CN109851765B - Metal-free catalytic system for organic concerted catalysis of lactone ring-opening polymerization - Google Patents

Metal-free catalytic system for organic concerted catalysis of lactone ring-opening polymerization Download PDF

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CN109851765B
CN109851765B CN201811623377.7A CN201811623377A CN109851765B CN 109851765 B CN109851765 B CN 109851765B CN 201811623377 A CN201811623377 A CN 201811623377A CN 109851765 B CN109851765 B CN 109851765B
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heterocyclic
thiourea
opening polymerization
olefin
exo
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CN109851765A (en
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王庆刚
周丽
徐广强
咸漠
吕承东
孙西同
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Qingdao Institute of Bioenergy and Bioprocess Technology of CAS
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Abstract

The invention discloses a metal-free catalytic system for organic concerted catalysis of lactone ring-opening polymerization, which belongs to the field of polymer synthetic materials and is applied to controllable active ring-opening polymerization of lactone by high-efficiency catalysis. The preparation method is characterized in that under the protection of inert gas, lactone is taken as a monomer, N-heterocyclic exo-olefin and thiourea are used for concerted catalysis or N-heterocyclic exo-olefin and urea are used for concerted catalysis in an organic solvent, and the lactone is initiated by alcohol to carry out ring-opening polymerization reaction. The synthesis method has the advantages that in an organic solvent, the obtained aliphatic hydrocarbon polyester polymer has no metal residue, the reaction condition is mild, the reaction is rapid, and the polymerization process is simple and easy to operate; can obtain high conversion rate under the action of very small amount of catalyst and can obtain polyester material with narrow molecular weight distribution.

Description

Metal-free catalytic system for organic concerted catalysis of lactone ring-opening polymerization
Technical Field
The invention relates to a metal-free catalytic system for ring-opening polymerization of lactone under organic concerted catalysis, belonging to the technical field of polymer synthetic materials.
Background
In recent years, small-molecule organic compounds have been widely used as catalysts or initiators in ring-opening polymerization of lactones. Through different catalytic reaction mechanisms, the aliphatic polyester/polyether/polyamine material with biocompatibility and biodegradability and without metal is obtained. Because the aliphatic hydrocarbon polyester material has good mechanical properties, the aliphatic hydrocarbon polyester material is widely applied to the fields of chemistry, food packaging, medical polymers and the like.
Currently, the catalytic ring-opening polymerization is the most important method for preparing synthetic aliphatic polyester, and the catalytic system includes metal-ligand or metal alkane compound catalysis, enzyme catalysis and organic small molecule catalysis. The metal in the metal-ligand includes iron, cobalt, aluminum, zinc and other metals, and the metal alkane compound includes zinc isopropoxide, alkyl aluminum, aryl aluminum, stannous octoate and RE alkoxy compound. The residual catalyst in the polymer has more or less potential toxicity to human cells, so that the application of the polymer is limited. The catalytic activity of enzyme catalysis is high, but the catalysis has specificity, and the catalytic activity only aims at certain lactone, and has poor universality on monomer types. Compared with the former two catalytic polymerization systems, the organic catalytic lactone ring-opening polymerization has the advantages of mild reaction conditions, controllable polymerization reaction, narrow molecular weight distribution (PDI) and the like, and the produced polymer does not contain metal, is used as a biocompatible material, and can be applied to the fields of food packaging or drug release or transfer and the like. However, the prior organic catalysis lactone ring-opening polymerization reaction has the problems of poor catalytic activity and low conversion rate.
Disclosure of Invention
In order to solve the problems of poor catalytic activity and low conversion rate in the ring-opening polymerization reaction of polyester materials, the invention provides a metal-free catalytic system for organic concerted catalysis of lactone ring-opening polymerization, namely an N-heterocyclic exo-olefin (NHOs) and Thiourea (TUs)/urea (Us) concerted catalytic system, and takes alcohols such as benzyl alcohol, butanediol and the like as initiators, so that an efficient, rapid and controllable active ring-opening polymerization catalytic system is realized, and the polyester materials with narrow molecular weight distribution and no metal are obtained. The technical scheme is as follows:
the invention aims to provide a metal-free catalytic system for organic concerted catalysis ring-opening polymerization, which is characterized in that under the protection of inert gas, the metal-free catalytic system takes lactone as a monomer, under the concerted catalysis of N-heterocyclic exo-olefin and thiourea or under the concerted catalysis of N-heterocyclic exo-olefin and urea in an organic solvent, and the ring-opening polymerization reaction of lactone is initiated by alcohols.
Preferably, the structural formula of the N-heterocyclic exoolefin is selected from any one of the following structural formulas:
Figure BDA0001927423180000011
wherein R is1Represents hydrogen, alkyl or aryl; r2Represents hydrogen, alkyl or aryl; r3Represents an alkyl or aryl group; r4Represents an alkyl or aryl group; r5Represents hydrogen, alkyl or aryl; r6Represents hydrogen, alkyl or aryl; x represents a heteroatom B, N, O, S, Si or P; y represents a heteroatom B, N, O, S, Si or P;
Figure BDA0001927423180000021
and
Figure BDA0001927423180000022
represents chiral chain alkyl with different configurations or chiral naphthenic base with different configurations or chiral aryl with different configurations.
