Method for catalyzing and regulating molecular weight distribution of polymer by using two-component catalyst for preparing polyester through ring-opening polymerization
By regulating the molecular weight distribution of polymers using (sulfur) urea catalyst and organic alkali reagent, the problem of regulation difficulties in the prior art is solved, efficient and simple single peak molecular weight distribution is achieved, and the mechanical and processing performance of the polymer is improved.
Patent Information
- Application Number
- CN202510525194.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-07-25
AI Technical Summary
The prior art is difficult to effectively regulate polymer molecular weight distribution over a wide range, especially in controlling dispersion and shape, and traditional methods are cumbersome and may lead to multimodal molecular weight distribution.
Using a (sulfur) urea catalyst and two organic alkali reagents with different activities, the regulation of the polymer molecular weight distribution index is achieved by adjusting the monomer equivalent and proportion, and a polymer with a single peak molecular weight distribution is provided.
It realizes a simple process, low cost, efficient and controllable polymerization reaction, and the prepared polyester does not contain metal residues and has good mechanical properties and processing properties.
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Figure CN120365544A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical fields of organocatalysis and polymer materials, and particularly relates to a method for controlling the molecular weight distribution of polymers by organocatalysis. Background Art
[0002] Polymers are different from small molecules in that they do not have a unique molecular weight but exhibit a molecular weight distribution (MWD). The dispersity is a measure of the width of the MWD, which describes the uniformity of the molecular weights of the individual chains in the polymer material. The dispersity is a key parameter that determines the physical properties of the material, where M w and M n are the weight-average molecular weight and the number-average molecular weight, respectively. In living / controlled polymerization, a narrow molecular weight distribution usually aims at good control of the molecular weight and high end-group functionality. The development of controlled polymerization techniques provides an effective means for preparing various structurally precise functional polymer materials. However, a low dispersity of polymers is not sufficient for many applications because low-dispersity and high-dispersity polymers exhibit complementary properties and functions. In fact, the molecular weight distribution can significantly affect the processability of the polymer material melt, the glass transition temperature, and rheological properties (such as shear and extensional viscosities, storage modulus, etc.), as well as the self-assembly (spacing and morphology) of polymer samples in bulk and in solution. Therefore, in order to improve physical properties (such as miscibility and processability), polymers with a wider molecular weight distribution are sometimes required. Thus, manipulating the polymer molecular weight and shape is an important topic in living / controlled polymerization and remains challenging.
[0003] The most traditional method for adjusting the molecular weight distribution is to mix polymer samples with pre-synthesized various molecular weight compositions. This method can indeed obtain a wide range. However, due to the need for multiple syntheses and subsequent purifications (possibly requiring mixing up to 20 polymers), this can be cumbersome and time-consuming, and usually results in a multimodal molecular weight distribution. Boyer, Xu et al. successfully and simply adjusted the dispersity by using flow chemistry to adjust reagent concentration, pump flow rate, viscosity, and residence time. However, this method may be incompatible with heterogeneous systems (e.g., surface-initiated polymerization and brush synthesis), and requires extensive optimization of all flow components and additional equipment (Corrigan, N.; Manahan, R.; Lew, Z. T.; Yeow, J.; Xu, J.; Boyer, C., Copolymers with Controlled Molecular Weight Distributions and Compositiona1 Gradients through Flow Polymerization. Macromolecules 2018, 51(12), 4553 - 4563). Recently, alternative examples of polymerization schemes have been reported in which polymers can be controlled through polymerization operations. For example, Goto and his colleagues used a small amount of copolymer to regulate methacrylate in reversible complexation-mediated polymerization, while Chiu's group reported the use of photochromic initiators in cationic polymerization. Matyjaszewski and his colleagues made independent customizations in ATRP by changing the concentrations of copper and iron catalysts respectively. Despite these significant advances, a major weakness of current strategies is that they are limited to the monomer scope because they are usually only applicable to a specific monomer class. Other issues include polymers showing low end-group fidelity and multimodal molecular weight distributions (MWDs), limited demonstrations of block copolymers, complex multi-component systems, narrow accessible value ranges, low initiator efficiency, and the use of copolymers, additives, and pump-assisted procedures; the latter may be incompatible with surface polymerization. Arthina et al. reported a strategy of mixing chain transfer agents with different chain transfer constants in RAFT polymerization and PET-RAFT polymerization, which provided a unimodal molecular weight distribution in all cases and allowed convenient access to a series of different dispersity values. This method can regulate the molecular weight distribution index within a range.
