阅读说明：本技术 一种pH响应型多孔吸附材料及其制备方法、应用 (pH response type porous adsorption material and preparation method and application thereof ) 是由 周寅宁 吴优 周鸣亮 李锦锦 周宏斌 张鹏 于 2021-09-07 设计创作，主要内容包括：本发明提供一种pH响应型多孔吸附材料及其制备方法、应用,所述制备方法包括：将氯化钙水溶液加入到含有单体、交联剂、稳定剂和引发剂的混合溶液中形成高内相乳液,然后将所述高内相乳液进行加热引发聚合反应,得到pH响应型多孔吸附材料；所述单体包括pH响应型单体和苯乙烯；所述pH响应型单体为甲基丙烯酸二甲氨基乙酯或甲基丙烯酸二乙氨基乙酯；所述稳定剂为聚乙二醇-b-聚苯乙烯两嵌段共聚物。采用本申请的合成体系制备得到的pH响应型多孔吸附材料的孔道结构均匀,pH响应型单体含量高,具有对外界pH反应灵敏、响应可逆循环性好的特点,可应用在吸附分离领域。(The invention provides a pH response type porous adsorption material and a preparation method and application thereof, wherein the preparation method comprises the following steps: adding a calcium chloride aqueous solution into a mixed solution containing a monomer, a cross-linking agent, a stabilizing agent and an initiator to form a high internal phase emulsion, and then heating the high internal phase emulsion to initiate polymerization reaction to obtain a pH response type porous adsorption material; the monomers comprise pH response type monomers and styrene; the pH response type monomer is dimethylaminoethyl methacrylate or diethylaminoethyl methacrylate; the stabilizing agent is a polyethylene glycol-b-polystyrene diblock copolymer. The pH response type porous adsorption material prepared by the synthesis system has the characteristics of uniform pore channel structure, high pH response type monomer content, sensitive response to external pH and good response reversible cyclicity, and can be applied to the field of adsorption separation.)

1. A preparation method of a pH response type porous adsorption material is characterized in that a calcium chloride aqueous solution is added into a mixed solution containing a monomer, a cross-linking agent, a stabilizing agent and an initiator to form a high internal phase emulsion, and then the high internal phase emulsion is heated to initiate polymerization reaction to obtain the pH response type porous adsorption material;

the monomers comprise pH response type monomers and styrene; the pH response type monomer is dimethylaminoethyl methacrylate or diethylaminoethyl methacrylate; the stabilizing agent is a polyethylene glycol-b-polystyrene diblock copolymer.

2. The method of claim 1, wherein: the structural formula of the polyethylene glycol-b-polystyrene diblock copolymer is as follows:

wherein m is the polymerization degree of the polystyrene segment, and m is 40-130; n is the polymerization degree of the polyethylene glycol section, and n is 40-45.

3. The method of claim 2, wherein: the addition amount of the polyethylene glycol-b-polystyrene diblock copolymer is 5-15 wt% of the total mass of the monomers;

and/or: the addition amount of the pH response type monomer is 30-70 vol% of the total volume of the monomer;

and/or: when the pH response type monomer is dimethylaminoethyl methacrylate, the addition amount of the pH response type monomer is 30-50 vol% of the total volume of the monomer;

when the pH response type monomer is diethylaminoethyl methacrylate, the addition amount of the pH response type monomer is 30-70 vol% of the total volume of the monomer.

4. The method of claim 2, wherein the polyethylene glycol-b-polystyrene diblock copolymer is prepared by a method comprising the steps of:

1) carrying out esterification reaction on polyethylene glycol monomethyl ether, 2-bromine isobutyryl bromide and an acid-binding agent in a first reaction medium to obtain a monobromide-terminated polyethylene glycol macroinitiator;

2) heating a styrene monomer and the monobromo-terminated polyethylene glycol macroinitiator obtained in the step 1) in a second reaction medium under the condition of a reduction catalyst system to initiate polymerization reaction, thereby obtaining the polyethylene glycol-b-polystyrene diblock copolymer.

5. The method of claim 4, wherein: in step 1):

the acid-removing agent is triethylamine;

and/or: the first reaction medium is anhydrous dichloromethane;

and/or: the molar ratio of the polyethylene glycol monomethyl ether to the 2-bromoisobutyryl bromide to the acid-binding agent is 1: (2-3): (2-3).

