Aliphatic polycarbonate containing different cyclic substituents and preparation method thereof

Abstract

The present invention discloses an aliphatic polycarbonate containing different cyclic substituents and a preparation method thereof, and belongs to the technical field of polymer material synthesis. Compared with most aliphatic polycarbonates currently on the market, the present invention introduces a cyclic substituent on the basis of the original TMC, so that it has both the degradability of aliphatic polycarbonate and the good heat resistance and mechanical properties of aromatic polycarbonate. At the same time, the polymerization method provided by the present invention does not require high temperature and high pressure to eliminate small molecule by-products, the reaction conditions are relatively mild, the controllability is better, and the polymer molecular weight is higher. The 4C-TMC, 5C-TMC and 6C-TMC ring-opening polymerization provided by the present invention prepare polycarbonates with high molecular weight and high mechanical strength, which is of great significance for achieving high performance of polycarbonate and broadening the application range of degradable polycarbonate materials.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material synthesis, and particularly relates to aliphatic polycarbonate containing different cyclic substituents and a preparation method thereof. Background Art

[0002] Polycarbonate can be divided into aromatic, aliphatic, and aromatic-aliphatic polycarbonates according to the different R groups in the molecular chain. Aromatic polycarbonate is a thermoplastic engineering plastic with good comprehensive properties such as thermal properties, mechanical properties and optical properties. It is widely used in electronic appliances, panels, automotive parts, packaging, aviation, medical equipment and other fields, but it is difficult to process and not easy to degrade. Compared with aromatic polycarbonate, the molecular chain rigidity of aliphatic polycarbonate is weaker, and thus the thermal and mechanical properties are poor, which limits its industrial application. Biodegradable aliphatic polycarbonate has surface solubility and can be completely degraded into neutral diols and CO2. It also has good biocompatibility and the main chain chemical structure can be adjusted through reactions. A variety of products can be produced to meet the needs of different fields. In particular, the relative weight average molecular weight of 7×10 4 The above high molecular weight aliphatic polycarbonates have good thermal and mechanical properties and can replace polymer products previously used in the field of biodegradable plastics (Reference: Research Progress of Aliphatic Polycarbonates [J]. Contemporary Chemical Industry, 2018, 47, 1709-1712).

[0003] Currently, there are four methods for synthesizing aliphatic polycarbonates: phosgene, copolymerization of carbon dioxide with epoxides, ring-opening polymerization of aliphatic cyclic carbonates, and transesterification. Phosgene is relatively toxic, has low yields, low molecular weights, and poor product performance, limiting its application. The copolymerization of carbon dioxide with epoxides suffers from poor controllability and low molecular weights. The transesterification method requires harsh conditions such as high temperature and high vacuum, and the polymerization process is often accompanied by numerous side reactions, such as chain end backbiting to form cyclic low-molecular-weight polycarbonates and the dehydration of 1,4-butanediol to form tetrahydrofuran (Macromolecules 2013, 46, 3301-330). In contrast, the ring-opening polymerization of aliphatic cyclic carbonates not only has relatively mild reaction conditions and the advantages of high and controllable molecular weight, but can also be ring-opened copolymerized with a variety of carbonate monomers to adjust polymer properties. For example, the ring-opening copolymerization of trimethylene carbonate and 2,2-diethyl-trimethylene carbonate not only has a controllable molecular weight, but also has the advantages of two polymers (Reference: Macromolecules 2023, 56, 3641-3649).

