Polylactic acid block copolymer as well as preparation process and application thereof

Abstract

The invention relates to the technical field of polylactic acid, and discloses a polylactic acid block copolymer as well as a preparation process and application thereof. Firstly, lactic acid is used as a raw material, 1, 4-butanediol is used as an initiator, stannous octoate is used for catalyzing ring opening polymerization of the lactic acid, a polymer with hydroxyl at the tail end is prepared, then hydroxyl-polylactic acid-hydroxyl (OH-PLA-OH) generates chlorine-polylactic acid-chlorine under the action of triethylamine and methanesulfonamide, namely an ATRP macromolecular initiator, and the ATRP macromolecular initiator is used for preparing the polylactic acid-chlorine polymer. The preparation method comprises the following steps: reacting with 4-hydroxybenzaldehyde by using an ATRP (Atom Transfer Radical Polymerization) method to synthesize a benzyl alcohol-terminated polylactic acid copolymer, then reacting the obtained product with sulfur-dodecane-sodium trithiocarbonate to synthesize a reversible addition fragmentation-chain transfer reagent (RAFT reagent), and finally reacting with 3-acrylamido phenylboronic acid to obtain a triblock hydrophilic copolymer. Finally, the formed gel is responsive to glucose.

Description

Technical Field

[0001] The invention relates to the technical field of polylactic acid, in particular to a polylactic acid block copolymer and a preparation process and application thereof. Background Art

[0002] Polylactic acid is a polymer made by dehydration polymerization of lactic acid as raw material. It degrades into carbon dioxide and water after being discarded. The intermediate products are also normal metabolites. It will not cause pollution after being discarded. It has been approved by the US Food and Drug Administration and has become a biomedical material. For example, patent application announcement number CN113501943B "A method for preparing polylactic acid" discloses a method of synthesizing a medical grade polylactic acid material with high purity and low metal residue using lactic acid as raw material and non-metallic catalyst.

[0003] Polylactic acid block copolymers are usually polymers composed of long chains formed by two or more units. According to the number of blocks, they can be divided into diblock copolymers, triblock copolymers, and multiblock copolymers; according to water solubility, they can be divided into amphiphilic block copolymers, double hydrophilic block copolymers, and double hydrophobic block copolymers. Amphiphilic block copolymers are formed by covalently connecting hydrophilic segments and hydrophobic segments to form special structures such as vesicles, micelles, and gels, which are used in the field of biomedicine. For example, the paper "Preparation and Performance Study of Polylactic Acid / Polyethylene Glycol Block Copolymer Composites" describes a PLLA-PEG-PLLA / PDLA-PEG-PDLA (PLLA and PDLA are two optical isomers of polylactic acid, and PEG is polyethylene glycol) hydrogel system, but its high crystallinity and poor toughness reduce biocompatibility and limit field applications. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the deficiencies in the prior art, the present invention provides a polylactic acid block copolymer and a preparation process and application thereof.

[0006] (II) Technical solution

[0007] A preparation process of a polylactic acid block copolymer, comprising the following steps:

[0008] (1) Preparation of hydroxy-polylactic acid-hydroxy

[0009] Add lactic acid to a flask, introduce nitrogen, stir until the temperature reaches 75-85°C, maintain for 2-3 hours, perform vacuum distillation, then add 1,4-butanediol and stannous octoate, stir until the temperature reaches 160-220°C, react for 10-12 hours, and take out the product;

[0010] (2) Preparation of Chloro-polylactic acid-Chloro

[0011] Add 5 mL of tetrahydrofuran to hydroxy-polylactic acid-hydroxy, fill with N2 under closed conditions, add triethylamine and methylsulfonamide, first stir in an ice water bath at a temperature of 0-2°C for 2-4 hours, then react at a temperature of 20-35°C for 48-58 hours, filter, concentrate, precipitate, wash, and vacuum dry;