6. The method of claim 4, wherein: in step 2):

in the reduction catalysis system, the catalysts are copper chloride and tri [ (2-pyridyl) methyl ] amine, and the reducing agent is stannous octoate;

and/or: the second reaction medium is dimethylformamide;

and/or: the heating temperature is 100-120 ℃;

and/or: the styrene monomer is added to the reaction system in portions.

7. The method of claim 1, wherein: based on the total volume of the high internal phase emulsion, the volume fraction of the calcium chloride aqueous solution is 75-95%;

and/or: the concentration of the calcium chloride aqueous solution is 0.05-0.10 mol/L;

and/or: dropwise adding a calcium chloride aqueous solution into the mixed solution;

and/or: in the process of forming the high internal phase emulsion, the stirring speed is 3000-10000 rpm;

and/or: the initiator is azobisisobutyronitrile, and the heating temperature is 60-70 ℃;

and/or: the addition amount of the initiator is 0.8-1.5 wt% of the total mass of the monomers;

and/or: the crosslinking agent is divinylbenzene;

and/or: the addition amount of the cross-linking agent is 8-12% of the total volume of the monomers.

8. A pH-responsive porous adsorbent material prepared by the preparation method according to any one of claims 1 to 7.

9. The pH-responsive porous adsorbent material of claim 8, wherein: the pH response type porous adsorption material has a communicated multi-stage pore structure, wherein the average pore diameter of large pores is 4.0-20.0 mu m, and the average pore diameter of small pores is 0.5-3.5 mu m;

and/or: the pH response type porous adsorption material has adsorption characteristics;

and/or: the pH response characteristic of the pH response type porous adsorption material has reversibility.

10. Use of the pH-responsive porous adsorbent material of claim 8 in the field of adsorptive separation.

Technical Field

The invention belongs to the field of high polymer engineering, and particularly relates to a pH response type porous adsorption material, and a preparation method and application thereof.

Background

Porous polymers are receiving wide attention due to their large specific surface area, high chemical stability, low skeletal density, and the like. The porous polymer containing acidic or basic functional groups generally has pH response wetting behavior, because the conformation and the charging condition of the porous polymer can be obviously influenced by solutions with different pH values, and the unique performance enables the porous polymer to have wide application prospects in the fields of intelligent surfaces, drug delivery, tissue engineering, sensor preparation and the like.

Generally, methods for synthesizing porous polymers include a breath-chart method (breath-fit method), a Layer-by-Layer assembly method (Layer-by-Layer assembly method), and a high internal phase emulsion template method (high phase emulsion template). At present, the high internal phase emulsion template method has the advantage that the operation is simple, and the material structure can be controlled in advance through simple regulation and control, so that the method is widely applied to preparation of polymer porous materials, and the porous materials prepared by the method are generally called polyHIPE. Surfactants useful for stabilizing high internal phase emulsions are mainly small molecule surfactants, solid nanoparticles, amphiphilic block copolymers, and the like. Compared with other two stabilizers, the amphiphilic block copolymer has more advantages in the aspects of interface stability and biocompatibility, and due to the special spatial arrangement, the amphiphilic block copolymer not only can be used as a surfactant for stabilizing emulsion in the preparation process of high internal phase emulsion, but also can realize the surface modification effect on materials. The unique properties lead the block copolymers to have wide application prospects in the preparation of high internal phase emulsions.

The existing high internal phase emulsion taking dimethylaminoethyl methacrylate (DMAEMA) or diethylaminoethyl methacrylate (DEAEMA) as an oil phase can exist in an oil-water two-phase due to certain solubility of the responsive monomer in water, so that the problem that stable water-in-oil HIPE is difficult to form or even cannot be formed. To achieve such stable water-in-oil emulsions, conventional small molecule surfactants (e.g., span80) are typically applied to the system by introducing a hydrophobic comonomer (e.g., styrene) to reduce the solubility of the monomer in the aqueous phase. The volume ratio of the comonomer is usually less than 50%, and the stability of the HIPE is influenced by continuously improving the proportion of the responsive monomer; meanwhile, a large amount of surfactant is needed for stabilizing the system, and the mass fraction of the surfactant is more than 30% of that of the oil phase component. Therefore, the organic phase of the prepared HIPE is not high in the content of the responsive monomer, and the prepared polyHIPE porous polymer is easy to contain small molecule surfactant residues. Therefore, the search for a new synthetic system for improving the stability of the high internal phase emulsion taking DMAEMA or DEAEMA as an oil phase has important research significance.

