CN109265722B - Ethylene-vinyl alcohol copolymer intelligent film with Janus structure, and preparation method and application thereof - Google Patents

Ethylene-vinyl alcohol copolymer intelligent film with Janus structure, and preparation method and application thereof Download PDF

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CN109265722B
CN109265722B CN201811056111.9A CN201811056111A CN109265722B CN 109265722 B CN109265722 B CN 109265722B CN 201811056111 A CN201811056111 A CN 201811056111A CN 109265722 B CN109265722 B CN 109265722B
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film
photoinitiator
ethylene
vinyl alcohol
alcohol copolymer
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CN109265722A (en
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叶卉
张玉忠
李昱
于腾飞
黄莉兰
焦蕊
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Unicore Membrane Science And Technology Tianjin Co ltd
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Tianjin Polytechnic University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/12—Chemical modification
    • C08J7/16—Chemical modification with polymerisable compounds
    • C08J7/18—Chemical modification with polymerisable compounds using wave energy or particle radiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0006—Organic membrane manufacture by chemical reactions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/38—Polyalkenylalcohols; Polyalkenylesters; Polyalkenylethers; Polyalkenylaldehydes; Polyalkenylketones; Polyalkenylacetals; Polyalkenylketals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
    • B01D71/78—Graft polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/08—Copolymers of ethene

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Abstract

The invention discloses an ethylene-vinyl alcohol copolymer intelligent membrane with a Janus structure, belongs to the field of membrane materials, and can solve the problems that when two responsive monomers are grafted on the surface of a membrane in the prior grafting technology, the responsive monomers mostly exist in a polymer form, the spatial positions of the two polymer units are close, the mutual influence is caused in the response process, and the response efficiency is low. The technical scheme comprises an ethylene-vinyl alcohol copolymer intelligent film with a Janus structure, wherein two sides of the ethylene-vinyl alcohol copolymer film are respectively grafted with a responsive monomer. The invention is applied to the aspects of separation and purification, water treatment and intelligent sensing.

Description

Ethylene-vinyl alcohol copolymer intelligent film with Janus structure, and preparation method and application thereof
Technical Field
The invention belongs to the field of membrane materials, and particularly relates to an ethylene-vinyl alcohol copolymer intelligent membrane with a Janus structure, and a preparation method and application thereof.
Background
The intelligent membrane is a novel membrane material prepared by introducing responsive macromolecules into a membrane substrate, and the membrane material can change the physical and chemical properties of the membrane material by sensing and responding to the change of environmental signals, so the membrane material has potential application prospects in the fields of material selective separation, drug controlled release, water treatment, tissue engineering and the like.
At present, grafting is a common means for modifying and modifying the surface of a membrane and is an effective method for constructing an intelligent membrane. In the grafting technology, the responsive monomer is connected with the base membrane polymer by chemical bonds, so that the intelligent membrane obtained by using the grafting method has the advantages of stability, durability and the like.
However, when two kinds of responsive monomers are grafted on the surface of the membrane by using the existing grafting technology, because the responsive monomers mostly exist in a polymer form, the two polymer units are close to each other in spatial position and influence each other in the response process, thereby reducing the response efficiency.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to improve the response efficiency of the intelligent film and provides the ethylene-vinyl alcohol copolymer intelligent film with the Janus structure, the preparation method and the application thereof, wherein two responsive monomers are independent in spatial position and have no influence on the performance.
In order to solve the technical problem, the technical scheme adopted by the invention is as follows:
the ethylene-vinyl alcohol copolymer intelligent film with the Janus structure is characterized in that two sides of the ethylene-vinyl alcohol copolymer film are respectively grafted with a responsive monomer.
Preferably, the ethylene-vinyl alcohol copolymer film is grafted with the responsive monomer on both sides by the following method:
using an ethylene-vinyl alcohol copolymer film as a base film, and immersing the base film into a photoinitiator solution prepared from a volatile solvent to obtain a photoinitiator pre-coated film;
the photoinitiator pre-coated film comprises a compact side and a porous side, the fixing of the photoinitiator on any side of the film is realized by firstly carrying out ultraviolet irradiation on any side of the compact side and the porous side, then a solution dissolved with a responsive monomer is coated, and the fixing of the responsive monomer on any side of the film is realized after the ultraviolet irradiation.
