CN111647150A - Method for preparing poly (gamma-butyrolactone) by efficiently catalyzing ring opening of gamma-butyrolactone - Google Patents
Method for preparing poly (gamma-butyrolactone) by efficiently catalyzing ring opening of gamma-butyrolactone Download PDFInfo
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Abstract
A method for preparing poly (gamma-butyrolactone) by efficiently catalyzing ring opening of gamma-butyrolactone, which comprises the following steps: the gamma-butyrolactone and the catalytic system are subjected to ring-opening polymerization reaction to obtain linear or cyclic poly-gamma-butyrolactone with different molecular weights and molecular weight distributions. The catalytic system comprises strong base, initiator and hydrogen donor electron, wherein the strong base is tetrabutyl ammonium hydroxide, and the initiator comprises various alcohols. The method has the advantages of high-efficiency controllable polymerization, low cost, capability of carrying out polymerization under mild conditions and wide molecular weight distribution. The hydrogen donor electron structure used therein is as follows:
the R group is an aliphatic group or an aryl group; the X group is O or S.
Description
Technical Field
The invention relates to the field of ring-opening polymerization of gamma-butyrolactone, in particular to a method for preparing poly (gamma-butyrolactone) by efficiently catalyzing ring opening of gamma-butyrolactone.
Background
The aliphatic polymer is used as a green chemical material with good biodegradability and biocompatibility, is mainly applied to the biomedical fields of absorbable suture lines, drug controlled release systems and the like at present, is mainly obtained by ring-opening polymerization, has the characteristics of good atom economy, capability of obtaining polymers with high molecular weight and narrow molecular weight distribution under mild conditions and the like, and can realize controllable polymerization by selecting a proper catalyst. Gamma-butyrolactone (gamma-BL) is used as lactone with five-membered ring structure, natural regeneration and low price, and is listed as the first place by the American energy department in twelve major derivatives, the polymer poly (gamma-butyrolactone) is the equivalent of poly (4-hydroxybutyrate) (P4 HB) prepared by a microbial fermentation method, and P4HB is used as a novel absorbable material and is commonly used in the medical fields of cardiac stents, drug delivery and the like, but the gamma-butyrolactone is obtained by a fermentation method and has the defects of complex process, poor repeatability and the like. However, since the low strain capacity of gamma-butyrolactone has traditionally been considered as "non-polymerizable", in 2016, the ring-opening polymerization of gamma-butyrolactone under mild conditions was first achieved by controlling conditions such as thermodynamics and kinetics.
The key to achieving efficient and controlled polymerization of poly (gamma-butyrolactone) is the choice of catalyst. At present, the catalysts applied to the ring-opening polymerization of gamma-butyrolactone mainly comprise metal catalysts and organic catalysts, and the metal catalysts can not be better applied to the biomedical field because of residue in products. The organic catalyst has the advantages of low toxicity, difficult residue and the like, and the organic catalyst is widely researched in recent years.
The high-efficiency ring-opening polymerization of gamma-BL under mild condition (-40 ℃) is firstly realized by the Hongmuio and Chen in 2016, and the phosphazene superbase is usedtBu-P4Alcohol is used as a catalytic synergistic system, and the polymerization is carried out for 4 hours to obtain the product with the conversion rate of 90 percent and the molecular weight of 26.7 kg-mol-1The poly (gamma-butyrolactone) with complete recoverability and no metal residue can avoid the metal residue in the polymer while having the high molecular weight and high activity polymer which can be prepared by the metal catalyst, thereby having no influence on the application in the aspects of biomedicine and the likeThis is disadvantageous for the polymerization. [ Angew.chem.Int.Ed.2016, 55, 4188-.
Mendong et al in 2018 polymerized urea/alkoxide as a catalyst system at-20 ℃ for the first time to obtain poly gamma-butyrolactone (up to 68.2 kg. mol.) with high molecular weight-1) The catalyst has the advantages of low cost and easy preparation. The literature studies the mechanism and found that alkoxides deprotonate the monomer, which acts as a strong base to initiate the monomer before anionic polymerization occurs, which also accelerates the polymerization rate. And the larger the molecular weight of the polymer, the greater the thermal stability of the polymer, so it is extremely advantageous to synthesize a polymer having a high molecular weight. Macromolecules.2018, 51, 9317-.
Li Shibo et al, using alkoxide or organic phosphonitrile superbase/urea as binary concerted catalysis system to carry out ring-opening polymerization of gamma-butyrolactone, the organic phosphonitrile superbase and appropriate urea electron-donating substituent compound act synergistically, and the molecular weight of synthesized poly gamma-butyrolactone reaches 35.0 kg/mol-1The catalytic activity of the organic base is obviously higher than that of alkoxide, the polymerization rate of adding the initiator BnOH is far faster than that of directly initiating polymerization by the monomer, namely, (thio) urea and BnOH can effectively inhibit the formation of active monomer species, and further accelerate the polymerization reaction. [ Polymer chemistry.2019, 10, 1231-1237 ].
