CN1156510C - Method for ring-opening polymerization of lactide catalyzed by divalent rare earth complex - Google Patents

Abstract

The invention belongs to a method for bulk and solution ring-opening polymerization of lactide catalyzed by divalent rare earth complexes. In the method, the bulk ring-opening polymerization of lactide is carried out at 100-150°C, and after 1-3 hours of reaction, the monomer conversion rate can reach 100%. The solvent used for the ring-opening polymerization of lactide solution is tetrahydrofuran or toluene. In tetrahydrofuran solution, the ring-opening polymerization of lactide can be carried out at room temperature to 70°C, and the monomer conversion rate can reach 100% after 3-15 hours of reaction; The ring-opening polymerization of lactide in toluene solvent can be carried out at 50-100°C, and the monomer conversion rate can reach 100% after 1-2 hours of reaction. The molecular weight of the product is controlled by the molar ratio of monomer to initiator, and the configuration of the obtained polylactide is maintained.

Description

Method for ring-opening polymerization of lactide catalyzed by divalent rare earth complex

Technical field: the invention belongs to the method for the ring-opening polymerization of lactide catalyzed by divalent rare earth complexes. Specifically, it relates to realizing ring-opening polymerization of lactide catalyzed by divalent rare earth complexes by means of bulk polymerization and solution polymerization.

Background technology: Polylactide is an important kind of aliphatic polyester. It is a kind of biodegradable and biocompatible material. It is widely used in medical devices to replace human active materials. It can repair, repair, and replace damaged materials. Infected or infected tissue or interaction with biological systems such as temporary scaffolding or supports (surgical sutures, bone fixation components), temporary barriers (to prevent tissue adhesion), this non-persistent material can be hydrolyzed to degrade into energy The product absorbed by the human body has little impact on organs, and can also reduce the number of operations; in the field of pharmaceutical preparations, it is used as a coating component in sustained-release, controlled-release or targeted preparations.

The use of polyester material depends on its composition and structure. For example, as a supporting material, high molecular weight and high mechanical strength are required; as a medical membrane material, it should be permeable to drugs. The composition and structure of materials are largely determined by the catalytic systems used to synthesize them. The polymerization of lactide was the first to use alkoxy compounds such as tin, aluminum, zinc, etc., but due to the polymerization mechanism, the catalyst is covalently connected to the polymer chain, which is difficult to remove, which will pollute the degradation environment. It may lead to accumulation in the body, especially when used in medicine, it is required that whether it is a polymer, a degradation product, or a catalyst residue, it should be non-toxic. Iron is an element existing in active tissues in the body. Its compounds can catalyze the polymerization of lactide, but the catalytic activity is low. The polymerization reaction is carried out at a high temperature of 170-210 ° C, and the racemization is obvious.

Because rare earth complexes are easy to remove after polymerization, they have become a research hotspot in recent years. Rare earth alkoxides, rare earth amides, rare earth amides, and rare earth compounds-trialkylaluminum-water systems can all catalyze lactide polymerization. Macromolecules 1996.29, 3332 reported rare earth aryl oxygen complexes, i.e. three (2,6-di-tert-butylphenol) rare earth compounds, and a catalyst system composed of various alcohols, which can make two kinds of lactone monomers through step-by-step Block copolymers can be obtained by adding method, and another monomer can be initiated to carry out block copolymerization with hydroxyl-functionalized prepolymer. And L-LA has no transesterification and configuration conversion in the polymerization process. For example, the catalytic system composed of [2,6-(tBu) ₂ OAr] ₃ Ln (Ln=Y, La) (1a) and 2-PrOH (50/1) respectively initiates lactide, caprolactone, valerolactone Take ester polymerization as an example, in dichloromethane solvent, at room temperature, the monomer conversion rate reaches 85-90% within a few minutes, and the number average molecular weight is equal to the theoretical value calculated by the molar ratio of monomer/alcohol. Although the catalytic system composed of various rare earth compounds mentioned above can catalyze the polymerization of lactide, the polymerization reaction speed is slow and the reaction temperature is high, so that the optical configuration retention rate of the product is low.