[0012] (3) Preparation of benzyl alcohol-terminated polylactic acid polymers

[0013] Add chloro-polylactic acid-chloro, potassium tert-butoxide and 5 mL of anhydrous tetrahydrofuran into a flask, add nitrogen in an ice-water bath at a temperature of 0-2°C, then add catalyst CuBr and 2,2-bipyridine, and finally add 4-hydroxybenzaldehyde, maintain the reaction temperature at 80-90°C for 10-18 hours, evaporate, concentrate, precipitate, wash, and vacuum dry;

[0014] (4) Synthesis of reversible addition-fragmentation-chain transfer reagents

[0015] Dissolve the benzyl alcohol-terminated polylactic acid polymer in 50 mL of dichloromethane solvent, add N,N-dimethylformamide, cool, add thionyl chloride, the temperature is 25-35°C, the reaction time is 8-10 hours, rotary evaporation, purification, dissolve the obtained product in 50 mL of dichloromethane, add sulfur-dodecane-sodium trithiocarbonate, the temperature is 25-35°C, the reaction temperature is 24-36 hours, concentrate, filter, precipitate, and dry;

[0016] (5) Polylactic acid block copolymer

[0017] 3-Acrylamidophenylboronic acid was added to a double-row tube and added to a mixed solvent of a reversible addition-fragmentation-chain transfer reagent at a concentration of 0.8-1.0 mg / mL azobisisobutyronitrile in N,N-dimethylformamide. The solution was subjected to 3-5 freeze-vacuum-thaw operations on a vacuum line, the tube was sealed, precipitated, and vacuum dried.

[0018] Preferably, in step (1), the molar ratio of lactic acid, 1,4-butanediol and stannous octoate is 1:0.01-0.015:0.0015-0.0025.

[0019] Preferably, in step (2), the molar ratio of hydroxy-polylactic acid-hydroxy, triethylamine, methylsulfonamide, CuBr and 2,2-bipyridine is 1:2.5-3.5:2.8-3.6:1.8-2.4:3.8-4.6.

[0020] Preferably, in step (3), the molar ratio of chloro-polylactic acid-chloro, 4-hydroxybenzaldehyde and potassium tert-butoxide is.

[0021] Preferably, in the step (4), the mass ratio of the benzyl alcohol-terminated polylactic acid polymer, N,N-dimethylformamide, thionyl chloride, and sulfur-dodecane-sodium trithiocarbonate is 0.4-0.8:0.003-0.004:0.4-0.5:1.

[0022] Preferably, in step (5), the mass ratio of 3-acrylamidophenylboronic acid to the reversible addition fragmentation-chain transfer reagent is 0.3-0.6:1.

[0023] Preferably, the reaction temperature in step (5) is 65-80°C and the reaction time is 20-30h.

[0024] Preferably, the method for preparing the polylactic acid block copolymer hydrogel is: pouring the polylactic acid block copolymer into a flask, adding phosphate buffer, centrifuging, and standing for 4-8 hours.

[0025] Preferably, the phosphate buffer is Na2HPO4 or Na2H2PO4.

[0026] Preferably, the pH is maintained at 7.2-7.6.

[0027] (III) Beneficial technical effects

[0028] The invention first uses lactic acid as a raw material, 1,4-butanediol as an initiator, and uses stannous octoate to catalyze the ring-opening polymerization to prepare a polymer with a hydroxyl group at the end; then, hydroxy-polylactic acid-hydroxy (OH-PLA-OH) generates chlorine-polylactic acid-chlorine, that is, an ATRP macromolecular initiator, under the action of triethylamine and methylsulfonamide; the ATRP method is used to react with 4-hydroxybenzaldehyde to synthesize a polylactic acid copolymer with a terminal benzyl alcohol; then, the obtained product reacts with sulfur-dodecane-sodium trithiocarbonate to synthesize a reversible addition fragmentation-chain transfer reagent (RAFT reagent); finally, the product reacts with 3-acrylamidophenylboronic acid to obtain a triblock hydrophilic copolymer; and the finally formed gel is responsive to glucose. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the degree to which the gel dissolves over time.

