CN105949449B - It is used to prepare polyethers-polylactide-fatty poly-ester carbonate ternary block polymer composite catalyst and its application - Google Patents

Abstract

The present invention relates to be used to prepare polyethers-polylactide-fatty poly-ester carbonate ternary block polymer composite catalyst and its application, the composite catalyst is made of metal salen catalyst with co-catalyst, the molar ratio of metal salen catalyst and co-catalyst is 1:0.5-2, the co-catalyst is double-(dihalotriphenylphosphoranes base) ammonium chloride, 4-dimethylaminopyridine or 2,6- lutidines.The beneficial effects of the present invention are: 1, present invention the used in composite catalyst catalytic effect good, and high catalytic efficiency, gained terpolymer number-average molecular weight is larger, narrow molecular weight distribution.2, polyether segment in copolymer, polylactide segment, PPC segment composition can effectively be controlled by adjusting stepwise reaction time and monomer ratio, the glass transition temperature of copolymer is 2-42 DEG C, elongation at break is 55-331%, tensile strength 6-39MPa.

Description

For the preparation of polyether-polylactide-aliphatic polycarbonate terpolymers Composite catalyst and its application

technical field

The invention relates to the technical field of polymers, in particular to a composite catalyst for preparing a polyether-polylactide-aliphatic polycarbonate ternary block copolymer and its application.

Background technique

Carbon dioxide is considered to be the main gas responsible for the "greenhouse effect", which causes climate change such as global warming, melting glaciers, and extreme weather, so the utilization and fixation of carbon dioxide has attracted great attention. One way to solve this problem is to turn this abundant and cheap source of carbon dioxide into polymer products. Since 1969, the pioneering work of Inoue Sho and others, the use of carbon dioxide and epoxy compounds to synthesize aliphatic polycarbonate has become a potentially important way to effectively utilize carbon dioxide. Carbon dioxide and propylene oxide can be used as raw materials to synthesize carbon dioxide copolymer (polypropylene carbonate PPC) with high alternating structure. Due to the presence of ester bonds in the main chain, the polymer is not only photodegradable, but also a fully biodegradable plastic. It has the defects of low glass transition temperature (35°C), low thermal decomposition temperature (170°C), and long degradation time. It is well known that polylactic acid (PLA), polyglycolic acid and copolymers of polylactic acid and polyglycolic acid are the few polymer materials approved by the US Food and Drug Administration for clinical use in the medical field. They are widely used in the fields of drug delivery and human tissue engineering scaffolds. PLA exhibits four different morphological polymers. Among them, the optically active stereoregular PLLA and PDLA are semi-crystalline substances with high melting point (170°C) and high mechanical strength, which are often used in the manufacture of surgery. Sutures, nails and orthopedic devices, etc. Racemic polylactic acid PDLLA is an amorphous material, and the drug is easy to distribute uniformly in the PDLLA single-phase matrix, so it is often used in drug controlled release systems. The complexation of PDLA and PLLA can form a stereocomplex, and its melting point is significantly higher than that of PLLA or PDLA (up to 230°C). However, when polylactic acid is used as a material, it is relatively brittle, has poor impact resistance, and the degradation products in the body are acidic, which can easily lead to non-infectious inflammation in some patients, which limits its application. The introduction of PLA segments into the main chain of PPC is expected to combine the advantages of both to prepare new biodegradable plastics with good biodegradability, biocompatibility, thermal properties, and mechanical properties.