More preferably, the structural formula of the N-heterocyclic external olefin is selected from any one of compounds NHO 1-NHO 7; the structural formulas of the compounds NHO 1-NHO 7 are as follows:
Figure BDA0001927423180000023
preferably, the urea has a structural formula selected from any one of the following structural formulas:
Figure BDA0001927423180000024
wherein R1 represents an alkyl or aryl group; r2 represents alkyl or aryl; x represents O;
Figure BDA0001927423180000025
and
Figure BDA0001927423180000026
represents chiral chain alkyl with different configurations or chiral naphthenic base with different configurations or chiral aryl with different configurations.
Preferably, the structural formula of the thiourea is selected from any one of the following structural formulas:
Figure BDA0001927423180000027
wherein R1 represents an alkyl or aryl group; r2 represents alkyl or aryl; x represents a heteroatom S;
Figure BDA0001927423180000028
and
Figure BDA0001927423180000029
represents chiral chain alkyl with different configurations or chiral naphthenic base with different configurations or chiral aryl with different configurations.
More preferably, the structural formula of the thiourea is selected from any one of compounds TU 1-TU 6; the structural formulas of the compounds TU 1-TU 6 are as follows:
Figure BDA00019274231800000210
Figure BDA0001927423180000031
more preferably, the structural formula of the urea is selected from any one of compounds U1-U3; the structural formulas of the compounds U1-U3 are as follows:
Figure BDA0001927423180000032
preferably, the lactone is selected from any one of gamma-butyrolactone, delta-valerolactone, epsilon-caprolactone, trimethylene carbonate and lactide; the structural formulas of the gamma-butyrolactone, delta-valerolactone, epsilon-caprolactone, trimethylene carbonate and lactide are as follows:
Figure BDA0001927423180000033
preferably, the molar ratio of the N-heterocyclic exoolefin, thiourea or urea and lactone is 1: (0.5-10): (100-1000); the reaction temperature of the ring-opening polymerization reaction is-60 ℃ to 60 ℃, and the reaction time is 1s to 24 h; the concentration of the lactone is 1 mol/L-10 mol/L.
More preferably, the molar ratio of the N-heterocyclic exoolefin, thiourea or urea and lactone is 1: (0.5-10): (50-1000); the reaction temperature of the ring-opening polymerization reaction is-60 ℃ to 100 ℃, and the reaction time is 5min to 24 h; the concentration of the lactone is 1 mol/L-5 mol/L.
Most preferably, the molar ratio of the N-heterocyclic exoolefin to thiourea or urea is 1: 2.
More preferably, the molar ratio of the N-heterocyclic exoolefin to thiourea or urea to lactone is 1: 2; the molar ratio of the initiator benzyl alcohol to the lactone is 1: (50-1000); the reaction temperature of the ring-opening polymerization reaction is-60 ℃ to 30 ℃, and the reaction time is 5min to 24 h; the concentration of the lactone is 3.5 mol/L.
Preferably, the organic solvent is toluene, tetrahydrofuran or dichloromethane.
Preferred inert gases for the present invention are argon or nitrogen.
The preferred alcohol compound of the present invention is benzyl alcohol or butylene glycol.
The invention utilizes the synergistic catalysis of N-heterocyclic exo-olefin (NHOs) and Thiourea (TUs) or urea (Us), one molecule of TU (or U) is combined with a monomer to activate the monomer, and NHO (TU (or U) ═ 1:1 is subjected to synergistic deprotonation with an initiator BnOH to form active species, so that the activated monomer is attacked, and the effect of activity controllable polymerization is achieved. When no alcohol is contained in the polymerization system, the molecular weight of the polymer is larger than that of the polymer containing alcohol, the molecular weight distribution is not greatly different, and the monomer conversion rate is up to more than 97%.
The molar ratio of the catalytic system is NHO: TU (or U) ═ 1:2 is the optimal synergetic catalysis ratio; too high or too low a Thiourea (TUs)/urea (Us) ratio relative to N-heterocyclic exo-olefins (NHOs) results in reduced monomer conversion; on the other hand, the ratio of initiator to monomer can be in the range of 1: in the case of 1000, an extremely high conversion is still achieved.
The invention has the beneficial effects that:
in the prior art, the effect of single N-heterocyclic exo-olefin (NHOs) or thiourea in catalyzing the ring-opening polymerization reaction of lactone is poor, the invention provides a non-metal organic co-catalysis system, and two organic small molecular catalysts are combined for the first time to form a set of brand-new co-catalysis system. The catalytic system takes N-heterocyclic exo-olefin (NHOs) and Thiourea (TUs)/urea (Us) as a synergistic catalyst, takes alcohols such as benzyl alcohol, butanediol and the like as initiators, and initiates lactone to carry out metal-activity-free controllable active ring-opening polymerization at room temperature, and the aliphatic hydrocarbon polyester material can be synthesized by taking the lactone as a raw material monomer according to the catalytic system. The catalytic system adopts a 'double-activation' reaction mode, the catalyst for ring-opening polymerization can only activate lactone carbonyl or initiator alcohol generally, and the invention adopts N-heterocyclic external olefin to activate the initiator alcohol and thiourea to activate monomer lactone.
