阅读说明：本技术 一种路易斯酸碱对催化丙交酯开环聚合的方法 (Method for catalyzing lactide ring-opening polymerization by Lewis acid-base pair ) 是由 李志波 沈勇 马钰琨 于 2021-08-13 设计创作，主要内容包括：本发明属于化工领域,涉及一种路易斯酸碱对用于制备聚丙交酯的方法。本发明中,路易斯酸碱对成功用于丙交酯的开环聚合反应,能够促进丙交酯的可控开环聚合,且能通过简单的方法制备环形聚丙交酯。路易斯酸碱对协同作用激活单体,从而获得高分子量聚丙交酯。本发明使用的路易斯酸碱对毒性低,为合成环境友好的聚丙交酯材料提供了新的途径。(The invention belongs to the field of chemical industry, and relates to a method for preparing polylactide by using a Lewis acid-base pair. In the invention, the Lewis acid-base pair is successfully used for the ring-opening polymerization reaction of the lactide, can promote the controllable ring-opening polymerization of the lactide, and can prepare the annular polylactide by a simple method. The Lewis acid-base pair synergistically activates the monomers to obtain high molecular weight polylactide. The Lewis acid and base used in the invention have low toxicity and provide a new way for synthesizing environment-friendly polylactide material.)

1. A method for preparing polylactide, comprising the steps of:

uniformly mixing lactide, a Lewis acid-base pair and an initiator, reacting for 0.25-24 h at the temperature of 130-180 ℃, and precipitating in methanol after the reaction is finished to obtain the polylactide.

2. The lewis acid-base pair of claim 1, comprising a lewis acid and a lewis base, wherein the lewis acid is one of ferric chloride and ferric methyl dichloride, and the lewis base is one of 1, 8-diazabicycloundecen-7-ene (DBU), 4-Dimethylaminopyridine (DMAP), 7-methyl-1, 5, 7-triazabicyclo [4.4.0] dec-5-ene (MTBD), and 1,5, 7-triassincyclo (4.4.0) dec-5-ene (TBD).

3. The lewis acid-base pair of claim 2, wherein the molar ratio of lewis acid to lewis base is from 0.3/1 to 3/1; the molar ratio of the Lewis base to the initiator is 0.1/1 to 1/1.

4. The process according to claim 1, wherein the molar ratio of Lewis base to lactide is from 1/50 to 1/1000.

5. The method of claim 1, wherein the initiator is at least one of methanol, ethanol, benzyl alcohol, phenethyl alcohol, terephthalyl alcohol, and water.

Technical Field

The invention relates to the fields of catalysts and chemical engineering, in particular to a method for catalyzing lactide ring-opening polymerization by a Lewis acid-base pair.

Background

Polylactic acid (PLA) is an important aliphatic polyester material, and has important applications in food packaging, surgical sutures, tissue engineering scaffolds and the like due to its excellent physical properties, biocompatibility and environmental-friendly characteristics.

Polylactic acid is made from fermentation of corn, sugar beet or other biomass into lactic acid. Dimerization of lactic acid produces Lactide (LA) followed by Ring Opening Polymerization (ROP) of the lactide to PLA. The catalyst plays a very critical role in ROP, and stannous octoate (Sn (Oct))₂) PLA is produced as a catalyst. Sn (Oct)₂Has higher performance in ring-opening polymerizationAnd is capable of producing polymers having a relatively high molecular weight. However, stannous octoate has potential health risks. In addition, PLA is widely used in biomedical applications. Therefore, the development of a non-toxic catalytic system is very important for the application of polylactide in biomedicine. The combination of the most recent lewis acids with nucleophilic organic bases (lewis bases) has been widely used in the polymerization of cyclic esters and polar olefins. Compared with other catalytic systems, the Lewis acid-base pair has more advantages in catalytic polymerization, and the synergistic effect of the Lewis acid and the Lewis base not only improves the catalytic activity, but also widens the selectivity of the cyclic ester.

In view of the above, the present invention provides a novel method for catalyzing the ring-opening polymerization of lactide, that is, the ring-opening polymerization of lactide is catalyzed by using an iron-based lewis acid/organic base binary catalytic system. Iron, as a biocompatible metal, is one of the trace elements essential to the human body. Compared with the prior method, the method provided by the invention has the following advantages: 1) the organic base and the iron Lewis acid used have low toxicity and are easy to remove from the product, and the obtained product can be used in the field of biomedicine and electronic devices; 2) the iron-based Lewis acid used in the system is low in price and is simple and easy to obtain.

Disclosure of Invention

The invention provides a low-toxicity Lewis acid and Lewis base composed of Lewis acid and Lewis base, which has both catalysis and initiation functions, can be used for ring-opening polymerization of lactide, and has extremely high catalytic activity.