Preferably, the concentration of the photoinitiator in the photoinitiator solution is 80-200 g/L.
The invention also provides a preparation method of the ethylene-vinyl alcohol copolymer intelligent film with the Janus structure, which comprises the following steps:
using an ethylene-vinyl alcohol copolymer film as a base film, and immersing the base film into a photoinitiator solution prepared from a volatile solvent to obtain a photoinitiator pre-coated film;
the photoinitiator pre-coated film comprises a compact side and a porous side, the fixing of the photoinitiator on any side of the film is realized by firstly carrying out ultraviolet irradiation on any side of the compact side and the porous side, then a solution dissolved with a responsive monomer is coated, and the fixing of the responsive monomer on any side of the film is realized after the ultraviolet irradiation.
Preferably, the concentration of the photoinitiator in the photoinitiator solution is 80-200 g/L.
Preferably, the photoinitiator is at least one of benzophenone, benzoin dimethyl ether or azobisisobutyronitrile.
Preferably, the volatile solvent is at least one of acetone, ethanol, diethyl ether, dichloromethane, chloroform or tetrahydrofuran.
Preferably, the responsive monomer is any two of acrylic acid, methacrylic acid, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, tetravinylpyridine, divinylpyridine, acryloylisopropylamine, glycidyl methacrylate, ethylene glycol dimethacrylate, N-dimethylacrylamide, N-diethylacrylamide, 2-hydroxyethyl methacrylate, N-vinylcaprolactam or 2-methyl 5-vinylpyridine.
The invention also provides application of the ethylene-vinyl alcohol copolymer intelligent membrane with the Janus structure in the fields of separation and purification, water treatment and intelligent sensing.
Compared with the prior art, the invention has the beneficial effects that:
1. the two responsive monomers of the ethylene-vinyl alcohol copolymer intelligent film with the Janus structure provided by the invention are mutually independent in spatial position, the performances are not mutually influenced, and the response efficiency is higher.
2. The ethylene-vinyl alcohol copolymer film is a porous film and has permeation and separation performance, and the ethylene-vinyl alcohol copolymer intelligent film with the Janus structure, which is prepared by taking the ethylene-vinyl alcohol copolymer film as a base film, can realize intelligent fine control on the permeation and separation performance of the film.
Drawings
FIG. 1 is a graph of the diffuse reflectance of UV light on the low and high beam sides of the films after fixing the initiator in example 1 and comparative examples 1 and 2;
FIG. 2 is a schematic representation of a two-sided Fourier transform infrared spectrum of films of example 1 and comparative example 3 of the present invention;
FIG. 3 is a schematic diagram showing the change of contact angle pH response on both sides of the films of example 1 and comparative example 3 according to the present invention;
FIG. 4 is a schematic diagram showing the permeation flux pH-responsive changes of the membranes of example 1 and comparative example 3 according to the present invention;
FIG. 5 is a Zeta potential pH response change diagram of the membrane of example 2 of the present invention;
FIG. 6 is a schematic diagram showing the change of the permeation flux temperature (a) and pH (b) responses of the membrane in example 3 of the present invention;
FIG. 7 is a schematic diagram showing the response changes of the membrane permeation flux pH (a) and temperature (b) in example 4 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be fully described in detail below. It is obvious that the described embodiments are only some specific embodiments, not all embodiments, of the general technical solution of the present invention. All other embodiments, which can be derived by a person skilled in the art from the general idea of the invention, fall within the scope of protection of the invention.