[0030] Figure 2 Temperature-dependent dynamic storage modulus and loss modulus as a function of angular frequency. DETAILED DESCRIPTION

[0031] Example 1

[0032] (1) Preparation of hydroxy-polylactic acid-hydroxy

[0033] 2 mol of lactic acid was added to the flask, nitrogen was introduced, the temperature was stirred to 75°C, maintained for 2 hours, and vacuum distilled, and then 0.02 mol of 1,4-butanediol and 0.003 mol of stannous octoate were added, the temperature was stirred to 160°C, the reaction time was 10 hours, and the product was taken out;

[0034] (2) Preparation of Chloro-polylactic acid-Chloro

[0035] Add 1.2 mol of hydroxy-polylactic acid-hydroxy to 5 mL of tetrahydrofuran, fill with N2 under closed conditions, add 3 mol of triethylamine and 3.4 mol of methylsulfonamide, first stir in an ice-water bath at 0°C for 2 hours, then react at 20-35°C for 48 hours, filter, concentrate, precipitate, wash, and vacuum dry;

[0036] (3) Preparation of benzyl alcohol-terminated polylactic acid polymers

[0037] 0.8 mol of chloro-polylactic acid-chloro, 1 mol of potassium tert-butoxide and 5 mL of anhydrous tetrahydrofuran were added to a flask, and nitrogen was added in an ice-water bath at 0°C, and then 1.4 mol of CuBr catalyst and 3 mol of 2,2-bipyridine were added, and finally 1.6 mol of 4-hydroxybenzaldehyde were added, and the reaction temperature was maintained at 80-90°C for 10 hours, and then evaporated, concentrated, precipitated, washed, and vacuum dried;

[0038] (4) Synthesis of reversible addition-fragmentation-chain transfer reagents

[0039] Dissolve 0.4 mol of benzyl alcohol-terminated polylactic acid polymer in 50 mL of dichloromethane solvent, add 0.003 mol of N,N-dimethylformamide, cool, add 0.4 mol of thionyl chloride, the temperature is 25°C, the reaction time is 8 hours, rotary evaporation, purification, dissolve the obtained product in 50 mL of dichloromethane, add 1 mol of sulfur-dodecane-sodium trithiocarbonate, the temperature is 25°C, the reaction temperature is 24 hours, concentrate, filter, precipitate, and dry;

[0040] (5) Polylactic acid block copolymer

[0041] 0.15 mol of 3-acrylamidophenylboronic acid was added to a double-row tube and added to a mixed solvent of 0.5 mol of a reversible addition-fragmentation-chain transfer reagent and 0.8 mg / mL azobisisobutyronitrile in N,N-dimethylformamide solution. The reaction temperature was 65°C and the reaction time was 20 h. The solution was subjected to three freeze-vacuum-thaw operations on a vacuum line, the tube was sealed, precipitated, and dried in vacuum.

[0042] (6) Pour the polylactic acid block copolymer into a flask, add Na2HPO4 and Na2H2PO4 buffer solutions, maintain the pH at 7.2, centrifuge, and let stand for 4 hours.

[0043] Example 2

[0044] (1) Preparation of hydroxy-polylactic acid-hydroxy

[0045] 4 mol of lactic acid was added to the flask, nitrogen was introduced, the temperature was stirred to 85°C, maintained for 3 hours, and distilled under reduced pressure, and then 0.06 mol of 1,4-butanediol and 0.010 mol of stannous octoate were added, the temperature was stirred to 220°C, the reaction time was 12 hours, and the product was taken out;

[0046] (2) Preparation of Chloro-polylactic acid-Chloro

[0047] 2.4 mol of hydroxy-polylactic acid-hydroxy was added to 5 mL of tetrahydrofuran, filled with N2 under closed conditions, 8.4 mol of triethylamine and 8.6 mol of methylsulfonamide were added, first stirred in an ice-water bath at 2°C for 4 h, then reacted at 35°C for 58 h, filtered, concentrated, precipitated, washed, and vacuum dried;