The catalytic reaction of the invention has high catalytic activity and controllable reaction: the synthetic polymerization system has mild condition, quick reaction and simple and easy operation of polymerization process, the generated polymer does not contain metal elements, the molecular weight is controllable and the molecular weight distribution is narrow, the catalytic system can obtain high conversion rate under the action of extremely small amount of catalyst, the monomer conversion rate can reach more than 97 percent, and the high-efficiency, quick and controllable active ring-opening polymerization catalytic system is realized.
Drawings
FIG. 1 is a scheme showing the preparation of N-heterocyclooectoolefin NHO6 in example 61H NMR chart.
FIG. 2 is a drawing of poly-delta-valerolactone (PVL) prepared in example 81H NMR chart.
FIG. 3 is a MALDI-TOF plot of poly-delta-valerolactone (PVL) prepared in example 8.
FIG. 4 is an enlarged view of MALDI-TOF plot of poly-delta-valerolactone (PVL) prepared in example 8.
FIG. 5 is a drawing showing the preparation of Poly epsilon-caprolactone (PCL) in example 91H NMR chart.
FIG. 6 is a graph of poly gamma-butyrolactone (PGBL) prepared in example 101H NMR chart.
FIG. 7 is a drawing of polytrimethylene carbonate prepared in example 111H NMR chart.
Detailed description of the preferred embodiments
The present invention will be further described with reference to the following specific examples, but the present invention is not limited to these examples.
The following examples 1 to 7 provide synthetic methods for the preparation of N-heterocyclic exoolefins (NHOs).
Example 1: synthesis of N-Heterocycloexo-olefin NHO1
The reaction for the synthesis of the N-heterocyclooectoolefin NHO1 is as follows:
Figure BDA0001927423180000051
a 50mL Schlenk reaction tube was evacuated under an argon or nitrogen atmosphere three times, dried compound Pre 1(2.38g, 10mmol), 5mL of freshly distilled anhydrous tetrahydrofuran were added to the 50mL Schlenk reaction tube, a tetrahydrofuran solution of KHMDS (10mL, 1M in THF) was injected, stirred at room temperature for 6h, filtered, and evacuated to constant weight under vacuum to give NHO1 as a yellow solid (0.73g, yield ═ 66%).1H NMR(400MHz,d8-Toluene)δ(ppm)5.32(s,2H,N-CH＝CH-N),2.55(s,2H,-C＝CH2),2.41(s,6H,N-CH3)。13C NMR(400MHz,d8-Toluene)δ(ppm)112.54,39.92,32.07。
Example 2: synthesis of N-heterocyclic exo-olefin NHO2
The reaction for the synthesis of the N-heterocyclooectoolefin NHO2 is as follows:
Figure BDA0001927423180000052
under an argon or nitrogen atmosphere, 10mL Schlenk reaction tubeAfter baking three times with suction, dry compound Pre 2(0.53g, 2mmol), 3mL of freshly distilled anhydrous tetrahydrofuran was added to a 10mL Schlenk reaction tube, a solution of KHMDS in tetrahydrofuran (2mL, 1M in THF) was injected, stirred at room temperature for 6h, filtered, and vacuum-dried to constant weight to give NHO2 as a yellow solid (0.26g, yield ═ 19%).1H NMR(400MHz,d8-Toluene)δ(ppm)2.67(s,2H,-C＝CH2),2.53(s,6H,N-CH3),1.42(s,6H,C-CH3)。13C NMR(400MHz,d8-Toluene)δ(ppm)153.11,113.83,40.12,28.81,8.16。
Example 3: synthesis of N-heterocyclic exo-olefin NHO3
The reaction for the synthesis of the N-heterocyclooectoolefin NHO3 is as follows:
Figure BDA0001927423180000053
a 25mL Schlenk reaction tube was evacuated under an argon or nitrogen atmosphere three times, dried compound Pre 3(1.47g, 5mmol), 5mL of freshly distilled anhydrous tetrahydrofuran was added to the 25mL Schlenk reaction tube, a tetrahydrofuran solution of KHMDS (5mL, 1M in THF) was injected, stirred at room temperature for 6h, filtered, and evacuated to constant weight under vacuum to give NHO 3(0.64g, yield ═ 77%) as a yellow solid.1H NMR(400MHz,d8-Toluene)δ(ppm)2.59(s,6H,N-CH3),1.86(s,6H,C-CH3),1.47(s,6H,-C＝CCH3)。
Example 4: synthesis of N-heterocyclic exo-olefin NHO 4
The reaction for the synthesis of the N-heterocyclooectoolefin NHO 4 is as follows:
Figure BDA0001927423180000061