The invention provides an ethylene-vinyl alcohol copolymer intelligent film with a Janus structure, and particularly, responsive monomers are respectively grafted on two sides of the ethylene-vinyl alcohol copolymer film. In this embodiment, an ethylene-vinyl alcohol copolymer (EVAL) membrane is a hydrophilic porous membrane containing hydroxyl groups, has permeation and separation properties, and has been widely used in medical engineering, blood purification, protein separation, and the like. According to the invention, responsive monomers with different properties are respectively grafted on two sides of the EVAL membrane through a grafting technology, so that the purposes that the two responsive monomers are mutually independent in spatial position and do not influence each other in performance are realized, the response efficiency of the intelligent membrane is improved, the two sides of the EVAL membrane have different response characteristics, and meanwhile, the intelligent fine regulation and control on the permeation and separation performance of the EVAL membrane can be realized.
In a preferred embodiment, the ethylene-vinyl alcohol copolymer film is grafted with the responsive monomer on both sides thereof by the following method:
s1: the ethylene-vinyl alcohol copolymer film is taken as a base film, and the base film is immersed in a photoinitiator solution prepared from a volatile solvent to obtain a photoinitiator pre-coated film.
In this step, the EVAL membrane is used as a base membrane, and it should be noted that, compared with a non-porous membrane, the EVAL membrane is used as a base membrane, and the double-sided modification design of the EVAL membrane is more difficult, in that the EVAL membrane has a plurality of through pores capable of communicating with both sides of the membrane, so that in the modification process, the reaction solution can permeate to the other side of the membrane through the pores, thereby simultaneously modifying both sides of the membrane.
S2: the photoinitiator pre-coated film comprises a compact side and a porous side, the fixing of the photoinitiator on any side of the film is realized by firstly carrying out ultraviolet irradiation on any side of the compact side and the porous side, then a solution dissolved with a responsive monomer is coated, and the fixing of the responsive monomer on any side of the film is realized after the ultraviolet irradiation.
In the step, the EVAL membrane is modified by adopting an ultraviolet grafting technology, and the ultraviolet grafting technology has the advantages of low energy consumption, short reaction time, mild conditions, easiness in industrial amplification and the like. The method comprises the steps of irradiating one side of a pre-coated film of a photoinitiator in a wet state under ultraviolet light, reducing ultraviolet light reaction in an EVAL film by utilizing the shielding effect of the photoinitiator on the ultraviolet light, simultaneously driving the photoinitiator to migrate to the surface of the EVAL film by utilizing the volatilization effect of a solvent, firstly realizing the fixation of the photoinitiator on one side of the EVAL film, further effectively reducing grafting reaction sites in the EVAL film, and realizing the one-side grafting of a responsive monomer on the surface of the EVAL film.
In a preferred embodiment, the concentration of photoinitiator in the photoinitiator solution is 80-200 g/L. In this example, the concentration of photoinitiator in the photoinitiator solution is specifically defined, since a suitable photoinitiator concentration is a key parameter for achieving the fixation of the photoinitiator only on the surface of the EVAL film, and a photoinitiator concentration lower than 80g/L causes the movement of the grafting reaction sites of the photoinitiator on the EVAL film, since, when the initiator concentration is low, the uv-shielding effect of the near-light side of the film is reduced, the grafting reaction sites inside the film are increased, and it is difficult to achieve one-sided grafting of the film. When the initiator concentration is higher than 200g/L, it is difficult to dissolve part of the photoinitiator in the solvent, and the graft reaction is not facilitated. It is understood that the photoinitiator concentration may also be 100g/L, 120g/L, 140g/L, 160g/L, 180g/L, and any point within the range thereof.
The invention also provides a preparation method of the intelligent film of the ethylene-vinyl alcohol copolymer with the Janus structure, which comprises the following steps:
s1: using an ethylene-vinyl alcohol copolymer film as a base film, and immersing the base film into a photoinitiator solution prepared from a volatile solvent to obtain a photoinitiator pre-coated film;
s2: the photoinitiator pre-coated film comprises a compact side and a porous side, the fixing of the photoinitiator on any side of the film is realized by firstly carrying out ultraviolet irradiation on any side of the compact side and the porous side, then a solution dissolved with a responsive monomer is coated, and the fixing of the responsive monomer on any side of the film is realized after the ultraviolet irradiation.
