Method for preparing polyether / polyester-polyether random copolymer through electrochemical polymerization

Abstract

The invention discloses a method for preparing a polyether / polyester-polyether random copolymer through electrochemical polymerization. According to the preparation method, under the electrifying condition, the lactone and the epoxy compound monomer can be subjected to ring-opening copolymerization reaction at the same time, the composition and proportion of polyester and polyether in the obtained copolymer can be effectively controlled by adjusting the dosage of the polymerization monomer and the reaction time, a catalyst and an initiator are not used in the polymerization reaction, and the polymerization reaction can be stably implemented under the room-temperature reaction condition. The molecular weight of the polyether / polyester-polyether random copolymer prepared by the method disclosed by the invention is 10kg / mol to 45kg / mol, and the molecular weight distribution index is 1.10 to 1.30. The method for preparing the polyester-polyether random copolymer through electrochemical polymerization, provided by the invention, is green and pollution-free, is convenient to operate and has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer preparation and relates to a method for preparing polyester-polyether random copolymer by electrochemically controlling copolymerization of lactone and epoxide. Background Art

[0002] Polyethers have unique chemical and physical properties and are widely used in industry and scientific research. However, in a humid environment, polyether materials will absorb moisture, swell, deform, and deteriorate in performance, which limits their application in specific environments. Polyester-polyether random copolymers have the properties of both polyester and polyether and can be used in food packaging, biomedicine, medical devices and other fields. At present, polyester-polyether random copolymers are mainly synthesized by regulating the copolymerization activity of lactones and epoxides with metal catalysts. The metal catalysts used include organoaluminum, organozinc catalysts, Cr (salen) two-component catalysts, Co-Zn or Co-Al bimetallic complexes, and rare earth metal indium complexes. The catalyst system is mainly a metal complex, which not only has the problem of selectivity of the polymerization monomer, but also increases the purification cost of the copolymerization product using metal catalysts. Therefore, the development of a simple and effective method for the ring-opening copolymerization of lactones and epoxides is of great significance for the preparation of a variety of polyester-polyether copolymers.

[0003] Electrochemical polymerization can regulate the activity of the reaction monomers through the redox potential, and then regulate the copolymerization reaction activity of the monomers, thereby achieving the regulation of the polymer structure and composition. So far, there has been no report on the preparation of polyether / polyester-polyether random copolymers by electrochemical polymerization. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing polyether / polyester-polyether random copolymers by electrochemical polymerization without using a metal catalyst.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing polyether / polyester-polyether random copolymer by electrochemical polymerization, which is carried out according to the following steps: 1) Take a dry electrolytic cell equipped with a magnetic stirrer, add conductive salt, install an anode electrode and a cathode electrode on the electrolytic cell, evacuate the electrolytic cell, and add tetrahydrofuran and dry epoxide with a syringe; For every 0.3g of conductive salt, 5-10mL of tetrahydrofuran and 0.1-2mL of epoxide are required; Alternatively, a dry electrolytic cell equipped with a magnetic stirrer is taken, a conductive salt and a lactone monomer are added, an anode electrode and a cathode electrode are installed on the electrolytic cell, and after the electrolytic cell is evacuated, a dry epoxide is added with a syringe; Every 0.3g of conductive salt requires 5-10mmol of lactone monomer and 5-10mL of epoxide; Alternatively, a dry electrolytic cell equipped with a magnetic stirrer is taken, a conductive salt and a lactone monomer are added, an anode electrode and a cathode electrode are installed on the electrolytic cell, and after the electrolytic cell is evacuated, tetrahydrofuran and dry epoxide are added with a syringe; Every 0.3g of conductive salt requires 5-10mmol of lactone monomer, 4-9mL of tetrahydrofuran and 1-5mL of epoxide; 2) At room temperature, a constant current of 3 to 10 mA is passed through the electrolytic cell for reaction for 1 to 15 hours, and then water or anhydrous methanol is added to the electrolytic cell for precipitation. The precipitate is dried in a vacuum oven at 60° C. for 24 hours to obtain a polyester-polyether random copolymer.