The specific technical scheme is as follows:

a Lewis acid-base pair catalyst comprises Lewis acid and Lewis base, wherein the Lewis acid has a general structural formula shown as the following formula (I), and the Lewis base is 1, 8-diazabicycloundecen-7-ene (DBU), 4-Dimethylaminopyridine (DMAP), 7-methyl-1, 5, 7-triazabicyclo [4.4.0] dec-5-ene (MTBD) or 1,5, 7-triazabicyclo (4.4.0) dec-5-ene (TBD).

In the formula:

r is selected from the element Fe;

R₁、R₂、R₃independently selected from alkyl or halogen；

The number of carbon atoms of the alkyl group is 1-16;

preferably, the lewis acid is selected from at least one of ferric chloride (a) and dichloromethyl iron (b). Preferably, the Lewis base is selected from at least one of 1, 8-diazabicycloundecen-7-ene (a), 4-dimethylaminopyridine (b), 7-methyl-1, 5, 7-triazabicyclo [4.4.0] dec-5-ene (c), 157-triazabicyclo (4.4.0) dec-5-ene (d).

The invention also discloses application of the Lewis acid-base pair catalytic initiator in preparation of polylactide, so as to prove that the Lewis acid-base pair catalytic initiator has excellent catalytic activity.

The application comprises the preparation of polylactide, and in the application, the molar ratio of the Lewis acid to the Lewis base is 0.3/1-3/1; the molar ratio of the Lewis base to the initiator is 0.1/1 to 1/1.

Specifically, when the method is applied to the preparation of polylactide, the lactide is taken as a monomer, the Lewis acid-base pair is taken as a catalyst and an initiator, and homopolymerization is carried out under the condition of bulk.

The initiator can be selectively added in the homopolymerization reaction, on one hand, the effect of adjusting the molecular weight of a polymerization product is achieved, and on the other hand, the Lewis acid-base pair can be accelerated to be dissociated, so that the polymerization reaction speed is accelerated.

Specifically, the initiator is selected from small alcohol molecules, including methanol, ethanol, benzyl alcohol, phenethyl alcohol, terephthalyl alcohol, water and the like.

The temperature of the homopolymerization reaction is 130-180 ℃, and the reaction time is 0.25-24 h.

The invention provides a catalytic initiation system based on a Lewis acid-base pair, which realizes the high-efficiency ring-opening polymerization of lactide monomers and has extremely high reaction activity. Compared with the prior art, the catalytic system has the following remarkable structural characteristics and catalytic effects:

1) when the catalytic system is used for catalyzing the ring-opening polymerization of lactide, the annular polylactide can be obtained through simple synthesis conditions.

2) The catalyst has very low toxicity to human bodies, and can synthesize green, environment-friendly and environment-friendly polylactide.

Drawings

FIG. 1 is a drawing of the polylactide of example 4¹H NMR spectrum;

FIG. 2 is a GPC chart of polylactides prepared in examples 4, 5 and 6.

Specific examples the present invention is described in further detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto. All the technologies realized based on the above contents of the present invention belong to the scope of the present invention.

Example 1

In N₂In a 100mL single-neck flask, benzyl alcohol BnOH (2.1. mu.L, 0.02mmol), ferric chloride (3.2mg,0.02mmol), and DBU (3. mu.L, 0.02mmol) were added under an atmosphere, stirred for 5min, and L-LA (576mg,4mmol) was added. The reaction flask was then placed in an oil bath pan preheated to 130 ℃ and allowed to react for 1 h. The reaction flask was then rapidly cooled to stop the reaction. 4mL of methylene chloride was added to dissolve the sample. Taking a small amount of solution to carry out¹H NMR measurement, the remaining solution was settled in 40mL of cold methanol. The resulting polymer was dried overnight in a vacuum oven at 30 ℃.¹H NMR measurements showed 95% monomer conversion. The GPC test results show: number average molecular weight M_n24651g/mol, molecular weight distribution of

Example 2

In N₂In a 100mL single-neck flask, benzyl alcohol BnOH (2.1. mu.L, 0.02mmol), ferric chloride (3.2mg,0.02mmol), TBD (2.8mg,0.02mmol) were added under an atmosphere, stirred for 5min, and L-LA (288mg,2mmol) was added. The reaction flask was then placed in an oil bath preheated to 130 ℃ and allowed to react for 4.5 h. The reaction flask was then rapidly cooled to stop the reaction. 2mL of methylene chloride was added to dissolve the sample. Taking a small amount of solution to carry out¹H NMR measurement, the remaining solution was settled in 20mL of cold methanol. Will be describedThe resulting polymer was dried overnight in a vacuum oven at 30 ℃.¹H NMR testing showed 92% monomer conversion. The GPC test results show: number average molecular weight M_n13665g/mol, molecular weight distribution of

