwise specified, can all be obtained from commercial channels.

[0028] The 1H nuclear magnetic resonance spectra involved in the examples were measured using a Bruker Ascend TM-400 nuclear magnetic resonance spectrometer from Bruker Corporation, and the deuterated reagent used was deuterated chloroform (CDCl3).

[0029] Example 1

[0030] Preparation of (I)-1nBu4 quaternary ammonium salt: Add chloroacetic acid (1.83 g, 19.27 mmol, 1 eq) dissolved in a small amount of methanol solution to a 25 mL round-bottom flask. Take 40% wt tetrabutylammonium hydroxide (12.6 g, 19.27 mmol, 1 eq) and place it in the flask. Stir at 40 °C for 8 h, rotary evaporate to remove methanol, freeze-dry for 48 h, wash with THF, filter by suction, and dry to obtain catalyst 1.

[0031] Example 2

[0032] Preparation of (I)-2nBu4 quaternary ammonium salt: Add dichloroacetic acid (2.49 g, 19.27 mmol, 1 eq) dissolved in a small amount of methanol solution to a 25 mI round-bottom flask. Take 40% wt tetrabutylammonium hydroxide (12.6 g, 19.27 mmol, 1 eq) and place it in the flask. Stir at 40 °C for 8 h, rotary evaporate to remove methanol, freeze-dry for 48 h, wash with THF, filter by suction, and dry to obtain catalyst 2.

[0033] Example 3

[0034] Preparation of (I)-3nBu4 quaternary ammonium salt: Add trichloroacetic acid (3.148 g, 19.27 mmol, 1 eq) dissolved in a small amount of methanol solution to a 25 mL round-bottom flask. Take 40% wt tetrabutylammonium hydroxide (12.6 g, 19.27 mmol, 1 eq) and place it in the flask. Stir at 40 °C for 8 h, rotary evaporate to remove methanol, freeze-dry for 48 h, wash with THF, filter by suction, and dry to obtain catalyst 3.

[0035] Example 4

[0036] (I)-Preparation of tetrabutylammonium salt: Add cyclohexanecarboxylic acid (2.46 g, 19.27 mmol, 1 eq) dissolved in a small amount of methanol solution to a 25 mL round-bottom flask. Take 40% wt tetrabutylammonium hydroxide (12.6 g, 19.27 mmol, 1 eq) and place it in the flask. Stir at 40 °C for 8 h, rotary evaporate to remove methanol, freeze-dry for 48 h, wash with THF, filter by suction and dry to obtain catalyst 4.

[0037] Example 5

[0038] (I)-Preparation of tetrabutylammonium salt: Add trifluoroacetic acid (2.197 g, 19.27 mmol, 1 eq) dissolved in a small amount of methanol solution to a 25 mL round-bottom flask. Take 40% wt tetrabutylammonium hydroxide (12.6 g, 19.27 mmol, 1 eq) and place it in the flask. Stir at 40 °C for 8 h, rotary evaporate to remove methanol, freeze-dry for 48 h, wash with THF, filter by suction and dry to obtain catalyst 5.

[0039] Example 6

[0040] (I)-Preparation of tetrabutylammonium salt: Add pivalic acid (1.98 g, 19.27 mmol, 1 eq) dissolved in a small amount of methanol solution to a 25 mL round-bottom flask. Take 40% wt tetrabutylammonium hydroxide (12.6 g, 19.27 mmol, 1 eq) and place it in the flask. Stir at 40 °C for 8 h, rotary evaporate to remove methanol, freeze-dry for 48 h, wash with THF, filter by suction and dry to obtain catalyst 8.

[0041] Example 7

[0042] In the glove box, weigh oxetane (0.1 g, 1.66 mmol), succinic anhydride (0.17 g, 1.66 mmol), (I)-tetrabutylammonium salt (0.0055 g, 0.0166 mmol) and add them to a clamp-neck bottle. Then add I2 (0.008 g, 0.0332 mmol) outside the glove box. Stir magnetically at 85 °C for 24 h to stop the reaction. Dropwise add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drop the obtained solution into cold methanol. A black polymer precipitates. The conversion rate is 99.5%, the number-average molecular weight Mn of the copolymer is 4350 g / mol, and the molecular weight distribution PDI is 1.75.

[0043] Example 8

[0044] In the glove box, weigh out oxidized isobutane TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), and (I)-2nBu4 quaternary ammonium salt (0.006 g, 0.0166 mmol, 1 eq) and add them to a clamp bottle. Then, outside the glove box, add I2 (0.008 g, 0.0332 mmol, 2 eq). Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates out. The conversion rate is 98.4%, the number-average molecular weight Mn of the copolymer is 4570 g / mol, and the molecular weight distribution PDI is 1.78.