[0006] The conductive salt is tetrabutylammonium tetrafluoroborate.

[0007] The lactone monomer is δ-valerolactone, ε-caprolactone or L-lactide.

[0008] The epoxide may be one or two of ethylene oxide, propylene oxide, cyclohexene oxide, epichlorohydrin, styrene oxide, allyl glycidyl ether and tetrahydrofuran.

[0009] The anode electrode is a magnesium electrode, and the cathode electrode is a platinum electrode.

[0010] The polymerization method of the present invention uses an electrochemical polymerization system, with a magnesium electrode as an anode and a platinum electrode as a cathode. Lactone and epoxide monomers undergo ring-opening polymerization reactions simultaneously under the action of electric energy; that is, an electrochemically controllable ring-opening copolymerization method is adopted to reduce the difference in the reaction activity of the ring-opening polymerization of epoxide and lactone, and the proportion of the polyester and polyether components in the copolymer can be effectively adjusted by adjusting the amount of polymerization monomers and the reaction time, so as to synthesize a polyether / polyester-polyether random copolymer with a molecular weight of 10kg / mol to 45kg / mol and a molecular weight distribution index of 1.10 to 1.30.

[0011] The electrochemical polymerization of the present invention is a copolymerization method, which uses clean energy electricity, does not pollute the environment, does not require the use of chemical catalysts and initiators, avoids the steps of catalyst screening and polymer impurity removal, avoids the high temperature reaction conditions of polyester-polyether synthesis, effectively improves the safety of the polymerization reaction, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The P(PO- co -THF) H NMR spectrum.

[0013] Figure 2 The P(PO- co -THF) GPC composite chart.

[0014] Figure 3 The P(LA- co -PO) H NMR spectrum.

[0015] Figure 4 The P(LA- co -PO) GPC composite chart.

[0016] Figure 5 The P(LA- co -PO- co -THF) H NMR spectrum.

[0017] Figure 6 The P(LA- co -PO- co -THF) GPC composite chart.

[0018] Figure 7 The P(LA- co -PO- co -THF) purified product NMR spectrum. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with specific embodiments and accompanying drawings. The terms used in the present invention, unless otherwise specified, generally have the meanings commonly understood by those of ordinary skill in the art. In the following examples, various processes and methods not described in detail are conventional methods known in the art. At the same time, due to the various polymer structures and ratios, not all preparation methods are described in detail, and typical examples are taken to illustrate the specific process steps of the present invention.

[0020] Example 1 Take five dry electrolytic cells equipped with magnetic stirrers, add 0.3g of Bu4NBF4 to all the electrolytic cells, and install electrodes on all the electrolytic cells (magnesium electrode as anode electrode, platinum electrode as cathode electrode). After evacuating all the electrolytic cells for 30 minutes, use a syringe to add 6mL of dry tetrahydrofuran (THF) and 0.25mL of propylene oxide (PO) to all the electrolytic cells.

[0021] Then, at room temperature, 4 mA constant current was passed into five electrolytic cells for electropolymerization reaction: The first electrolytic cell has an electropolymerization reaction for 2 hours; the second electrolytic cell has an electropolymerization reaction for 3 hours; the third electrolytic cell has an electropolymerization reaction for 4 hours; the fourth electrolytic cell has an electropolymerization reaction for 5 hours; and the fifth electrolytic cell has an electropolymerization reaction for 6 hours.

[0022] After the reaction was completed, water was added to each electrolytic cell for sedimentation, and the sediment was vacuum dried at 60°C for 24 hours to obtain five random copolymers of PO and THF (P(PO- co -THF)).

[0023] The reaction process of Example 1 is: Figure 1 The five portions of P(PO- co -THF) H NMR spectrum ( 1 H-NMR, CDCl3) chart.