[0004] The thermal and mechanical properties of polycarbonates are not only related to molecular weight but also to their chain structure and pendant functional groups. These can be achieved by increasing the number of consecutive methylene groups between two adjacent carbonate groups, modifying the main chain structure, and introducing functional or reactive groups. Appropriate functional groups can effectively modulate the physical and chemical properties and biological properties of polymer materials, such as hydrophilicity, permeability, degradability, biocompatibility, and cell adhesion. The introduction of functional groups also opens up greater possibilities for further material modification. Research on the functionalization of six- and seven-membered cyclic carbonates is the most prevalent. Common functional groups, such as hydroxyl, carboxyl, amino, and sugar rings, can be incorporated into carbonate monomers (Reference: Research Progress on Trimethylene Carbonate-Responsive Aliphatic Polycarbonates [J]. Polymer Bulletin, 2024, 37, 603-615). Taking the monomer trimethylene carbonate (TMC) as an example, the polymer obtained by ring-opening polymerization cannot crystallize on its own, has poor mechanical properties, and a glass transition temperature of -17.8°C. However, when regular side groups are introduced into the monomer, such as two methyl groups, the monomer becomes 2,2-dimethyltrimethylene carbonate (DMTMC), and the resulting polymer exhibits crystallinity, a glass transition temperature of 19.7°C, and a melting point of around 120°C (Reference: Macromolecules 2023, 56, 2062-206). When two ethyl groups are introduced, the monomer becomes 2,2-diethyltrimethylene carbonate, and the resulting polymer also exhibits crystallinity, with a glass transition temperature of -6°C and a melting point of around 90°C (Reference: Macromolecules 2023, 56, 3641-3649). Although the above examples improve their crystallinity by introducing regular functional groups, the melting point is not high enough and the heat resistance is not good enough. In addition to introducing relatively regular groups, irregular side groups can also be introduced. Ethyl and allyloxymethyl groups are introduced at the same time, and the monomer becomes 2-allyloxymethyl-2-ethyltrimethylene carbonate (AOMEC). The side groups introduce double bonds, making the polymer suitable for post-functionalization (reference: Macromolecules 2014, 47, 6189-6195). The literature does not disclose relevant information such as the mechanical properties of this polycarbonate. Generally speaking, the structure is too irregular to crystallize, and the performance is usually poor.

[0005] As can be seen from the above analysis, in the field of polycarbonate synthesis, the preparation of aliphatic polycarbonates with both high molecular weight and high mechanical strength through ring-opening polymerization remains a significant challenge. High molecular weight and high mechanical strength can broaden the application range of polycarbonates. Therefore, providing a method for synthesizing polycarbonates with high molecular weight and high mechanical strength is essential to promote the development of high-performance polycarbonates. Summary of the Invention

[0006] The present invention aims to provide aliphatic polycarbonates containing different cyclic substituents and a preparation method thereof. The provided aliphatic polycarbonates containing different cyclic substituents have high molecular weight and high mechanical strength.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] One of the technical solutions of the present invention is to provide an aliphatic polycarbonate containing different cyclic substituents, the structural formula of which is as follows:

[0009]

[0010] In the above formula, x=1, 2 or 3.

[0011] When x=1, the aliphatic polycarbonate is P(4C-TMC); when x=2, the aliphatic polycarbonate is P(5C-TMC); when x=3, the aliphatic polycarbonate is P(6C-TMC).

[0012] The second technical solution of the present invention is to provide a method for preparing the above-mentioned aliphatic polycarbonate containing different cyclic substituents, wherein when x=1, 2 or 3, the preparation steps include:

[0013] Aliphatic polycarbonates containing cyclic substituent structures are prepared by ring-opening polymerization using 6,8-dioxaspiro[3.5]nonan-7-one (4C-TMC), 7,9-dioxaspiro[4.5]decan-8-one (5C-TMC), or 2,4-dioxaspiro[5.5]undecan-3-one (6C-TMC) as monomers, stannous octoate as a catalyst, and alcohol small molecules as initiators under molten conditions.

[0014] When x=3, the preparation steps include:

[0015] 2,4-Dioxaspiro[5.5]undecan-3-one (6C-TMC) monomer is dissolved in a solvent, a Lewis pair consisting of Lewis acid and Lewis base is used as a catalyst, and a small molecule alcohol is used as an initiator to carry out a ring-opening polymerization reaction to prepare an aliphatic polycarbonate containing a cyclic substituent structure.

[0016] The reaction formula is shown below:

[0017]

[0018] In the preparation method provided by the present invention, polymers such as P(4C-TMC) and P(5C-TMC) that are not easily soluble can be prepared by adding 4C-TMC or 5C-TMC monomers in the melt; and polymers such as P(6C-TMC) that can be dissolved under certain solvent conditions can be prepared by adding 6C-TMC monomers in the melt, or by dissolving 6C-TMC in a solvent and then performing a ring-opening polymerization reaction to prepare the polymer.

[0019] Preferably, the alcohol small molecule is benzyl alcohol.

[0020] Preferably, the molar ratio of the catalyst, initiator and monomer is 1:1:1000-2000.

[0021] Preferably, the ring-opening polymerization reaction is carried out at a temperature of 50 to 150° C. and for a time of 1 to 24 hours.

[0022] Preferably, the Lewis acid is diphenylzinc (Zn(C6H5)2); the Lewis base is 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU); and the molar ratio of Lewis acid to Lewis base in the Lewis pair is 1:1.

[0023] Preferably, the solvent is toluene, and the concentration of 2,4-dioxaspiro[5.5]undecan-3-one in toluene is 0.5 mol / L.