[0045] Example 9

[0046] In the glove box, weigh out oxidized isobutane TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), and (I)-3nBu4 quaternary ammonium salt (0.007 g, 0.0166 mmol, 1 eq) and add them to a clamp bottle. Then, outside the glove box, add I2 (0.008 g, 0.0332 mmol, 2 eq). Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates out. The conversion rate is 94%, the number-average molecular weight Mn of the copolymer is 4160 g / mol, and the molecular weight distribution PDI is 1.91.

[0047] Example 10

[0048] In the glove box, weigh out oxidized isobutane TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), and (I)-4nBu4 quaternary ammonium salt (0.0056 g, 0.0166 mmol, 1 eq) and add them to a clamp bottle. Then, outside the glove box, add I2 (0.008 g, 0.0332 mmol, 2 eq). Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates out. The conversion rate is 65%, the number-average molecular weight Mn of the copolymer is 4030 g / mol, and the molecular weight distribution PDI is 1.84.

[0049] Example 11

[0050] In a glove box, heterobutane oxide TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), and (I)-5nBu4 quaternary ammonium salt (0.006 g, 0.0166 mmol, 1 eq) were weighed and added to a crimp bottle. Then, I2 (0.008 g, 0.0332 mmol, 2 eq) was added outside the glove box. The mixture was magnetically stirred at 85°C for 24 hours, and the reaction was stopped. A small amount of dichloromethane was added dropwise to the resulting mixture to dissolve it. The resulting solution was then slowly added dropwise to cold methanol. A black polymer precipitated, and the conversion rate was 65.8%. The number average molecular weight Mn of the copolymer was 7010 g / mol, and the molecular weight distribution PDI was 1.57.

[0051] Example 12

[0052] In a glove box, heterobutane oxide TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), and (I)-6nBu4 quaternary ammonium salt (0.006 g, 0.0166 mmol, 1 eq) were weighed and added to a crimp bottle. Then, I2 (0.008 g, 0.0332 mmol, 2 eq) was added outside the glove box. The mixture was magnetically stirred at 85°C for 24 hours, and the reaction was stopped. A small amount of dichloromethane was added dropwise to the resulting mixture to dissolve it. The resulting solution was then slowly added dropwise to cold methanol. A black polymer precipitated with a conversion rate of 80.5%. The number average molecular weight Mn of the copolymer was 6170 g / mol, and the molecular weight distribution PDI was 1.36.

[0053] Example 13

[0054] In a glove box, heterobutane oxide TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), and (I)-7nBu4 quaternary ammonium salt (0.005 g, 0.0166 mmol, 1 eq) were weighed and added to a crimp bottle. Then, I2 (0.008 g, 0.0332 mmol, 2 eq) was added outside the glove box. The mixture was magnetically stirred at 85°C for 24 hours, and the reaction was stopped. A small amount of dichloromethane was added dropwise to the resulting mixture to dissolve it. The resulting solution was then slowly added dropwise to cold methanol. A black polymer precipitated with a conversion rate of 78.5%. The number average molecular weight Mn of the copolymer was 5580 g / mol, and the molecular weight distribution PDI was 1.68.

[0055] Example 14

[0056] In the glove box, weigh out oxetane oxide TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), and (I)-8nBu4 quaternary ammonium salt (0.006 g, 0.0166 mmol, 1 eq) and add them to a clamp bottle. Then, outside the glove box, add I2 (0.008 g, 0.0332 mmol, 2 eq). Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates out. The conversion rate is 76.1%, the number-average molecular weight Mn of the copolymer is 4260 g / mol, and the molecular weight distribution PDI is 1.91.

[0057] Example 15

[0058] In the glove box, weigh out oxetane oxide TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), and (I)-3nBu4 quaternary ammonium salt (0.0035 g, 0.0083 mmol, 0.5 eq) and add them to a clamp bottle. Then, outside the glove box, add I2 (0.004 g, 0.0166 mmol, 1 eq). Stir magnetically at 85 °C for 72 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates out. The conversion rate is 46%, the number-average molecular weight Mn of the copolymer is 1630 g / mol, and the molecular weight distribution PDI is 1.55.

[0059] Example 16

[0060] In the glove box, weigh out oxetane oxide TO (0.2 g, 3.32 mmol, 200 eq), succinic anhydride SA (0.34 g, 3.32 mmol, 200 eq), and (I)-3nBu4 quaternary ammonium salt (0.0035 g, 0.0083 mmol, 0.5 eq) and add them to a clamp bottle. Then, outside the glove box, add I2 (0.004 g, 0.0166 mmol, 1 eq). Stir magnetically at 85 °C for 72 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates out. The conversion rate is 26%, and the number-average molecular weight Mn of the copolymer is 500 g / mol.

