A method for preparing ultrathin ordered macrocyclic molecular films

Abstract

This invention discloses a method for preparing an ultrathin ordered macrocyclic molecular membrane. The method involves synthesizing macrocyclic molecules with high polymerization activity and amphiphilic guest molecules. The inclusion complexes formed by the macrocyclic molecules and guest molecules are orderedly assembled using Langmuir-Blodgett (LB) technology. Photopolymerization is then employed to achieve ordered cross-linking of the macrocyclic molecules, resulting in an ultrathin ordered macrocyclic molecular membrane. The macrocyclic molecular membrane prepared by this invention is monomolecular in thickness and possesses good mechanical strength. With the assisted orientation of the amphiphilic guest molecules, the macrocyclic molecules achieve ordered assembly at the water-air interface. The membrane preparation process proposed in this invention is simple, cost-effective, versatile, and easily scalable, making it significant for the field of high-performance separation membranes.

Description

Technical Field

[0001] This invention belongs to the field of organic membrane materials and relates to a method for preparing organic thin films, specifically a method for preparing ultrathin ordered macrocyclic molecular films. Background Technology

[0002] Membrane separation technology boasts advantages such as low energy consumption, convenient operation, and high reliability, and has been widely applied in separation processes in industries such as petroleum, chemical, and pharmaceutical. The core of membrane separation technology is the high-performance separation membrane, and precise control of the membrane pore size is crucial for achieving accurate molecular sieving. However, the amorphous structure of traditional polymers makes it difficult to achieve uniform and regular pores. Macrocyclic molecules, such as cyclodextrins, calixarenes, cucurbiturates, and columnar aromatics, possess precisely sized cavities within their structures. Constructing separation membranes using macrocyclic molecules as modules, achieving an ordered arrangement of macrocyclic molecules, and preparing ordered thin films with precise sub-nanometer pore sizes will effectively expand the application scope of membrane separation in accurate molecular sieving.

[0003] In recent years, researchers have been trying to prepare ordered macrocyclic molecular membranes. Andrew G. Livingston et al. (Nature, 2022, 609, 58-64) selectively modified the hydroxyl groups of cyclodextrin with flexible polyurethane long chains while keeping the lower functional groups unchanged. By relying on the long chains containing more active amino groups that extend into the oil phase, the cyclodextrin molecules are arranged in an orderly manner. Through interfacial polymerization, they prepared ultrathin ordered macrocyclic molecular membranes with a thickness of less than 10 nm, which showed excellent performance in drug separation.

[0004] Langmuir-Blodgett (LB) membranes are a unique molecular assembly system characterized by nanometer-thickness and highly ordered molecular arrangement. In the Langmuir-Blodgett technique (LB technique), insoluble molecules (amphiphilic molecules) are dispersed and spread at the water-air interface, and by compressing their area on the water surface, a tightly ordered monomolecular membrane is obtained. Researchers have long attempted to utilize LB technology to achieve the ordered assembly of macrocyclic molecules and prepare ultrathin films; however, most macrocyclic molecules are not amphiphilic, making direct application of LB technology difficult. Early research focused on first designing and preparing amphiphilic macrocyclic molecules (such as cyclodextrins and calixarenes), using their derivatives as raw materials for LB membranes (Chem. Lett., 1986, 1933-1934) (J. Am. Chem. Soc., 1989, 111, 8192-8200). However, modification methods are extremely limited for different macrocyclic molecules. In addition, the difficulty in modifying macrocyclic molecules and the uncertainty of the behavior of newly designed molecular interfaces greatly restrict the preparation and application of ultrathin ordered macrocyclic molecular films. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing ultrathin ordered macrocyclic molecular films. This method is applicable to the preparation of various types of macrocyclic molecules, has universality, is simple to prepare, and allows for easy control of pore size.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing an ultrathin ordered macrocyclic molecular membrane involves first synthesizing the macrocyclic cucurbita and its derivatives, as well as an amphiphilic guest molecule capable of forming a stable host-guest inclusion complex with the cucurbita molecule; then preparing a macrocyclic cucurbita-amphiphilic guest molecule inclusion complex solution and using the Langmuir-Blodgett technique to orderly assemble the inclusion complex molecules; finally, based on the functional group properties of the prepared macrocyclic cucurbita derivatives, direct polymerization or the introduction of reactive molecules at the interface for polymerization is selected to achieve orderly cross-linking of the macrocyclic molecules, thereby preparing an ultrathin ordered macrocyclic molecular membrane.

[0008] Furthermore, the cucurbituril derivative is a fully hydroxylated cucurbituril synthesized by the oxidation reaction of cucurbituril with potassium persulfate in water, or a fully allyloxylated cucurbituril synthesized by the substitution reaction of fully hydroxylated cucurbituril with bromopropene in anhydrous dimethyl sulfoxide under the action of sodium hydride.