In the embodiment, an EVAL film is taken as a base film, ultraviolet irradiation is carried out on the compact side of the EVAL film, the optical characteristic of a photoinitiator and the site guiding effect of the photoinitiator in the solvent volatilization process are utilized to realize the fixation of the photoinitiator only on the compact side of the EVAL film, then a solution dissolved with a responsive monomer is coated on the compact side of the EVAL film fixed with the photoinitiator, and the fixation of the responsive monomer on the compact side of the EVAL film is realized through an ultraviolet grafting technology; and then, with the porous side of the EVAL film as a light-facing side, repeating the steps, and utilizing the optical characteristics of a photoinitiator and the site guiding effect of the photoinitiator in the solvent volatilization process to realize the fixation of the photoinitiator only on the porous side of the EVAL film, so as to realize the fixation of another different responsive monomer on the porous side of the EVAL film, and finally obtaining the ethylene-vinyl alcohol copolymer intelligent film with the Janus structure, wherein different responsive monomers are respectively fixed on two sides of the ethylene-vinyl alcohol copolymer intelligent film.
In a preferred embodiment, the concentration of photoinitiator in the photoinitiator solution is 80-200 g/L. In this example, the concentration of photoinitiator in the photoinitiator solution was specifically defined, because, during the preparation of the ethylene-vinyl alcohol copolymer smart film having a Janus structure, the one-sided fixation of the photoinitiator on the surface of the EVAL film was critical to achieve the grafting of different responsive monomers on both sides of the EVAL film, respectively. In the embodiment, the concentration of the photoinitiator is limited, so that the adsorption amount of the photoinitiator to the light side of the EVAL film is increased, the photoreaction in the EVAL film is reduced based on the shielding effect of the photoinitiator on ultraviolet light, meanwhile, in the fixing process of the photoinitiator, the volatile solvent continuously drives the photoinitiator to migrate to the light side of the film, and the fixation of the photoinitiator and the grafting of the monomer only occur on one side of the film under the synergistic effect of the volatile solvent and the photoinitiator. It is understood that the photoinitiator concentration may also be 100g/L, 120g/L, 140g/L, 160g/L, 180g/L, and any point within the range thereof.
In a preferred embodiment, the photoinitiator is at least one of benzophenone, benzoin dimethyl ether or azobisisobutyronitrile. In this example, a specific kind of photoinitiator is defined, and it is understood that the photoinitiator listed in this example may be other substances reasonably selected and adjusted by those skilled in the art in combination with common knowledge in the field.
In a preferred embodiment, the volatile solvent is at least one of acetone, ethanol, diethyl ether, dichloromethane, chloroform or tetrahydrofuran. In this embodiment, specific types of volatile solvents are defined, and it is understood that the volatile solvents listed in this embodiment may be other substances reasonably selected and adjusted by those skilled in the art in combination with common knowledge in the field.
In a preferred embodiment, the responsive monomer is any two of acrylic acid, methacrylic acid, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, tetravinylpyridine, divinylpyridine, acryloylisopropylamine, glycidyl methacrylate, ethylene glycol dimethacrylate, N-dimethylacrylamide, N-diethylacrylamide, hydroxyethyl 2-methacrylate, N-vinylcaprolactam or 2-methyl 5-vinylpyridine. In this embodiment, specific types of the responsive monomers are specifically defined, and it is understood that the responsive monomers listed in this embodiment may be other substances reasonably selected and adjusted by those skilled in the art in combination with common knowledge in the field.
The invention also provides application of the ethylene-vinyl alcohol copolymer intelligent membrane with the Janus structure in the fields of separation and purification, water treatment and intelligent sensing. In the embodiment, the ethylene-vinyl alcohol copolymer intelligent membrane with the Janus structure can change the physical and chemical properties of the ethylene-vinyl alcohol copolymer intelligent membrane by sensing and responding to the change of the environmental signal, and meanwhile, the intelligent membrane combines the permeation and separation performance of the EVAL membrane, so that the intelligent fine control on the permeation and separation performance of the ethylene-vinyl alcohol copolymer intelligent membrane with the Janus structure can be realized, and the ethylene-vinyl alcohol copolymer intelligent membrane has a good application prospect in the fields of separation and purification, water treatment and intelligent sensing.