[0024] The beneficial technical effects of the present invention are as follows:

[0025] Compared to most aliphatic polycarbonates currently on the market, the present invention introduces cyclic substituents on the basis of the original 1,3-dioxane-2-one (TMC), so that it has both the degradability of aliphatic polycarbonates and the good heat resistance and mechanical properties of aromatic polycarbonates. At the same time, the polymerization method provided by the present invention does not require high temperature and high pressure to eliminate small molecule by-products. The reaction conditions are relatively mild, the controllability is better, and the polymer molecular weight is higher. The present invention uses Lewispair composed of Lewis acid and Lewis base as a catalyst. The Lewis acid / base synergistic effect can effectively suppress the ester exchange side reaction of the polymerization reaction, and it is easy to prepare high molecular weight polycarbonate materials. The polycarbonate obtained by the present invention has a number average molecular weight of 175,000 to 227,000 Da and a molecular weight distribution of 1.5 to 1.82. Both P(5C-TMC) and P(4C-TMC) are crystalline polymers with melting temperatures of 208.9°C to 217.5°C and 181.6°C to 187.2°C, respectively. The number average molecular weight of P(6C-TMC) is 14,700 to 153,500 Da, with a molecular weight distribution of 1.29 to 1.98 and a glass transition temperature of 34°C. The polycarbonate obtained by the present invention has excellent mechanical properties. For P(4C-TMC), the breaking strength is 72 MPa and the elongation at break is 4.5%; for P(5C-TMC), the breaking strength is 65 MPa and the elongation at break is 3.5%; and for P(6C-TMC), the yield strength is 29 MPa, the elongation at break is 300%, and the breaking strength is 21 MPa.

[0026] The present invention provides a polycarbonate with high molecular weight and high mechanical strength prepared by ring-opening polymerization of 6,8-dioxaspiro[3.5]nonan-7-one (4C-TMC), 7,9-dioxaspiro[4.5]decan-8-one (5C-TMC), and 2,4-dioxaspiro[5.5]undecan-3-one (6C-TMC), which is of great significance for achieving high performance of polycarbonate and broadening the application range of degradable polycarbonate materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The P(4C-TMC) prepared in Example 1 of the present invention 1 HNMR spectrum;

[0028] Figure 2 The DSC curve of P(4C-TMC) prepared in Example 1 of the present invention is shown in FIG.

[0029] Figure 3 : is the stress-strain curve of P(4C-TMC) prepared in Example 1 of the present invention;

[0030] Figure 4 The P(5C-TMC) prepared in Example 2 of the present invention 1HNMR spectrum;

[0031] Figure 5 This is the DSC curve of P(5C-TMC) obtained in Example 2 of the present invention;

[0032] Figure 6 : This is the stress-strain curve of P(5C-TMC) prepared in Example 2 of the present invention;

[0033] Figure 7 The P(6C-TMC) prepared in Example 3 of the present invention 1 HNMR spectrum;

[0034] Figure 8 This is the DSC curve of P(6C-TMC) obtained in Example 3 of the present invention;

[0035] Figure 9 This is the stress-strain curve of P(6C-TMC) prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0036] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0037] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

[0039] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0040] In the process of preparing aliphatic polycarbonate by ring-opening polymerization of monomers 6,8-dioxaspiro[3.5]nonan-7-one, 7,9-dioxaspiro[4.5]decan-8-one, and 2,4-dioxaspiro[5.5]undecan-3-one according to the present invention, all moisture- and oxygen-sensitive operations are carried out by professionals familiar with the art in an MBraun glove box or using standard Schlenk techniques under nitrogen protection.

[0041] When the prepared polymer was subjected to relevant tests, the structure of the polymer was determined by nuclear magnetic resonance spectroscopy, the molecular weight and molecular weight distribution index of the polymer were determined by gel permeation chromatography (GPC), the thermal properties of the polymer were determined by differential scanning calorimetry, and the mechanical properties of the polymer were determined by a universal tensile tester. 1 H and 13 C NMR was measured on a Bruker-400 NMR spectrometer at 25°C, with TMS as the internal standard and deuterated chloroform as the solvent. Gel permeation chromatography was performed on a Waters gel permeation chromatograph using tetrahydrofuran (THF) (with 0.05 wt% 2,6-di-tert-butyl-4-methylphenol added as an antioxidant) or hexafluoroisopropanol (HFIP) (with 0.05 wt% sodium trifluoroacetate added as an antioxidant) as the solvent. The test temperature was 40°C, the flow rate was 1.0 mL / min, and a PL EasiCal flowmeter was used. PS-1 was used as the standard sample. Differential scanning calorimetry (TA) was used for measurement. The temperature was first raised to 250.00°C at a rate of 2.000°C / min, maintained constant for 10.00 minutes, then cooled at a rate of 2.000°C / min to -50.00°C, and then heated a second time at a constant temperature for 10.00 minutes. When mechanical properties were measured using a universal tensile machine, the polymer was directly hot-pressed into 2×12 mm tensile strips at a temperature 10 to 20°C above the melting point, at a stretching rate of 10 mm / min.