There are currently three methods for synthesizing diblock or multiblock polymers of PPC. One of the methods is to add multiple monomers at the same time, and use catalysts to catalyze the selective polymerization of monomers to prepare random or block terpolymers. For example, Kroger et al. used imide zinc salt catalyst to realize the ternary copolymerization of carbon dioxide, epoxy cyclohexane and lactide, and synthesized random or block polycyclohexyl carbonate-polylactide. The composition of the segments can be changed as the reaction proceeds as the monomer concentration decreases. Therefore, it is difficult to effectively control the chain structure and molecular weight of the polymer by this method. Another method is to use hydroxyl-terminated PPC as a macromolecular chain transfer agent to prepare block polymers. For example, Darensbourg et al. first used a SalenCoX catalyst to catalyze the binary copolymerization of propylene oxide and carbon dioxide, and used water as a chain transfer agent to prepare a hydroxy-terminated aliphatic polycarbonate, and then added a catalyst 1,8-diazabicyclo[5 ,4,0]-undec-7-ene (DBU) and lactide monomer, the polylactide grows from the hydroxyl groups at both ends of the polycarbonate to prepare polylactide-polycarbonate-polylactide three Metablock copolymers. The method can effectively control the chain structure and molecular weight of the polymer, and may need to add a chain transfer agent and two catalysts to increase the influencing factors. The third method is to use the active catalyst to catalyze the polymerization of the first monomer to prepare the active copolymer, and then add the second monomer to continue to initiate the polymerization of the second monomer to prepare the block copolymer. For example, Coates et al. used active zinc imide catalyst to prepare various block polycyclohexene carbonate polymers by adding various epoxy compounds step by step. The segment structure and molecular weight of the polymer can be effectively controlled by controlling the step-by-step reaction time and the monomer ratio, which is an ideal method for preparing the block copolymer. Metalloporphyrin and metalsalen catalyst is a kind of catalyst with definite structure and good modifiability, which can be applied to the active ternary copolymerization of carbon dioxide, propylene oxide and lactide. The preparation of polyether-polylactide-polycarbonate block copolymers has not yet been reported in the literature.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a composite catalyst for the preparation of polyether-polylactide-aliphatic polycarbonate tertiary block copolymer in view of the above-mentioned deficiencies in the prior art. A polyether-polylactide-aliphatic polycarbonate tertiary block copolymer is obtained by the method of adding propylene oxide, lactide and carbon dioxide monomers in steps.

In order to solve the above technical problems, the technical solution provided by the present invention is: a composite catalyst for preparing polyether-polylactide-aliphatic polycarbonate tertiary block copolymer, characterized in that the composite catalyst is composed of Metal Saleen (SalenM, M=Cr, Co) catalyst and co-catalyst are composed, and the molar ratio of metal-salen catalyst and co-catalyst is 1:0.5-2, wherein the structural formula of metal-salen catalyst is:

M=Cr or Co; R ₁ =-C ₆ H ₄ -(ortho-disubstituted phenyl), 1,2-cyclohexyl, -CH ₂ CH ₂ - or -CH(CH ₃ )CH ₂ -; R ₂ =CH ₃ , t-Bu; R ₃ =Br, CH ₃ , t-Bu or CH ₂ Cl; X is -Cl, CF ₃ COO-, 2,4-dinitrophenoloxy or 2,4,6 - trinitrophenoloxy;

The cocatalyst is bis-(triphenylphosphoranyl)ammonium chloride, 4-dimethylaminopyridine or 2,6-lutidine.

A composite catalyst for preparing a polyether-polylactide-aliphatic polycarbonate ternary block copolymer, wherein the composite catalyst is composed of a metalloporphyrin catalyst and a cocatalyst, and the metalloporphyrin (PorphyrinM , M=Cr, Co, Al) the molar ratio of catalyst and cocatalyst is 1:0.5-2, wherein the structural formula of metalloporphyrin catalyst is:

M=Cr, Co or Al; R2=H, Br, F or -OMe; _R3 and R4 are F or H; X is -Cl, _-OEt , _CCl3COO- or 2,4 _- dinitro Phenoxy;

The cocatalyst is bis-(triphenylphosphoranyl)ammonium chloride, 4-dimethylaminopyridine or 2,6-lutidine.

The method for preparing a novel polyether-polylactide-aliphatic polycarbonate tertiary block copolymer by using the catalyst is characterized in that: adding a metal salen catalyst or a metalloporphyrin catalyst, a cocatalyst and propylene oxide to the In the autoclave, react for 0.5-24 hours, add lactide, the reaction time is 1-6 hours, quickly fill the autoclave with carbon dioxide to maintain the pressure in the autoclave at 1.0-5.0MPa, perform polymerization, and add after the polymerization is completed. A large amount of hydrochloric acid methanol (HCl mass percentage concentration of 1%) solution was used to terminate the reaction, and the obtained product was washed with a large amount of methanol to obtain a novel polyether-polylactide-aliphatic polycarbonate tertiary block copolymer.

