A fully isotactic poly(methyl methacrylate) and a method for its preparation

Abstract

The present application relates to a kind of isotactic poly (methyl methacrylate) and its preparation method, belong to polymer synthesis technical field, solve the existing preparation stereoregular poly (methyl methacrylate) The method template preparation is complex, and the problem of tedious operation.The preparation method includes: step 1: additive, initiator, methyl methacrylate are added to reaction vessel, mixed uniformly, and bulk polymerization reaction is carried out, and polymer solution is obtained;Step 2: solvent is added to dissolve the polymer solution obtained in step 1;The dissolved polymer solution is dropped into precipitant to make the polymer completely precipitate, and is dried to constant weight, to obtain isotactic poly (methyl methacrylate).

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis technology, and in particular to a isotactic polymethyl methacrylate and its preparation method. Background Technology

[0002] Polymethyl methacrylate (PMMA) is an important thermoplastic material with wide applications in plastics, adhesives, construction, and optical materials. However, PMMA has relatively weak mechanical properties, making it less effective in applications requiring high loads and impacts. To overcome this limitation, researchers are working to develop new modification techniques and high-strength composite materials, aiming to improve PMMA's mechanical properties while maintaining its ease of processing. The polymer's structure is crucial to its performance and applications.

[0003] Free radical polymerization is one of the main methods for synthesizing polymers, but due to the uncontrollable nature of the reaction process, most of the obtained polymers are random polymers. Currently, the main means of controlling the stereoregularity of polymers include preparing complex templates or introducing Lewis acids, but these methods are often costly, complex, and environmentally polluting. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a method for preparing stereoregular polymethyl methacrylate, thereby solving the problems of complex procedures and cumbersome operation in existing methods for preparing stereoregular polymethyl methacrylate.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing isotactic polymethyl methacrylate using bulk polymerization, comprising the following steps:

[0007] Step 1: Add the ionic liquid, initiator, and methyl methacrylate to the reaction vessel, mix thoroughly, and carry out bulk polymerization to obtain a polymer solution;

[0008] Step 2: Add solvent to dissolve the polymer solution obtained in Step 1; add the dissolved polymer solution to a precipitant to precipitate the polymer, dry it, and obtain isotactic polymethyl methacrylate.

[0009] Optionally, in step 1, the ionic liquid is selected from one or more of the following structures:

[0010]

[0011] Optionally, in step 1, the reaction temperature is 60–90°C.

[0012] Optionally, the amount of initiator is 0.01-1 wt% of the amount of methyl methacrylate.

[0013] Alternatively, the initiator may include azobisisobutyronitrile (AIBN).

[0014] Optionally, in step 2, the precipitant is methanol.

[0015] Optionally, in step 2, the drying is carried out in a vacuum drying oven at 60°C.

[0016] Optionally, in step 2, the solvent is acetone.

[0017] Optionally, in step 1, the reaction temperature is 65–85°C.

[0018] Secondly, the present invention provides a polymethyl methacrylate rich in isotactic structure, wherein the polymethyl methacrylate is prepared by the above-mentioned preparation method and has an isotactic regularity of 35%-50% and a molecular weight distribution of 1.49-2.11.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0020] (1) This invention uses ionic liquids as additives in bulk polymerization. Based on the designable structure of ionic liquids, the polymer chain structure is precisely constructed using the synergistic effect of the anions and cations in the ionic liquid with methyl methacrylate, thereby improving the isotactic regularity of polymethyl methacrylate. Specifically, the isotactic regularity of the polymethyl methacrylate prepared by the method of this invention is 35%-50%, and the molecular weight distribution is very narrow, only 1.49-2.11.

[0021] (2) The preparation method of the present invention does not require the preparation of a template as in the prior art. Therefore, the preparation method of the present invention is simple to operate, requires fewer controllable conditions, has low cost, and is easy to implement.

[0022] (3) By controlling the reaction temperature and additive dosage of bulk polymerization, the present invention further ensures that the prepared polymethyl methacrylate has high isotactic regularity and narrow molecular weight distribution.

[0023] (4) The additives and initiators used in this invention are in small quantities, which further reduces production costs.