[0042] Stannous octoate, Zn(C6H5)2 and DBU used in the examples of the present invention are all commercially available catalysts.

[0043] Example 1

[0044] Preparation of P(4C-TMC):

[0045] (1) Under an inert atmosphere, 20,000 μmol of 6,8-dioxaspiro[3.5]nonan-7-one was added to a dry 15 mL pressure bottle. 20 μmol of benzyl alcohol and 20 μmol of stannous octoate were added to 0.2 mL of toluene solvent to prepare a catalyst solution. After shaking evenly, 0.1 mL of the catalyst solution was injected into the pressure bottle. Ring-opening polymerization was carried out at 150°C. The polymerization reaction was carried out under strong stirring for 8 h.

[0046] (2) After the polymerization is completed, the polymer is first dissolved in a mixed solvent of dichloromethane and hexafluoroisopropanol, and then the polymer solution is added dropwise to 100 mL of ethanol for precipitation, and then filtered, washed, and vacuum dried to obtain P(4C-TMC).

[0047] The conversion rate of 6,8-dioxaspiro[3.5]nonan-7-one monomer in this example is >99%.

[0048] The prepared P(4C-TMC) was subjected to NMR analysis, GPC analysis, DSC analysis and mechanical property testing: NMR analysis showed that the polycarbonate content of the polymer was >99%; GPC analysis showed that the polymer molecular weight was 175kDa and the molecular weight distribution was 1.82; DSC analysis showed that the polymer T m The test results of the universal tensile machine show that the elongation at break of the polymer prepared in Example 1 is 4.5%, and the breaking strength is 72 MPa.

[0049] Example 1 prepared P (4C-TMC) 1 H NMR spectrum is shown in Figure 1 .

[0050] The DSC curve of P(4C-TMC) obtained in Example 1 is shown in FIG. Figure 2 .

[0051] The stress-strain curve of P(4C-TMC) obtained in Example 1 is shown in FIG. Figure 3 .

[0052] Example 2

[0053] Preparation of P(5C-TMC):

[0054] (1) Under an inert atmosphere, 20,000 μmol of 7,9-dioxaspiro[4.5]decan-8-one was added to a dry 15 mL pressure bottle. 20 μmol of benzyl alcohol and 20 μmol of stannous octoate were added to 0.2 mL of toluene solvent to prepare a catalyst solution. After shaking evenly, 0.1 mL of the catalyst solution was injected into the pressure bottle. Ring-opening polymerization was carried out at 150°C. The polymerization reaction was carried out under strong stirring for 8 h.

[0055] (2) After the polymerization is completed, the polymer is first dissolved in a mixed solvent of dichloromethane and hexafluoroisopropanol, and then the polymer solution is added dropwise to 100 mL of ethanol for precipitation, and then filtered, washed, and vacuum dried to obtain P(5C-TMC).

[0056] The conversion rate of 7,9-dioxaspiro[4.5]decan-8-one monomer in this example was 93.5%.

[0057] The prepared P(5C-TMC) was subjected to NMR analysis, GPC analysis, DSC analysis and mechanical property testing: NMR analysis showed that the polycarbonate content of the polymer was >99%; GPC analysis showed that the polymer molecular weight was 227.1 kDa and the molecular weight distribution was 1.50; DSC analysis showed that the polymer T m The test results of the universal tensile machine showed that the elongation at break of the polymer prepared in Example 2 was 3.5%, and the breaking strength was 65 MPa.

[0058] Example 2 prepared P (5C-TMC) 1 H NMR spectrum is shown in Figure 4 .

[0059] The DSC curve of P(5C-TMC) obtained in Example 2 is shown in FIG. Figure 5 .

[0060] The stress-strain curve of P(5C-TMC) obtained in Example 2 is shown in FIG. Figure 6 .