[0048] (3) Preparation of benzyl alcohol-terminated polylactic acid polymers

[0049] 1.2 mol of chloro-polylactic acid-chloro, 2 mol of potassium tert-butoxide and 5 mL of anhydrous tetrahydrofuran were added to a flask, and nitrogen was added in an ice-water bath at 2°C, and then 2.8 mol of CuBr catalyst and 5.5 mol of 2,2-bipyridine were added, and finally 3 mol of 4-hydroxybenzaldehyde were added, and the reaction temperature was maintained at 90°C for 18 hours, and then evaporated, concentrated, precipitated, washed, and vacuum dried;

[0050] (4) Synthesis of reversible addition-fragmentation-chain transfer reagents

[0051] Dissolve 1.2 mol of benzyl alcohol-terminated polylactic acid polymer in 50 mL of dichloromethane solvent, add 0.006 mol of N,N-dimethylformamide, cool, add 0.8 mol of thionyl chloride, the temperature is 35°C, the reaction time is 10 hours, rotary evaporation, purification, dissolve the obtained product in 50 mL of dichloromethane, add 1.5 mol of sulfur-dodecane-sodium trithiocarbonate, the temperature is 35°C, the reaction temperature is 36 hours, concentrate, filter, precipitate, and dry;

[0052] (5) Preparation of polylactic acid block copolymer

[0053] 0.42 mol of 3-acrylamidophenylboronic acid was added to a double-row tube and added to a mixed solvent of 0.8 mol of a reversible addition fragmentation-chain transfer reagent and 1.0 mg / mL azobisisobutyronitrile in N,N-dimethylformamide solution. The reaction temperature was 80°C for 30 h. The solution was subjected to 5 freeze-vacuum-thaw operations on a vacuum line, the tube was sealed, precipitated, and dried in vacuum.

[0054] (6) Pour the polylactic acid block copolymer into a flask, add Na2HPO4 and Na2H2PO4 buffer solutions, maintain the pH at 7.6, centrifuge, and let stand for 8 hours.

[0055] Example 3

[0056] (1) Preparation of hydroxy-polylactic acid-hydroxy

[0057] 3 mol of lactic acid was added to the flask, nitrogen was introduced, the temperature was stirred to 80°C, maintained for 2.5 hours, and distilled under reduced pressure. Then 0.04 mol of 1,4-butanediol and 0.008 mol of stannous octoate were added, the temperature was stirred to 200°C, the reaction time was 11 hours, and the product was taken out;

[0058] (2) Preparation of Chloro-polylactic acid-Chloro

[0059] 2 mol of hydroxy-polylactic acid-hydroxy was added to 5 mL of tetrahydrofuran, filled with N2 under closed conditions, 4 mol of triethylamine and 6 mol of methylsulfonamide were added, first stirred in an ice-water bath at 1°C for 3 h, then reacted at 30°C for 52 h, filtered, concentrated, precipitated, washed, and vacuum dried;

[0060] (3) Preparation of benzyl alcohol-terminated polylactic acid polymers

[0061] 0.9 mol of chloro-polylactic acid-chloro, 1.5 mol of potassium tert-butoxide and 5 mL of anhydrous tetrahydrofuran were added to a flask, and nitrogen was added to an ice-water bath at 1°C, and then 2.4 mol of CuBr catalyst and 4.2 mol of 2,2-bipyridine were added, and finally 2.5 mol of 4-hydroxybenzaldehyde were added, and the reaction temperature was maintained at 85°C for 12 hours, and then evaporated, concentrated, precipitated, washed, and vacuum dried;

[0062] (4) Synthesis of reversible addition-fragmentation-chain transfer reagents

[0063] Dissolve 0.8 mol of benzyl alcohol-terminated polylactic acid polymer in 50 mL of dichloromethane solvent, add 0.005 mol of N,N-dimethylformamide, cool, add 0.6 mol of thionyl chloride, the temperature is 30°C, the reaction time is 9 hours, rotary evaporation, purification, dissolve the obtained product in 50 mL of dichloromethane, add 1.2 mol of sulfur-dodecane-sodium trithiocarbonate, the temperature is 28°C, the reaction temperature is 30 hours, concentrate, filter, precipitate, and dry;

[0064] (5) Polylactic acid block copolymer

[0065] 0.32 mol of 3-acrylamidophenylboronic acid was added to a double-row tube and added to a mixed solvent of 0.6 mol of a reversible addition fragmentation-chain transfer reagent and 0.88 mg / mL azobisisobutyronitrile in N,N-dimethylformamide solution. The reaction temperature was 70°C and the reaction time was 25 h. The solution was subjected to four freeze-vacuum-thaw operations on a vacuum line, the tube was sealed, precipitated, and vacuum dried.