[0024] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages will become apparent from the description or may be learned by practicing the invention. Attached Figure Description

[0025] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0026] Figure 1 The stereoregularity of PMMA synthesized under conditions with ionic liquids (ILs) (Examples 1, 2, 4-6, 8) and without ILs (Comparative Example 1) 1 H-NMR spectrum (CD3COCD3, 600MHz);

[0027] Figure 2 The PMMA1H-NMR spectra synthesized at different temperatures (Examples 7-10) in the presence of ILs 3;

[0028] Figure 3 PMMA synthesized in the presence of different concentrations of ILs 3 (Examples 11-15) 1 H-NMR spectrum. Detailed Implementation

[0029] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0030] Except for the specific details mentioned below, the processes, conditions, and experimental methods for implementing this invention are all common knowledge and general information in the field, and this invention does not have any particular limitations. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0031] To address the technical problems of complex and cumbersome procedures in existing methods for preparing stereoregular polymethyl methacrylate (PMMA), this invention utilizes the designable structure of ionic liquids, which are composed of anions and cations. It proposes using ionic liquids as additives in the bulk polymerization of PMMA initiated by azobisisobutyronitrile (AIBN). By leveraging the synergistic effect of the anions and cations in the ionic liquid with PMMA, the polymer chain structure is precisely constructed, thereby improving the isotactic regularity of PMMA and ultimately preparing PMMA rich in isotactic structure.

[0032] It should be noted that in this invention, the ionic liquid does not participate in the reaction, but is used as an additive. On the one hand, it interacts with the monomer and the growing polymer chain to regulate the direction of monomer insertion, thereby controlling the stereoregularity and achieving the purpose of regulating the regularity of the polymer. On the other hand, it stabilizes the free radicals in the reaction, promotes the reaction, and thus accelerates the reaction rate.

[0033] In a first aspect, the present invention provides a method for bulk polymerization preparation of isotactic polymethyl methacrylate, comprising the following steps:

[0034] Step 1: Add the additives, initiator, and methyl methacrylate to the reaction vessel, mix thoroughly, and carry out bulk polymerization to obtain a polymer solution;

[0035] Step 2: Add solvent to dissolve the polymer solution obtained in Step 1; add the dissolved polymer solution dropwise into an excess of precipitant to completely precipitate the polymer, wash the precipitate repeatedly with the precipitant, and dry to constant weight to obtain isotactic polymethyl methacrylate.

[0036] Specifically, in step 1, the amount of additive used is 0.1-10 wt% of the amount of methyl methacrylate used, for example, 0.1 wt%, 0.3 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%. The additive is selected from one or more of the following ionic liquids:

[0037]

[0038] It should be noted that the ionic liquids with the above structures were selected according to specific selection rules, which are as follows: the ionic liquid does not react with the monomer, and the monomer and the ionic liquid are miscible.

[0039] The initiator is used in an amount of 0.01-1 wt% of methyl methacrylate, for example, 0.01 wt%, 0.03 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%. Initiators include azobisisobutyronitrile (AIBN).

[0040] In step 1, the reaction temperature is 60-90℃, for example, 60℃, 63℃, 65℃, 70℃, 73℃, 75℃, 78℃, 80℃, 82℃, 85℃, 87℃, 88℃, 89℃, preferably 65-85℃.

[0041] The reaction time is 20 to 60 minutes, for example, 20 minutes, 23 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 52 minutes, 55 minutes, 58 minutes, and 60 minutes.

[0042] Specifically, in step 2, the solvent is acetone and the precipitant is methanol.

[0043] Further drying was carried out in a vacuum drying oven at 60°C.

[0044] Secondly, the present invention also provides an isotactic polymethyl methacrylate (PMMA) prepared by the above method, which has a narrow molecular weight distribution, specifically 1.49-2.11, for example, 1.49, 1.50, 1.60, 1.70, 1.80, 1.90, 2.0, 2.10, and 2.11. The isotactic regularity of the polymer can reach up to 37.00%.

[0045] Example 1

[0046] (1) An ionic liquid with structure IL1 (6% of the mass of methyl methacrylate), azobisisobutyronitrile (0.1% of the mass of methyl methacrylate), and methyl methacrylate (50g) were added to a three-necked round-bottom flask equipped with a magnetic stirrer, reflux condenser, thermometer and inlet / outlet pipe. The mixture was purged with nitrogen and mixed evenly. The mixture was then purified with nitrogen to remove oxygen and placed in a constant temperature reactor. The reaction was carried out at 70°C for 45 min. The solution was then rapidly cooled to room temperature using an ice-water bath to obtain a polymer solution.