[0004] In summary, recent advances in polymer science have allowed the development of general and easily controllable methods, but there is still room for further research and exploration in terms of both controlling the dispersity of MWD and its shape. It is very necessary to develop more and more methods for regulating the polymer molecular weight distribution. Summary of the Invention
[0005] In view of the deficiencies of the existing technologies and inspired by Arthina et al., the object of the present invention is to provide a (thiourea)-based binary catalytic system for regulating the molecular weight distribution of polymers. By using a thiourea catalyst and two base reagents with sufficiently different chain transfer activities, the polydispersity index of the polymer is regulated within a certain range. Moreover, this method has the advantages of simple process, low cost, high reaction activity, high reaction rate, controllable process, and the prepared polyester has the advantage of being free of metal residues.
[0006] The technical solution for achieving the above object is as follows:
[0007] A method for regulating the molecular weight distribution of polymers:
[0008] It is achieved by using a (thiourea)-based catalyst and mixing two sufficiently different organic bases in different proportions and changing the equivalent of the monomer to control, and providing a polymer with a unimodal molecular weight distribution within a wide dispersity range.
[0009] The molecular formula of the (thiourea) catalyst is shown in Formula (I):
[0010]
[0011] The present invention also provides the synergistic catalysis of several different organic base reagents and the (thiourea) catalyst as follows:
[0012]
[0013] Beneficial effects
[0014] By means of the above solution, the present invention has at least the following advantages:
[0015] (1) The process is simple, the cost is low, the reaction activity is high, the reaction rate is high, the process is controllable, and the prepared polyester has the advantage of being free of metal residues.
[0016] (2) By using a thiourea catalyst and two organic bases with sufficiently different chain transfer activities, the present invention can regulate the polydispersity index of the polymer within a certain range and provide a polymer with a unimodal molecular weight distribution within a wide dispersity range. The polymer with a wide molecular weight distribution can ensure the mechanical properties of the polymer while having good processing properties. Brief description of the drawings
[0017] The embodiments of the present invention will be described in detail in conjunction with the accompanying drawings, where
[0018] Figure 1 : 1H NMR spectrum of poly(L-lactide) in Example 2;
[0019] Figure 2: Chromatogram in the size exclusion chromatography analysis of the poly-L-lactide prepared in Example 8;
[0020] Figure 3 : Chromatogram in the size exclusion chromatography analysis of the poly-L-lactide prepared in Example 16;
[0021] Figure 4 : 1 1H NMR spectrum of the catalyst I prepared in Example 1;
[0022] Figure 5 : 13 13C NMR spectrum of the catalyst I prepared in Example 1; Detailed implementation manner
[0023] The present invention can be further illustrated by the following examples, which are for illustration rather than limitation of the present invention. Any ordinary person skilled in the art can understand that these examples do not limit the present invention in any way, and appropriate modifications and data transformations can be made without departing from the essence of the present invention and deviating from the scope of the present invention.
[0024] The 1H nuclear magnetic resonance spectrum involved in the examples was measured using a Bruker Ascend TM-400 type nuclear magnetic resonance spectrometer of Bruker Corporation, and the deuterated reagent used was deuterated chloroform (CDCl3).
[0025] The structure of the RAFT reagent used in the examples is as follows:
[0026]
[0027] Example 1:
[0028] The preparation method of the catalyst (I) is as follows: Cyclohexylamine (0.42 mL, 3.70 mmol) was added to a THF (4 mL) solution of p-(trifluoromethyl)phenyl isothiocyanate (0.75 g, 3.70 mmol). The reaction mixture was stirred at 30 °C for 2 hours. THF was removed in vacuo to obtain an off-white solid. The solid was washed with n-pentane (4 × 10 mL).