[0009] Furthermore, the synthesis of fully hydroxylated cucurbituril involves adding cucurbituril and potassium persulfate to deionized water at a mass ratio of (0.5-1):(2-4), with the mass-to-volume ratio of cucurbituril to deionized water being (0.5-1):(25-100) g / mL. Before the reaction, the solvent should be deoxygenated, and the reaction should be carried out at 65-85℃ for 6-48 h under a nitrogen atmosphere.

[0010] Furthermore, the synthesis of all-allyloxy-substituted cucurbita involves mixing all-hydroxy-substituted cucurbita, sodium hydride, bromopropylene, and anhydrous dimethyl sulfoxide in a mass ratio of (0.1-2):(0.06-1.2):(0.14-3.2):(0.1-30), and reacting at room temperature under a nitrogen atmosphere for 10-12 hours to obtain the product.

[0011] Furthermore, the amphiphilic guest molecule in the above step is an alkylamine.

[0012] Furthermore, the cucurbituril and its derivatives mentioned in the steps are cucurbituril[5] or cucurbituril[6] and their corresponding derivatives; the amphiphilic guest molecule is hexadecyl 1,6-hexanediamine.

[0013] Furthermore, the solvent used in the step of preparing the macrocyclic cucurbita-amphiphilic guest molecule inclusion complex solution is n-hexane, chloroform, diethyl ether, hexane-ethanol solution or chloroform-methanol solution, and the concentration of the inclusion complex solution is 1 mg / mL.

[0014] Furthermore, the Langmuir-Blodgett technique was used to assemble the inclusion complex molecules in an ordered manner. Specifically, the prepared macrocyclic cucurbita-amphiphilic guest molecule inclusion complex solution was dropped onto the water surface, and due to barrier compression, an ordered macrocyclic molecule-amphiphilic guest molecule film was formed at the water-air interface. Direct polymerization was specifically carried out by using an ultraviolet light source to irradiate the highly reactive cucurbita derivative molecules at the water-air interface to achieve molecular cross-linking, thereby obtaining an ultrathin ordered molecular film of cucurbita group.

[0015] Furthermore, the drop volume of the inclusion complex solution is 8-12 μL, the power of the ultraviolet light source is 500 W, and the photopolymerization irradiation time is 0.5-1 h.

[0016] Furthermore, the prepared ultrathin ordered macrocyclic molecular membrane is transferred onto a solid substrate using the Langmuir-Blodgett vertical deposition method or the Langmuir-Schaefer horizontal contact deposition method. Then, guest molecules within the macrocyclic molecular pores are removed by solvent exchange or pH adjustment to obtain a pure macrocyclic molecular membrane. The solid substrate material is anodic aluminum oxide, polycarbonate, polyacrylonitrile, polyimide, polysulfone, or polyphenylene benzoylmibazole.

[0017] Features and advantages of the preparation method provided by this invention:

[0018] This invention combines supramolecular chemistry with Langmuir-Blodgett technology, utilizing the host-guest interaction between the host molecule and the amphiphilic guest molecule to form a stable host-guest inclusion complex. The hydrophobic alkyl chain on the guest molecule ensures that the inclusion complex forms a stable monolayer at the water-air interface in a phospholipid-like manner, overcoming the problems of poor film formation and inconsistent orientation of unmodified macrocyclic molecules at the water-air interface due to their water solubility. This method for preparing ultrathin macrocyclic molecular membranes avoids the cumbersome process of synthesizing amphiphilic macrocyclic molecules, effectively utilizing the molecular recognition function of the macrocyclic host and employing amphiphilic guest molecules with good film-forming properties at the water-air interface as "guides" to promote the orderly assembly of the macrocyclic host molecules. The resulting membrane has great application potential in the field of precise molecular sieving. This preparation process is simple, convenient, low-cost, and fast, enabling the controllable preparation of centimeter-sized ultrathin ordered macrocyclic molecular membranes, which will help further advance the research and application of high-performance separation membranes.

[0019] The preparation method of this invention is applicable to a variety of macrocyclic molecules and has a certain degree of universality. The prepared organic thin film material contains ordered macrocyclic cavities and has a certain mechanical strength. The preparation method is simple and the pore size is easy to control, which has good application prospects in the field of precise molecular separation. Attached Figure Description

[0020] Figure 1A schematic diagram of the structure of a fully hydroxylated cucurbita[6]urea;

[0021] Figure 2 A schematic diagram of the structure of allallyloxy-substituted cucurbita[6]urea;

[0022] Figure 3 This is a graph showing the pressure (π)-area (A) curve of the Langmuir membrane surface in step 4 of Example 1 of the present invention.