According to the above scheme, the lactide is dissolved in propylene oxide or an appropriate amount of solvent, and the molar ratio of lactide to propylene oxide or the solvent is 1:5-10; the solvent is dichloromethane, toluene or dichloromethane. Oxane.

According to the above scheme, the molar ratio of the metal salen catalyst or the metalloporphyrin catalyst to the cocatalyst is 1:0.5-2, and the molar ratio of the metal salen catalyst or the metalloporphyrin catalyst to the propylene oxide is 1:100-5000.

According to the above scheme, the molar ratio of lactide and propylene oxide is 1:1-50.

According to the above scheme, the polymerization temperature is 25-100° C., and the reaction time is 15-48 hours.

In the present invention, under the catalysis of metal porphyrin catalyst or metal Saren catalyst, propylene oxide, lactide and carbon dioxide are subjected to block copolymerization according to anionic coordination polymerization, and the co-catalyst is coordinated at the catalyst center to promote the input of monomers.

The polyether-polylactide-aliphatic polycarbonate tertiary block copolymer prepared according to the above method has a number average molecular weight of 10000-25500 and a molecular weight distribution of 1.1-1.5. The mole percentage of ether PPO segment is 3-23%, the mole percentage of polylactide PLA segment is 11-70%, and the mole percentage of polycarbonate PPC segment is 18-69%. The glass transition temperature of the material is 2-42°C (test conditions, under nitrogen atmosphere, the heating rate is 10°C/min, the heating range is -30°C to 200°C), the elongation at break is 55-331%, and the tensile strength is It is 6-39MPa (according to ASTM-D638 standard method, tested at 15°C lower than the glass transition temperature, and the tensile rate is 50mm/min).

The beneficial effects of the present invention are as follows: 1. The composite catalyst used in the present invention has a good catalytic effect, and can catalyze the polymerization of propylene oxide, the polymerization of lactide and the copolymerization of carbon dioxide and propylene oxide step by step, and the catalytic efficiency is high, and the obtained ternary The copolymer has a large number average molecular weight (Mn is 10000-25500) and a narrow molecular weight distribution (PDI is less than 1.5). 2. The composition of the polyether segment, polylactide segment and PPC segment in the copolymer can be effectively controlled by adjusting the step-by-step reaction time and monomer ratio, and the mole percentage of the PPO segment is 3-23% , the molar content of the polylactide PLA segment is 11-70%, and the molar content of the polycarbonate PPC segment is 18-69%. 3. The polyether-polylactide-aliphatic polycarbonate tertiary block copolymer prepared by the present invention has thermal and mechanical properties that can be adjusted in a wide range: the glass transition temperature of the copolymer is 2- At 42°C, the elongation at break is 55-331%, and the tensile strength is 6-39MPa.

Description of drawings

Fig. 1 is the ¹ H NMR chart of the polymer prepared in Example 1 of the present invention;

Fig. 2 is the carbon nuclear magnetic spectrum ¹³ C NMR chart of the polymer prepared in Example 1;

Figure 3 is a comparison of the DSC charts of the polymers prepared in Examples 2 and 7 with PPC and PLA.

Detailed ways

In order to make those skilled in the art better understand the technical solutions of the present invention, the present invention is further described in detail below with reference to examples.

Example 1

22.7 mg (0.036 mmol) of the SalenCrCl catalyst shown in the above formula, 8.78 mg (0.072 mmol) of the cocatalyst DMAP and 0.5 mL of propylene oxide were respectively added to the autoclave (SalenCrCl catalyst: cocatalyst: propylene oxide=1:2 : 200 (molar ratio)), the polymerization temperature was 60°C, after 12 hours of reaction, 1.037g of lactide (molar ratio of lactide and propylene oxide was 1:1) and 5mL of solvent dioxane were added , after 2 hours of reaction, feed carbon dioxide into the autoclave again to keep the pressure in the still at 3MPa, the reaction time is 18 hours, and 100 mL of hydrochloric acid methanol (HCl mass percentage concentration is 1%) is added after the reaction to terminate the reaction, and the resulting The product was washed with a large amount of methanol, and dried in vacuum to obtain 1.6 g of a white polyether-polylactide-aliphatic polycarbonate tertiary block copolymer with a number average molecular weight of 10,000 and a molecular weight distribution of 1.25.