[0061] Example 3

[0062] Preparation of P(6C-TMC):

[0063] (1) Under an inert atmosphere, 20,000 μmol of 2,4-dioxaspiro[5.5]undecan-3-one was added to a dry 15 mL pressure bottle. 20 μmol of benzyl alcohol and 20 μmol of stannous octoate were added to 0.2 mL of toluene solvent to prepare a catalyst solution. After shaking evenly, 0.1 mL of the catalyst solution was injected into the pressure bottle. Ring-opening polymerization was carried out at 150°C. The polymerization reaction was carried out under strong stirring for 8 h.

[0064] (2) After the polymerization is completed, the polymer is first dissolved in dichloromethane, and then the polymer solution is added dropwise to 100 mL of ethanol for precipitation. The product is then filtered, washed, and vacuum-dried to obtain P(6C-TMC).

[0065] The conversion rate of 2,4-dioxaspiro[5.5]undecan-3-one monomer in this example was 70.4%.

[0066] The prepared P(6C-TMC) was subjected to NMR analysis, GPC analysis, DSC analysis and mechanical property test: NMR analysis showed that the polycarbonate content of the polymer was >99%; GPC analysis showed that the polymer molecular weight was 153.5kDa and the molecular weight distribution was 1.98; DSC analysis showed that the polymer T g The temperature is 34°C; the test results of the universal tensile machine show that the polymer prepared in Example 3 has a yield strength of 29 MPa, an elongation at break of 300%, and a breaking strength of 21 MPa.

[0067] Example 3 prepared P (6C-TMC) 1 H NMR spectrum is shown in Figure 7 .

[0068] The DSC curve of P(6C-TMC) obtained in Example 3 is shown in FIG. Figure 8 .

[0069] The stress-strain curve of P(6C-TMC) obtained in Example 3 is shown in Figure 9 .

[0070] Example 4

[0071] Preparation of P(6C-TMC):

[0072] (1) Under an inert atmosphere, 10,000 μmol of 2,4-dioxaspiro[5.5]undecan-3-one and 19.8 mL of toluene were added to a dry 50 mL pressure bottle. In another sample bottle, 0.4 mL of toluene, 20 μmol of benzyl alcohol, 20 μmol of Zn(C6H5)2, and 20 μmol of DBU were added to prepare a catalyst solution. After shaking evenly, 0.2 mL of the catalyst solution was injected into the pressure bottle. Ring-opening polymerization was carried out at 50°C. The polymerization reaction was carried out under strong stirring for 24 h.

[0073] (2) After the polymerization is completed, the polymer is first dissolved in dichloromethane, and then the polymer solution is added dropwise to 100 mL of ethanol for precipitation. The product is then filtered, washed, and vacuum-dried to obtain P(6C-TMC).

[0074] The conversion rate of 2,4-dioxaspiro[5.5]undecan-3-one monomer in this example was 70.4%.

[0075] The prepared P(6C-TMC) was subjected to NMR analysis, GPC analysis, DSC analysis and mechanical property testing: NMR analysis showed that the polycarbonate content of the polymer was >99%; GPC analysis showed that the polymer molecular weight was 142.4 kDa and the molecular weight distribution was 1.45; DSC analysis showed that the polymer T g is 34℃.

[0076] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. Aliphatic polycarbonates containing different cyclic substituents, characterized in that: The structural formula is as follows: ； In the above formula, x=1 or 2; The number average molecular weight of the aliphatic polycarbonate containing different cyclic substituents is 175,000 to 227,000 Da, and the molecular weight distribution is 1.5 to 1.

82.

2. The method for preparing aliphatic polycarbonate containing different cyclic substituents according to claim 1, characterized in that: When x=1 or 2, the preparation steps include: Aliphatic polycarbonates containing cyclic substituents are prepared by ring-opening polymerization using 6,8-dioxaspiro[3.5]nonan-7-one or 7,9-dioxaspiro[4.5]decan-8-one as monomers, stannous octoate as catalyst and alcohol small molecules as initiators under the condition of monomer melting.

3. The method for preparing aliphatic polycarbonate containing different cyclic substituents according to claim 2, characterized in that: The alcohol small molecule is benzyl alcohol.

4. The method for preparing aliphatic polycarbonate containing different cyclic substituents according to claim 2, characterized in that: The molar ratio of the catalyst, initiator and monomer is 1:1:1000-2000.

5. The method for preparing aliphatic polycarbonate containing different cyclic substituents according to claim 2, characterized in that: The temperature of the ring-opening polymerization reaction is 50-150° C., and the time is 1-24 hours.

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