Example 3

In N₂Benzyl alcohol BnOH (2.1. mu.L, 0.02mmol), ferric chloride (3.2mg,0.02mmol), DMAP (2.4mg,0.02mmol) were added to a 100mL single-neck flask under an atmosphere, stirred for 5min, and L-LA (288mg,2mmol) was added. The reaction flask was then placed in an oil bath preheated to 130 ℃ and allowed to react for 4.5 h. The reaction flask was then rapidly cooled to stop the reaction. 2mL of methylene chloride was added to dissolve the sample. Taking a small amount of solution to carry out¹H NMR measurement, the remaining solution was settled in 20mL of cold methanol. The resulting polymer was dried overnight in a vacuum oven at 30 ℃.¹H NMR measurements showed a monomer conversion of 94%. The GPC test results show: number average molecular weight M_n13931g/mol, molecular weight distribution of

Example 4

In N₂In a 100mL single-neck flask, benzyl alcohol BnOH (2.1. mu.L, 0.02mmol), ferric chloride (3.2mg,0.02mmol), and DBU (3. mu.L, 0.02mmol) were added under an atmosphere, stirred for 5min, and L-LA (576mg,4mmol) was added. Then the reaction flask is put into an oil bath kettle preheated to 180 ℃ for reaction for 2 h. The reaction flask was then rapidly cooled to stop the reaction. 4mL of methylene chloride was added to dissolve the sample. Taking a small amount of solution to carry out¹H NMR measurement, the remaining solution was settled in 40mL of cold methanol. The resulting polymer was dried overnight in a vacuum oven at 30 ℃.¹H NMR measurements showed a monomer conversion of 94%. The GPC test results show: number average molecular weight M_n27945g/mol, molecular weight distribution of

Example 5

In N₂In a 100mL single-neck flask, benzyl alcohol BnOH (2.1. mu.L, 0.02mmol), ferric chloride (3.2mg,0.02mmol), and DBU (3. mu.L, 0.02mmol) were added under an atmosphere, stirred for 5min, and L-LA (864mg,6mmol) was added. Then the reaction flask is put into an oil bath kettle preheated to 180 ℃ for reaction for 2 h. The reaction flask was then rapidly cooled to stop the reaction. 4mL of methylene chloride was added to dissolve the sample. Taking a small amount of solution to carry out¹H NMR measurement, the remaining solution was settled in 40mL of cold methanol. The resulting polymer was dried overnight in a vacuum oven at 30 ℃.¹H NMR measurements showed 97% monomer conversion. The GPC test results show: number average molecular weight M_n41456g/mol, molecular weight distribution of

Example 6

In N₂In a 100mL single-neck flask, benzyl alcohol BnOH (2.1. mu.L, 0.02mmol), ferric chloride (3.2mg,0.02mmol), and DBU (3. mu.L, 0.02mmol) were added under an atmosphere, stirred for 5min, and L-LA (1152mg,8mmol) was added. Then the reaction flask is put into an oil bath kettle preheated to 180 ℃ for reaction for 2 h. The reaction flask was then rapidly cooled to stop the reaction. 8mL of methylene chloride was added to dissolve the sample. Taking a small amount of solution to carry out¹H NMR measurement, the remaining solution was settled in 80mL of cold methanol. The resulting polymer was dried overnight in a vacuum oven at 30 ℃.¹H NMR measurements showed 98% monomer conversion. The GPC test results show: number average molecular weight M_n55692g/mol, molecular weight distribution of

Example 7

In N₂Under the atmosphere, in a 100mL single-necked flask, ferric chloride (3.2mg,0.02mmol) and DBU (3. mu.L, 0.02mmol) were added, and stirred for 5min, followed by addition of L-LA (2304mg,16 mmol). Then the reaction flask is put into an oil bath kettle preheated to 180 ℃ for reaction for 2 h. The reaction flask was then rapidly cooled to stop the reaction. 8mL of methylene chloride was added to dissolve the sample. Taking a small amount of solution to carry out¹H NMR measurement, the remaining solution was settled in 80mL of cold methanol. The resulting polymer was dried overnight in a vacuum oven at 30 ℃.¹H NMR measurements showed a monomer conversion of 96%. The GPC test results show: number average molecular weight M_n119622g/mol, molecular weight distribution of

The above examples are preferred embodiments of the present invention for the ring-opening polymerization of lactide catalyzed by lewis acid-base pair catalyst system, but the embodiments of the present invention are not limited by the above examples, and any other changes, modifications, substitutions, combinations, simplifications, and equivalents without departing from the spirit and principle of the present invention are all included in the scope of the present invention.