In order to more clearly and specifically describe the intelligent film of ethylene-vinyl alcohol copolymer with a Janus structure, the preparation method and the application thereof provided by the embodiment of the invention, the following description is provided with reference to specific embodiments.
Example 1
(1) Weighing 10g of ethylene-vinyl alcohol polymer (EVAL) and 40g of dimethyl sulfoxide solvent, putting into a three-neck flask, heating to 60 ℃, and stirring for 4 hours to obtain a homogeneous and transparent casting solution, wherein the EVAL content in the casting solution is 20%, and the dimethyl sulfoxide content in the casting solution is 80%. Vacuum defoaming, scraping with a scraper to obtain film, placing in pure water at 25 deg.C, and immersing to obtain EVAL film with thickness of 150 μm by precipitation phase conversion method. Soaking in purified water for 2 days, and freeze drying.
(2) Taking the EVAL film prepared in the step (1) as a base film, immersing the EVAL film into a benzophenone acetone solution with benzophenone concentration of 100g/L, oscillating and adsorbing for 120min, directly irradiating the wetted EVAL benzophenone pre-coated film for 20min under ultraviolet light, taking the compact side of the film as a light-facing side, fixing the photoinitiator on the surface of the EVAL film only under the light absorption shielding effect of the photoinitiator on the surface of the EVAL film and the migration effect of the benzophenone in the acetone volatilization process, then uniformly distributing methacrylic acid (PDMAEMA) monomers on the surface of the film, and irradiating for 20min under the ultraviolet light to prepare the EVAL film only with PDMAEMA grafted chains distributed on the compact side of the film.
(3) And (3) taking the porous side of the EVAL film as a light-facing side, repeating the step (2), and grafting tetravinyl pyridine (P4VP) on the porous side of the EVAL film to obtain the ethylene-vinyl alcohol copolymer intelligent film with the Janus structure, wherein PDMAEMA and P4VP are distributed on two sides of the intelligent film respectively.
Example 2
The preparation method of the EVAL film is the same as that of example 1 except that: the concentration of benzophenone is 80g/L, and the responsive monomer grafted on the porous side of the EVAL membrane is acrylic acid (AAc).
Example 3
The preparation method of the EVAL film is the same as that of example 1 except that: the concentration of benzophenone is 200g/L, and the responsive monomer grafted on the dense side of the EVAL membrane is acryloyl isopropylamine (PNiPAAm).
Example 4
The preparation method of the EVAL film is the same as that of example 1 except that: the concentration of benzophenone is 120g/L, the responsive monomer grafted on the dense side of the EVAL membrane is methacrylic acid (MAA), and the responsive monomer grafted on the porous side of the EVAL membrane is N-vinyl caprolactam (PVCL).
Comparative example 1
The preparation method of the EVAL film is the same as that of example 1 except that: the concentration of benzophenone was 60 g/L.
Comparative example 2
The preparation method of the EVAL film is the same as that of example 1 except that: the concentration of benzophenone was 20 g/L.
Comparative example 3
The preparation method of the EVAL film is the same as that of example 1 except that: both responsive monomers were co-grafted on the dense side of the EVAL membrane.
Performance testing
The light intensities of both sides of the film of the precoats prepared in examples 1 to 4 and comparative examples 1 to 2 were measured, and the light transmittance, which is the percentage of the light intensities of the high beam side and the low beam side, was calculated, and the measurement results are shown in table 1.
TABLE 1 transmittance of both sides of film of precoats prepared in examples 1 to 4 and comparative examples 1 to 2
Example 1 Example 2 Example 3 Example 4 Comparative example 1 Comparative example 2
Light transmittance 0.08％ 0.10％ 0.05％ 0.08％ 0.50％ 3.43％
From the experimental results in table 1, it can be seen that the transmittance of the film in examples 1-4 is less than 0.10% because the uv light is shielded by the high concentration photoinitiator on the low beam side of the film and the uv light incident on the inner and high beam sides of the film is significantly reduced in the range of photoinitiator concentration 80-200 g/L; when the concentration of the photoinitiator in the comparative examples 1-2 is 60g/L and 20g/L, the initiator on the low light side of the film is not enough to shield the incidence of ultraviolet light in the film, so that the light transmittance on the high light side of the film is higher, and the unilateral grafting of the film is difficult to realize.