The ¹ H NMR spectrum of the polymer prepared in this example is shown in Figure 1, and the peak at 5.15 ppm in the figure is the peak of methine hydrogen in the polyester PLA segment (-CH(CH ₃ )COO-) unit in the polymer , 5.0ppm is the peak of methine hydrogen in the polycarbonate PPC segment (-CH ₂ CH(CH ₃ )OCOO-) in the polymer, and 4.2 ppm is the polycarbonate PPC segment (-CH ) in the polymer Peaks of methylene hydrogens in ₂ CH(CH ₃ )OCOO-), methine and methylene peaks in polyether PPO segments (-OCH(CH ₃ )CH ₂ -) at 3.5 ppm , it can be seen that the polymer structure is (-OCH(CH ₃ )CH ₂ -) _a (-CH(CH ₃ )COO-) _b (-CH ₂ CH(CH ₃ )OCOO) _c -H, aliphatic polycarbonate PPC The molar content of the segment PPC%=A _5.0 /(A _5.0 +A _5.1 +A _3.5 /3). The ¹³ C NMR spectrum of the polymer prepared in this example is shown in Figure 2, and the peak at 169.5 ppm in the figure is the ester group-COO in the polyester PLA segment (-CH(CH ₃ )COO-) unit in the polymer -carbon peak, 154.6ppm is the peak of carbonate group -OCOO- carbon in the polycarbonate PPC segment (-CH2CH( _{CH3 )} OCOO-) unit in the polymer, 74.1ppm is the polymer in the polymer Peak of -OCH- carbon in ether PPO segment (-OCH(CH ₃ )CH ₂ -) unit, mole percentage of aliphatic polycarbonate PPC segment PPC%=A _154.6 /(A _169.5 +A _154.6 + A _74.1 ), the ^1H NMR spectrum or the ^13C NMR spectrum of the polymer can be calculated to obtain that the mole percentage of the PPC segment in the terpolymer is about 23%, and the mole percentage of the PPO segment is about 14%. %, the molar percentage of PLA segments is about 63%, the glass transition temperature of the copolymer is 40°C, the elongation at break is 68%, and the tensile strength is 35MPa.

Example 2

29 mg (0.035 mmol) of SalenCo (OC ₆ H ₃ (NO ₂ ) ₂ ) catalyst represented by the above formula, 7.58 mg (0.07 mmol) of cocatalyst 2,6-lutidine and 12.2 mL (175 mmol) of propylene oxide were respectively added to the autoclave (molar ratio SalenCo(OC ₆ H ₃ (NO ₂ ) ₂ ) catalyst: cocatalyst: propylene oxide=1:2:5000), the polymerization temperature was 25°C, and after 24 hours of reaction, Add lactide 2.52g (the mol ratio of lactide and propylene oxide is 1:10) and solvent dichloromethane 10mL, react after 6 hours, then fill carbon dioxide rapidly in the autoclave, and the pressure in the still is maintained at 1.5MPa, and the reaction time was 22 hours. After the reaction, 100 mL of hydrochloric acid methanol (HCl mass percentage concentration was 1%) was added to terminate the reaction. The obtained product was washed with a large amount of methanol, and vacuum dried to obtain a white polyether-polylactide-aliphatic polyether. The carbonate ternary block copolymer is 3.3g, the number average molecular weight is 14350, the molecular weight distribution is 1.25, the mole percentage of PPO segment in the copolymer is 9%, and the mole percentage of PLA segment is 70%, The molar content of the PPC segment is 21%, the glass transition temperature of the copolymer is 42°C, the elongation at break is 55%, and the tensile strength is 39MPa.