after being evacuated and baked three times in a 25mL Schlenk reaction tube under an argon or nitrogen atmosphere, the dried compound Pre 4(1.44g, 5mmol), 5mL of freshly distilled anhydrous tetrahydrofuran was added to the 25mL Schlenk reaction tube, a tetrahydrofuran solution of KHMDS (5mL, 1M in THF) was injected, stirred at room temperature for 6h, filtered, and evacuated to constant weight under vacuum to obtain a yellow solidNHO 4(0.69g，yield＝86％)。1H NMR(400MHz,d8-Toluene)δ(ppm)6.66-6.64(dd,2H,Ph),6.17-6.15(dd,2H,Ph),2.81(s,2H,-C＝CH2),2.53(s,6H,N-CH3)。
Example 5: synthesis of N-heterocyclic exo-olefin NHO 5
The reaction for the synthesis of the N-heterocyclooectoolefin NHO 5 is as follows:
Figure BDA0001927423180000062
a 25mL Schlenk reaction tube was evacuated under an argon or nitrogen atmosphere three times, dried compound Pre 5(0.6g, 3mmol), 3mL of freshly distilled anhydrous tetrahydrofuran was added to the 25mL Schlenk reaction tube, a tetrahydrofuran solution of KHMDS (3mL, 1M in THF) was injected, stirred at room temperature for 6h, filtered, and evacuated to constant weight under vacuum to give yellow liquid NHO 5(0.21g, yield ═ 19%).1H NMR(400MHz,d8-Toluene)δ(ppm)2.94(s,2H,-C＝CH2),2.55(s,4H,-N-CH2-),2.34(s,6H,-N-CH2)。
Example 6: synthesis of N-heterocyclic exo-olefin NHO6
First, compound Rac-2 was synthesized: the reaction formula for synthesizing the compound Rac-2 is as follows:
Figure BDA0001927423180000063
ammonium tetrafluoroborate (0.79, 7.5mmol) was added to a 50mL two-necked flask under an argon or nitrogen atmosphere, and a suitable magnetic rotor was added; racemic compound Rac-1(1.47g,5mmol) was weighed and dissolved in triethyl carbonate (15mL) solvent, and a solution of Rac-1 was injected into a two-necked flask, warmed to 110 ℃, and refluxed overnight. After cooling to room temperature, the mixture was rotary evaporated under vacuum to remove the remaining triethyl carbonate, washed three times with dry ether (20mL) with stirring and vacuum dried to constant weight to give Rac-2 as a pale yellow solid (1.28g, yield 63%).1H NMR(400MHz,CDCl3)δ(ppm)7.42-7.38(m,4H,Ph),7.35-7.31(m,2H,Ph),7.27-7.24(m,4H,Ph),4.85-4.66(dd,4H,PhCH2-),3.56-3.53(m,2H,-CHN-),2.46(s,3H,-CH3),2.05-2.02(d,2H,-CHCH2-),1.82-1.79(d,2H,-CHCH2CH2-),1.48-1.40(d,2H,-CHCH2CH2-),1.30-1.19(d,2H,-CH2CH2CH2-)。13C NMR(400MHz,CDCl3)δ(ppm)170.25,133.82,129.36,128.53,127.05,67.19,49.09,27.70,23.76,11.96。
Secondly, synthesizing N-heterocyclic exo-olefin NHO6, wherein the reaction formula for synthesizing the N-heterocyclic exo-olefin NHO6 is as follows:
Figure BDA0001927423180000071
after roasting three times in a 10mL Schlenk reaction tube under an argon or nitrogen atmosphere, NaH (48mg, 2mmol, dried n-hexane washed three times), dried compound Rac-2(0.406g, 1mmol) were added to a 10mL Schlenk reaction tube, 3mL of freshly distilled anhydrous tetrahydrofuran was injected, stirred at room temperature for 12h, filtered, and vacuum-dried to constant weight to give NHO6 as a tan solid (0.2g, yield ═ 63%).1H NMR(400MHz,CDCl3)δ(ppm)7.39-7.37(d,4H,Ph),7.20-7.16(m,4H,Ph),7.10-7.06(t,4H,Ph),4.15-4.00(dd,4H,PhCH2-),3.28(s,2H,＝CH2),2.58-2.51(m,2H,-CHN-),1.59-1.55(d,2H,-CHCH2-),1.44-1.32(m,6H,-CH2CH2CH2-)。
The N-heterocyclic exoolefin NHO6 prepared in this example was subjected to1H NMR detection, detecting the obtained1The H NMR chart is shown in fig. 1, and the results of the measurements show that all chemical shifts in the hydrogen spectrum of the sample tested are consistent with the chemical structure of N-heterocyclooectoolefin NHO6, thus indicating that this example indeed provides a new compound, N-heterocyclooectoolefin NHO 6.
Example 7: general synthetic Process for preparing Thiourea (TUs)/ureas (Us)
The synthesis of Thiourea (TUs) or urea (Us) is from the corresponding organic amine (1eq) with isothiocyanate (1eq) or isocyanate (1eq) in methanol solution (0.5M) with stirring at room temperature for 30 min. The mixed system is rotary evaporated under vacuum, methanol is removed, the mixture is stirred and washed for three times by anhydrous ether (30mL), filtered, and is vacuumized for 24 hours at 50 ℃ until the weight is constant, so that light white solid is obtained.