[0023] Figure 4 This is a scanning electron microscope image of the cucurbita membrane prepared in Example 1 of the present invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0025] Unless otherwise specified, the experimental methods in the following specific embodiments are conventional methods; the reagents and consumables used are commercially available unless otherwise specified.

[0026] Cucurbituril was synthesized according to the literature (J.Org.Chem.,2001,66,8094-8100).

[0027] Example 1

[0028] 1. Synthesis of cucurbit[6]urea derivatives:

[0029] (1) Synthesis of all-hydroxy substituted cucurbit[6]urea: Weigh 1.0 g of cucurbit[6]urea and 3.9 g of potassium persulfate, add 50 mL of deionized water to form a suspension, and perform three cycles of freezing and deoxygenation. The mixture is heated and stirred at 85 °C for 6 h under a nitrogen atmosphere. After the reaction is complete, cool naturally to room temperature and filter to remove the precipitate. Concentrate the filtrate to 20 mL, add the concentrate to acetone to precipitate a white solid, and filter to obtain the crude product. Add 6 mL of anhydrous dimethyl sulfoxide to dissolve the crude product, stir vigorously for 30 min and filter. Add the filtrate to acetone to precipitate a white solid. After filtration, wash the filter cake with methanol and acetone several times, dry it under vacuum at 60 °C overnight, and then recrystallize with 1 M hydrochloric acid to obtain the white solid pure all-hydroxy substituted cucurbit[6]urea, the structure of which is as follows. Figure 1 As shown;

[0030] (2) Synthesis of perallyloxy-substituted cucurbit[6]urea: 56 mg of sodium hydride was weighed and added to a flask, followed by 2.5 mL of anhydrous dimethyl sulfoxide. 100 mg of perallyloxy-substituted cucurbit[6]urea was added under nitrogen protection at 0 °C and stirred for 1 h. 114 μL of bromopropene was added to the flask under nitrogen protection at 0 °C and stirred at room temperature for 12 h. After the reaction was complete, the reaction mixture was poured into 20 mL of ice water, and a white precipitate was collected by filtration. The precipitate was washed several times with water and ether, and dried under vacuum to obtain perallyloxy-substituted cucurbit[6]urea, with the structure shown below. Figure 2 As shown.

[0031] 2. Synthesis of hexadecyl 1,6-hexanediamine:

[0032] Weigh 4.65 g of hexanediamine and add 50 mL of anhydrous methanol. At reflux temperature, slowly add 2.45 mL of hexadecane bromide to the system and react for 48 h. After the reaction is complete, allow it to cool naturally to room temperature. Concentrate the reaction solution to 20 mL by rotary evaporation, and extract three times with water / dichloromethane. Evaporate the organic layer to dryness to obtain a white solid. Recrystallize this solid in n-hexane to obtain a white solid, hexadecyl-1,6-hexanediamine.

[0033] 3. Preparation of host-guest inclusion complex solution:

[0034] 10 mg (6 μmol) of perallyloxysubstituted cucurbita[6]urea was weighed and dissolved in 10 mL of chloroform-methanol solution, and 2 mg (6 μmol) of hexadecyl 1,6-hexanediamine was weighed and dissolved in 2 mL of chloroform-methanol solution. Under stirring conditions, the guest hexadecyl 1,6-hexanediamine solution was slowly added dropwise to the host perallyloxysubstituted cucurbita[6]urea solution to obtain a host-guest inclusion complex solution with a concentration of 1 mg / mL.

[0035] 4. Assemble the Langmuir membrane:

[0036] Using a microsyringe, 20 μL of the host-guest inclusion complex solution was uniformly added dropwise to the water-air interface in the Langmuir membrane analyzer. After the solvent evaporated, the molecules were slowly compressed by controlling the barrier, such as... Figure 3 Under a surface pressure of 10 mN / m, cucurbituril molecules complete orderly assembly on the water surface, forming a tightly packed, ultrathin, ordered cucurbituril Langmuir membrane.

[0037] 5. Polymeric cucurbita Langmuir membrane:

[0038] The assembled Langmuir cucurbita membrane was polymerized at the water-air interface using a xenon lamp light source. The xenon lamp light source was carefully placed 5 cm above the water surface in the Langmuir membrane apparatus, ensuring that the entire water surface was covered by the beam. The xenon lamp light was turned on for 30 minutes to complete the polymerization, forming an ultrathin, ordered cucurbita membrane.

[0039] 6. Transferring the cucurbita membrane:

[0040] The Langmuir-Schaefer method was used to transfer the cucurbita membrane. First, the anodic aluminum oxide substrate was brought into horizontal contact with the cucurbita membrane at the interface. After about 2 seconds, it was lifted until it was completely removed from the water surface. After deposition, it was vacuum dried at 60°C for 10 minutes to remove moisture.

[0041] like Figure 4 As shown, the cucurbita film transferred to the TEM grid is a monolayer thickness and has an ordered porous structure.