SUMMARY OF THE INVENTION: The object of the present invention is to provide a method for catalyzing the polymerization of lactide with a divalent rare earth complex. The method has the characteristics of controllable polymerization, fast polymerization reaction speed and low reaction temperature. The obtained polylactide has high molecular weight and maintains configuration. At the same time, the central rare earth ion is easily removed from the polymer product. Rare earth ions have large ionic radii and strong acidity, while lactide monomers have high electronegativity, so rare earth complexes or compounds are easy to coordinate with lactide monomers.

The selected rare earth complexes of the present invention have the following structure:

(1)

((R) _m L) ₂ Ln(S) _x

Wherein R is methyl, tert-butyl, cyclopentyl, trimethylsilyl, or 2-methoxyethyl, m=1 or 2, and L is cyclopentadienyl, indenyl or fluorenyl; Ln is samarium or ytterbium, (S) _x is solvent, R ¹ is ethyl-(CH ₂ CH ₂ )-, L ¹ and L ² are cyclopentadienyl, indenyl or fluorenyl, L ¹ and L ² Can be the same or different.

The process is as follows: L-lactide is purified by recrystallization of ethyl acetate at 65°C, and racemic lactide is purified by recrystallization of ethyl acetate at 80°C.

Bulk polymerization method of L-lactide and ex-lactide: Divalent rare earth cyanocene complex is used as catalyst, the molar ratio of monomer to catalyst is 100-3000, the optimum molar ratio of monomer to catalyst is 500-2500, and the reaction temperature It can be 110-210°C, the optimum polymerization reaction temperature is 120-140°C, and the reaction time is 0.5-2 hours.

The solution polymerization method of L-lactide and ex-lactide: the solvent used is toluene or tetrahydrofuran, the monomer concentration is 15-50wt%, the polymerization temperature is 50-110°C, and the optimum polymerization temperature is 60-100 °C, the optimum molar ratio of monomer to catalyst is 300-2000, and the reaction time is 1-8 hours. After the reaction was completed, it was cooled, and the reaction was terminated with 10% hydrochloric acid in chloroform to obtain a light yellow solid product. Wherein the optical rotation [α] _D ²⁵ of the L-lactide polymer = -123--149.

The method provided by the invention can prepare high-molecular-weight polylactide with configuration retention, the polymerization reaction temperature is low, the side reaction is few, the polymerization reaction speed is fast, and has the characteristics of controllable polymerization. The molecular weight of the product is determined by the ratio of the monomer and the initiator. molar ratio control.

Detailed ways:

Example 1

Weigh 1.3g of racemic lactide (D, L-LA) (9mmol) into a 40ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), and place the reaction bottle at a constant temperature of 120°C In the oil bath, add ((CH ₂ CH ₂ (C ₅ H ₉ C ₅ H ₃ ) ₂ )Sm(THF) solution 0.20ml (0.09M, 0.018mmol) after the lactide is melted, [D, L-LA ]/[((CH ₂ CH ₂ (C ₅ H ₉ C ₅ H ₃ ) ₂ )Sm(THF))=500, reacted for 0.5h, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% hydrochloric acid After the chloroform solution was terminated, it was poured into ethanol for precipitation to obtain a pale yellow solid, which was vacuum-dried for 48 hours to obtain 1.13 g of the product, with a conversion rate of 86.9%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=27,000, Mw/Mn=1.88.

Example 2

Weigh 1.0g of L-lactide (L-LA) (7mmol) into a 50ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), and place the reaction bottle in a constant temperature oil bath at 130°C. After the lactide is melted, add (C ₅ H ₉ C ₅ H ₄ ) ₂ Sm (DME) solution 0.1ml (0.07M, 0.007mmol), [L-LA]/[(C ₅ H ₉ C ₅ H ₄ ) ₂ Sm(DME)]=1000, react for 1h, place the reaction bottle in ice water at 0°C to cool, add 1ml of 10% hydrochloric acid chloroform solution to terminate, pour into ethanol to settle, and obtain light yellow spongy solid, vacuum After drying for 48 hours, 1.0 g of the product was obtained, and the conversion rate was 100%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=31,000 and Mw/Mn=1.83. Optical rotation [α] _D ²⁵ = -149.1 (25°C, 0.025g/25ml chloroform).