The above prior art solutions have the following drawbacks: the linear poly (gamma-butyrolactone) is prepared while side reactions are usually accompanied, namely the prepared linear poly (gamma-butyrolactone) is doped with cyclic poly (gamma-butyrolactone), and the preparation of the linear poly (gamma-butyrolactone) has poor controllable polymerization property, so that the mechanical property of the linear poly (gamma-butyrolactone) is influenced.
Disclosure of Invention
The invention aims to provide a method for preparing poly (gamma-butyrolactone) by efficiently catalyzing ring opening of gamma-butyrolactone, which has the advantages of efficiently and controllably polymerizing linear poly (gamma-butyrolactone) or cyclic poly (gamma-butyrolactone), low price, capability of polymerizing under mild conditions and wide molecular weight distribution.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for preparing poly (gamma-butyrolactone) by efficiently catalyzing ring opening of gamma-butyrolactone, wherein one or more of hydrogen electron donor, strong base or initiator is/are added into a solvent to prepare a plurality of catalytic systems, each catalytic system can control the gamma-butyrolactone to perform polymerization reaction to obtain cyclic or linear poly (gamma-butyrolactone) with different molecular weights, and the plurality of catalytic systems comprises four catalytic systems as shown in the following: (1) a strong base; (2) strong base + hydrogen donor electron; (3) strong base + initiator; (4) strong base + initiator + hydrogen donor electron.
By adopting the technical scheme, cyclic poly (gamma-butyrolactone) with different molecular weights can be obtained for the catalytic systems (1), (2) and (3), wherein the cyclic poly (gamma-butyrolactone) is a main product, and the linear poly (gamma-butyrolactone) is a byproduct; for the catalytic system (4), linear poly (gamma-butyrolactone) with different molecular weights can be obtained, the linear poly (gamma-butyrolactone) is the main product, and cyclic poly (gamma-butyrolactone) is not generated, so that efficient and controllable polymerization of linear poly (gamma-butyrolactone) or cyclic poly (gamma-butyrolactone) is realized. Meanwhile, the cyclic poly (gamma-butyrolactone) with different molecular weights prepared by the method provided by the invention can expand the application range and application range of the product. In addition, the inventor finds that the four catalyst systems can be used for not only the polymerization of gamma-butyrolactone, but also the polymerization of common cyclic lactone monomers such as caprolactone, valerolactone and lactide, and the research of catalyzing and polymerizing the gamma-butyrolactone by using the catalyst system (4) is not reported.
The invention is further configured to: the strong base is tetrabutylammonium hydroxide, and the structural formula of the tetrabutylammonium hydroxide is as follows:
。
the invention is further configured to: the hydrogen-donating electron body is one of the following compounds:
the R group is one of ethyl, isopropyl, cyclohexyl, phenyl or Cl-substituted phenylIn one embodiment, the R' group may be the same as the R group or one of ethyl, isopropyl, cyclohexyl, phenyl or Cl-substituted phenyl.
The invention is further configured to: the hydrogen-donating electron body is any one of the following compounds:
。
by adopting the technical scheme, different hydrogen-donating electron body structures are used, and the activity of the ring-opening polymerization of the gamma-butyrolactone and the molecular weight of the poly gamma-butyrolactone are greatly influenced.
The invention is further configured to: the tetrabutylammonium hydroxide and hydrogen donor electron forming catalyst having the formula:
wherein X = S or O, R = ethyl, isopropyl or phenyl when X = S, and R = phenyl, cyclohexyl or Cl substituted for one or both of the phenyl groups when X = O.
The invention is further configured to: the initiator is at least one of methanol, ethanol, isopropanol, tert-butanol, benzyl alcohol, phenethyl alcohol, phenylpropyl alcohol, diphenylmethyl alcohol, 2-diphenylethanol, hydroxyl-terminated oligomeric ethylene glycol monomethyl ether, 2-diphenylethanol, ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 4-butylene glycol, 1, 2-benzenedimethanol, 1, 3-benzenedimethanol, 1, 4-benzenedimethanol, 2' -biphenyldimethanol, glycerol and pentaerythritol, and the initiator is preferably benzyl alcohol.
By adopting the technical scheme, the alcohol initiator can efficiently initiate the ring-opening polymerization reaction of the gamma-butyrolactone, and the raw materials are wide in source, cheap and easy to obtain. In addition, the process of the present invention can also be used to prepare poly (γ -butyrolactone) -containing block copolymers, preferably benzyl alcohol, by using a hydroxyl-terminated macroalcohol as an initiator.
The invention is further configured to: the molar ratio of the tetrabutylammonium hydroxide to the initiator may be (1-60): 3, in other words, the molar ratio of the tetrabutylammonium hydroxide to the initiator may be 1/3-20/1, for example, 1/3, 1/1, 3/1, 5/1, 10/1, 20/1.