[0024] Figure 2 The five portions of P(PO- co -THF) GPC composite chart. Figure 2 It can be seen that with the increase of polymerization reaction time, the conversion rates of PO and THF gradually increase, the molecular weight of the polymer increases, and the molecular weight distribution index does not change much, indicating that the polymerization method of the present invention has good controllability over the molecular weight and molecular weight distribution index of the polymer.

[0025] Example 2 Take seven dry electrolytic cells equipped with magnetic stirrers, add 0.3g Bu4NBF4 and 1g (7mmol) L-lactide (LA) to all electrolytic cells, and place electrodes (magnesium electrode as anode electrode, platinum electrode as cathode electrode) on all electrolytic cells. After evacuating all electrolytic cells for 30 minutes, add 6mL of dry propylene oxide to each electrolytic cell with a syringe.

[0026] Then, at room temperature, 4 mA constant current was passed into seven electrolytic cells for electropolymerization reaction: The first electrolytic cell has an electropolymerization reaction of 1 hour, the second electrolytic cell has an electropolymerization reaction of 2 hours, the third electrolytic cell has an electropolymerization reaction of 3 hours, the fourth electrolytic cell has an electropolymerization reaction of 4 hours, the fifth electrolytic cell has an electropolymerization reaction of 5 hours, the sixth electrolytic cell has an electropolymerization reaction of 6 hours, and the seventh electrolytic cell has an electropolymerization reaction of 7 hours.

[0027] After the reaction was completed, anhydrous methanol was added to the seven electrolytic cells for precipitation, and the precipitate was vacuum dried at 60°C for 24 hours to obtain a random copolymer of PO and LA (P(LA- co -PO)).

[0028] The reaction process of Example 2 is: Figure 3 The P(LA- co -PO) 1 H-NMR, CDCl3) chart.

[0029] Figure 4 The P(LA- co -PO) GPC composite chart. Figure 4 It shows that with the increase of polymerization reaction time, the conversion rate of PO and LA gradually increases, the molecular weight of the polymer increases, and the molecular weight distribution index does not change much, indicating that the polymerization method of the present invention has good controllability over the molecular weight and molecular weight distribution index of the polymer.

[0030] Example 3 Take six dry electrolytic cells equipped with magnetic stirrers, add 0.3g Bu4NBF4 and 1g LA to each electrolytic cell, and install electrodes on all electrolytic cells (magnesium electrode as anode electrode, platinum electrode as cathode electrode). After all electrolytic cells are evacuated for 30 minutes, add 2mL of dry propylene oxide and 5mL of tetrahydrofuran to each electrolytic cell with a syringe.

[0031] Then, at room temperature, 4 mA constant current was passed into the six electrolytic cells for electropolymerization reaction: The first electrolytic cell has an electropolymerization reaction of 2 hours, the second electrolytic cell has an electropolymerization reaction of 3 hours, the third electrolytic cell has an electropolymerization reaction of 4 hours, the fourth electrolytic cell has an electropolymerization reaction of 5 hours, the fifth electrolytic cell has an electropolymerization reaction of 6 hours, and the sixth electrolytic cell has an electropolymerization reaction of 7 hours.

[0032] After the reaction was completed, anhydrous methanol was added to each electrolytic cell for precipitation, and the precipitate was vacuum dried at 60°C for 24 hours to obtain a random copolymer of PO, THF and LA (P(LA- co -PO- co -THF)).

[0033] The reaction process of Example 3 is: Figure 5 The P(LA- co -PO- co -THF) H NMR spectrum ( 1 H-NMR, CDCl3) chart.

[0034] Figure 6 The P(LA- co -PO- co -THF) GPC composite chart. Figure 6It shows that with the increase of polymerization reaction time, the conversion rates of PO, THF and LA gradually increase, the molecular weight of the polymer increases, and the molecular weight distribution index does not change much, indicating that the polymerization method of the present invention has good controllability over the molecular weight and molecular weight distribution index of the polymer.