Example 3

Weigh 2g of L-lactide (L-LA) (14mmol) in a 50ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), and place the reaction bottle in a constant temperature oil bath at 140°C. Add 0.08ml (0.07M, 0.0056mmol) of (C ₅ H ₉ C ₅ H ₄ ) ₂ Sm(DME) solution after melting lactide, [L-LA]/[(C ₅ H ₉ C ₅ H ₄ ) ₂ Sm(DME)]=2500, react for 2h, place the reaction bottle in ice water at 0°C to cool, add 1ml of 10% hydrochloric acid in chloroform to terminate, pour into ethanol to settle, and obtain light yellow spongy solid, vacuum dry After 48 hours, 2.0 g of the product was obtained, and the conversion rate was 100%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=53,000 and Mw/Mn=2.53. Optical rotation [α] _D ²⁵ = -132.8 (25°C, 0.025g/25ml chloroform).

Example 4

Weigh 1.0g of L-lactide (L-LA) (7mmol) in a 50ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 3ml of toluene with a syringe, and place the reaction bottle at 60 In a constant temperature oil bath at ℃, add (C ₅ H ₉ C ₅ H ₄ ) ₂ Sm (DME) solution 0.2ml (0.07M, 0.014mmol) after the lactide is melted, [L-LA]/[(C ₅ H ₉ C ₅ H ₄ ) ₂ Sm(DME)]=500, reacted for 1 h. Cool the reaction bottle in ice water at 0°C, add 1ml of 10% hydrochloric acid in chloroform to terminate, pour into ethanol for sedimentation, and obtain a pale yellow spongy solid, vacuum-dry for 48 hours to obtain 0.995g of the product, with a conversion rate of 99.5% . The molecular weight of polylactide was analyzed by GPC to obtain Mn=31,000 and Mw/Mn=1.83. Optical rotation [α] _D ²⁵ = -129.7 (25°C, 0.025g/25ml chloroform).

Example 5

Weigh 1.0g of L-lactide (L-LA) (7mmol) in a 50ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 2ml of toluene with a syringe, and place the reaction bottle at 80 In a constant temperature oil bath at ℃, add (C ₅ H ₉ C ₅ H ₄ ) ₂ Yb (Et ₂ O) solution 0.35ml (0.04M, 0.014mmol) after the lactide is melted, [L-LA]/[( C ₅ H ₉ C ₅ H ₄ ) ₂ Yb(Et ₂ O)]=500, react for 2 hours, place the reaction bottle in ice water at 0°C to cool, add 1 mL of 10% hydrochloric acid in chloroform to terminate, pour into ethanol to settle , to obtain a light yellow spongy solid, vacuum-dried for 48 hours to obtain 0.93 g of the product, and the conversion rate was 93%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=31,000 and Mw/Mn=1.83. Optical rotation [α] _D ²⁵ = -129.7 (25°C, 0.025g/25ml chloroform).

Example 6

Weigh 4.0g of L-lactide (L-LA) (28mmol) in a 50ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 4ml of toluene with a syringe, and place the reaction bottle at 60 In a constant temperature oil bath at ℃, add (C ₅ H ₉ C ₉ H ₆ ) ₂ Sm (DME) solution 0.1ml (0.1213M, 0.014mmol) after the lactide is dissolved, [L-LA]/[(C ₅ H ₉ C ₉ H ₆ ) ₂ Sm(DME)]=2000, when reacting for 2 hours, place the reaction bottle in ice water at 0°C to cool, add 1ml of 10% hydrochloric acid in chloroform to terminate, pour into ethanol to settle, and obtain Pale yellow spongy solid was vacuum-dried for 48 hours to obtain 3.4 g of the product with a conversion rate of 85%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=74,000, and Mw/Mn=2.50. Optical rotation [α] _D ²⁵ = -133.5 (25°C, 0.025g/25ml chloroform).