Disclosure of Invention

In view of the above disadvantages of the prior art, the present invention aims to provide a pH-responsive porous adsorption material, a preparation method thereof, and an application thereof, which are used to solve the problems of poor stability, low content of responsive monomers, uncontrollable size and low purity of the prepared porous polymer, and easiness in containing small molecule surfactant residues in the high internal phase emulsion using DMAEMA or DEAEMA as an oil phase in the prior art.

To achieve the above objects and other related objects, the present invention includes the following technical solutions.

The invention provides a preparation method of a pH response type porous adsorption material, which comprises the steps of adding a calcium chloride aqueous solution into a mixed solution containing a monomer, a cross-linking agent, a stabilizing agent and an initiator to form a high internal phase emulsion, and then heating the high internal phase emulsion to initiate polymerization reaction to obtain the pH response type porous adsorption material; the monomers include pH-responsive monomers and styrene (St); the pH response type monomer is dimethylaminoethyl methacrylate (DMAEMA) or diethylaminoethyl methacrylate (DEAEMA); the stabilizer is polyethylene glycol-b-polystyrene two-block copolymer (PEO-b-PS).

Preferably, the polyethylene glycol-b-polystyrene diblock copolymer has the following structural formula:

wherein m is the polymerization degree of the polystyrene segment, and m is 40-130; n is the polymerization degree of the polyethylene glycol section, and n is 40-45.

Preferably, the addition amount of the polyethylene glycol-b-polystyrene diblock copolymer is 5-15 wt% of the total mass of the monomers.

Preferably, the addition amount of the pH-responsive monomer is 30 to 70 vol% of the total volume of the monomers.

Preferably, when the pH-responsive monomer is dimethylaminoethyl methacrylate, the addition amount of the pH-responsive monomer is 30-50 vol% of the total volume of the monomers; when the pH response type monomer is diethylaminoethyl methacrylate, the addition amount of the pH response type monomer is 30-70 vol% of the total volume of the monomer.

Preferably, the polyethylene glycol-b-polystyrene diblock copolymer is prepared by a method comprising the following steps:

1) carrying out esterification reaction on polyethylene glycol monomethyl ether, 2-bromine isobutyryl bromide and an acid-binding agent in a first reaction medium to obtain a monobromide-terminated polyethylene glycol macroinitiator;

2) heating a styrene monomer and the monobromo-terminated polyethylene glycol macroinitiator obtained in the step 1) in a second reaction medium under the condition of a reduction catalyst system to initiate polymerization reaction, thereby obtaining the polyethylene glycol-b-polystyrene diblock copolymer.

Preferably, in step 1): the acid-removing agent is triethylamine.

Preferably, in step 1): the first reaction medium is anhydrous dichloromethane.

Preferably, in step 1): the molar ratio of the polyethylene glycol monomethyl ether to the 2-bromoisobutyryl bromide to the acid-binding agent is 1: (2-3): (2-3).

Preferably, in the step 1), the reaction is carried out at-10 to 5 ℃ and then at 20 to 30 ℃.

Preferably, the step 1) further comprises post-treatment steps including extraction, water removal, concentration, precipitation and drying. More preferably, a saturated sodium hydroxide aqueous solution is used as an extraction solution during extraction, and after extraction, the mixture is kept stand for layering, and an organic layer is taken; the drying agent adopted in the dehydration process is anhydrous magnesium sulfate; the precipitator in the precipitation treatment is anhydrous ether; the drying temperature does not exceed 40 ℃.

Preferably, in step 2): in the reduction catalysis system, the catalyst is cupric chloride and tri [ (2-pyridyl) methyl ] amine, and the reducing agent is stannous octoate.

Preferably, in step 2): the second reaction medium is dimethylformamide.

Preferably, in step 2): the heating temperature is 100-120 ℃, specifically 100 ℃, 105 ℃, 110 ℃, 115 ℃ and 120 ℃.

Preferably, in step 2): the styrene monomer is added to the reaction system in portions.

Preferably, in step 2), the reaction is carried out in an inert atmosphere. More preferably, the inert atmosphere is nitrogen, and more preferably, the nitrogen is high-purity nitrogen with a mass percentage of more than 99.995%.

Preferably, in step 2), a post-treatment step is further included, comprising catalyst removal, concentration, precipitation and drying. More preferably, the catalyst is removed by passing the reaction solution through an alumina packed column; the concentration is carried out by adopting normal temperature reduced pressure distillation; the precipitator in the precipitation treatment is petroleum ether with the temperature of 65-85 ℃.

