CN101880431A - In situ preparation method and application of nanomolecularly imprinted polymer film - Google Patents

Abstract

The invention discloses a method for in-situ preparation of a nanometer molecularly imprinted polymer film, which is characterized in that the method comprises the following steps: (1) mixing an auxiliary film-forming material, a functional monomer, a template molecule and an initiator in a suitable solvent Mix evenly, and form a composite film of the molecularly imprinted polymer precursor by spin coating on a flat substrate by spin coating; (2) form a nanofilm by photoinitiating or thermally polymerizing the composite film of the molecularly imprinted polymer precursor; (3 ) to remove template molecules in the nanometer membrane to obtain a nanometer-thick molecularly imprinted polymer film. The method introduces suitable auxiliary film-forming materials into the molecularly imprinted prepolymerization system, which can effectively improve the stability of in-situ preparation of molecularly imprinted films with nanoscale optical thickness. Meanwhile, the base material used in the method is not limited to conductive materials.

Description

In situ preparation method and application of nanomolecularly imprinted polymer film

technical field

The invention belongs to the technical field of sensing and separation, and in particular relates to an in-situ preparation method of a nano-molecular imprinted polymer film and its application in white light interference reflection spectrum sensing.

Background technique

Molecular imprinting (molecular imprinting) technology is one of the more popular technologies in the prior art. Its principle is that when template molecules (imprinting molecules) come into contact with polymer monomers, multiple action points will be formed. Through the polymerization process, this effect will It is memorized that when the template molecule is removed, a cavity with multiple action points matching the spatial configuration of the template molecule is formed in the polymer. Such a cavity will have selective recognition characteristics for the template molecule and its analogues. This technology has a wide range of applications in bionics, separation technology, and sensing technology. The molecularly imprinted polymer material prepared by molecular imprinting technology is a molecular imprinting material, which is a polymer material with the ability to simulate biomolecules. It not only has high affinity and selectivity for specific template molecules, but also has It has the advantages of strong anti-harsh environment ability and good stability.

Due to the poor solubility of molecularly imprinted polymer materials, in situ polymerization methods under mold confinement are usually used to prepare imprinted polymer films. The method of dispersing the pre-prepared molecularly imprinted polymer particles with a low-boiling point solvent, and then dipping, dripping or spin-coating the solution onto the substrate surface, and forming a molecularly imprinted polymer film on the substrate surface through solvent volatilization is simple. The thickness of molecularly imprinted polymer membranes prepared by this method is generally on the order of microns or above, which can be used for selective separation or preparation. However, due to the common film-forming methods such as film-pressing, in-situ polymerization, and spin-coating, the films often have shortcomings such as large thickness, poor uniformity, poor reproducibility and stability, and difficulty in repeating, which greatly It affects the sensitivity of the chemical sensor and the finalization of the design of the instrument, and is difficult to be used in the production of actual products.

Molecularly imprinted polymer membranes with nanoscale thickness have the advantages of short mass transfer distance and fast adsorption process, and are especially suitable for dielectric membranes used in sensing technology. At present, electropolymerization is generally used to prepare molecularly imprinted polymer films with nanoscale optical thickness on flat substrates. The electropolymerization method adopts cyclic voltammetry scanning in the solution of functional monomers and template molecules for a certain period of time, and the nano-film is deposited on the surface of the electrode. After the template molecules are eluted and removed, nano-molecular imprinting with holes in the template molecular configuration can be obtained. polymer film. The preparation of molecularly imprinted sensors by electropolymerization has some outstanding advantages, such as simple preparation, which can be realized by cyclic voltammetry scanning in the solution of functional monomers and template molecules; film. But its disadvantage is that the selected substrate needs to be a conductive substrate, and the monomer must be able to form a polymer through the redox reaction of the electrode. This largely limits the types of molecularly imprinted polymer materials that can form nanoscale optically thick films in situ. The present invention comes from this.

Contents of the invention

The purpose of the present invention is to provide a method for in-situ preparation of nano-molecularly imprinted polymer films, which solves the problem that molecularly imprinted polymer films can only be prepared by electropolymerization in the prior art, and the preparation conditions strictly limit the types of molecularly imprinted polymer films. question.

In order to solve these problems in the prior art, the technical solution provided by the invention is:

A method for preparing a nanomolecularly imprinted polymer film in situ, characterized in that the method comprises the following steps:

(1) Mix the auxiliary film-forming materials, functional monomers, template molecules and initiators in an appropriate solvent, and spin-coat on a flat substrate by spin-coating technology to form a composite film of molecularly imprinted polymer precursors;

(2) Photoinitiation or thermal polymerization of composite films of molecularly imprinted polymer precursors to form nanofilms;

(3) Eluting and removing the template molecules in the nano-membrane to obtain a nano-thick molecularly imprinted polymer film.