Example 7

Weigh 1.5g of L-lactide (L-LA) (10.5mmol) in a 50ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 6ml of toluene with a syringe, and place the reaction bottle in In a constant temperature oil bath at 80°C, add ((CH ₃ ) ₃ SiC ₅ H ₄ ) ₂ Sm(DME) 0.20ml (0.067M, 0.014mmol) after the lactide is dissolved, [L-LA]/[(( CH ₃ ) ₃ SiC ₅ H ₄ ) ₂ Sm(DME)]=800, reacted for 3 hours, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% hydrochloric acid in chloroform to stop, poured into ethanol to settle, A pale yellow spongy solid was obtained, which was dried in vacuum for 48 hours to obtain 1.23 g of the product, with a conversion rate of 82%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=63,000 and Mw/Mn=1.71. Optical rotation [α] _D ²⁵ = -146.8 (25°C, 0.025g/25ml chloroform).

Example 8

Weigh 2.0g of L-lactide (L-LA) (14mmol) in a 50ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 10ml of toluene with a syringe, and place the reaction bottle at 90 In a constant temperature oil bath at ℃, add (C ₆ H ₅ CH ₂ C ₉ H ₆ ) ₂ Sm (DME) solution 0.14ml (0.1027M, 0.014mmol) after the lactide is dissolved, [L-LA]/[( C ₆ H ₅ CH ₂ C ₉ H ₆ ) ₂ Sm(DME)]=1000, react for 2 hours, place the reaction bottle in ice water at 0°C to cool, add 1ml of 10% hydrochloric acid in chloroform to stop, pour ethanol Settled in medium to obtain a pale yellow spongy solid, which was dried in vacuum for 48 hours to obtain 1.68 g of the product with a conversion rate of 84%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=78,000, and Mw/Mn=2.0. Optical rotation [α] _D ²⁵ = -138.7 (25°C, 0.025g/25ml chloroform).

Example 9

Weigh 1.3 grams of L-lactide (L-LA) (9.1mmol) in a 50ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 6ml of toluene with a syringe, and place the reaction bottle in In a constant temperature oil bath at 85°C, after the lactide is dissolved, add 0.20ml (0.038M, 0.014mmol) of ((CH ₃ ) ₂ Si(C ₅ H ₄ ) ₂ )Sm(THF) solution, [L-LA] /[((CH ₃ ) ₂ Si(C ₅ H ₄ ) ₂ )Sm(THF)]=600, react for 3 hours, cool the reaction bottle in ice water at 0°C, add 1ml of 10% hydrochloric acid in chloroform to stop Afterwards, it was poured into ethanol for sedimentation to obtain a light yellow spongy solid, which was vacuum-dried for 48 hours to obtain 1.23 g of the product with a conversion rate of 82%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=63,000 and Mw/Mn=1.71. Optical rotation [α] _D ²⁵ = -146.8 (25°C, 0.025g/25ml chloroform).

Example 10

Weigh 1.1 grams of L-lactide (L-LA) (7.6mmol) in a 40ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 4.5ml of toluene with a syringe, and place the reaction bottle In a constant temperature oil bath at 70°C, add 0.18ml (0.042M, 0.0076mmol) of ((CH ₃ ) ₃ CC ₅ H ₄ ) ₂ Sm(THF) solution after the lactide is dissolved, [L-LA]/[ ((CH ₃ ) ₃ CC ₅ H ₄ ) ₂ Sm(THF)]=1000, reacted for 2.5 hours, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% hydrochloric acid in chloroform to terminate, poured into ethanol Settled in medium to obtain a pale yellow spongy solid, which was dried in vacuum for 48 hours to obtain 1.0 g of the product with a conversion rate of 90.1%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=104,000, and Mw/Mn=2.0. Optical rotation [α] _D ²⁵ = -139.7 (25°C, 0.025g/25ml chloroform).

Example 11

Weigh 2.13 grams of L-lactide (L-LA) (14.7mmol) in a 40ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 7ml of toluene with a syringe, and place the reaction bottle in In a constant temperature oil bath at 100°C, add ((CH ₃ ) ₃ CC ₅ H ₄ ) ₂ Yb(THF) solution 0.23ml (0.043M, 0.0098mmol) after the lactide is dissolved, [L-LA]/[( (CH ₃ ) ₃ CC ₅ H ₄ ) ₂ Yb(THF)]=1500, reacted for 1.5 hours, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% hydrochloric acid in chloroform to stop, poured into ethanol After sedimentation, a pale yellow spongy solid was obtained, which was dried in vacuum for 48 hours to obtain 1.98 g of the product, with a conversion rate of 93%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=113,000, and Mw/Mn=2.3. Optical rotation [α] _D ²⁵ = -136.2 (25°C, 0.025g/25ml chloroform).