[0029] Example 2:
[0030] In the glove box, weigh (thiourea) catalyst (0.006 g, 0.02 mmol), compound 1 (0.002 g, 0.01 mmol), compound 2 (0.002 g, 0.01 mmol), and phenylpropanol (0.94 μl, 0.0069 mmol) and add them to the clamp mouth bottle 1, and dissolve them with 0.5 ml of THF.
[0031] Weigh lactide (0.1 g, 0.69 mmol) with another clamp-neck bottle 2, add 0.5 ml of THF, and dissolve it by gentle shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the lactide in clamp-neck bottle 2 and inject it into clamp-neck bottle 1, and stir the reaction.
[0032] The reaction was quenched with benzoic acid 210 s after the start of the polymerization reaction. The conversion rate was 94%, the number-average molecular weight Mn of poly(lactide) was 14,500 g / mol, and the molecular weight distribution PDI was 1.55.
[0033] Example 3:
[0034] In the glove box, weigh (thiourea) catalyst (0.006 g, 0.02 mmol), compound 1 (0.0004 g, 0.002 mmol), compound 2 (0.003 g, 0.018 mmol), and phenylpropanol (0.94 μl, 0.0069 mmol) and add them to clamp-neck bottle 1, and dissolve them with 0.5 ml of THF.
[0035] Weigh lactide (0.1 g, 0.69 mmol) with another clamp-neck bottle 2, add 0.5 ml of THF, and dissolve it by gentle shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the lactide in clamp-neck bottle 2 and inject it into clamp-neck bottle 1, and stir the reaction.
[0036] The reaction was quenched with benzoic acid 540 s after the start of the polymerization reaction. The conversion rate was 96%, the number-average molecular weight Mn of poly(lactide) was 13,900 g / mol, and the molecular weight distribution PDI was 1.45.
[0037] Example 4:
[0038] In the glove box, weigh (thiourea) catalyst (0.006 g, 0.02 mmol), compound 1 (0.003 g, 0.018 mmol), compound 2 (0.0003 g, 0.002 mmol), and phenylpropanol (0.94 μl, 0.0069 mmol) and add them to clamp-neck bottle 1, and dissolve them with 0.5 ml of THF.
[0039] Weigh lactide (0.1 g, 0.69 mmol) with another clamp-neck bottle 2, add 0.5 ml of THF, and dissolve it by gentle shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the lactide in clamp-neck bottle 2 and inject it into clamp-neck bottle 1, and stir the reaction.
[0040] The reaction was quenched with benzoic acid 540 s after the start of the polymerization reaction. The conversion rate was 97%, and the number-average molecular weight M n of poly(lactide) was 14,100 g / mol, and the molecular weight distribution PDI was 1.47.
[0041] Example 5:
[0042] In a glove box, weigh out (thiourea) catalyst (0.006 g, 0.02 mmol), compound 1 (0.002 g, 0.01 mmol), compound 2 (0.002 g, 0.01 mmol), and phenylpropanol (0.94 μl, 0.0069 mmol) and add them to clamp bottle 1, and dissolve with 0.5 ml of THF.
[0043] Weigh out 1-lactide (0.2 g, 1.38 mmol) with another clamp bottle 2, add 1.5 ml of THF, and dissolve it by gently shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the 1-lactide in clamp bottle 2 and inject it into clamp bottle 1, and stir the reaction.
[0044] Quench the reaction with benzoic acid 10 min after the start of the polymerization reaction, the conversion rate is 98%, and the number-average molecular weight M of poly-1-lactide n is 33100 g / mol, and the molecular weight distribution PDI is 1.37.
[0045] Example 6:
[0046] In a glove box, weigh out (thiourea) catalyst (0.006 g, 0.02 mmol), compound 1 (0.003 g, 0.018 mmol), compound 2 (0.0003 g, 0.002 mmol), and phenylpropanol (0.94 μl, 0.0069 mmol) and add them to clamp bottle 1, and dissolve with 0.5 ml of THF.