Preferably, the auxiliary film-forming material is selected from polystyrene and polyvinyl alcohol; the concentration of the auxiliary film-forming material in the mixture solution is 5 mg/ml-100 mg/ml.

Preferably, the functional monomer is selected from N, N-diethylamine ethyl methacrylate, acrylic acid, methacrylic acid, trifluoromethacrylic acid, vinyl benzoic acid, methylene succinic acid, 2 -Acrylamide-2-methyl-1-propanesulfonic acid, 2-vinylpyridine, 4-vinylpyridine, vinylimidazole, methyl methacrylate, hydroxyethyl methacrylate, acrylamide, methacryl A type of amide.

Preferably, the solvent is selected from toluene, acetonitrile, chloroform, tetrahydrofuran, n-hexane, ethanol, methanol and the like. Preferably, the crosslinking agent is selected from ethylene glycol dimethacrylate, ethylene glycol dimethacrylate, divinylbenzene, trimethylol propane trimethacrylate, pentaerythritol triacrylate, A kind of N,N'-methylenebisacrylamide.

Preferably, the base material is selected from glass, silicon wafer, and gold film.

Preferably, the optical thickness of the nanometer molecularly imprinted polymer film is within 50-1000 nm.

The present invention also provides an application of the nano-molecularly imprinted polymer film as claimed in claim 1 as a sensing medium for a white light interference reflectance spectrum sensor.

The in-situ preparation technology of the molecularly imprinted polymer film of the present invention uses auxiliary film-forming materials such as polystyrene to improve the stability of the in-situ prepared molecularly imprinted polymer film on the substrate. The optical thickness of the molecularly imprinted polymer film prepared in situ is controllable in the nanometer range, and the molecularly imprinted polymer film with an optical thickness ranging from tens of nanometers to 1 micron can be prepared. The molecularly imprinted polymer film prepared in situ has the sensing property of white light reflectance interference spectroscopy (RIfS).

The monomers used in the in-situ preparation of the molecularly imprinted polymer film include, but are not limited to, conventional monomers such as methacrylic acid, vinylpyridine, and acrylamide. The in-situ molecularly imprinted polymer film preparation technology refers to preparing a composite film of a molecularly imprinted polymer precursor on a flat substrate by using spin coating technology in the presence of auxiliary film-forming materials, and then performing photoinitiation or thermal polymerization to form a nanometer-thick film. Molecularly imprinted polymers. The auxiliary film-forming material includes but not limited to polystyrene and polyvinyl alcohol, and its film-forming concentration is variable from 5 mg/ml to 100 mg/ml. The base material includes, but is not limited to, conventional materials such as glass, silicon wafer, and gold film.

The purpose of the present invention is to form a film on the substrate by spin coating technology by mixing the pre-polymerization system of monomer, template molecule and initiator with the auxiliary film-forming material in a suitable solvent, so as to limit the polymerization process to the film layer Inside. In the method, suitable auxiliary film-forming materials are added to enhance the stability of spin-coating film formation, and at the same time control the optical thickness of the film in the nanoscale range. The prepared molecularly imprinted polymer film can be used as the medium film of the sensor.

The invention provides a technique for in-situ preparation of a molecularly imprinted polymer film with nanoscale thickness on a non-conductive substrate. In the present invention, suitable auxiliary film-forming materials are mixed with molecularly imprinted polymerized monomers, template molecules and initiators in a suitable solvent, and a molecularly imprinted film with controllable thickness is formed on a selected substrate by using spin coating technology. The auxiliary film-forming material improves the viscosity and polymerization environment of the molecularly imprinted pre-polymerization system, and effectively improves the film-forming quality. The optical thickness of the prepared molecularly imprinted polymer film is on the nanometer scale and is sensitive to the amount of adsorbed template molecules.

Compared with the scheme in the prior art, the advantages of the present invention are:

The invention introduces suitable auxiliary film-forming materials into the molecular imprinting pre-polymerization system, which can effectively improve the stability of in-situ preparation of molecularly imprinted films with nanoscale optical thickness.

The method proposed by the present invention can be used in general molecularly imprinted polymerization systems, and both common functional monomers and template molecules can be used to prepare molecularly imprinted films with nanoscale optical thickness; meanwhile, the substrate materials used in this method are not limited to conductive materials. The molecularly imprinted film prepared by the invention can be used as a sensing medium of a sensor.