Preferably, the volume fraction of the aqueous calcium chloride solution is 75-95%, specifically 75%, 80%, 85%, 90%, 95%, based on the total volume of the high internal phase emulsion.

Preferably, the concentration of the calcium chloride aqueous solution is 0.05-0.10 mol/L, such as 0.05mol/L, 0.06mol/L, 0.07mol/L, 0.08mol/L, 0.09mol/L, 0.10 mol/L.

Preferably, an aqueous calcium chloride solution is added dropwise to the mixed solution.

Preferably, the stirring rate during formation of the high internal phase emulsion is 3000 to 10000rpm, such as 3000rpm, 5000rpm, 7000rpm, 8000rpm, 10000 rpm.

Preferably, the initiator is azobisisobutyronitrile, and the heating temperature is 60-70 ℃, 60 ℃, 65 ℃ and 70 ℃.

Preferably, the addition amount of the initiator is 0.8 to 1.5 wt%, such as specifically 0.9 wt%, 1.0 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt% of the total mass of the monomers.

Preferably, the crosslinking agent is divinylbenzene.

Preferably, the addition amount of the cross-linking agent is 8-12% of the total volume of the monomers, such as 8%, 9%, 10%, 12%.

The second purpose of the invention is to provide a pH response type porous adsorbing material prepared by the preparation method.

Preferably, the pH response type porous adsorption material has a connected multi-stage pore structure, wherein the average pore diameter of large pores is 4.0-20.0 μm, and the average pore diameter of small pores is 0.5-3.5 μm.

Preferably, the pH-responsive porous adsorbent material has adsorption properties.

Preferably, the pH response characteristic of the pH-responsive porous adsorbent material is reversible.

The invention also aims to provide application of the pH response type porous adsorbing material in the field of adsorption and separation.

Preferably, the pH response type porous adsorption material is used in the fields of oil spill recovery, oil product dewatering, industrial acid-containing wastewater treatment and the like.

As described above, the present invention has the following advantageous effects:

the pH-responsive porous adsorption material is prepared by taking a polyethylene glycol-b-polystyrene diblock copolymer as a stabilizer, forming an oil phase by using pH-responsive monomers DMAEMA or DEAEMA and St together and passing through a W/O HIPE template. The method has the advantages that the intrinsic characteristic that the length of the molecular chain segment of the polyethylene glycol-b-polystyrene diblock copolymer is adjustable and the characteristic that the hydrophobic segment enhances the hydrophobicity and viscosity of the oil phase are utilized, so that the stability of the high internal phase emulsion taking DMAEMA or DEAEMA as the oil phase is effectively improved on the premise of less addition amount; the pH response type porous adsorption material prepared by the synthesis system has the characteristics of uniform pore channel structure, high pH response type monomer content, sensitive response to external pH and good response reversible cyclicity, and can be applied to the field of adsorption separation.

Drawings

Fig. 1 is a pH response mechanism diagram of the pH responsive porous adsorbent material according to the present invention.

FIG. 2 shows SEM images of pH-responsive porous adsorbent materials prepared in examples 1-3: (a) example 1; (b) example 2; (c) example 3.

FIG. 3 is a surface contact angle test chart of pH-responsive porous adsorption materials prepared in examples 4 and 8 to 10 under different pH environments: (a) example 4; (b) example 8; (c) example 9; (d) example 10.

FIG. 4 is a graph showing the adsorption amount qt versus time t of the PDEAEMA co-St-based pH-responsive porous adsorption material prepared in example 10 in aqueous solutions with different pH values.

Fig. 5 shows an adsorption cycle test chart of the PDEAEMA co-St-based pH-responsive porous adsorption material prepared in example 10 in a solution with pH of 1.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

It is to be understood that the processing equipment or apparatus not specifically identified in the following examples is conventional in the art.

Furthermore, it is to be understood that one or more method steps mentioned in the present invention does not exclude that other method steps may also be present before or after the combined steps or that other method steps may also be inserted between these explicitly mentioned steps, unless otherwise indicated; it is also to be understood that a combined connection between one or more devices/apparatus as referred to in the present application does not exclude that further devices/apparatus may be present before or after the combined device/apparatus or that further devices/apparatus may be interposed between two devices/apparatus explicitly referred to, unless otherwise indicated. Moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.