The invention is further configured to: the molar ratio of the tetrabutylammonium hydroxide to the hydrogen donor electron donor may be 1 (1-10), in other words, the molar ratio of the tetrabutylammonium hydroxide to the hydrogen donor electron donor may be 1/1-1/10, such as 1/1, 1/2, 1/3, 1/4, 1/5, 1/6, 1/7, 1/8, 1/9 or 1/10.
The invention is further configured to: the molar ratio of the hydrogen donor electron body to the gamma-butyrolactone can be 0 (10-3000), in other words, the molar ratio of the hydrogen donor electron body to the gamma-butyrolactone can be 1/10-1/3000, such as 1/10, 1/100, 1/200, 1/300, 1/500, 1/1000, 1/1500, 1/2000, 1/2500 or 1/3000.
The invention is further configured to: the molar concentration of the gamma-butyrolactone in the catalytic system is 1-10 mol/L, such as 4mol/L, 5mol/L, 6mol/L, 7mol/L, 8mol/L, 9mol/L, 10mol/L, 1mol/L, 2mol/L or 3 mol/L.
By adopting the technical scheme, the molar concentration of the gamma-butyrolactone refers to the molar concentration of the gamma-butyrolactone in different catalytic systems, and if the concentration of the gamma-butyrolactone is too low, the polymerization rate is slow, the conversion rate is low, and the molecular weight of the obtained product is low.
The invention is further configured to: in the polymerization reaction of the gamma-butyrolactone, the molar ratio of the catalyst to the initiator is 1/0-5/1, the molar ratio of the catalyst to the hydrogen donor electron body is 0 (0-10), and can be 1:1 or 1:0, and the molar ratio of the hydrogen donor electron body to the gamma-butyrolactone is 0/50-1/300, and can be 50:0, 100:1, or 300: 1.
The invention is further configured to: the temperature of the polymerization reaction is-50 to 20 ℃, and the reaction time is 0.5 to 18 hours.
The invention is further configured to: the molar concentration of the gamma-butyrolactone in the various catalytic systems is 1 mol.L-1～10mol·L-1。
The invention is further configured to: the polymerization reaction needs to be added with a solvent, wherein the solvent is at least one of toluene, tetrahydrofuran, dichloromethane, trichloromethane, dioxane, acetonitrile and N, N-dimethylformamide, and the solvent is preferably tetrahydrofuran or toluene.
By adopting the technical scheme, the organic solvent can provide good solubility for the initiator, the tetrabutylammonium hydroxide and the gamma-butyrolactone monomer, and the tetrabutylammonium hydroxide can show strong basicity in the organic solvent, so that the conversion rate and the yield of the poly (gamma-butyrolactone) are improved. In addition, because tetrabutylammonium hydroxide and hydrogen donor have high solubility in methanol, the poly (gamma-butyrolactone) product can be easily separated from the reaction system in a precipitation mode, and the application requirements in the field of biological medicines can be met.
The invention is further configured to: the molecular weight of the prepared linear poly (gamma-butyrolactone) is 1-52 Kg/mol, and the molecular weight of the prepared cyclic poly (gamma-butyrolactone) is 0.3-10 Kg/mol.
In conclusion, the method for preparing the poly (gamma-butyrolactone) by efficiently catalyzing the ring opening of the gamma-butyrolactone, disclosed by the invention, comprises the following steps: dissolving one or more of hydrogen-feeding electron, strong base or initiator in an organic solvent, stirring for 10-30 min at-50-0 ℃, adding gamma-butyrolactone into the mixed solution, reacting for 0.5-18 h to obtain poly (gamma-butyrolactone), adding one or more of hydrogen-feeding electron, strong base or initiator into the organic solvent to prepare different catalytic systems, adding gamma-butyrolactone, and carrying out polymerization reaction on the gamma-butyrolactone in different catalytic systems to realize efficient and controllable preparation of cyclic or linear poly (gamma-butyrolactone) with different molecular weights; the polymerization mechanism to cyclic poly (γ -butyrolactone) and linear poly (γ -butyrolactone) are different, and for the (3) th catalytic system, the possible formation mechanism is as follows (e.g. the initiator is methanol):
for the (3) th catalytic system, the possible mechanism of formation is as follows (e.g., the initiator is benzyl alcohol):
for the (4) th catalytic system, the mechanism of formation is likely as follows (for example, the initiator is benzyl alcohol, and the hydrogen donor is thiourea):
in conclusion, the invention has the following beneficial effects:
firstly, different catalytic systems can be prepared by using different hydrogen-donating electron body structures, and polymer structures and molecular weights of the catalytic systems are screened, so that linear and cyclic poly gamma-butyrolactone synthesis can be selectively achieved, and poly (gamma-butyrolactone) with different molecular weights can be obtained.