[0047] (2) After the reaction is complete, acetone (4 times the volume of the reaction solution) is added to dissolve the polymer solution; the dissolved polymer solution is added dropwise to methanol to completely precipitate the polymer. The obtained polymer is washed with methanol three times to precipitate repeatedly, and then placed in a vacuum drying oven at 60°C to dry to constant weight to obtain isotactic polymethyl methacrylate.

[0048] Example 2

[0049] This embodiment is basically the same as Embodiment 1, except that the structure of the ionic liquid is IL2.

[0050] Example 3

[0051] This embodiment is basically the same as Embodiment 1, except that the structure of the ionic liquid is IL3.

[0052] Example 4

[0053] This embodiment is basically the same as Embodiment 1, except that the structure of the ionic liquid is IL4.

[0054] Example 5

[0055] This embodiment is basically the same as Embodiment 1, except that the structure of the ionic liquid is IL5.

[0056] Example 6

[0057] This embodiment is basically the same as Embodiment 1, except that the structure of the ionic liquid is IL6.

[0058] Example 7

[0059] This embodiment is basically the same as Embodiment 3, except that the reaction temperature is 65℃ and the reaction time is 45min.

[0060] Example 8

[0061] This embodiment is basically the same as Embodiment 7, except that the reaction temperature is 90℃ and the reaction time is 20min.

[0062] Example 9

[0063] This embodiment is basically the same as Embodiment 7, except that the reaction temperature is 75°C and the reaction time is 30 min.

[0064] Example 10

[0065] This embodiment is basically the same as Embodiment 7, except that the reaction temperature is 80°C and the reaction time is 25 min.

[0066] Example 11

[0067] This embodiment is basically the same as that of Embodiment 10, except that the amount of ionic liquid used accounts for 1% of the mass of methyl methacrylate.

[0068] Example 12

[0069] This embodiment is basically the same as that of embodiment 10, except that the amount of ionic liquid used accounts for 3% of the mass of methyl methacrylate.

[0070] Example 13

[0071] This embodiment is basically the same as that of embodiment 10, except that the amount of ionic liquid used accounts for 5% of the mass of methyl methacrylate.

[0072] Example 14

[0073] This embodiment is basically the same as that of Embodiment 10, except that the amount of ionic liquid used accounts for 7% of the mass of methyl methacrylate.

[0074] Example 15

[0075] This embodiment is basically the same as that of Embodiment 10, except that the amount of ionic liquid used accounts for 9% of the mass of methyl methacrylate.

[0076] Example 16

[0077] This embodiment is basically the same as that of Example 10, except that the amount of azobisisobutyronitrile is 0.01% of the mass of methyl methacrylate.

[0078] Example 17

[0079] This embodiment is basically the same as that of Example 10, except that the amount of azobisisobutyronitrile is 0.5% of the mass of methyl methacrylate.

[0080] Example 18

[0081] This embodiment is basically the same as that of Example 10, except that the amount of azobisisobutyronitrile is 1% of the mass of methyl methacrylate.

[0082] Comparative Example 1

[0083] This comparative example is basically the same as Example 1, except that no ionic liquid is added.

[0084] Comparative Example 2

[0085] This comparative example is basically the same as Example 7, except that no ionic liquid is added.

[0086] Comparative Example 3

[0087] This comparative example is basically the same as Example 10, except that the reaction temperature is 50°C.

[0088] Comparative Example 4

[0089] This comparative example is basically the same as Example 10, except that the reaction temperature is 95°C.

[0090] Comparative Example 5

[0091] This comparative example is basically the same as Example 10, except that the amount of ionic liquid used is 0.05 wt% of the amount of methyl methacrylate.

[0092] Comparative Example 6

[0093] This comparative example is basically the same as Example 10, except that the amount of ionic liquid used accounts for 20 wt% of the amount of methyl methacrylate.

[0094] A series of tests were performed on the polymethyl methacrylate obtained in the above examples and comparative examples. The test results are listed in Table 1 and... Figure 1-3 The specific tests conducted are as follows:

[0095] (1) The molecular weight (M) of the synthesized polymethyl methacrylate was determined by gel permeation chromatography (GPC). n The molecular weight (Mn) and polydispersity (PDI) were determined using gel permeation chromatography (GPC) (LC-20ADXR, Japan) with tetrahydrofuran as the eluent. The sample concentration used in the experiment was approximately 4 mg / mL. -1The GPC analysis data were corrected using PST as the standard.