[0047] Weigh out 1-lactide (0.2 g, 1.38 mmol) with another clamp bottle 2, add 1.5 ml of THF, and dissolve it by gently shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the 1-lactide in clamp bottle 2 and inject it into clamp bottle 1, and stir the reaction.
[0048] Quench the reaction with benzoic acid 20 min after the start of the polymerization reaction, the conversion rate is 97%, and the number-average molecular weight M of poly-1-lactide n is 28100 g / mol, and the molecular weight distribution PDI is 1.26.
[0049] Example 7:
[0050] In a glove box, weigh out (thiourea) catalyst (0.006 g, 0.02 mmol), compound 1 (0.003 g, 0.018 mmol), compound 2 (0.0003 g, 0.002 mmol), and phenylpropanol (0.94 μl, 0.0069 mmol) and add them to clamp bottle 1, and dissolve with 0.5 ml of THF.
[0051] Weigh 1-lactide (0.2 g, 1.38 mmol) with another jaw bottle 2, add 1.5 ml of THF, and dissolve it by gently shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the 1-lactide in jaw bottle 2 and inject it into jaw bottle 1, and stir the reaction.
[0052] After 20 min from the start of the polymerization reaction, quench the reaction with benzoic acid, the conversion rate is 97%, and the number-average molecular weight M of poly-1-lactide n is 29000 g / mol, and the molecular weight distribution PDI is 1.25.
[0053] Example 8:
[0054] In the glove box, weigh (thiourea) catalyst (0.006 g, 0.02 mmol), compound 1 (0.002 g, 0.01 mmol), compound 2 (0.002 g, 0.01 mmol), phenylpropanol (0.94 μl, 0.0069 mmol) and add them to jaw bottle 1, and dissolve them with 0.5 ml of THF.
[0055] Weigh 1-lactide (0.5 g, 3.45 mmol) with another jaw bottle 2, add 4.5 ml of THF, and dissolve it by gently shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the 1-lactide in jaw bottle 2 and inject it into jaw bottle 1, and stir the reaction.
[0056] After 40 min from the start of the polymerization reaction, quench the reaction with benzoic acid, the conversion rate is 95%, and the number-average molecular weight M of poly-1-lactide n is 61400 g / mol, and the molecular weight distribution PDI is 1.22.
[0057] Example 9:
[0058] In the glove box, weigh (thiourea) catalyst (0.006 g, 0.02 mmol), compound 1 (0.003 g, 0.018 mmol), compound 2 (0.0003 g, 0.002 mmol), phenylpropanol (0.94 μl, 0.0069 mmol) and add them to jaw bottle 1, and dissolve them with 0.5 ml of THF.
[0059] Weigh 1-lactide (0.5 g, 3.45 mmol) with another jaw bottle 2, add 4.5 ml of THF, and dissolve it by gently shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the 1-lactide in jaw bottle 2 and inject it into jaw bottle 1, and stir the reaction.
[0060] The reaction was quenched with benzoic acid 50 min after the start of the polymerization reaction. The conversion rate was 97%, and the number-average molecular weight M of poly(1-lactide) n was 58,300 g / mol, and the polydispersity index PDI of the molecular weight was 1.07.
[0061] Example 10:
[0062] In a glove box, (thiourea) catalyst (0.006 g, 0.02 mmol), Compound 1 (0.003 g, 0.018 mmol), Compound 2 (0.0003 g, 0.002 mmol), and phenylpropanol (0.94 μl, 0.0069 mmol) were weighed and added to Clamp Bottle 1, and dissolved with 0.5 ml of THF.
[0063] Using another Clamp Bottle 2, 1-lactide (0.5 g, 3.45 mmol) was weighed, 4.5 ml of THF was added, and it was gently shaken and dissolved. The bottle cap was clamped tightly, and the reaction bottle was quickly placed on a 25 °C heating block. The 1-lactide in Clamp Bottle 2 was aspirated and injected into Clamp Bottle 1, and the reaction was stirred.