[0061] Example 17

[0062] In a glove box, 0.4 g (6.64 mmol, 400 eq) of oxytetrahydrofuran (TO), 0.68 g (6.64 mmol, 400 eq) of succinic anhydride (SA), and 0.0035 g (0.0083 mmol, 0.5 eq) of (I)-3nBu4 quaternary ammonium salt were weighed and added to a clamp-neck bottle. Then, 0.004 g (0.0166 mmol, 1 eq) of I2 was added outside the glove box. The mixture was magnetically stirred at 85 °C for 72 hours. The reaction was stopped, and a small amount of dichloromethane was added dropwise to the resulting mixture to dissolve it. Then, the obtained solution was slowly dropped into cold methanol, and a black polymer precipitated. The conversion rate was 22%, and the number-average molecular weight Mn of the copolymer was 1000 g / mol.

[0063] Example 18

[0064] In a glove box, 0.1 g (1.66 mmol) of oxytetrahydrofuran (TO), 0.17 g (1.66 mmol) of succinic anhydride, and 0.0046 g (0.0166 mmol) of (I)-1nPr4 quaternary ammonium salt were weighed and added to a clamp-neck bottle. Then, 0.008 g (0.0332 mmol) of I2 was added outside the glove box. The mixture was magnetically stirred at 85 °C for 24 hours. The reaction was stopped, and a small amount of dichloromethane was added dropwise to the resulting mixture to dissolve it. Then, the obtained solution was slowly dropped into cold methanol, and a black polymer precipitated. The conversion rate was 86.5%.

[0065] Example 19

[0066] In a glove box, 0.1 g (1.66 mmol, 100 eq) of oxytetrahydrofuran (TO), 0.17 g (1.66 mmol, 100 eq) of succinic anhydride (SA), and 0.0052 g (0.0166 mmol, 1 eq) of (I)-2nPr4 quaternary ammonium salt were weighed and added to a clamp-neck bottle. Then, 0.008 g (0.0332 mmol, 2 eq) of I2 was added outside the glove box. The mixture was magnetically stirred at 85 °C for 24 hours. The reaction was stopped, and a small amount of dichloromethane was added dropwise to the resulting mixture to dissolve it. Then, the obtained solution was slowly dropped into cold methanol, and a black polymer precipitated. The conversion rate was 70.4%.

[0067] Example 20

[0068] In the glove box, weigh out oxidized isobutane TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), (I)-3nPr4 quaternary ammonium salt (0.0058 g, 0.0166 mmol, 1 eq) and add them to a clamp bottle. Then add I2 (0.008 g, 0.0332 mmol, 2 eq) outside the glove box. Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates, and the conversion rate is 90.3%.

[0069] Example 21

[0070] In the glove box, weigh out oxidized isobutane TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), (I)-4nPr4 quaternary ammonium salt (0.0052 g, 0.0166 mmol, 1 eq) and add them to a clamp bottle. Then add I2 (0.008 g, 0.0332 mmol, 2 eq) outside the glove box. Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates, and the conversion rate is 50.4%.

[0071] Example 22

[0072] In the glove box, weigh out oxidized isobutane TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), (I)-5nPr4 quaternary ammonium salt (0.005 g, 0.0166 mmol, 1 eq) and add them to a clamp bottle. Then add I2 (0.008 g, 0.0332 mmol, 2 eq) outside the glove box. Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates, and the conversion rate is 40.3%.

[0073] Example 23

[0074] In the glove box, weigh out oxidized tetrahydrofuran TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), (I)-6nPr4 quaternary ammonium salt (0.0047 g, 0.0166 mmol, 1 eq) and add them to a clamp-neck bottle. Then add I2 (0.008 g, 0.0332 mmol, 2 eq) outside the glove box. Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drip the obtained solution into cold methanol. A black polymer precipitates, and the conversion rate is 77.6%.

[0075] Example 24

[0076] In the glove box, weigh out oxidized tetrahydrofuran TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), (I)-7nPr4 quaternary ammonium salt (0.0041 g, 0.0166 mmol, 1 eq) and add them to a clamp-neck bottle. Then add I2 (0.008 g, 0.0332 mmol, 2 eq) outside the glove box. Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drip the obtained solution into cold methanol. A black polymer precipitates, and the conversion rate is 50.8%.