Example 12

Weigh 1.65 grams of L-lactide (L-LA) (11.45mmol) in a 40ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 10ml of toluene with a syringe, and place the reaction bottle in In a constant temperature oil bath at 90°C, add 0.10ml (0.164M, 0.0164mmol) of ((CH ₃ ) ₃ CC ₉ H ₆ ) ₂ Sm(THF) solution after the lactide is dissolved, [L-LA]/[( (CH ₃ ) ₃ CC ₉ H ₆ ) ₂ Sm(THF)]=700, reacted for 3 hours, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% hydrochloric acid in chloroform to stop, poured into ethanol After settling, a pale yellow spongy solid was obtained, which was dried under vacuum for 48 hours to obtain 1.47 g of the product, with a conversion rate of 89%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=62,000, and Mw/Mn=1.89. Optical rotation [α] _D ²⁵ = -135.4 (25°C, 0.025g/25ml chloroform).

Example 13

Weigh 1.4 grams of L-lactide (L-LA) (9.7mmol) in a 40ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 3.0ml of toluene with a syringe, and place the reaction bottle In a constant temperature oil bath at 60°C, add (CH ₃ OCH ₂ CH ₂ C ₅ H ₄ ) ₂ Sm (THF) solution 0.22ml (0.055M, 0.012mmol) after the lactide is dissolved, [L-LA]/ [(CH ₃ OCH ₂ CH ₂ C ₅ H ₄ ) ₂ Sm(THF)]=800, reacted for 2 hours, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% hydrochloric acid in chloroform to stop, poured Pour into ethanol and settle to obtain a pale yellow spongy solid, which was vacuum-dried for 48 hours to obtain 1.2 g of the product with a conversion rate of 85.7%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=72,000, and Mw/Mn=2.1. Optical rotation [α] _D ²⁵ = -133.4 (25°C, 0.025g/25ml chloroform).

Example 14

Weigh 1.3 grams of racemic lactide (D, L-LA) (9mmol) in a 40ml reaction bottle with a rubber tube (through fire baking, cooling and argon filling three times), then add 6.5ml toluene with a syringe, and The reaction bottle was placed in a constant temperature oil bath at 65°C, and after the lactide was dissolved, 0.15ml (0.086M, 0.0129mmol) of (CH ₃ OCH ₂ CH ₂ C ₉ H ₆ ) ₂ Sm(THF) solution was added, [D, L-LA]/[(CH ₃ OCH ₂ CH ₂ C ₉ H ₆ ) ₂ Sm(THF)]=700, reacted for 2 hours, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% hydrochloric acid in chloroform After the solution was terminated, it was poured into ethanol for sedimentation to obtain a light yellow solid, which was dried in vacuum for 48 hours to obtain 1.0 g of the product with a conversion rate of 76.9%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=57,000 and Mw/Mn=1.84.

Example 15

Weigh 1.7 grams of racemic lactide (D, L-LA) (11.8mmol) in a 40ml reaction bottle with a rubber tube (through fire baking, cooling and argon filling three times), then add 8ml of toluene with a syringe, and The reaction flask was placed in a constant temperature oil bath at 85°C, and after the lactide was dissolved, 0.28ml (0.11M, 0.0295mmol) of (CH ₂ CH ₂ (C ₉ H ₆ ) ₂ )Sm(THF) solution was added, [D, L-LA]/[(CH ₂ CH ₂ (C ₉ H ₆ ) ₂ )Sm(THF)]=400, reacted for 1.5 hours, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% hydrochloric acid in chloroform After the solution was terminated, it was poured into ethanol for sedimentation to obtain a light yellow solid, which was dried in vacuum for 48 hours to obtain 1.31 g of the product with a conversion rate of 76.9%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=32,000 and Mw/Mn=1.71.