Example 3

23 mg (0.035 mmol) of the catalyst of SalenCr (OOCCF ₃ ) shown in the above formula, 10 mg (0.0175 mmol) of bis-(triphenylphosphoranyl) ammonium chloride PPNCl and 12.2 mL (175 mmol) of propylene oxide were added to the high pressure reaction. In the kettle (molar ratio of SalenCr(OOCCF ₃ ) catalyst: cocatalyst: propylene oxide=1:0.5:5000), the polymerization temperature was 60° C., after 10 hours of reaction, 0.504 g of lactide (lactide and The mol ratio of propylene oxide is the propylene oxide 5mL solution of 1:50), after the reaction for 6 hours, carbon dioxide is quickly charged into the autoclave, the pressure in the kettle is maintained at 4.5MPa, and the reaction times is 22 hours, and the reaction finishes Then, 100 mL of hydrochloric acid methanol (HCl mass percentage concentration of 1%) was added to terminate the reaction, the obtained product was washed with a large amount of methanol, and vacuum-dried to obtain 0.6 g of white polyether-polylactide-aliphatic polycarbonate ternary block copolymer, The number average molecular weight is 11000, the molecular weight distribution is 1.35, the mole percentage of PPO segment in the copolymer is 10%, the mole percentage of PLA segment is 54%, and the mole percentage of PPC segment is 36%. , the glass transition temperature of the copolymer is 39℃, the elongation at break is 73%, and the tensile strength is 33MPa.

Example 4

21 mg (0.035 mmol) of the catalyst of SalenCr (OC ₆ H ₂ (NO ₂ ) ₃ ), 40 mg (0.07 mmol) of cocatalyst PPNCl and 12.2 mL (175 mmol) of propylene oxide as shown in the above formula were added to the autoclave respectively (molar Than SalenCr (OC ₆ H ₂ (NO ₂ ) ₃ ) catalyst: co-catalyst: propylene oxide = 1:2:5000), the polymerization temperature is 60 ° C, after 18 hours of reaction, add 2.52 g of lactide (propylene oxide) The mol ratio of lactide and propylene oxide is 1:50) the solution of propylene oxide 12.5mL, after reacting for 1 hour, then quickly fill carbon dioxide into the autoclave, the pressure in the kettle is maintained at 3.5MPa, and the reaction time is After 22 hours, 100 mL of hydrochloric acid methanol (HCl mass percentage concentration of 1%) was added to terminate the reaction after the reaction, the obtained product was washed with a large amount of methanol, and vacuum-dried to obtain a white polyether-polylactide-aliphatic polycarbonate ternary block Copolymer 3g, its number average molecular weight is 17000, molecular weight distribution is 1.3, the mole percentage of PPO segment in the copolymer is 13%, the mole percentage of PLA segment is 35%, and the mole percentage of PPC segment is 35%. The content is 52%, the glass transition temperature of the copolymer is 35°C, the elongation at break is 153%, and the tensile strength is 23MPa.

Example 5

With the porphyrin aluminum PorphyrinAl (OEt) catalyst 23.9mg (0.035mmol), cocatalyst PPNCl 20mg (0.035mmol) and propylene oxide 12.2mL (175mmol) as shown in the above formula, add in the autoclave respectively (mol ratio porphyrin aluminum PorphyrinAl (OEt) catalyst: co-catalyst: propylene oxide = 1:1:5000), the polymerization temperature is 60 °C, after 8 hours of reaction, 2.52 g of lactide (molar ratio of lactide and propylene oxide) is added be 1:10) dichloromethane 10mL solution, after reacting for 1 hour, then quickly fill carbon dioxide into the autoclave, the pressure in the still is maintained at 3.5MPa, the reaction time is 22 hours, and after the reaction finishes, add 100mL hydrochloric acid methanol solution ( HCl mass percentage concentration of 1%) to terminate the reaction, the obtained product was washed with a large amount of methanol, and vacuum-dried to obtain 3.2 g of a white polyether-polylactide-aliphatic polycarbonate tertiary block copolymer with a number-average molecular weight of 18,700. , the molecular weight distribution is 1.43, the mole percentage of the PPO segment in the copolymer is 3%, the mole percentage of the PLA segment is 28%, and the mole percentage of the PPC segment is 69%. The transition temperature was 35°C, the elongation at break was 194%, and the tensile strength was 21 MPa.