[0077] Example 25

[0078] In the glove box, weigh out oxidized tetrahydrofuran TO (0.1 g, 1.66 mmol, 100 eq), succinic anhydride SA (0.17 g, 1.66 mmol, 100 eq), (I)-8nPr4 quaternary ammonium salt (0.0048 g, 0.0166 mmol, 1 eq) and add them to a clamp-neck bottle. Then add I2 (0.008 g, 0.0332 mmol, 2 eq) outside the glove box. Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane to dissolve the resulting mixture, and then slowly drip the obtained solution into cold methanol. A black polymer precipitates, and the conversion rate is 67.9%.

[0079] Example 26

[0080] In the glove box, weigh out oxidized tetrahydrofuran TO (0.1 g, 1.66 mmol, 100 eq), (1s,5s)-3-oxabicyclo[3.2.2]nonane-2,4-dione (0.26 g, 1.66 mmol, 100 eq), and (I)-3nBu4 quaternary ammonium salt (0.0035 g, 0.0083 mmol, 1 eq) and add them to a clamp-neck flask. Then, outside the glove box, add I2 (0.004 g, 0.0166 mmol, 2 eq). Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane dropwise to the resulting mixture to dissolve it, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates, and the conversion rate is 70.5%.

[0081] Example 27

[0082] In the glove box, weigh out oxidized tetrahydrofuran TO (0.1 g, 1.66 mmol, 100 eq), cis-1,3-cyclohexanedicarboxylic anhydride (0.26 g, 1.66 mmol, 100 eq), and (I)-3nBu4 quaternary ammonium salt (0.0035 g, 0.0083 mmol, 1 eq) and add them to a clamp-neck flask. Then, outside the glove box, add I2 (0.004 g, 0.0166 mmol, 2 eq). Stir magnetically at 85 °C for 24 hours, stop the reaction, add a small amount of dichloromethane dropwise to the resulting mixture to dissolve it, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates, and the conversion rate is 75.7%.

[0083] Example 28

[0084] In the glove box, weigh out oxidized tetrahydrofuran TO (0.1 g, 1.66 mmol, 100 eq), trans-1,2-cyclohexanedicarboxylic anhydride (0.26 g, 1.66 mmol, 100 eq), and (I)-3nBu4 quaternary ammonium salt (0.0035 g, 0.0083 mmol, 1 eq) and add them to a clamp-neck flask. Then, outside the glove box, add I2 (0.004 g, 0.0166 mmol, 2 eq). Stir magnetically at 85 °C for 72 hours, stop the reaction, add a small amount of dichloromethane dropwise to the resulting mixture to dissolve it, and then slowly drop the resulting solution into cold methanol. A black polymer precipitates, and the conversion rate is 60.8%.

[0085] Example 29

[0086] In the glove box, 1,1,1-trimethyloxetane TO (0.1 g, 1.66 mmol, 100 eq), hexahydrophthalic anhydride (0.26 g, 1.66 mmol, 100 eq), and (I)-3nBu4 quaternary ammonium salt (0.0035 g, 0.0083 mmol, 1 eq) were added to a clamp bottle. Then, outside the glove box, I2 (0.004 g, 0.0166 mmol, 2 eq) was added. The mixture was magnetically stirred at 85 °C for 72 h. The reaction was stopped. A small amount of dichloromethane was added dropwise to the obtained mixture to dissolve it, and then the resulting solution was slowly dropped into cold methanol. A black polymer precipitated, and the conversion rate was 88.5%.

Claims

1. A novel metal-free iodine-based binary catalyst system, in which an iodine-based charge transfer complex composed of I2 and a quaternary ammonium salt catalyzes the alternating copolymerization of cyclic anhydrides and epoxides monomers.

2. The quaternary ammonium salt described in claim 1 is divided into two parts. The cationic part is nBu4 or nPr4, and the anionic part is as shown in formula (I) 1-8:

3. The cyclic anhydride described in claim 1 is as shown in formula (II) 9-13:

4. The copolymerization reaction described in claim 1 preferably occurs under bulk conditions.

5. The molar ratio of I2 to the quaternary ammonium salt described in claim 1 is 0.5:1 - 2:1, preferably 2:

1.

6. The molar ratio of the cyclic anhydride to the epoxide described in claim 1 is 1:1 - 1:10, preferably 1:

1.

7. The molar ratio of the quaternary ammonium salt to the cyclic anhydride described in claim 1 is 0.125:100 - 5:100, preferably 1:

100.

8. The reaction temperature described in claim 1 is 65 - 105 °C, preferably 85 °C.

9. The reaction time described in claim 1 is 3 - 72 h, preferably 12 - 48 h.

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