[0066] (6) Pour the polylactic acid block copolymer into a flask, add Na2HPO4 and Na2H2PO4 buffer solutions, maintain the pH at 7.4, centrifuge, and let stand for 6 hours.

[0067] Example 4

[0068] (1) Preparation of hydroxy-polylactic acid-hydroxy

[0069] 3 mol of lactic acid was added to the flask, nitrogen was introduced, the temperature was stirred to 80°C, maintained for 2.5 hours, and distilled under reduced pressure. Then 0.04 mol of 1,4-butanediol and 0.008 mol of stannous octoate were added, the temperature was stirred to 200°C, the reaction time was 11 hours, and the product was taken out;

[0070] (2) Preparation of Chloro-polylactic acid-Chloro

[0071] 2 mol of hydroxy-polylactic acid-hydroxy was added to 5 mL of tetrahydrofuran, filled with N2 under closed conditions, 4 mol of triethylamine and 6 mol of methylsulfonamide were added, first stirred in an ice-water bath at 1°C for 3 h, then reacted at 30°C for 52 h, filtered, concentrated, precipitated, washed, and vacuum dried;

[0072] (3) Preparation of benzyl alcohol-terminated polylactic acid polymers

[0073] 1.2 mol of chloro-polylactic acid-chloro, 2 mol of potassium tert-butoxide and 5 mL of anhydrous tetrahydrofuran were added to a flask, and nitrogen was added in an ice-water bath at 2°C, and then 2.8 mol of CuBr catalyst and 5.5 mol of 2,2-bipyridine were added, and finally 3 mol of 4-hydroxybenzaldehyde were added, and the reaction temperature was maintained at 90°C for 18 hours, and then evaporated, concentrated, precipitated, washed, and vacuum dried;

[0074] (4) Synthesis of reversible addition-fragmentation-chain transfer reagents

[0075] Dissolve 1.2 mol of benzyl alcohol-terminated polylactic acid polymer in 50 mL of dichloromethane solvent, add 0.006 mol of N,N-dimethylformamide, cool, add 0.8 mol of thionyl chloride, the temperature is 35°C, the reaction time is 10 hours, rotary evaporation, purification, dissolve the obtained product in 50 mL of dichloromethane, add 1.5 mol of sulfur-dodecane-sodium trithiocarbonate, the temperature is 35°C, the reaction temperature is 36 hours, concentrate, filter, precipitate, and dry;

[0076] (5) Polylactic acid block copolymer

[0077] 0.15 mol of 3-acrylamidophenylboronic acid was added to a double-row tube and added to a mixed solvent of 0.5 mol of a reversible addition-fragmentation-chain transfer reagent and 0.8 mg / mL azobisisobutyronitrile in N,N-dimethylformamide solution. The reaction temperature was 65°C and the reaction time was 20 h. The solution was subjected to three freeze-vacuum-thaw operations on a vacuum line, the tube was sealed, precipitated, and dried in vacuum.

[0078] (6) Pour the polylactic acid block copolymer into a flask, add Na2HPO4 and Na2H2PO4 buffer solutions, maintain the pH at 7.2, centrifuge, and let stand for 4 hours.