[0042] The prepared ultrathin ordered macrocyclic molecular films are transferred onto a solid substrate using the Langmuir-Blodgett vertical deposition method or the Langmuir-Schaefer horizontal contact deposition method. Then, guest molecules inside the macrocyclic molecular pores are removed by solvent exchange or pH control to obtain a pure macrocyclic molecular film. The solid substrate material can also be anodic aluminum oxide, polycarbonate, polyacrylonitrile, polyimide, polysulfone, or polyphenylene benzoate.

Claims

1. A method for preparing an ultrathin ordered macrocyclic molecular film, characterized in that: First, macrocyclic cucurbita derivatives and amphiphilic guest molecules capable of forming stable host-guest inclusion complexes with the cucurbita derivative molecules are synthesized. Then, a macrocyclic cucurbita derivative-amphiphilic guest molecule inclusion complex solution is prepared, and the inclusion complex molecules are assembled in an orderly manner using the Langmuir-Blodgett technique. Finally, based on the functional group properties of the prepared macrocyclic cucurbita derivatives, direct polymerization or the introduction of reactive molecules into the interface polymerization is selected to achieve ordered cross-linking of macrocyclic molecules and prepare an ultrathin ordered macrocyclic molecular film. The cucurbituril derivative is a fully hydroxylated cucurbituril synthesized by the oxidation reaction of cucurbituril with potassium persulfate in water, or a fully allyloxylated cucurbituril synthesized by the substitution reaction of fully hydroxylated cucurbituril with bromopropene in anhydrous dimethyl sulfoxide under the action of sodium hydride. The amphiphilic guest molecule is an alkylamine.

2. The method for preparing the ultrathin ordered macrocyclic molecular film as described in claim 1, characterized in that: The synthesis of fully hydroxylated cucurbituril involves adding cucurbituril and potassium persulfate to deionized water at a mass ratio of (0.5-1):(2-4), with the mass-to-volume ratio of cucurbituril to deionized water being (0.5-1):(25-100) g / mL. The solvent should be deoxygenated before the reaction, and the reaction should be carried out at 65-85℃ for 6-48 h under a nitrogen atmosphere.

3. The method for preparing the ultrathin ordered macrocyclic molecular film as described in claim 1, characterized in that: The synthesis of all-allyloxy-substituted cucurbita involves mixing all-hydroxy-substituted cucurbita, sodium hydride, bromopropylene, and anhydrous dimethyl sulfoxide in a mass ratio of (0.1-2):(0.06-1.2):(0.14-3.2):(0.1-30), and reacting at room temperature under a nitrogen atmosphere for 10-12 h to obtain the product.

4. The method for preparing the ultrathin ordered macrocyclic molecular film as described in claim 1, characterized in that: The cucurbituril derivative is a cucurbituril[5] or a corresponding derivative of cucurbituril[6]; the amphiphilic guest molecule is hexadecyl 1,6-hexanediamine.

5. The method for preparing the ultrathin ordered macrocyclic molecular film as described in claim 1, characterized in that: The solvents used to prepare the macrocyclic cucurbituril-amphiphilic guest molecule inclusion complex solution are hexane, chloroform, diethyl ether, hexane-ethanol solution, or chloroform-methanol solution, and the concentration of the inclusion complex solution is 1 mg / mL.

6. The method for preparing an ultrathin ordered macrocyclic molecular film as described in claim 1, characterized in that: The Langmuir-Blodgett technique was used to assemble inclusion complex molecules in an ordered manner. A prepared macrocyclic cucurbita derivative-amphiphilic guest molecule inclusion complex solution was dropped onto the water surface. Due to barrier compression, an ordered macrocyclic cucurbita derivative-amphiphilic guest molecule film was formed at the water-air interface. Direct polymerization was carried out by irradiating the highly reactive cucurbita derivative molecules at the water-air interface with ultraviolet light to achieve molecular cross-linking, thus obtaining an ultrathin ordered molecular film of cucurbita group.

7. The method for preparing the ultrathin ordered macrocyclic molecular film as described in claim 6, characterized in that: The volume of the inclusion complex solution added was 8-12 μL, the power of the ultraviolet light source was 500 W, and the photopolymerization irradiation time was 0.5-1 h.

8. The method for preparing an ultrathin ordered macrocyclic molecular film as described in claim 1, characterized in that: The ultrathin ordered macrocyclic molecular films prepared by Langmuir-Blodgett vertical deposition or Langmuir-Schaefer horizontal contact deposition were transferred onto a solid substrate. Then, guest molecules in the macrocyclic molecular pores were removed by solvent exchange or pH control to obtain pure macrocyclic molecular films. The solid substrate materials were anodic aluminum oxide, polycarbonate, polyacrylonitrile, polyimide, polysulfone, or polyphenylene benzoate.

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