The film materials obtained by fixing the photoinitiator in example 1 and comparative examples 1 and 2 were subjected to ultraviolet diffuse reflection spectroscopy (general purpose, TU-1901, beijing puzzel) to detect changes in chemical compositions on both sides of the film, as shown in fig. 1.
The film materials prepared in example 1 and comparative example 3 were subjected to fourier infrared spectroscopy (tens 37, bruker axs) to detect changes in chemical composition on both sides of the film, using EVAL film as a control, as shown in fig. 2.
The change in hydrophilicity and hydrophobicity of both sides of the membrane was measured using a contact angle measuring instrument (CM3250, KRUSS, Germany), as shown in FIGS. 2 and 3.
The Janus intelligent membrane materials prepared in examples 1, 3 and 4 were subjected to a permeability test using a cross-flow membrane filtration apparatus, as shown in fig. 4, 6 and 7.
The change in potential with pH on both sides of the film material obtained in example 2 was examined by a solid Zeta potentiometer (SurPASS, Anton Parr GmbH, Austria), and the result is shown in FIG. 5.
From the experimental results of fig. 1, it can be found that the initiator-immobilized film exhibited a characteristic absorption peak of the surface initiator benzophenone at 256nm, corresponding to the absorption peak of the benzene ring in the benzophenone structure, wherein the film material prepared in example 1 had the photoinitiator immobilized only on the near-beam side of the film, and no absorption peak of benzophenone was observed on the far-beam side of the film, while in comparative examples 1 and 2, absorption peaks were observed on both the near-beam side and the far-beam side of the film.
From the experimental results of FIG. 2, it can be found that the Janus intelligent membrane prepared in example 1 is found with 1726cm on the dense side only-1An absorption peak exists, which corresponds to a stretching vibration peak of C ═ O on PDMAEMA, and shows that the graft chain PDMAEMA is grafted on the dense side of the EVAL membrane only; while the smart film was only 1602cm on the porous side-1The absorption peak is present and represents the pyridine ring on 4VPThe stretching vibration peak of C ═ N, indicates that 4VP is grafted only on the porous side of EVAL membrane, which has Janus double-sided structure. The same side modified intelligent film prepared in comparative example 3 is 1602cm on the dense side of the film-1、1726cm-1Absorption peaks exist at the positions, the two kinds of grafted chains on the surface are mainly distributed on the dense side of the membrane, and the characteristic absorption peaks of the two kinds of grafted chains hardly exist on the porous side of the EVAL membrane.
From the experimental results in fig. 3, it can be seen that the dense side of the Janus smart membrane prepared in example 1 has close contact angles at pH 3.6 and 6.4, and the porous side has close contact angles at pH 6.4 and 11.0, which indicates that the hydrophilic and hydrophobic pH responsiveness of PDMAEMA (pKa of 8.0-9.0) and P4VP (pKa of 4.0-4.5) are maintained on both sides of the membrane, and the smart responsiveness on both sides of the membrane are independent and do not affect each other. The ipsilateral modified intelligent membrane compact side contact angle prepared by the comparative example 3 has no pH response change, and is expressed by the hydrophilic and hydrophobic characteristics of the copolymer of PDMAEMA and P4VP, while the hydrophilic and hydrophobic characteristics of the porous side of the membrane are similar to those of the original membrane, which shows that the performances of the membrane are mutually influenced when two intelligent monomers are respectively grafted on the same side of the membrane, and the performances are expressed by the copolymer properties of the two intelligent monomers.