Secondly, the polymerization of the gamma-butyrolactone can be realized under a mild condition, the polymerization temperature is 0-10 ℃, the gamma-butyrolactone superior product is biomass succinic acid with large yield, and the method has the characteristics of easily obtained raw materials and low price.
The strong base is tetrabutylammonium hydroxide, is an organic super-strong base, is easy to decompose by heating, is also suitable for the low-temperature ring-opening polymerization reaction of gamma-butyrolactone, and the compound is commercialized.
Drawings
FIG. 1 is a nuclear magnetic hydrogen spectrum of linear poly (gamma-butyrolactone) obtained by using TU-1 and benzyl alcohol as a catalytic system;
FIG. 2 is a GPC chart of linear poly (γ -butyrolactone);
FIG. 3 is a GPC chart of linear poly (γ -butyrolactone);
FIG. 4 is a MALDI-TOF plot of low molecular weight linear poly (γ -butyrolactone);
FIG. 5 is a nuclear magnetic hydrogen spectrum of a catalytic system intermediate obtained by reacting TU-1 with a strong base in a tetrahydrofuran solvent;
FIG. 6 is a single crystal diffraction diagram of the hydrogen donor substituent as the reaction product of phenyl and tetrabutylammonium hydroxide;
FIG. 7 is a nuclear magnetic hydrogen spectrum of linear poly (. gamma. -butyrolactone) obtained with TU-2 and benzyl alcohol as the catalytic system (entry 8);
FIG. 8 is a nuclear magnetic hydrogen spectrum of linear poly (. gamma. -butyrolactone) obtained with TU-2 and benzyl alcohol as the catalytic system (entry 18);
FIG. 9 is a nuclear magnetic hydrogen spectrum of an intermediate obtained by reacting TU-2 with a strong base;
FIG. 10 is a nuclear magnetic hydrogen spectrum of an intermediate obtained by TU-3 and a strong base;
FIG. 11 is a nuclear magnetic hydrogen spectrum of an intermediate obtained by reacting TU-6 with a strong base;
FIG. 12 is a graph comparing the nuclear magnetic hydrogen spectra of TU-7 and the catalytic system intermediate obtained by reacting TU-7 with strong base in a toluene solvent;
FIG. 13 is a nuclear magnetic hydrogen spectrum of an intermediate obtained from TBD and a strong base.
Detailed Description
The following describes embodiments of the present invention in detail. The following examples are illustrative only and are not to be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by manufacturers, and are all conventional products which can be obtained commercially.
Example 1
Benzyl alcohol (0.02mmol, 2.1. mu.L), 1, 3-diisopropylthiourea (0.02mmol, 3.2 mg), tetrabutylammonium hydroxide (0.8M in methanol, 25. mu.L) and 0.13mL of toluene were added to a reaction flask, placed in a low temperature cooling bath at-40 ℃ and stirred for 10min, and gamma-butyrolactone (6mmol, 0.46mL) was added to the reaction tube using a syringe. The reaction is carried out for 4h under the protection of nitrogen, and 2-3 drops of acetic acid are added to stop the reaction. The reaction mixture was dissolved in 4mL of dichloromethane, poured into 50mL of methanol, and the precipitate was centrifuged to give poly (. gamma. -butyrolactone). The polymer is a linear polymer. In this example, linear poly (. gamma. -butyrolactone) was prepared using the catalytic system of (4). In this example, tetrabutylammonium hydroxide, benzyl alcohol and 1, 3-diisopropylthiourea constitute the catalytic system of the combination of strong base + initiator + hydrogen donor.
The number average molecular weight was 10.4kg/mol and the molecular weight distribution was 2.0 by GPC.
Example 2
Benzyl alcohol (0.02mmol, 2.1. mu.L), 1, 3-diisopropylthiourea (0.02mmol, 3.2 mg), tetrabutylammonium hydroxide (0.8M in methanol, 25. mu.L) and 0.13mL of toluene were added to a reaction flask, placed in a low temperature cooling bath at-50 ℃ and stirred for 10min, and gamma-butyrolactone (24mmol, 1.84mL) was added to the reaction tube using a syringe. The reaction is carried out for 4h under the protection of nitrogen, and 8-12 drops of acetic acid are added to stop the reaction. The reaction mixture was dissolved in 16mL of dichloromethane, poured into 200mL of methanol, and the precipitate was centrifuged to give poly (. gamma. -butyrolactone). The polymer is a linear polymer. In this example, linear poly (. gamma. -butyrolactone) was prepared using the catalytic system of (4). In this example, tetrabutylammonium hydroxide, benzyl alcohol and 1, 3-diisopropylthiourea constitute the catalytic system of the combination of strong base + initiator + hydrogen donor.
The number average molecular weight was 54.0kg/mol and the molecular weight distribution was 1.60 by GPC.