[0064] The reaction was quenched with benzoic acid 50 min after the start of the polymerization reaction. The conversion rate was 92%, and the number-average molecular weight M of poly(1-lactide) n was 60,100 g / mol, and the polydispersity index PDI of the molecular weight was 1.07.
[0065] Example 11:
[0066] In a glove box, (thiourea) catalyst (0.03 g, 0.099 mmol), Compound 1 (0.01 g, 0.058 mmol), Compound 2 (0.01 g, 0.058 mmol), and phenylpropanol (4.5 μl, 0.033 mmol) were weighed and added to Clamp Bottle 1, and dissolved with 0.5 ml of THF.
[0067] Using another Clamp Bottle 2, 1-lactide (0.1 g, 0.69 mmol) was weighed, 0.5 ml of THF was added, and it was gently shaken and dissolved. The bottle cap was clamped tightly, and the reaction bottle was quickly placed on a 25 °C heating block. The 1-lactide in Clamp Bottle 2 was aspirated and injected into Clamp Bottle 1, and the reaction was stirred.
[0068] The reaction was quenched with benzoic acid 15 s after the start of the polymerization reaction. The conversion rate was 96%, and the number-average molecular weight M of poly(1-lactide) n was 3,700 g / mol, and the polydispersity index PDI of the molecular weight was 2.04.
[0069] Example 12:
[0070] In the glove box, weigh (thiourea) catalyst (0.03 g, 0.099 mmol), compound 1 (0.015 g, 0.09 mmol), compound 2 (0.0015 g, 0.01 mmol), and phenylpropanol (4.5 μl, 0.033 mmol) and add them to flask 1, then dissolve with 0.5 ml of THF.
[0071] Weigh 1-lactide (0.1 g, 0.69 mmol) with another flask 2, add 0.5 ml of THF, and dissolve it by gently shaking. Clamp the bottle cap tightly, quickly place the reaction flask on a 25 °C heating block, suck out the 1-lactide in flask 2 and inject it into flask 1, then stir the reaction.
[0072] Quench the reaction with benzoic acid 15 s after the start of the polymerization reaction, with a conversion rate of 90%, and the number-average molecular weight M of poly(1-lactide) n is 3000 g / mol, and the molecular weight distribution PDI is 1.85.
[0073] Example 13:
[0074] In the glove box, weigh (thiourea) catalyst (0.03 g, 0.099 mmol), compound 1 (0.002 g, 0.01 mmol), compound 2 (0.015 g, 0.09 mmol), and phenylpropanol (4.5 μl, 0.033 mmol) and add them to flask 1, then dissolve with 0.5 ml of THF.
[0075] Weigh 1-lactide (0.1 g, 0.69 mmol) with another flask 2, add 0.5 ml of THF, and dissolve it by gently shaking. Clamp the bottle cap tightly, quickly place the reaction flask on a 25 °C heating block, suck out the 1-lactide in flask 2 and inject it into flask 1, then stir the reaction.
[0076] Quench the reaction with benzoic acid 15 s after the start of the polymerization reaction, with a conversion rate of 94%, and the number-average molecular weight M of poly(1-lactide) n is 3080 g / mol, and the molecular weight distribution PDI is 1.85.
[0077] Example 14:
[0078] In the glove box, weigh (thiourea) catalyst (0.012 g, 0.04 mmol), compound 1 (0.004 g, 0.023 mmol), compound 2 (0.004 g, 0.023 mmol), and phenylpropanol (1.88 μl, 0.0138 mmol) and add them to flask 1, then dissolve with 0.5 ml of THF.
[0079] Weigh 1-lactide (0.1 g, 0.69 mmol) using another clamp-neck bottle 2, add 0.5 ml of THF, and dissolve it by gentle shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the 1-lactide in clamp-neck bottle 2 and inject it into clamp-neck bottle 1, and stir the reaction.
[0080] After 15 s from the start of the polymerization reaction, quench the reaction with benzoic acid, the conversion rate is 98%, and the number-average molecular weight M of poly-1-lactide n is 7100 g / mol, and the molecular weight distribution PDI is 1.77.