As can be seen from the experimental results in fig. 4, the Janus intelligent membrane material prepared in example 1 has two relatively independent flux reduction mutation processes, which respectively correspond to pKa variation ranges of two intelligent monomers, and thus, it is shown that the intelligent response performances on two sides of the membrane are independent from each other and do not affect each other. The flux of the ipsilateral modified intelligent membrane prepared by the comparative example 3 is gradually reduced from pH 9.0 to pH 3.6, and the whole flux attenuation process is shown as the result of the combined action of PDMAEMA and P4VP units in the copolymer of PDMAEMA and P4VP, which shows that the performances of the ipsilateral modified intelligent membrane are mutually influenced when two intelligent monomers are respectively grafted on the same side of the membrane, and are shown as the copolymer properties of the two intelligent monomers.
The response change of the membrane material obtained in example 3 with temperature and pH was detected, and the results are shown in fig. 6, where the temperature-sensitive polymer PNiPAAm and the pH-sensitive substance P4VP were grafted on both sides of the membrane, respectively, and the membrane permeability showed the response of temperature and pH, respectively.
The response change of the membrane material obtained in example 4 with temperature and pH was examined, and the results shown in fig. 7 show that the membrane permeability can have both temperature and pH responsiveness when the pH sensor MAA and the temperature sensitive polymer PVCL are grafted to both sides of the membrane.
From the detection results of fig. 5, it can be seen that the potentials at two sides of the Janus intelligent film material prepared in example 2 have mutually independent pH response characteristics, which respectively correspond to the variation ranges of PDMAEMA (pKa of 8.0-9.0) and PAA (pKa of 3.5-4.5), indicating that the intelligent response characteristics at two sides of the film are mutually independent and do not influence each other.

Claims (6)

1. The intelligent ethylene-vinyl alcohol copolymer film with the Janus structure is characterized in that responsive monomers with different properties are respectively grafted to two sides of the ethylene-vinyl alcohol copolymer film, and the intelligent ethylene-vinyl alcohol copolymer film is obtained by the following method:
using an ethylene-vinyl alcohol copolymer film as a base film, and immersing the base film into a photoinitiator solution prepared from a volatile solvent to obtain a photoinitiator pre-coated film;
the photoinitiator pre-coated film comprises a compact side and a porous side, the either side of the compact side and the porous side in a wet state is irradiated by ultraviolet light to realize the fixation of the photoinitiator on the either side of the film, then a solution dissolved with a responsive monomer is coated, and the fixation of the responsive monomer on the either side of the film is realized after the irradiation of the ultraviolet light;
the concentration of the photoinitiator in the photoinitiator solution is 80-200 g/L.
2. The method for preparing the intelligent film of ethylene-vinyl alcohol copolymer with Janus structure as claimed in claim 1, comprising the following steps:
using an ethylene-vinyl alcohol copolymer film as a base film, and immersing the base film into a photoinitiator solution prepared from a volatile solvent to obtain a photoinitiator pre-coated film;
the photoinitiator pre-coated film comprises a compact side and a porous side, the either side of the compact side and the porous side in a wet state is irradiated by ultraviolet light to realize the fixation of the photoinitiator on the either side of the film, then a solution dissolved with a responsive monomer is coated, and the fixation of the responsive monomer on the either side of the film is realized after the irradiation of the ultraviolet light; the concentration of the photoinitiator in the photoinitiator solution is 80-200 g/L.
3. The method of claim 2, wherein the photoinitiator is at least one of benzophenone, benzoin dimethyl ether, or azobisisobutyronitrile.
4. The method of claim 2, wherein the volatile solvent is at least one of acetone, ethanol, diethyl ether, dichloromethane, chloroform, or tetrahydrofuran.
5. The method of claim 2, wherein the responsive monomer is any two of acrylic acid, methacrylic acid, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, tetravinylpyridine, divinylpyridine, acryloylisopropylamine, glycidyl methacrylate, ethylene glycol dimethacrylate, N-dimethylacrylamide, N-diethylacrylamide, hydroxyethyl 2-methacrylate, N-vinylcaprolactam, or 2-methyl 5-vinylpyridine.
6. The application of the intelligent film of ethylene-vinyl alcohol copolymer with Janus structure in the fields of separation and purification, water treatment and intelligent sensing according to claim 1.
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