The embodiment of the application provides a preparation method of a pH response type porous adsorption material, which comprises the steps of adding a calcium chloride aqueous solution into a mixed solution containing a monomer, a cross-linking agent, a stabilizing agent and an initiator to form a high internal phase emulsion, and then heating the high internal phase emulsion to initiate polymerization reaction to obtain the pH response type porous adsorption material; the monomers include pH-responsive monomers and styrene (St); the pH response type monomer is dimethylaminoethyl methacrylate (DMAEMA) or diethylaminoethyl methacrylate (DEAEMA); the stabilizer is polyethylene glycol-b-polystyrene two-block copolymer (PEO-b-PS).

The high internal phase emulsion takes a mixed solution (oil phase) as a continuous phase, a calcium chloride aqueous solution as a dispersed phase, a polyethylene glycol-b-polystyrene diblock copolymer as a stabilizer, and the characteristic that the hydrophobicity and the viscosity of the oil phase are enhanced by the hydrophobic segment of the copolymer solves the problem that the high internal phase emulsion taking DMAEMA or DEAEMA as the oil phase is difficult to stabilize, and the specific mechanism is as follows: PS-b-PEO is adsorbed on the water-oil interface of the emulsion, wherein the PS chain segment of the hydrophobic section extends into the oil phase, so that on one hand, the viscosity of the oil phase is increased, the mechanical strength of the interface film is improved, and the oil-water interface film has stronger toughness; on the other hand, the PS segment has a certain degree of physical entanglement, so that the moving capability of the PS segment is reduced. The synergistic effect of the two aspects enables the stability of the high internal phase emulsion to be obviously improved. Wherein the calcium chloride aqueous solution is capable of inhibiting the Ostwald ripening effect and improving the stability of the high internal phase emulsion.

In one embodiment, the polyethylene glycol-b-polystyrene diblock copolymer has the following structural formula:

wherein m is the polymerization degree of the polystyrene segment, and m is 40-130; n is the polymerization degree of the polyethylene glycol segment, and n is 40-45, such as 40, 41, 42, 43, 44, 45.

The length of a hydrophobic PS block in the polyethylene glycol-b-polystyrene diblock copolymer is related to the aperture ratio of the prepared pH response type porous adsorption material, the mobility of the polyethylene glycol-b-polystyrene diblock copolymer in a high internal phase emulsion system is reduced due to the overlong length of the PS block, the cohesion force displayed at an interface is stronger, the aperture ratio of the material is reduced, even the hole closing phenomenon occurs, and the adsorption performance is reduced.

In a specific embodiment, the addition amount of the polyethylene glycol-b-polystyrene diblock copolymer is 5 to 15 wt% of the total mass of the monomers. The dosage of the polyethylene glycol-b-polystyrene diblock copolymer is related to the stability of the high internal phase emulsion and the pore structure of the finally prepared pH response type porous adsorption material. The polyethylene glycol-b-polystyrene diblock copolymer has the functions of increasing the viscosity of an oil phase and enhancing the mechanical property of an interfacial film, and the poor stability of a system can be caused due to the excessively low addition amount of the polyethylene glycol-b-polystyrene diblock copolymer; the addition amount of the catalyst is too high, so that the pore diameter of macropores in the material is too low, the formation of open pores is limited, and the adsorption performance of the material is reduced. In a specific embodiment, the amount of the pH-responsive monomer added is 30 to 70 vol% based on the total volume of the monomers.

Although the addition amount of the pH-responsive monomer determines the pH-responsive property of the final material, the addition amount is related to the PS block length of the polyethylene glycol-b-polystyrene diblock copolymer and the addition amount of the polyethylene glycol-b-polystyrene diblock copolymer, and an excessively high addition amount of the pH-responsive monomer lowers the stability of the high internal phase emulsion, and an excessively low addition amount of the pH-responsive monomer lowers or even disappears the pH-responsive property of the material, so that the specific addition range thereof must be strictly controlled. The nature of the different pH-responsive monomer species in the synthesis system of the present application determines the preferred amount used in forming the stable high internal phase emulsion. The nature of the different pH-responsive monomer species in the synthesis system of the present application determines the preferred amount used in forming the stable high internal phase emulsion. Specifically, when the pH response type monomer is dimethylaminoethyl methacrylate, the addition amount of the pH response type monomer is 30-50 vol% of the total volume of the monomer; when the pH response type monomer is diethylaminoethyl methacrylate, the addition amount of the pH response type monomer is 30-70 vol% of the total volume of the monomer.