[0081] Example 15:
[0082] In the glove box, weigh (thio)urea catalyst (0.012 g, 0.04 mmol), compound 1 (0.006 g, 0.036 mmol), compound 2 (0.0006 g, 0.004 mmol), and phenylpropanol (1.88 μl, 0.0138 mmol) and add them to clamp-neck bottle 1, and dissolve them with 0.5 ml of THF.
[0083] Weigh 1-lactide (0.1 g, 0.69 mmol) using another clamp-neck bottle 2, add 0.5 ml of THF, and dissolve it by gentle shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the 1-lactide in clamp-neck bottle 2 and inject it into clamp-neck bottle 1, and stir the reaction.
[0084] After 15 s from the start of the polymerization reaction, quench the reaction with benzoic acid, the conversion rate is 96%, and the number-average molecular weight M of poly-1-lactide n is 6500 g / mol, and the molecular weight distribution PDI is 1.50.
[0085] Example 16:
[0086] In the glove box, weigh (thio)urea catalyst (0.012 g, 0.04 mmol), compound 1 (0.0008 g, 0.004 mmol), compound 2 (0.006 g, 0.036 mmol), and phenylpropanol (1.88 μl, 0.0138 mmol) and add them to clamp-neck bottle 1, and dissolve them with 0.5 ml of THF.
[0087] Weigh 1-lactide (0.1 g, 0.69 mmol) using another clamp-neck bottle 2, add 0.5 ml of THF, and dissolve it by gentle shaking. Clamp the bottle cap tightly, quickly place the reaction bottle on a 25 °C heating block, suck out the 1-lactide in clamp-neck bottle 2 and inject it into clamp-neck bottle 1, and stir the reaction.
[0088] After 15 s from the start of the polymerization reaction, quench the reaction with benzoic acid, the conversion rate is 97%, and the number-average molecular weight M of poly-1-lactide nIt is 6500 g / mol, and the polydispersity index (PDI) of the molecular weight distribution is 1.55.
Claims
1. A method for regulating the molecular weight distribution of a polymer, characterized in that: It includes the following steps: (1) Synthesis of (thiourea) catalyst: (Trifluoromethyl)phenyl isothiocyanate and cyclohexylamine are synthesized into (thiourea) catalyst under certain conditions. The molecular formula of the catalyst is shown in formula (I): (2) Control is achieved by a (thiourea) catalyst and mixing two RAFT reagents with sufficiently different chain transfer activities in different proportions and changing the equivalents of monomers, providing polymers with a unimodal molecular weight distribution within a wide dispersity range.
2. The preparation method according to claim 1, wherein the preparation method of the catalyst of formula I is: Step 1: Add cyclohexylamine (0.42 mL, 3.70 mmol) to a THF (4 mL) solution of (trifluoromethyl)phenyl isothiocyanate (0.75 g, 3.70 mmol); Step 2: Stir the reaction mixture at 30 °C for 2 hours; Step 3: Remove THF from the mixture obtained in Step 2 under vacuum to obtain an off-white solid, and wash the solid with n-pentane (4 × 10 mL).
3. The preparation method according to claim 1, characterized in that, The several RAFT reagents with different chain transfer activities are as follows:
4. The preparation method according to claim 1, characterized in that, The alcohol initiator is selected from 3-phenylpropanol, and the cyclic monomer is selected from L-lactide.
5. The preparation method according to claim 1, characterized in that, The ring-opening polymerization reaction is as follows: The cyclic monomer, the catalyst of formula I, the reagent of formula 2, and the alcohol initiator are added to a reaction vessel for reaction. Among them, the good solvent is selected from dichloromethane; The reaction conditions for ring-opening polymerization are: the reaction temperature is 25 °C, and the reaction time is 5 s to 50 min; the molar ratio of the catalyst of formula I to the feed of formula II is 1:1; the molar ratio of the catalyst of formula I to the cyclic monomer is 3:20 to 500; the molar ratio of the catalyst of formula I to the alcohol initiator is 3 to 1.