[0096] (2) Application of nuclear magnetic resonance hydrogen spectroscopy (NMR) 1 The synthesized polymethyl methacrylate (PMMA) was characterized by 1H NMR, and the stereoregularity of the synthesized PMMA was obtained by analysis and calculation of the α-methyl splitting peak in the 1H NMR spectrum of PMMA (using NMR analysis of polymer structure and estimation of stereoregularity). The experimental conditions were room temperature, deuterated acetone as solvent, and Bruker 600-MHz spectrometer was used for analysis, with a small amount of tetramethylsilane (TMS) as an internal standard.

[0097] (3) The glass transition temperature (T0) of the synthesized polymethyl methacrylate was tested using differential scanning calorimetry (DSC). g The glass transition temperature (Tg) of the polymer was measured using a Mettler-Toledo (Switzerland) DSC1. g The experimental conditions were a nitrogen atmosphere, a heating rate of 10℃ / min, and a temperature range from 0℃ to 180℃.

[0098] Table 1 Test results of polymethyl methacrylate

[0099]

[0100] Note: a. The undissolved portion in methanol; bc. Molecular weight and molecular weight distribution measured by GPC; d. Ternary stereoregularity of polymethyl methacrylate; e. Glass transition temperature measured by DSC.

[0101] All the polymer reaction systems of polymethyl methacrylate in this invention are bulk polymerization systems, and the initiator is azobisisobutyronitrile. Solubility observation shows that the ionic liquid additives are all soluble in the reactant monomer methyl methacrylate.

[0102] As can be seen from Table 1, the isotactic regularity (mm) of Examples 1-18 with added ionic liquids is 35%-50%, which is significantly higher than that of Comparative Examples 1-2 (7.77% and 11.11%). Furthermore, the molecular weight distribution is very narrow, ranging from only 1.49 to 2.11.

[0103] Furthermore, Table 1 also shows that as the content of additive IL 3 increases (Examples 11-15), the isotactic regularity (mm) of polymethyl methacrylate shows a trend of first increasing and then decreasing, while the syndiotactic regularity (rr) decreases slightly. When the content of ionic liquid additive IL 3 is 5 wt% (Example 13), the mm value of polymethyl methacrylate reaches a maximum of 50%, which is 38.89% higher than the mm value of the polymer obtained without the addition of ionic liquid additive IL 3 (Comparative Example 2).

[0104] Furthermore, data from Comparative Examples 3 and 4 show that both excessively low and excessively high reaction temperatures resulted in lower isotactic regularity of the obtained polymethyl methacrylate. Similarly, data from Comparative Examples 5 and 6 show that both excessively low and excessive amounts of ionic liquid also resulted in lower isotactic regularity of the obtained polymethyl methacrylate.

[0105] It should be noted that the stereoregularity and molecular weight distribution values ​​of different polymerization reaction types vary greatly. Therefore, the stereoregularity and molecular weight distribution values ​​of different reaction types are not comparable.

[0106] and Figures 1-3 The proton NMR spectroscopy confirmed the reliable structures of polymethyl methacrylate with different stereoregularities, indicating that under the reaction conditions of this invention, the ionic liquid did not cause any side reactions such as ester bond cleavage, and the product structure met the expected target.

[0107] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing isotactic polymethyl methacrylate, characterized in that, The ontology aggregation approach includes the following steps: Step 1: Add the ionic liquid, initiator, and methyl methacrylate to the reaction vessel, mix thoroughly, and carry out bulk polymerization to obtain a polymer solution; Step 2: Add solvent to dissolve the polymer solution obtained in Step 1; add the dissolved polymer solution to a precipitant to precipitate the polymer, dry it, and obtain isotactic polymethyl methacrylate. In step 1, the ionic liquid is selected from one or more of the following structures: ； In step 1, the amount of ionic liquid used accounts for 0.1-10 wt% of the amount of methyl methacrylate used. The reaction temperature is 65–85°C.

2. The preparation method according to claim 1, characterized in that, The amount of initiator is 0.01-1 wt% of the amount of methyl methacrylate.

3. The preparation method according to claim 2, characterized in that, In step 1, the initiator includes azobisisobutyronitrile (AIBN).

4. The preparation method according to claim 2, characterized in that, In step 2, the precipitant is methanol.

5. The preparation method according to claim 1, characterized in that, In step 2, drying is carried out in a vacuum drying oven at 60°C.

6. The preparation method according to claim 5, characterized in that, In step 2, the solvent is acetone.

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