Example 3
Benzyl alcohol (0.02mmol, 2.1. mu.L), 1, 3-diethylthiourea (0.02mmol, 2.65 mg), tetrabutylammonium hydroxide (0.8M in methanol, 25. mu.L) and 0.13mL of toluene were added to a reaction flask, placed in a low temperature cooling bath at-40 ℃ and stirred for 10min, and gamma-butyrolactone (6mmol, 0.46mL) was added to the reaction tube using a syringe. The reaction is carried out for 4h under the protection of nitrogen, and 2-3 drops of acetic acid are added to stop the reaction. The reaction mixture was dissolved in 4mL of dichloromethane, poured into 50mL of methanol, and the precipitate was centrifuged to give poly (. gamma. -butyrolactone). The polymer is a linear polymer. In this example, linear poly (. gamma. -butyrolactone) was prepared using the catalytic system of (4). In this example, tetrabutylammonium hydroxide, benzyl alcohol and 1, 3-diisopropylthiourea constitute the catalytic system of the combination of strong base + initiator + hydrogen donor.
The number average molecular weight was 10.0kg/mol as determined by GPC, and the molecular weight distribution was 1.60.
Example 4
Benzyl alcohol (0.02mmol, 2.1. mu.L), 1, 3-diphenylurea (0.02mmol, 4.25 mg), tetrabutylammonium hydroxide (0.8M in methanol, 25. mu.L) and 0.13mL of toluene were added to a reaction flask, placed in a low temperature cooling bath at-40 ℃ and stirred for 10min, and gamma-butyrolactone (6mmol, 0.46mL) was added to the reaction tube using a syringe. The reaction is carried out for 4h under the protection of nitrogen, and 2-3 drops of acetic acid are added to stop the reaction. The reaction mixture was dissolved in 4mL of dichloromethane, poured into 50mL of methanol, and the precipitate was centrifuged to give poly (. gamma. -butyrolactone). The polymer is a linear polymer. In this example, linear poly (. gamma. -butyrolactone) was prepared using the catalytic system of (4). In this example, tetrabutylammonium hydroxide, benzyl alcohol and 1, 3-diisopropylthiourea constitute the catalytic system of the combination of strong base + initiator + hydrogen donor. The number-average molecular weight by GPC was 9.0kg/mol, and the molecular weight distribution was 1.90.
Example 5
Benzyl alcohol (0.02mmol, 2.1. mu.L), 1, 3-diisopropylthiourea (0.02mmol, 3.2 mg), tetrabutylammonium hydroxide (0.8M in methanol, 25. mu.L) and 0.13mL of toluene were added to a reaction flask, placed in a low temperature cooling bath at 0 ℃ and stirred for 10min, and gamma-butyrolactone (6mmol, 0.46mL) was added to the reaction tube using a syringe. The reaction is carried out for 4h under the protection of nitrogen, and 2-3 drops of acetic acid are added to stop the reaction. The reaction mixture was dissolved in 4mL of dichloromethane, poured into 50mL of methanol, and the precipitate was centrifuged to give poly (. gamma. -butyrolactone). The polymer is a linear polymer. In this example, linear poly (. gamma. -butyrolactone) was prepared using the catalytic system of (4). In this example, tetrabutylammonium hydroxide, benzyl alcohol and 1, 3-diisopropylthiourea constitute the catalytic system of the combination of strong base + initiator + hydrogen donor. The number-average molecular weight by GPC was 14.0kg/mol, with a molecular weight distribution of 1.9.
Example 6
Tetrabutylammonium hydroxide (0.8M methanol solution, 25. mu.L) and 0.13mL of toluene were added to a reaction flask, and stirred in a low-temperature cooling bath at-40 ℃ for 10min, and gamma-butyrolactone (6mmol, 0.46mL) was added to the reaction tube by syringe. The reaction is carried out for 4h under the protection of nitrogen, and 2-3 drops of acetic acid are added to stop the reaction. The reaction mixture was dissolved in 4mL of dichloromethane, poured into 50mL of methanol, and the precipitate was centrifuged to give poly (. gamma. -butyrolactone). The polymer is a cyclic polymer. In this example, cyclic poly (. gamma. -butyrolactone) was prepared using the catalytic system of (1). In this example, tetrabutylammonium hydroxide constitutes the catalytic system for the action of a strong base alone. The number-average molecular weight by GPC was 1.3kg/mol, with a molecular weight distribution of 1.2.
Example 7
1, 3-diisopropylthiourea (0.02mmol, 3.2 mg), tetrabutylammonium hydroxide (0.8M methanol solution, 25. mu.L) and 0.13mL of toluene were added to a reaction flask, stirred in a-40 ℃ cold bath for 10min, and gamma-butyrolactone (6mmol, 0.46mL) was added to the reaction tube using a syringe. The reaction is carried out for 4h under the protection of nitrogen, and 2-3 drops of acetic acid are added to stop the reaction. The reaction mixture was dissolved in 4mL of dichloromethane, poured into 50mL of methanol, and the precipitate was centrifuged to give poly (. gamma. -butyrolactone). The polymer is a cyclic polymer. In this example, cyclic poly (. gamma. -butyrolactone) was prepared using the catalyst system of (2). In this example, tetrabutylammonium hydroxide and 1, 3-diisopropylthiourea constitute the catalytic system of the strong base + hydrogen donor combination.