In summary, the present invention belongs to the field of sensing, and specifically relates to a method for in-situ preparation of a molecularly imprinted polymer film for selective adsorption on a flat substrate. Specifically, in the presence of auxiliary film-forming materials, an organic solution containing functional monomers, template molecules, and initiators is used to form a pre-polymerized film on a selected substrate by spin-coating technology, and then irradiated or heated for a certain period of time in an inert atmosphere. . The molecularly imprinted polymer film thus prepared has an optical thickness in the nanometer range and can be used as a sensitive film medium for white light interference reflectance spectroscopy.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment:

Fig. 1 is the infrared spectrograms of (a) and after (b) desorption of chloramphenicol imprinted membrane on _Ta2O5 substrate _;

Figure 2 is a scanning electron micrograph of a chloramphenicol imprinted polymer film on _{a Ta2O5} substrate;

Figure 3 is the RIfS spectrum of chloramphenicol imprinted polymer film after multiple elutions and adsorption of template molecules;

Fig. 4 is the infrared spectrum of diethylstilbestrol imprinted polymer film;

Fig. 5 is the RIfS spectrum of diethylstilbestrol imprinted polymer film;

Figure 6 is the relationship between the change of optical thickness of chloramphenicol imprinted polymer film and the concentration of chloramphenicol solution.

Detailed ways

The above solution will be further described below in conjunction with specific embodiments. It should be understood that these examples are used to illustrate the present invention and not to limit the scope of the present invention. The implementation conditions used in the examples can be further adjusted according to the conditions of specific manufacturers, and the implementation conditions not indicated are usually the conditions in routine experiments.

Example 1 Preparation of Chloramphenicol Imprinted Polymer Film and Measurement of Optical Properties

The molecularly imprinted polymer in this embodiment is a chloramphenicol imprinted polymer. The selected auxiliary film-forming material is polystyrene, and the substrate is a glass slide coated with tantalum pentoxide. Take 1ml 15mg/ml polystyrene toluene solution, mix with 0.0646g chloramphenicol, 0.08ml diethylamine ethyl methacrylate, 1ml ethylene glycol dimethacrylate and add 0.02g dimethacrylate after ultrasonication for 10-60 minutes NBCN, place the glass slide coated with tantalum pentoxide on the homogenizer, first shake the film at a speed of 100-1000 rpm for 2-20 seconds, and then shake it at a speed of 1000-6000 rpm Film for 20-200 seconds, then put it in a vacuum drying oven at 40-80 degrees, and take it out after 15-60 minutes.

Fig. 1 is the infrared absorption spectrum of the chloramphenicol imprinted polymer film on the Ta ₂ O ₅ substrate before (a) and after (b) desorption. Figure 1(a) is the infrared absorption spectrum before the imprinted polymer film is not desorbed from the template molecule, and there is an obvious absorption peak of the characteristic functional group of chloramphenicol; Figure 1(b) is the image after the imprinted polymer film is desorbed from the template molecule In the infrared absorption spectrum, 1728.5cm ^-1 is the characteristic absorption peak of C=O of the ester in the monomer, 967.8cm ^-1 is the characteristic absorption peak of the tertiary amine in the monomer, 3032cm ^-1 , 2926cm ^-1 , and 1620cm ^-1 are The characteristic absorption peak of polystyrene. Infrared showed the formation of imprinted polymers.

Figure 2 is a scanning electron microscope image of a chloramphenicol imprinted polymer film on a Ta ₂ O ₅ substrate, showing that the film surface is relatively uniform.

Figure 3 shows the RIfS spectrum of the prepared chloramphenicol imprinted polymer film after multiple elution and adsorption of template molecules, thus obtaining the optical thickness of the chloramphenicol imprinted polymer film after elution and adsorption of template molecules ( Optical thickness=nd, n is the refractive index of thin film, and d is the physical thickness of thin film), is listed in Table 1, wherein R ² is the non-linear regression correlation coefficient calculated thin film optical thickness by RIfS spectrum. It can be drawn that the average optical thickness of the polymer film after three elutions is 80.09nm, the standard deviation is 0.78nm, and the relative standard deviation is 0.97%; The deviation of the results was 1.17 nm. Therefore, the prepared chloramphenicol-imprinted polymer films showed high stability after multiple elution and adsorption experiments.

Table 1 Optical thickness of chloramphenicol imprinted polymer films after elution and adsorption of template molecules

Example 2 Preparation of Diethylstilbestrol Imprinted Polymer Film and Measurement of Optical Properties

The molecularly imprinted polymer in this embodiment is diethylstilbestrol imprinted polymer. The selected auxiliary film-forming material is polystyrene, and the substrate is silicon wafer. Take 1ml 80mg/ml polystyrene toluene solution, mix with 0.03g diethylstilbestrol, 0.03g acrylamide, 1ml ethylene glycol dimethacrylate and ultrasonically add 0.02g azobisisobutyronitrile for 10-60 minutes. Place it on the glue homogenizer, first spin the film at 100-1000 rpm for 2-20 seconds, then spin the film at 1000-6000 rpm for 20-200 seconds, then put it into a vacuum drying oven at 40-80 degrees Medium, take it out after 15-60 minutes.