Example 16

Weigh 2.1 grams of racemic lactide (D, L-LA) (14.6mmol) in a 40ml reaction bottle with a rubber tube (through fire baking, cooling and argon filling three times), then add 6ml of toluene with a syringe, and The reaction flask was placed in a constant temperature oil bath at 85°C, and after the lactide was dissolved, 0.17ml (0.286M, 0.0487mmol) of (CH ₃ OCH ₂ CH ₂ C ₉ H ₆ ) ₂ Yb(THF) solution was added, [D, L-LA]/[(CH ₃ OCH ₂ CH ₂ C ₉ H ₆ ) ₂ Yb(THF)]=300, reacted for 1 hour, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% hydrochloric acid in chloroform After the solution was terminated, it was poured into ethanol for sedimentation to obtain a light yellow solid, which was dried in vacuum for 48 hours to obtain 1.82 g of the product with a conversion rate of 86.6%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=23,000 and Mw/Mn=1.65.

Example 17

Weigh 2.3 grams of racemic lactide (D, L-LA) (16mmol) in a 40ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 5ml of toluene with a syringe, and the reaction Place the bottle in a constant temperature oil bath at 100°C, add (C ₅ H ₉ C ₅ H ₄ )Sm (C ₅ H ₉ C ₉ H ₆ ) (THF) solution 1.33ml (0.04M, 0.0533 mmol), [D, L-LA]/[(C ₅ H ₉ C ₅ H ₄ ) Sm(C ₅ H ₉ C ₉ H ₆ )(THF)]=300, reacted for 1.5 hours, and placed the reaction bottle at 0 Cool in ice water at °C, add 1ml of 10% hydrochloric acid in chloroform to stop, pour into ethanol for sedimentation to obtain a pale yellow solid, and dry in vacuo for 48 hours to obtain 2.1g of the product with a conversion rate of 91.3%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=14,000 and Mw/Mn=1.55.

Example 18

Weigh 1.56 grams of L-lactide (L-LA) (10.82mmol) in a 40ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 2.2ml of toluene with a syringe, and place the reaction bottle In a constant temperature oil bath at 70°C, add (CH ₂ CH ₂ (C ₅ H ₉ C ₅ H ₃ ) ₂ )Sm(THF) solution 0.22ml (0.061M, 0.0135mmol) after the lactide is dissolved, [L -LA]/[(CH ₂ CH ₂ (C ₅ H ₉ C ₅ H ₃ ) ₂ )Sm(THF)]=800, reacted for 1.5 hours, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% After the chloroform solution of hydrochloric acid was terminated, it was poured into ethanol for sedimentation to obtain a light yellow solid, which was dried in vacuum for 48 hours to obtain 1.50 g of the product with a conversion rate of 96.2%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=60,100, and Mw/Mn=2.14. Optical rotation [α] _D ²⁵ = -141.7 (25°C, 0.025g/25ml chloroform).

Example 19

Weigh 0.97 grams of L-lactide (L-LA) (6.73mmol) in a 40ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 1.0ml of toluene with a syringe, and place the reaction bottle In a constant temperature oil bath at 60°C, add (CH ₂ CH ₂ (C ₅ H ₉ C ₅ H ₃ ) ₂ )Yb(THF) solution 0.188ml (0.072M, 0.0135mmol) after the lactide is dissolved, [L -LA]/[(CH ₂ CH ₂ (C ₅ H ₉ C ₅ H ₃ ) ₂ )Yb(THF)]=500, react for 3 hours, cool the reaction bottle in ice water at 0°C, add 1ml of 10% After the chloroform solution of hydrochloric acid was terminated, it was poured into ethanol for sedimentation to obtain a pale yellow solid, which was dried in vacuum for 48 hours to obtain 0.75 g of the product with a conversion rate of 77.3%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=29,900, and Mw/Mn=1.68. Optical rotation [α] _D ²⁵ = -140.5 (25°C, 0.025g/25ml chloroform).