The number-average molecular weight by GPC was 1.48kg/mol, with a molecular weight distribution of 1.3.
Example 8
Benzyl alcohol (0.02mmol, 2.1. mu.L), tetrabutylammonium hydroxide (0.8M in methanol, 25. mu.L) and 0.13mL of toluene were added to a reaction flask, and the mixture was stirred in a low-temperature cooling bath at-50 ℃ for 10min, and gamma-butyrolactone (24mmol, 1.84mL) was added to the reaction tube by syringe. The reaction is carried out for 4h under the protection of nitrogen, and 8-12 drops of acetic acid are added to stop the reaction. The reaction mixture was dissolved in 16mL of dichloromethane, poured into 200mL of methanol, and the precipitate was centrifuged to give poly (. gamma. -butyrolactone). The polymer is a cyclic polymer. In this example, cyclic poly (. gamma. -butyrolactone) was prepared using the catalyst system of (3). In this example, tetrabutylammonium hydroxide and benzyl alcohol constitute the catalytic system of the strong base + initiator combination.
The number-average molecular weight by GPC was 1.4kg/mol, with a molecular weight distribution of 1.2.
As can be seen from examples 1-8, by adding one or more of a hydrogen electron donor, a strong base, or an initiator to a solvent to produce a plurality of catalytic systems, each catalytic system can control the polymerization of gamma-butyrolactone to produce cyclic or linear poly (gamma-butyrolactone), the plurality of catalytic systems comprising four of the following:
(1) a strong base;
(2) strong base + hydrogen donor electron;
(3) strong base + initiator;
(4) strong base + initiator + hydrogen donor electron.
See table 4 for relevant parameters for the preparation of poly (gamma-butyrolactone) in examples 1-8.
Poly-gamma-butyrolactone was prepared using different hydrogen donor electron structures and different gamma-butyrolactone/base/hydrogen donor electron/initiator molar ratios, different reaction conditions, etc., as shown in tables 1, 2 and 3.
Structural and performance testing and other examples
Reactants required by different catalytic systems are sequentially added into a reaction bottle in a glove box, gamma-butyrolactone is added at the temperature of 0-50 ℃, and the mixture is put into a low-temperature reactor for reaction. 3mL of benzoic acid/CHCl was added3（10mg·mL-1) The reaction was quenched with CHCl3Cleaning, rotary steaming (40 deg.C, 80mmbar), precipitating with 10 times of methanol (standing in refrigerator for 1h), vacuum filtering, oven drying at 25 deg.C in vacuum drying oven to constant weight, and sampling for related structure and performance test.
The poly-gamma-butyrolactone materials prepared using different hydrogen donor electron structures and different gamma-butyrolactone: strong base: hydrogen donor: initiator molar ratios (M: P: Tu-2: I), different reaction conditions, etc., were subjected to structural analysis tests, and the results are shown in tables 1, 2 and 3:
table 1 relevant parameters for the different catalytic systems for the catalysis of gamma-butyrolactone and the results of the tests.
Reaction conditions in table 1: butyrolactone concentration =10M (0.52g, 6mmol), in the reaction step, base alone or after reaction of base with hydrogen donor electron, initiator is added, with benzyl alcohol being the most effective, then solvent and gamma-butyrolactone are added.aRepresents toluene as a solvent;bTHF is used as a solvent;cis represented by [ gamma-BL]=6M。
In table 1, the four catalytic systems are mainly screened for relevant parameters and tested and confirmed for relevant structures. Specifically, entries 8 to 11, entry 13, and entries 15 to 18 are (4) th catalytic system, and the measurement-related parameters of the structure of the linear poly (γ -butyrolactone) produced by the catalytic system are shown in fig. 1, and the GPC-related parameters of the obtained linear poly (γ -butyrolactone) are shown in fig. 2 to 4; in the catalytic system (4), strong organic base (tetrabutylammonium hydroxide) can interact with hydrogen donor to deprotonate hydrogen electron to form urea/thiourea anion, and the urea/thiourea anion simultaneously activates the polymer growing chain end and the monomer through hydrogen bond interaction, so that the catalytic system shows high polymerization activity; on the other hand, after the urea/thiourea anion is combined with the tail end of the growing chain through hydrogen bonds, the alkalinity of a functional group at the tail end of the growing chain is reduced, and the steric hindrance at the tail end of the growing chain is increased, so that the possibility of ester exchange and chain tail end back biting is reduced, the controllability of polymerization reaction is improved, and the preparation of linear high molecular weight poly (gamma-butyrolactone) is facilitated. In particular, tetrabutylammonium hydroxide is a strong electron donor, and easily abstracts proton hydrogen in urea/thiourea groups in a catalytic system to form urea/thiourea anions.