The reaction formula is as follows:
Figure BDA0001927423180000081
TU 1:2.24g，yield＝60％,1H NMR(400MHz,d8-Toluene)δ(ppm)7.49-7.46(d,3H,Ph),5.37(s,1H,Ph-NH),4.29(s,1H,Hex-NH),1.97-1.95(d,2H,cyclohexyl-),1.53-1.40(m,3H,cyclohexyl-),1.25-1.14(m,2H,cyclohexyl-),1.02-0.84(m,3H,cyclohexyl-)。
TU 2:4.469g，yield＝89％,1H NMR(400MHz,d6-DMSO)δ(ppm)7.08-7.06(d,2H,J＝8Hz),3.96(s,2H),1.85-1.83(m,4H),1.66-1.63(m,4H),1.55-1.52(m,2H),1.31-1.09(m,10H)。13C NMR(400MHz,d6-DMSO)δ(ppm)180.48,51.93,32.83,25.69,24.96。
TU 3:4.469g，yield＝89％,1H NMR(400MHz,d6-DMSO)δ(ppm)10.66(s,2H,Ph),8.22(s,4H,Ph),7.86(s,2H,NH)。13C NMR(400MHz,d6-DMSO)δ(ppm)181.04,141.65,131.30,130.97,130.64,130.32,127.69,124.98,124.55,122.27,119.56,118.18。
Figure BDA0001927423180000082
U 1:0.85g，yield＝24％,1H NMR(400MHz,d6-DMSO)δ(ppm)9.04(s,1H,Ph),8.06(s,2H,Ph),7.52(s,1H,-NH),6.41-6.39(s,1H,-NH),3.53-3.45(m,1H,cyclohexyl-),1.83-1.80(m,2H,cyclohexyl-),1.69-1.66(m,2H,cyclohexyl-),1.57-1.54(m,1H,cyclohexyl-),1.36-1.13,-8.58(m,1H,cyclohexyl-)。13C NMR(400MHz,d6-DMSO)δ(ppm)159.21,147.81,136.30,135.98,135.65,135.33,129.94,127.23,122.36,118.52,53.24,37.91,30.37,29.62。
U 2:3.66g，yield＝82％,1H NMR(400MHz,d6-DMSO)δ(ppm)5.58-5.56(d,2H,J＝16Hz,cyclohexyl-),1.73-1.49(m,4H,cyclohexyl-),1.29-1.00(m,4H,cyclohexyl-)。13C NMR(400MHz,d6-DMSO)δ(ppm)157.07,47.97,33.82,25.79,24.93。
U 3:0.98g，yield＝20％,1H NMR(400MHz,d6-(CD)2CO)δ7.35(s,2H,Ph),7.27(s,1H,Ph)。13C NMR(400MHz,d6-(CD)2CO)δ152.23,141.38,132.18,131.85,131.52,131.19,127.55,124.85,122.14,119.44,118.70,118.67,115.49,115.45,115.41,115.37,115.33。
Figure BDA0001927423180000091
TU 4:1H NMR(400MHz,d6-DMSO)δ(ppm)9.84(s,1H,Ph),8.25(s,2H,Ph),8.16(s,1H,-NH),7.70(s,1H,-NH),4.40(s,1H,-CH-),1.21-1.20(d,6H,-CH3)。
TU 5:1H NMR(400MHz,d6-DMSO)δ(ppm)8.62(s,1H,Ph),7.91(s,1H,-NH),7.26-7.20(t,2H,Ph),4.03(s,1H,-NH),1.90-1.88(d,2H,cyclohexyl-),1.71-1.55(m,3H,cyclohexyl-),1.33-1.04(m,5H,cyclohexyl-)。
the following examples 8-13 provide for catalyzing the ring-opening polymerization of lactone monomers.
Example 8: ring-opening polymerization of delta-valerolactone (delta-VL)
The addition of the catalyst was carried out in a glove box, and the N-heterocycloaexo-olefin (NHOs), Thiourea (TUs) or urea (Us), and initiator (benzyl alcohol BnOH) were added in a Schlenk tube (10mL) in this order, and the reaction solvent was added. The reaction tube was removed from the glove box, monomer delta-valerolactone (delta-VL) (0.45mL,5mmol) was injected, the reaction was carried out at room temperature (20 ℃ -30 ℃) and timing was started, the monomer polymerization was stopped after 4h-24h, and the polymerization was quenched by adding glacial methanol to the system. Centrifugation, washing with ice methanol, separation of the polymer and vacuum drying to constant weight. The obtained polymer is prepared by1H NMR detection, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF Ms) to identify the structure of the polymer. Molecular weight of the Polymer measured by gel permeation chromatography in combination with laser light Scattering apparatus (GPC) ((Mn) and molecular weight distribution (PDI).1H NMR(400MHz,CDCl3)δ(ppm)7.37-7.32(m,5H,Aromatic),5.12(s,2H,ArCH2-),4.10-4.08(t,2H×n,J＝8.0Hz,(-CH2CH2O-)n),3.67-3.64(t,2H,J＝12.0Hz,-CH2CH2OH),2.36-2.32(t,2H×n,J＝16.0Hz,(-OCOCH2CH2-)n),1.68(m,2H×n,(-COCH2CH2CH2-)n),1.67(m,2H×n,(-CH2CH2CH2O-)n)。
The results obtained by catalyzing the ring-opening polymerization of delta-valerolactone with the different reaction conditions and catalyst ratios of catalyst N-heterocycloaexo-olefin (NHO 1)/thiourea (TU1) and initiator (BnOH) are summarized in Table 1 below. In the catalytic polymerization reaction, when Thiourea (TU) or the initiator (BnOH) is not present in the system, the conversion of the monomer can only reach 48% or 52%, while when N-heterocyclic exoolefin (NHO1), thiourea (TU1) and the initiator (BnOH) are simultaneously present, the monomer can reach the degree of substantially complete conversion (table 1, entry 2 and entry 3). The polymerization was carried out in organic solvents of different polarity (tolumen and THF) respectively, and from experimental data it can be seen that the conversion of the monomers is relatively high when reacting in toluene. Meanwhile, the conversion of the monomer is reduced by reducing the concentration of the polymerization reaction system (Table 1, entry 3, entry 4 and entry 5).