Example 6

PorphyrinAl (O(C ₆ H ₃ (NO ₂ ) ₂ ) catalyst 26.6 mg (0.035 mmol), 4.27 mg (0.035 mmol) of cocatalyst DMAP and 12.2 mL of propylene oxide as shown in the above formula were added to the autoclave respectively. (molar ratio PorphyrinAl(O(C ₆ H ₃ (NO ₂ ) ₂ ) catalyst: co-catalyst: propylene oxide=1:1:5000), the polymerization temperature is 25°C, and after 24 hours of reaction, lactide is added The propylene oxide 12.5mL solution of 5.04g (the mol ratio of lactide and propylene oxide is 1:5), after reacting for 2 hours, quickly fill carbon dioxide into the still, the pressure in the still is maintained at 3.5MPa, and the reaction times After 48 hours, 100 mL of hydrochloric acid methanol solution (HCl mass percentage content of 1%) was added to terminate the reaction, the obtained product was washed with a large amount of methanol, and vacuum-dried to obtain a white polyether-polylactide-aliphatic polycarbonate ternary The block copolymer is 5.5g, its number average molecular weight is 25500, the molecular weight distribution is 1.5, the mole percentage of PPO segment in the copolymer is 15%, the mole percentage of PLA segment is 67%, and the mol percentage of the PPC segment is 15%. The molar percentage is 18%, the glass transition temperature of the copolymer is 39°C, the elongation at break is 97%, and the tensile strength is 30MPa.

Example 7

The PorphyrinCrCl catalyst 37.6mg (0.035mmol), the cocatalyst 2,6-lutidine 7.5g (0.07mmol) and the propylene oxide 12.2mL as shown in the above formula were respectively added into the 100mL autoclave (PorphyrinCrCl catalyst: co-catalyst). Catalyst: lactide: propylene oxide = 1:2:500:5000 (molar ratio)), the polymerization temperature is 60 ° C, and after the reaction for 30 min, 2.52 g of lactide (the mixture of lactide and propylene oxide) is added. Molar ratio is 10mL solution of dioxane of 1:10), after reacting for 1 hour, then quickly fill carbon dioxide into the autoclave, the pressure in the autoclave is maintained at 1MPa, the reaction time is 15 hours, and 100mL hydrochloric acid is added after the reaction is finished Methanol solution (HCl mass percentage concentration of 1%) terminated the reaction, the obtained product was washed with a large amount of methanol, and vacuum dried to obtain 2.8 g of white polyether-polylactide-aliphatic polycarbonate tertiary block copolymer with a number average of 2.8 g. The molecular weight is 14600, the molecular weight distribution is 1.5, the mole percentage of the PPO segment in the copolymer is 23%, the mole percentage of the PLA segment is 11%, and the mole percentage of the PPC segment is 66%. The glass transition temperature is 2°C, the elongation at break is 331%, and the tensile strength is 6MPa.

Example 8

PorphyrinCoCl catalyst 37.3mg (0.035mmol), cocatalyst PPNCl 20mg (0.035mmol) and propylene oxide 0.98mL (14mmol) as shown in the above formula were added in the autoclave respectively, the mol ratio PorphyrinCoCl catalyst: cocatalyst: propylene oxide =1:1:400, the polymerization temperature is 100°C, and after 4 hours of reaction, 10 mL of dioxane solution of 2.016 g of lactide (molar ratio of lactide and propylene oxide is 1:1) is added, After 6 hours of reaction, carbon dioxide was quickly charged into the autoclave, the pressure in the autoclave was maintained at 3.5MPa, and the reaction time was 22 hours. After the reaction was completed, 100 mL of hydrochloric acid methanol was added to terminate the reaction, and the obtained product was washed with a large amount of methanol, and vacuum-dried to obtain White polyether-polylactide-aliphatic polycarbonate tertiary block copolymer 2.1g, its number average molecular weight is 10000, molecular weight distribution is 1.25, the mole percentage of PPO segment in the copolymer is 10%, PLA The molar content of the segment is 27%, the molar content of the PPC segment is 63%, the glass transition temperature of the copolymer is 33°C, the elongation at break is 205%, and the tensile strength is 18MPa.