Example 20

Weigh 1.5 grams of L-lactide (L-LA) (10.5mmol) in a 50ml reaction bottle with a rubber tube (heated, cooled and filled with argon three times), then add 5ml THF with a syringe, and place the reaction bottle at 50 In a constant temperature oil bath at ℃, add 0.5ml (0.07M, 0.035mmol) of (C ₅ H ₉ C ₅ H ₄ ) ₂ Sm (DME) solution after the lactide is completely dissolved, [L-LA]/[(C ₅ H ₉ C ₅ H ₄ ) ₂ Sm(DME)]=300, reacted for 3 hours, cooled the reaction bottle in ice water at 0°C, added 1ml of 10% hydrochloric acid in chloroform to stop, poured into ethanol to settle, A pale yellow solid was obtained, which was dried under vacuum for 48 hours to obtain 1.24 g of the product, with a conversion rate of 83%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=12,600 and Mw/Mn=1.57. Optical rotation [α] _D ²⁵ = -123.1 (25°C, 0.025g/25ml chloroform).

Example 21

Weigh 1.42 grams of racemic lactide (D, L-LA) (9.85mmol) in a 40ml reaction bottle with a rubber tube (through fire, cooling, argon charging three times), then add 3 THF with a syringe, and The reaction flask was placed in a constant temperature oil bath at 60°C, and after the lactide was dissolved, 3.1ml (0.053M, 0.0164mmol) of (C ₅ H ₉ C ₅ H ₄ )Sm(C ₁₃ H ₁₁ )(THF) solution was added, [D,L-LA]/[(C ₅ H ₉ C ₅ H ₄ )Sm(C ₁₃ H ₁₁ )(THF)]=600, react for 6 hours, add 1ml of 10% hydrochloric acid chloroform solution to stop, pour into It settled in ethanol to obtain a pale yellow solid, which was dried in vacuum for 48 hours to obtain 0.7 g of the product with a conversion rate of 49.3%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=19,000 and Mw/Mn=1.46.

Example 22

Weigh 3.90g of racemic lactide (D, L-LA) (27mmol) in a 40ml reaction bottle with a rubber tube (through fire baking, cooling and argon charging three times), then add 1.5ml of toluene with a syringe, and _The reaction _{flask was} placed in a _constant temperature oil _bath at ₆₀ ° _C , and after the lactide was dissolved _, 0.23ml (0.066M, 0.015mmol), [D, L-LA]/[(C ₅ H ₉ C ₅ H ₄ )Yb(C ₅ H ₉ C ₉ H ₆ )(THF)]=1800, reacted for 8 hours, and placed the reaction bottle in Cool in ice water at 0°C, add 1ml of 10% hydrochloric acid in chloroform, and pour into ethanol to settle to obtain a pale yellow solid, which was dried in vacuo for 48 hours to obtain 3.16g of the product, with a conversion rate of 81%. The molecular weight of polylactide was analyzed by GPC to obtain Mn=52,000, and Mw/Mn=1.87.

Claims (1)

1. A kind of method of catalyzing ring-opening polymerization of lactide by 2-valence cyclopentadienyl rare-earth complex is characterized in that the cyclopentadienyl rare-earth complex of selecting has following structure:

   (1)

   ((R) _mL) ₂Ln(S) _x

   

   Wherein R is methyl, the tertiary butyl, pentamethylene base, trimethyl silicon based or 2-methoxy ethyl, and m=1 or 2, L are cyclopentadienyl, indenyl or fluorenyl; Ln is samarium or ytterbium, (S) _xBe solvent, R ¹Be ethyl-(CH ₂CH ₂)-, L ¹And L ²Be cyclopentadienyl, indenyl or fluorenyl, L ¹With L ²Can be identical, also can be different;

   Technological process is as follows:

   Levorotatory lactide and outward turning rac-Lactide bulk polymerization: the bivalent rare earth half metallocene is a catalyzer, the mol ratio 100-3000 of monomer and catalyzer, and temperature of reaction is 110-210 ℃, the reaction times is 0.5-2 hour;

   The solution polymerization process of levorotatory lactide and outward turning rac-Lactide: the solvent of employing is toluene or tetrahydrofuran (THF), and monomer concentration is 15-50wt%, and polymeric reaction temperature is 50-110 ℃, and the mol ratio of monomer and catalyzer is 300-2000, and the reaction times is 1-8 hour;

   Reaction finishes postcooling, and the chloroformic solution termination reaction with 10% hydrochloric acid obtains the faint yellow solid product; The specific rotation of levorotatory lactide polymkeric substance [α] wherein _D ²⁵=-123--149.