TABLE 1. Ring opening polymerization of delta-valerolactone
Figure BDA0001927423180000101
The reaction was carried out using toluene (1mL) as a nonpolar solvent, varying the ratios of N-heterocycloaexo-olefin (NHO1) and thiourea (TU1) added, and the results obtained by the reaction and catalyst ratios under the same conditions for the ring-opening polymerization of delta-valerolactone are summarized in Table 2 below. In screening the best catalytic polymerization conditions, we carried out experiments by adjusting the addition ratio of the N-heterocyclic exoolefin (NHO1) to the thiourea (TU1), and as can be seen from Table 2, the too low or too high proportion of the thiourea (TU1) decreases the conversion of the monomers (entry 1, 71%; entry 4, 65%; entry5, 42%). When the addition ratio of the N-heterocyclic exoolefin (NHO1) to thiourea (TU1) was as given in 1:1 and 1:2, the monomer conversion rate is best, and when the ratio is 1:1.5-1:2, the catalytic activity is higher, and the polymerization can be finished in only 4 hours at room temperature.
TABLE 2 Ring opening polymerization of delta-valerolactone
Figure BDA0001927423180000111
TABLE 3 Ring opening polymerization of delta-valerolactone
Figure BDA0001927423180000112
Figure BDA0001927423180000121
In the table: n.d. represents in1Conversion of monomer in H NMR data was less than 3%; - -represents that no polymer was obtained and the molecular weight (Mn) and molecular weight distribution (PDI) of the polymer were not measured by gel permeation chromatography in combination with a laser light scattering apparatus.
The results obtained from the reaction of different N-heterocyclic exoolefins (NHOs) and different Thioureas (TUs) under the same conditions and with a catalyst ratio catalysing the ring-opening polymerization of delta-valerolactone are summarized in Table 3 below. In N-heterocyclic exo-olefin (NHOs) and different Thiourea (TUs) catalytic systems, three N-heterocyclic exo-olefin compounds including NHO1, NHO2 and NHO3 and three thiourea compounds including TU1, TU2 and TU 3 are respectively screened. The following table 3 shows 9 combinations of experimental data, and from the 9 sets of data in the table, we can see that the catalytic effect of NHO1/TU1 is the best (conversion 97%, table 3, entry 1) in the ring-opening polymerization process of delta-valerolactone catalyzed by NHOs/TUs system, while other combinations are relatively poor (table 3, entries 2-9).
The poly delta valerolactone (PVL) prepared in this example was subjected to1H NMR detection, detecting the obtained1The graph of H NMR is shown in FIG. 2, and this examplePreparation of poly-delta-valerolactone (PVL)1The H NMR chart shows that the chain end group of poly delta-valerolactone (PVL) is benzyloxy, which indicates that the ring-opening polymerization of delta-valerolactone is initiated by benzyl alcohol.
Matrix-assisted laser desorption/tandem time of flight mass spectrometry (MALDI-TOF) detection is carried out on the poly delta-valerolactone (PVL) prepared in the example, and a detected spectrogram is shown in FIG. 3, and FIG. 4 is a partial enlarged view of FIG. 3. Since the molecular weight of the delta-valerolactone monomer is 100.05 and the molecular weight of the benzyl alcohol is 108.06, testing in positive ion mode of MALDI-TOF gave FIG. 3, according to the formula: the molecular weight (Mn) of the polymer is equal to the molecular weight of the monomer times the number of repeat units (n) plus the molecular weight of the initiator benzyl alcohol plus the cation (Na)+Or K+) Molecular weight of (2). The molecular weight of the polymer in FIG. 4 is consistent with this equation, indicating that the ring-opening polymerization is indeed initiated by benzyl alcohol.
Example 9 Ring opening polymerization of ε -caprolactone (. epsilon. -CL)
The addition of the catalyst was carried out in a glove box, and the N-heterocycloaexo-olefin (NHOs), Thiourea (TUs) or urea (Us), and initiator (benzyl alcohol BnOH) were added in a Schlenk tube (10mL) in order, and the reaction solvent (toluene 1mL) was added. The reaction tube was removed from the glove box, monomer epsilon-caprolactone (epsilon-CL) (0.55mL,5mmol) was injected, the reaction was carried out at room temperature (20-30 ℃ C.), timing was started, the polymerization of the monomer was stopped after 1min-24h, and the polymerization was quenched by adding glacial methanol to the system. Centrifugation, washing with ice methanol, separation of the polymer and vacuum drying to constant weight. The molecular weight (Mn) and molecular weight distribution (PDI) of the resulting polymer were measured by gel permeation chromatography in combination with a laser light scattering apparatus (GPC).
The results obtained for the reaction of different N-heterocycloaexoolefins (NHOs) and different Thioureas (TUs) under different conditions (a, b different concentrations, a: N (e-caprolactone): V (toluene): 5mmol:1mL, b: N (e-caprolactone): V (toluene): 1mmol:1mL) and the catalyst ratio for the ring-opening polymerization of e-caprolactone (e-CL) are summarized in table 4 below. The catalytic activity was low when different N-heterocyclic exoolefins (NHOs) were co-catalyzed with TU1 or TU 3 regardless of high or low monomer concentration (table 4, entry 1, 2, entry5, entry 7), and similarly, the catalytic activity was high and the reaction rate was fast when different N-heterocyclic exoolefins (NHOs) were co-catalyzed with TU2 regardless of high or low monomer concentration (table 4, entry 3, 4, entry 6). However, with very high catalytic activity and fast reaction rate, there was a slight increase in the molecular weight distribution of the polymers obtained by co-catalytic polymerization of N-heterocycloolefins (NHOs) with TU2 (table 4, PDI 1.62, 1.50, 1.34, entry 3, 4, entry 6).