Figure 4 is the infrared spectrum of the prepared diethylstilbestrol imprinted polymer film. 1714.7cm ^-1 is the characteristic absorption peak of C=O in the monomer, 1598.6cm ^-1 and 1486.6cm ^-1 are the characteristic absorption peaks of the primary amine in the monomer, 3025cm ^-1 and 2921cm ^-1 are the characteristic absorption peaks of polystyrene peak. Infrared showing the formation of diethylstilbestrol-imprinted polymers on silicon substrates.

Figure 5 is the RIfS spectrum of the diethylstilbestrol imprinted polymer film prepared in situ on the silicon substrate, and the optical thickness of the film calculated from the RIfS spectrum is 257 nm.

Example 3 Preparation of chloramphenicol imprinted polymer film and research on the relationship between film thickness and concentration of chloramphenicol imprinted polymer

The molecularly imprinted polymer in this embodiment is a chloramphenicol imprinted polymer. The selected auxiliary film-forming material is polystyrene. The substrate is a glass slide coated with tantalum pentoxide. Take 1ml 32mg/ml polystyrene toluene solution, mix with 0.064g chloramphenicol, 0.08ml diethylaminoethyl methacrylate, 1ml ethylene glycol dimethacrylate and add 0.02g dimethacrylate after ultrasonication for 10-60 minutes NBCN, place the glass slide coated with tantalum pentoxide on the homogenizer, first shake the film at a speed of 100-1000 rpm for 2-20 seconds, and then shake it at a speed of 1000-6000 rpm Film for 20-200 seconds, then put it in a vacuum drying oven at 40-80 degrees, and take it out after 15-60 minutes. After the prepared chloramphenicol-imprinted polymer film desorbs template molecules, its optical thickness changes after being adsorbed in different concentrations of chloramphenicol solutions for the same time (Δ=optical thickness of the film after adsorption-optical thickness of the film before adsorption ). Figure 6 is the relationship between the change Δ of the optical thickness of the chloramphenicol-imprinted polymer film and the concentration of the chloramphenicol solution. It can be seen that the change Δ of the optical thickness of the polymer film imprinted with chloramphenicol has a good linear relationship with the concentration of the chloramphenicol solution. Obviously, the prepared chloramphenicol imprinted polymer membrane can be used as a mediator membrane for RIfS sensors.

The above examples are only to illustrate the technical conception and characteristics of the present invention, and its purpose is to allow those familiar with this technology to understand the content of the present invention and implement it accordingly, and these embodiments cannot limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (8)

1. the in-situ preparation method of a nanometer molecular imprinting polymer membrane is characterized in that said method comprising the steps of:

(1) will assist film forming material, function monomer, template molecule, linking agent and initiator in appropriate solvent, to mix, by the composite membrane of spin coating technique spin coating in smooth substrate formation molecularly imprinted polymer presoma;

(2) undertaken light-initiated by composite membrane or heat polymerization formation nanometer film to the molecularly imprinted polymer presoma;

(3) template molecule in the wash-out removal nanometer film promptly gets the molecular imprinting polymer membrane of nano thickness.

2. method according to claim 1 is characterized in that auxiliary film forming material is selected from polystyrene, polyvinyl alcohol in the described method; Described auxiliary film forming material in the concentration of mixture solution at 5mg/ml～100mg/ml.

3. method according to claim 1, it is characterized in that function monomer is selected from N in the described method, N-diethylamide ethyl-methyl acrylate, vinylformic acid, methacrylic acid, trifluoromethyl acrylate, vinyl benzoic acid, methylene-succinic acid, 2-acrylamide-2-methyl isophthalic acid-propanesulfonic acid, 2-vinyl pyridine, 4-vinylpridine, vinyl imidazole, methyl methacrylate, hydroxyethyl methylacrylate, acrylamide, Methacrylamide a kind of.

4. method according to claim 1 is characterized in that described solvent is selected from toluene, acetonitrile, chloroform, tetrahydrofuran (THF), normal hexane, ethanol, methyl alcohol.

5. method according to claim 1 is characterized in that base material is selected from glass, silicon chip, golden film in the described method.

6. method according to claim 1, it is characterized in that described linking agent is selected from Ethylene glycol dimethacrylate, ethylene glycol dimethacrylate, Vinylstyrene, trishydroxymethyl base propane trimethyl acrylic ester, pentaerythritol triacrylate, N, N '-methylene-bisacrylamide a kind of.

7. method according to claim 1 is characterized in that preparing the nanometer molecular imprinting polymer membrane optical thickness of gained in 50～1000nm.

8. the application of the described method of claim 1 aspect the sensor information film of preparation white light interference reflection spectrum transmitter.

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