[0079] Example 5

[0080] (1) Preparation of hydroxy-polylactic acid-hydroxy

[0081] 4 mol of lactic acid was added to the flask, nitrogen was introduced, the temperature was stirred to 85°C, maintained for 3 hours, and distilled under reduced pressure, and then 0.06 mol of 1,4-butanediol and 0.010 mol of stannous octoate were added, the temperature was stirred to 220°C, the reaction time was 12 hours, and the product was taken out;

[0082] (2) Preparation of Chloro-polylactic acid-Chloro

[0083] 2.4 mol of hydroxy-polylactic acid-hydroxy was added to 5 mL of tetrahydrofuran, filled with N2 under closed conditions, 8.4 mol of triethylamine and 8.6 mol of methylsulfonamide were added, first stirred in an ice-water bath at 2°C for 4 h, then reacted at 35°C for 58 h, filtered, concentrated, precipitated, washed, and vacuum dried;

[0084] (3) Preparation of benzyl alcohol-terminated polylactic acid polymers

[0085] 0.9 mol of chloro-polylactic acid-chloro, 1.5 mol of potassium tert-butoxide and 5 mL of anhydrous tetrahydrofuran were added to a flask, and nitrogen was added to an ice-water bath at 1°C, and then 2.4 mol of CuBr catalyst and 4.2 mol of 2,2-bipyridine were added, and finally 2.5 mol of 4-hydroxybenzaldehyde were added, and the reaction temperature was maintained at 85°C for 12 hours, and then evaporated, concentrated, precipitated, washed, and vacuum dried;

[0086] (4) Synthesis of reversible addition-fragmentation-chain transfer reagents

[0087] Dissolve 0.8 mol of benzyl alcohol-terminated polylactic acid polymer in 50 mL of dichloromethane solvent, add 0.005 mol of N,N-dimethylformamide, cool, add 0.6 mol of thionyl chloride, the temperature is 30°C, the reaction time is 9 hours, rotary evaporation, purification, dissolve the obtained product in 50 mL of dichloromethane, add 1.2 mol of sulfur-dodecane-sodium trithiocarbonate, the temperature is 28°C, the reaction temperature is 30 hours, concentrate, filter, precipitate, and dry;

[0088] (5) Polylactic acid block copolymer

[0089] 0.42 mol of 3-acrylamidophenylboronic acid was added to a double-row tube and added to a mixed solvent of 0.8 mol of a reversible addition fragmentation-chain transfer reagent and 1.0 mg / mL azobisisobutyronitrile in N,N-dimethylformamide solution. The reaction temperature was 80°C for 30 h. The solution was subjected to 5 freeze-vacuum-thaw operations on a vacuum line, the tube was sealed, precipitated, and dried in vacuum.

[0090] (6) Pour the polylactic acid block copolymer into a flask, add Na2HPO4 and Na2H2PO4 buffer solutions, maintain the pH at 7.4, centrifuge, and let stand for 6 hours.

[0091] Rheological property test: Dynamic rheological experiment was carried out using Physica MCR301 stress-controlled rheometer, and cone-plate measurement system was measured using CP25-2.

[0092] The G' corresponding to the angular frequency of 70.8 rad / s in the plateau region is selected to illustrate the strength of the sample.

[0093] Transition temperature: gel-solution transition of supramolecular gel.

[0094] Tanα = gel viscosity / elasticity.

[0095]

[0096]

[0097] The strength of the samples in various embodiments of the present invention reaches 635-1980Pa, the ratio of Tanα reaches 0.18-0.38, the relaxation time reaches 2.2-6.4s, and the transition temperature reaches 28.6-42.5. The larger the ratio of Tanα, the closer the properties of the gel are to those of a liquid, so the lower the concentration of the copolymer, the smaller the hardness of the gel and the shorter the relaxation time.