TABLE 4 Ring-opening polymerization of epsilon-caprolactone
Figure BDA0001927423180000131
In the table: a. b represents different concentrations, a represents n (. epsilon. -caprolactone): v (toluene) ═ 5mmol:1mL, b represents n (epsilon-caprolactone): 1mL of 1mmol of V (toluene); n.d. represents in1Conversion of monomer in H NMR data was less than 3%; - -represents that no polymer was obtained and the molecular weight (Mn) and molecular weight distribution (PDI) of the polymer were not measured by gel permeation chromatography in combination with a laser light scattering apparatus.
Example 10: ring opening polymerization of gamma-butyrolactone (GBL)
The addition of the catalyst was carried out in a glove box, and the N-heterocycloaexoolefin (NHO2), thiourea (TU2), and initiator (benzyl alcohol BnOH) were added in order to a Schlenk tube (10mL), and the reaction solvent (toluene, 1mL) was added. The reaction tube was removed from the glove box, monomer gamma-butyrolactone (GBL) (1mL,13mmol) was injected, the reaction was carried out at low temperature (-40 ℃ C.), timing was started, the monomer polymerization was stopped after 9h-24h, and the polymerization reaction was quenched by adding glacial methanol to the system. Centrifugation, washing with ice methanol, separation of the polymer and vacuum drying to constant weight. The molecular weight (Mn) and molecular weight distribution (PDI) of the resulting polymer were measured by gel permeation chromatography in combination with a laser light scattering apparatus (GPC).
The results obtained from the reaction of N-heterocycloaexo-olefin (NHO2) and thiourea (TU2) under different conditions and the catalytic ratio for the ring-opening polymerization of gamma-butyrolactone (GBL) are summarized in Table 5 below. Under low temperature conditions, benzyl alcohol is used as an initiator, N-heterocyclic exoolefin (NHO2) and thiourea (TU2) jointly catalyze the ring-opening polymerization reaction of butyrolactone (GBL), the catalytic polymerization effect of the N-heterocyclic exoolefin (NHO2) and thiourea (TU2) on butyrolactone (GBL) is observed by changing the amount (from 1% to 0.2%) of the catalytic system (N-heterocyclic exoolefin (NHO2) and thiourea (TU2)), and as can be seen from Table 5, when the amount of the catalyst is as low as 0.2%, the catalytic polymerization effect of butyrolactone (GBL) still exists.
TABLE 5. Ring opening polymerization of gamma-butyrolactone
Figure BDA0001927423180000141
Example 11: ring opening polymerization of DL-lactide (DL-LA)
The addition of the catalyst and monomer was carried out in a glove box, and the N-heterocycloaexo-olefin (NHOs), Thiourea (TUs) or urea (Us), and initiator (benzyl alcohol BnOH) were added in a Schlenk tube (10mL) in order, and the reaction solvent (tetrahydrofuran THF, 1mL) was added. Adding monomer DL-lactide (144mg,1mmol), removing the reaction tube from the glove box, reacting at room temperature (20-30 ℃), timing, adding methanol into the system after the monomer polymerization is stopped, and quenching the polymerization reaction. Centrifugation, washing with ice methanol, separation of the polymer and vacuum drying to constant weight. The molecular weight (Mn) and molecular weight distribution (PDI) of the resulting polymer were measured by gel permeation chromatography in combination with a laser light scattering apparatus (GPC).
TABLE 6 Ring opening polymerization of DL-lactide
Figure BDA0001927423180000142
Figure BDA0001927423180000151
The results obtained with benzyl alcohol as initiator and N-heterocyclic exo-olefin (NHO1) and thiourea (TU1) concertedly catalysing the ring-opening polymerisation of DL-lactide at 25 ℃ are summarized in Table 6 below. As is apparent from Table 6, when the amount of N-heterocyclic exoolefin (NHO1) added was 1% and the degree of polymerization was 50, the reaction rate was high; as the amount of N-heterocyclic exoolefin (NHO1) added continues to decrease and the degree of polymerization increases, the reaction rate slows and the monomer conversion decreases.
Example 12 Ring opening polymerization of trimethylene carbonate
The addition of the catalyst and monomer was carried out in a glove box, the N-heterocyclic exo-olefins (NHOs), the ureas (Us), the initiator (benzyl alcohol) were added in a Schlenk tube (10mL) in order, and the reaction solvent (2mL) was added (see Table 7). The monomer trimethylene carbonate (204.2mg,2mmol) was added, the reaction tube was removed from the glove box, the reaction was carried out at room temperature (20-30 ℃), and after 1 hour of the polymerization of the monomer was stopped, glacial methanol was added to the system to quench the polymerization. Centrifugation, washing with ice methanol, separation of the polymer and vacuum drying to constant weight. The molecular weight (Mn) and molecular weight distribution (PDI) of the resulting polymer were measured by gel permeation chromatography in combination with a laser light scattering apparatus (GPC).