[0035] Example 4 Take a dry electrolytic cell equipped with a magnetic stirrer, add 0.3g of Bu4NBF4 and 1g of LA, and install electrodes on the electrolytic cell (magnesium electrode as anode electrode, platinum electrode as cathode electrode). After the electrolytic cell is evacuated for 30 minutes, add 1mL of dry propylene oxide and 6mL of tetrahydrofuran to the electrolytic cell with a syringe. Then, at room temperature, pass a 4mA constant current electropolymerization reaction into the electrolytic cell for 7 hours. After the reaction is completed, water is added to the electrolytic cell for sedimentation, and the sediment is vacuum dried at 60°C for 24 hours to obtain a random copolymer of PO, THF and LA (P(LA- co -PO- co -THF)).

[0036] It can be found from Example 4 that after adjusting the amount of propylene oxide and tetrahydrofuran compared with Example 3, the polymerization method of the present invention is still applicable. The structure of the pure polymer product synthesized in Example 4 was characterized. Figure 7 The H NMR spectrum shown in FIG. 1 shows that the H NMR signal peaks of ester-ether bond connection can be clearly observed, indicating that the random copolymer of PO, THF and LA (P(LA- co -PO- co -THF)) was successfully prepared.

Claims

1. A method for preparing polyether / polyester-polyether random copolymer by electrochemical polymerization, characterized in that: The preparation of the polyether random copolymer is as follows: 1) Take a dry electrolytic cell equipped with a magnetic stirrer, add conductive salt, install an anode electrode and a cathode electrode on the electrolytic cell, evacuate the electrolytic cell, and add tetrahydrofuran and dry epoxide with a syringe; 5-10mL tetrahydrofuran and 0.1-2mL epoxide are required for every 0.3g conductive salt; 2) At room temperature, a constant current of 3 to 10 mA is passed through the electrolytic cell for 1 to 15 hours, and then water or anhydrous methanol is added to the electrolytic cell for precipitation. The precipitate is dried in a vacuum oven at 60° C. for 24 hours to obtain a polyether random copolymer; The preparation of the polyester-polyether random copolymer is as follows: 1) Take a dry electrolytic cell equipped with a magnetic stirrer, add conductive salt and lactone monomer, install anode and cathode electrodes on the electrolytic cell, evacuate the electrolytic cell, and add dry epoxide with a syringe; 5-10mmol lactone monomer and 5-10mL epoxide are required for every 0.3g conductive salt; Alternatively, a dry electrolytic cell equipped with a magnetic stirrer is used, and a conductive salt and a lactone monomer are added. An anode electrode and a cathode electrode are installed on the electrolytic cell. After the electrolytic cell is evacuated, tetrahydrofuran and a dry epoxide are added with a syringe; 5 to 10 mmol of lactone monomer, 4 to 9 mL of tetrahydrofuran and 1 to 5 mL of epoxide are required for every 0.3 g of conductive salt; 2) At room temperature, a constant current of 3 to 10 mA is passed through the electrolytic cell for reaction for 1 to 15 hours, and then water or anhydrous methanol is added to the electrolytic cell for precipitation. The precipitate is dried in a vacuum oven at 60° C. for 24 hours to obtain a polyester-polyether random copolymer.

2. A method for preparing polyether / polyester-polyether random copolymer by electrochemical polymerization as claimed in claim 1, characterized in that: The conductive salt is tetrabutylammonium tetrafluoroborate.

3. A method for preparing polyether / polyester-polyether random copolymer by electrochemical polymerization as claimed in claim 1, characterized in that: The lactone monomer is δ-valerolactone, ε-caprolactone or L-lactide.

4. A method for preparing polyether / polyester-polyether random copolymer by electrochemical polymerization as claimed in claim 1, characterized in that: The epoxide is at least one of ethylene oxide, propylene oxide, cyclohexene oxide, epichlorohydrin, styrene oxide and allyl glycidyl ether.

5. A method for preparing polyether / polyester-polyether random copolymer by electrochemical polymerization as claimed in claim 1, characterized in that: The anode electrode is a magnesium electrode, and the cathode electrode is a platinum electrode.

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