For entries 5 to 18, in the catalyst system in which cyclic poly (γ -butyrolactone) of different molecular weights and molecular weight widths is mainly produced when the initiator is absent in the catalyst system, and linear poly (γ -butyrolactone) is mainly produced when the initiator is added, for example, in the catalyst system in which cyclic or linear poly (γ -butyrolactone) of different molecular weights is produced when the solvent is tetrahydrofuran, the measurement-related parameters of the structures of the intermediates obtained for the catalyst system obtained by the hydrogen electron donor (for example, TU-1) and the strong base (for example, the (2) th or (4) th catalyst system) are shown in fig. 5, and the confirmation-related parameters of the structures of the obtained catalyst for the hydrogen electron donor (for example, TU-3) and the strong base are shown in fig. 6.
For the catalyst systems (1), (2) and (3), tetrabutylammonium hydroxide itself is strongly basic, and can activate aliphatic alcohol initiators to obtain cyclic poly (gamma-butyrolactone) with different molecular weights, wherein cyclic poly (gamma-butyrolactone) is the main product and linear poly (gamma-butyrolactone) is the byproduct.
According to some embodiments of the present invention, the conversion of gamma-butyrolactone and the molecular weight of the resulting poly (gamma-butyrolactone) can be further increased by first preparing various catalytic systems under the above conditions and then adding gamma-butyrolactone monomer, as opposed to directly reacting gamma-butyrolactone monomer with one or more of initiator, tetrabutylammonium hydroxide, or hydrogen donor. It can be seen from entries 8 and 18 that as the molar ratio of γ -butyrolactone increases, the conversion of γ -butyrolactone and the molecular weight of the resulting poly (γ -butyrolactone) can be further increased, the relevant parameters for the linear poly (γ -butyrolactone) made in entry 8 are shown in fig. 7, and the relevant parameters for the linear poly (γ -butyrolactone) made in entry 18 are shown in fig. 8.
From entries 15-16 it can be seen that the catalytic system of the present invention can also perform gamma-butyrolactone polymerisation at higher temperatures than the reported catalytic systems. It can be seen from items 3 and 4 that, when the temperature is higher and the reaction time is too short, the conversion rate of γ -butyrolactone is lower, the molecular weight of the obtained poly (γ -butyrolactone) is lower, the reaction time is prolonged, and the conversion rate of γ -butyrolactone and the molecular weight of the product can be effectively increased.
The tetrabutyl ammonium hydroxide and hydrogen donor residues in the high molecular weight linear poly (gamma-butyrolactone) product prepared by the method provided by the invention are extremely low or have no residues, can meet the application requirements in the field of biological medicine, and have high molecular weight and good mechanical properties.
Table 2 (2) catalyst system catalyzes the relevant parameters of gamma-butyrolactone and the results of the test.
In the context of Table 2, the following examples are,awhich represents toluene as solvent.
In table 2, the screening of relevant parameters and the testing and confirmation of relevant structures are mainly performed on the (2) th catalytic system. Specifically, table 2 shows the experiments on the hydrogen donor electron bodies having different structures, and cyclic poly (γ -butyrolactone) having different molecular weights and widths of molecular weight distribution is mainly produced under the reaction conditions lacking the action of benzyl alcohol and the catalyst, for example, the structure-related parameters of TU-2 and the intermediate obtained by strong base are shown in fig. 9, the structure-related parameters of TU-3 and the intermediate obtained by strong base are shown in fig. 10, the structure-related parameters of TU-6 and the intermediate obtained by strong base are shown in fig. 11, the structure-related parameters of TU-7 and the intermediate obtained by strong base are shown in fig. 12, and the structure-related parameters of TBD and the intermediate obtained by strong base are shown in fig. 13.
Table 3 (4) catalyst system catalyzes the relevant parameters of gamma-butyrolactone and the results of the test.
Reaction conditions in table 3: butyrolactone concentration =10M (0.52g, 6 mmol). The reaction step is that after strong base reacts with hydrogen-donating electron, initiator is added, wherein benzyl alcohol has the best effect, then solvent and gamma-butyrolactone are added, toluene is used as solvent, and the reaction time is 4 h.
In table 3, the screening of relevant parameters and the testing and validation of relevant structures were mainly performed on the above-mentioned (4) th catalytic system. In the present invention, different hydrogen donor electron structures are used, which have a great influence on the activity of ring-opening polymerization of gamma-butyrolactone and the molecular weight of poly-gamma-butyrolactone prepared. Specifically, the structures corresponding to TU-3, TU-4 and TU-5 lack activity for the (4) th catalytic system, and thus linear poly (γ -butyrolactone) could not be obtained when the hydrogen donor was TU-3, TU-4 or TU-5, and linear poly (γ -butyrolactone) of different molecular weights could be obtained for TU-2, TU-6 and TU-7.