Example 9

PorphyrinAl (OOCCCl ₃ ) catalyst 39mg (0.035mmol) as shown in the above formula, cocatalyst PPNCl 20mg (0.035mmol) and propylene oxide 12.2mL (175mmol) were added in the autoclave respectively (PorphyrinAl (OOCCCl ₃ ) catalyst: PPNCl: Propylene oxide = 1:1:5000 (molar ratio)), the polymerization temperature is 60°C, and after 20 hours of reaction, 2.52 g of lactide is added (molar ratio of lactide and propylene oxide is 1:10) 10mL solution of dioxane, reacted for 1 hour, then quickly filled the autoclave with carbon dioxide, the pressure in the autoclave was maintained at 3.5MPa, and the reaction time was 22 hours. A large amount of methanol was washed to obtain 3.2 g of a white polyether-polylactide-aliphatic polycarbonate tertiary block copolymer with a number-average molecular weight of 14,000 and a molecular weight distribution of 1.1. The mole percentage of PPO segments in the copolymer is 14%, the mole percentage of PLA segments is 31%, the mole percentage of PPC segments is 55%, the glass transition temperature of the copolymer is 35°C, the elongation at break is 187%, and the tensile strength is 20MPa.

The descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (5)

1. The method for preparing the polyether-polylactide-aliphatic polycarbonate ternary block copolymer by using the composite catalyst is characterized by comprising the following steps of: adding a metal salen catalyst or a metal porphyrin catalyst, a cocatalyst and propylene oxide into a high-pressure reaction kettle, reacting for 0.5-24 hours, adding lactide, reacting for 1-6 hours, quickly filling carbon dioxide into the high-pressure reaction kettle to maintain the pressure in the kettle at 1.0-5.0MPa, carrying out polymerization reaction, adding a large amount of hydrochloric acid methanol solution to stop the reaction after the polymerization reaction is finished, and washing the obtained product with a large amount of methanol to obtain the polyether-polylactide-aliphatic polycarbonate ternary block copolymer;

the composite catalyst consists of a metal salen catalyst and a cocatalyst, the molar ratio of the metal salen catalyst to the cocatalyst is 1:0.5-2, wherein the structural formula of the metal salen catalyst is as follows:

m ═ Cr or Co; r₁＝-C₆H₄-ortho-disubstituted phenyl, 1, 2-cyclohexyl, -CH₂CH₂-or-CH (CH)₃)CH₂-；R₂＝CH₃、t-Bu；R₃＝Br、CH₃t-Bu or CH₂Cl; x is-Cl, CF₃COO-, 2, 4-dinitrophenoloxy or 2,4, 6-trinitrophenoloxy;

the cocatalyst is bis- (triphenyl phosphorane) ammonium chloride, 4-dimethylaminopyridine or 2, 6-dimethylpyridine;

or,

the composite catalyst consists of a metalloporphyrin catalyst and a cocatalyst, the molar ratio of the metalloporphyrin catalyst to the cocatalyst is 1:0.5-2, wherein the metalloporphyrin catalyst has the structural formula as follows:

m ═ Cr, Co, or Al; r₂H, Br, F or-OMe; r₃And R₄Is F or H; x is-Cl, -OEt, CCl₃COO-or 2, 4-dinitrophenoloxy;

the cocatalyst is bis- (triphenyl phosphoranylidene) ammonium chloride, 4-dimethylaminopyridine or 2, 6-dimethylpyridine.

2. The method according to claim 1, characterized in that the lactide is dissolved in propylene oxide or a suitable amount of solvent, the molar ratio of lactide to propylene oxide or solvent being 1: 5-10; the solvent is dichloromethane, toluene or dioxane.

3. The method of claim 1, wherein the molar ratio of metallosalen catalyst or metalloporphyrin catalyst to co-catalyst is 1:0.5-2, and the molar ratio of metallosalen catalyst or metalloporphyrin catalyst to propylene oxide is 1: 100-.

4. The process according to claim 1, characterized in that the molar ratio of lactide to propylene oxide is from 1:1 to 50.

5. The process according to claim 1, wherein the polymerization temperature is from 25 to 100 ℃ and the reaction time is from 15 to 48 hours.