In Table 7, the data of the polymer obtained by ring-opening polymerization of trimethylene carbonate under the concerted catalysis of N-heterocyclic exoolefin (NHO1) and thiourea (U1) show that when NHO1/U1/BnOH/M (trimethylene carbonate) ═ 1:2:2:500 is reacted in toluene, the conversion of the monomer is higher than that in tetrahydrofuran. Indicating that less polar solvents are more favorable for the polymerization of trimethylene carbonate. The molecular weight (Mn) obtained in the polymerization reaction is relatively low and greatly differs from the designed theoretical molecular weight (M/I: 250, theoretical molecular weight 25500).
TABLE 7 Ring opening polymerization of trimethylene carbonate
Figure BDA0001927423180000152
In the table: m represents monomeric trimethylene carbonate.
Respectively, poly-epsilon-caprolactone (PCL), poly-gamma-butyrolactone (PGBL), and poly-trimethylene carbonate prepared in examples 9, 10, and 11 were subjected to1H NMR detection, detecting the obtained1The H NMR charts are shown in FIG. 5, FIG. 6 and FIG. 7, respectivelyAnd the detection result shows that chain end groups of poly-epsilon-caprolactone (PCL), poly-gamma-butyrolactone (PGBL) and poly-trimethylene carbonate are benzyloxy, which indicates that the epsilon-caprolactone, the gamma-butyrolactone and the trimethylene carbonate are all ring-opening polymerization reactions which take place under the synergistic catalysis of N-heterocyclic exo-olefin (NHO1) and thiourea (U1) by using benzyl alcohol as an initiator.
The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the illustrated embodiments, and any other changes, modifications, combinations, substitutions and simplifications which do not depart from the spirit and principle of the present invention are deemed to be equivalent substitutions and shall be included within the protection scope of the present invention.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (4)

1. A non-metal catalytic system for the ring-opening polymerization of lactone by organic concerted catalysis is characterized by that under the protection of inert gas, the lactone is used as monomer, and in organic solventN-the heterocyclic exo-olefin and thiourea are co-catalyzed or consist ofN-the heterocyclic exo-olefin and urea are co-catalyzed and the lactone is initiated by the alcohol compound to undergo ring-opening polymerization;
wherein N-heterocyclic exo-olefin NHO2 and thiourea TU2 are subjected to concerted catalysis, and benzyl alcohol is used for initiating gamma-butyrolactone to carry out ring-opening polymerization reaction;
n-heterocyclic exo-olefin NHO1 or NHO2 and thiourea TU1 or thiourea TU2 are used for concerted catalysis, and benzyl alcohol is used for initiating delta-valerolactone to carry out ring-opening polymerization;
n-heterocyclic exo-olefin NHO3 is synergistically catalyzed by thiourea TU1 or thiourea TU2, and benzyl alcohol is used for initiating delta-valerolactone to carry out ring-opening polymerization;
n-heterocyclic exo-olefin NHO1 or NHO2 and thiourea TU1 are subjected to concerted catalysis, and benzyl alcohol is used for initiating epsilon-caprolactone to carry out ring-opening polymerization reaction;
n-heterocyclic exo-olefin NHO1 or NHO3 and thiourea TU2 are subjected to concerted catalysis, and benzyl alcohol is used for initiating epsilon-caprolactone to carry out ring-opening polymerization reaction;
n-heterocyclic exo-olefin NHO3 and thiourea TU2 are cooperatively catalyzed, and benzyl alcohol is used for initiating epsilon-caprolactone to carry out ring-opening polymerization reaction;
n-heterocyclic exo-olefin NHO1 and thiourea TU1 are cooperatively catalyzed, and benzyl alcohol is used for initiating DL-lactide to carry out ring-opening polymerization reaction;
n-heterocyclic exo-olefin NHO1 was co-catalyzed with urea U1 and benzyl alcohol initiated to ring-opening polymerization of trimethylene carbonate;
the structural formula of the N-heterocyclic exo-olefin NHO1 is shown as
Figure 82867DEST_PATH_IMAGE002
The structural formula of the N-heterocyclic exo-olefin NHO2 is shown as
Figure DEST_PATH_IMAGE004
The structural formula of the N-heterocyclic exo-olefin NHO3 is shown as
Figure DEST_PATH_IMAGE006
The structural formula of thiourea TU1 is
Figure DEST_PATH_IMAGE007
The structural formula of thiourea TU2 is shown as follows;
Figure DEST_PATH_IMAGE008
urea U1 of the formula
Figure DEST_PATH_IMAGE009
。
2. The metal-free catalytic system of claim 1, wherein the metal-free catalytic system is selected from the group consisting ofN-the molar ratio between the heterocyclic exoolefin, thiourea or urea and the lactone is 1: (0.5-10): (100-1000); the reaction temperature of the ring-opening polymerization reaction is-60 ℃ to 60 ℃, and the reaction time is 1s to 24 h; the concentration of the lactone is 1-10 mol/L.
3. The metal-free catalytic system of claim 1, wherein the molar ratio of the N-heterocyclic exoolefin to thiourea or urea is 1: 2.
4. The metal-free catalytic system of claim 1, wherein the organic solvent is toluene, tetrahydrofuran, or dichloromethane.
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