Claims

1. A process for preparing a polylactic acid block copolymer, characterized in that: The following steps are described: (1) Preparation of hydroxy-polylactic acid-hydroxy Add lactic acid to a flask, introduce nitrogen, stir until the temperature reaches 75-85°C, maintain for 2-3 hours, perform vacuum distillation, then add 1,4-butanediol and stannous octoate, stir until the temperature reaches 160-220°C, react for 10-12 hours, and take out the product; (2) Preparation of Chloro-polylactic acid-Chloro Add hydroxy-polylactic acid-hydroxy to tetrahydrofuran, fill with N2 under closed conditions, add triethylamine and methylsulfonamide, first stir in an ice water bath at a temperature of 0-2°C for 2-4 hours, then react at a temperature of 20-35°C for 48-58 hours, filter, concentrate, precipitate, wash, and vacuum dry; (3) Preparation of benzyl alcohol-terminated polylactic acid polymers Add chloro-polylactic acid-chloro, potassium tert-butoxide and anhydrous tetrahydrofuran into a flask, add nitrogen in an ice water bath at a temperature of 0-2°C, then add catalyst CuBr and 2,2-bipyridine, and finally add 4-hydroxybenzaldehyde, maintain the reaction temperature at 80-90°C, the reaction time is 10-18h, evaporate, concentrate, precipitate, wash, and vacuum dry; (4) Synthesis of reversible addition-fragmentation-chain transfer reagents Dissolve the benzyl alcohol-terminated polylactic acid polymer in dichloromethane solvent, add N,N-dimethylformamide, cool, add thionyl chloride, the temperature is 25-35°C, the reaction time is 8-10h, rotary evaporation, purification, dissolve the obtained product in 50mL dichloromethane, add sulfur-dodecane-sodium trithiocarbonate, the temperature is 25-35°C, the reaction temperature is 24-36h, concentrate, filter, precipitate, and dry; (5) Polylactic acid block copolymer 3-Acrylamidophenylboronic acid was added to a double-row tube and added to a mixed solvent of a reversible addition-fragmentation-chain transfer reagent at a concentration of 0.8-1.0 mg / mL azobisisobutyronitrile in N,N-dimethylformamide. The solution was subjected to 3-5 freeze-vacuum-thaw operations on a vacuum line, the tube was sealed, precipitated, and vacuum dried.

2. The process for preparing a polylactic acid block copolymer according to claim 1, characterized in that: In the step (1), the molar ratio of lactic acid, 1,4-butanediol and stannous octoate is 1:0.01-0.015:0.0015-0.0025.

3. The process for preparing a polylactic acid block copolymer according to claim 1, characterized in that: In the step (2), the molar ratio of hydroxy-polylactic acid-hydroxy, triethylamine and methylsulfonamide is 1:2.5-3.5:2.8-3.

6.

4. The process for preparing a polylactic acid block copolymer according to claim 1, characterized in that: In the step (3), the molar ratio of chloro-polylactic acid-chloro, 4-hydroxybenzaldehyde, potassium tert-butoxide, CuBr and 2,2-bipyridine is 1:2-2.5:1.2-1.6:1.8-2.4:3.8-4.

6.

5. The process for preparing a polylactic acid block copolymer according to claim 1, characterized in that: The mass ratio of the benzyl alcohol-terminated polylactic acid polymer, N,N-dimethylformamide, thionyl chloride, and sulfur-dodecane-sodium trithiocarbonate in step (4) is 0.4-0.8:0.003-0.004:0.4-0.5:

1.

6. The process for preparing a polylactic acid block copolymer according to claim 1, characterized in that: In the step (5), the mass ratio of 3-acrylamidophenylboronic acid to the reversible addition fragmentation-chain transfer reagent is 0.3-0.6:

1.

7. The process for preparing a polylactic acid block copolymer according to claim 1, characterized in that: The reaction temperature of step (5) is 65-80°C and the reaction time is 20-30h.

8. The process for preparing a polylactic acid block copolymer according to claim 1, characterized in that: The method for preparing the polylactic acid block copolymer hydrogel is as follows: pouring the polylactic acid block copolymer into a flask, adding phosphate buffer, centrifuging, and placing for 4-8 hours.

9. The process for preparing a polylactic acid block copolymer according to claim 8, characterized in that: The phosphate buffer is Na2HPO4 or Na2H2PO4.

10. The process for preparing a polylactic acid block copolymer according to claim 8, characterized in that: The pH was maintained at 7.2-7.

6.

11. Use of the polylactic acid block copolymer according to claims 8-10 in glucose.

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