Table 4 examples 1-8 relevant parameters for the preparation of poly (gamma-butyrolactone).
As can be seen from examples 1-8, Table 1, Table 2, Table 3 and Table 4, by adding one or more of a hydrogen electron donor, a strong base or an initiator to a solvent to produce a plurality of catalytic systems, each catalytic system can control the polymerization of gamma-butyrolactone to produce cyclic or linear poly (gamma-butyrolactone) of different molecular weights, and the plurality of catalytic systems comprises four of the following: (1) a strong base; (2) strong base + hydrogen donor electron; (3) strong base + initiator; (4) strong base + initiator + hydrogen donor electron.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (10)
1. A method for preparing poly (gamma-butyrolactone) by efficiently catalyzing ring opening of gamma-butyrolactone, which is characterized in that one or more of hydrogen electron donor, strong base or initiator is/are added into a solvent to prepare a plurality of catalytic systems, each catalytic system can control the gamma-butyrolactone to be catalyzed to perform polymerization reaction to obtain cyclic or linear poly (gamma-butyrolactone) with different molecular weights, and the plurality of catalytic systems comprises four catalytic systems as follows:
(1) a strong base;
(2) a strong base and a hydrogen donor electron;
(3) a strong base and an initiator;
(4) strong base, initiator and hydrogen donor electron.
2. The method for preparing poly (gamma-butyrolactone) by efficiently catalyzing ring opening of gamma-butyrolactone according to claim 1, wherein the strong base is tetrabutylammonium hydroxide, and the formula of tetrabutylammonium hydroxide is as follows:
3. the method for preparing poly (gamma-butyrolactone) by efficiently catalyzing the ring opening of gamma-butyrolactone according to claim 2, wherein the hydrogen donor is one of the following compounds:
4. The method for preparing poly (gamma-butyrolactone) by ring-opening catalysis of gamma-butyrolactone according to claim 3, wherein said tetrabutylammonium hydroxide and hydrogen-donating electron-forming catalyst have the following structural formula:
5. The method for preparing poly (gamma-butyrolactone) by ring-opening catalysis of gamma-butyrolactone according to claim 1, wherein the initiator is any one of methanol, ethanol, isopropanol, tert-butanol, benzyl alcohol, phenethyl alcohol, phenylpropyl alcohol, diphenylmethanol, 2-diphenylethanol, hydroxyl-terminated oligoethylene glycol monomethyl ether, 2-diphenylethanol, ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol, 1, 2-benzenedimethanol, 1, 3-benzenedimethanol, 1, 4-benzenedimethanol, 2' -biphenyldimethanol, glycerol and pentaerythritol.
6. The method for preparing poly (gamma-butyrolactone) through ring opening of gamma-butyrolactone by using high-efficiency catalysis, according to claim 4, is characterized in that the molar ratio of the catalyst to the initiator is 1/0-5/1, the molar ratio of the catalyst to the hydrogen donor is 0 (0-10), and the molar ratio of the hydrogen donor to the gamma-butyrolactone is 0/50-1/300.
7. The method for preparing poly (gamma-butyrolactone) by efficiently catalyzing the ring opening of gamma-butyrolactone according to any one of claims 1 to 6, wherein the temperature of polymerization is-50 to 20 ℃ and the reaction time is 0.5 to 18 hours.
8. The method for preparing cyclic or linear poly-gamma-butyrolactone in different molecular weights according to any of claims 1-6, characterized in that the molar concentration of gamma-butyrolactone in the various catalytic systems is 1 mol-L-1～10mol·L-1。
9. The method for preparing poly (gamma-butyrolactone) by efficiently catalyzing the ring opening of gamma-butyrolactone according to claim 1, wherein the polymerization reaction further requires the addition of a solvent, and the solvent is any one of toluene, tetrahydrofuran, dichloromethane, chloroform, dioxane, acetonitrile and N, N-dimethylformamide.
10. The method according to any one of claims 1 to 6, wherein the molecular weight of the prepared linear poly (gamma-butyrolactone) is 1 to 52Kg/mol, and the molecular weight of the prepared cyclic poly (gamma-butyrolactone) is 0.3 to 10 Kg/mol.
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| CN112979849A (en) * | 2020-12-29 | 2021-06-18 | 青岛大学 | Method for catalyzing methyl methacrylate anion polymerization |
| CN114262420A (en) * | 2021-12-29 | 2022-04-01 | 青岛科技大学 | Preparation method of recyclable bio-based polyester polyurethane |
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| CN112979849A (en) * | 2020-12-29 | 2021-06-18 | 青岛大学 | Method for catalyzing methyl methacrylate anion polymerization |
| CN112979849B (en) * | 2020-12-29 | 2023-12-29 | 青岛大学 | Method for catalyzing anionic polymerization of methyl methacrylate |
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