In one embodiment, the polyethylene glycol-b-polystyrene diblock copolymer is prepared by a process comprising the steps of:

1) carrying out esterification reaction on polyethylene glycol monomethyl ether, 2-bromine isobutyryl bromide and an acid-binding agent in a first reaction medium to obtain a monobromide-terminated polyethylene glycol macroinitiator;

2) heating a styrene monomer and the monobromo-terminated polyethylene glycol macroinitiator obtained in the step 1) in a second reaction medium under the condition of a reduction catalyst system to initiate polymerization reaction, thereby obtaining the polyethylene glycol-b-polystyrene diblock copolymer.

Firstly, synthesizing mono-bromine end-capped polyethylene glycol through esterification reaction; the mono-bromine terminated polyethylene glycol is used as a macroinitiator, and the polyethylene glycol-b-polystyrene diblock copolymer is synthesized by an Atom Transfer Radical Polymerization (ATRP) technology; then the polyethylene glycol-b-polystyrene two-block copolymer is used as a stabilizer to stabilize water-in-oil high internal phase emulsion taking DMAEMA or DEAEMA and styrene as oil phases, and a porous material with pH responsiveness is synthesized. The synthetic route is as follows:

in a particular embodiment, in step 1): the acid-removing agent is triethylamine.

In a particular embodiment, in step 1): the first reaction medium is anhydrous dichloromethane.

In a particular embodiment, in step 1): the molar ratio of the polyethylene glycol monomethyl ether to the 2-bromoisobutyryl bromide to the acid-binding agent is 1: (2-3): (2-3), specifically 1: 2: 2.

in a specific embodiment, in the step 1), the reaction is carried out at-10 to 5 ℃ and then at 20 to 30 ℃.

In a specific embodiment, step 1) further comprises post-treatment steps including extraction, water removal, concentration, precipitation and drying. More preferably, a saturated sodium hydroxide aqueous solution is used as an extraction solution during extraction, and after extraction, the mixture is kept stand for layering, and an organic layer is taken; the drying agent adopted in the dehydration process is anhydrous magnesium sulfate; the precipitator in the precipitation treatment is anhydrous ether; the drying temperature does not exceed 40 ℃.

In a particular embodiment, in step 2): in the reduction catalysis system, the catalyst is cupric chloride and tri [ (2-pyridyl) methyl ] amine, and the reducing agent is stannous octoate.

In a particular embodiment, in step 2): the second reaction medium is dimethylformamide.

In a particular embodiment, in step 2): the heating temperature is 100-120 ℃, specifically 100 ℃, 105 ℃, 110 ℃, 115 ℃ and 120 ℃.

In a particular embodiment, in step 2): the styrene monomer is added to the reaction system in portions.

In a particular embodiment, in step 2), the reaction is carried out in an inert atmosphere. More preferably, the inert atmosphere is nitrogen, and more preferably, the nitrogen is high-purity nitrogen with a mass percentage of more than 99.995%.

In a specific embodiment, step 2) further comprises a post-treatment step comprising catalyst removal, concentration, precipitation and drying. More preferably, the catalyst is removed by passing the reaction solution through an alumina packed column; the concentration is carried out by adopting normal temperature reduced pressure distillation; the precipitator in the precipitation treatment is petroleum ether with the temperature of 65-85 ℃. Preferably, the volume fraction of the aqueous calcium chloride solution is 75-95%, specifically 75%, 80%, 85%, 90%, 95%, based on the total volume of the high internal phase emulsion.

In a specific embodiment, the concentration of the calcium chloride aqueous solution is 0.05 to 0.10mol/L, such as 0.05mol/L, 0.06mol/L, 0.07mol/L, 0.08mol/L, 0.09mol/L, 0.10 mol/L.

In a specific embodiment, an aqueous calcium chloride solution is added dropwise to the mixed solution.

In a specific embodiment, the stirring rate during formation of the high internal phase emulsion is 3000 to 10000rpm, specifically 3000rpm, 5000rpm, 7000rpm, 8000rpm, 10000 rpm.

In a specific embodiment, a high-shear emulsifying machine is used for stirring, the higher homogenization rate is helpful for crushing and dispersing the droplets of the calcium chloride aqueous solution to obtain emulsion droplets with smaller diameter and uniform size distribution, and the high internal phase emulsion dispersing machine and the stability are effectively improved, so that the cavity size of the porous material formed by polymerization is smaller and more uniform.

In a specific embodiment, the initiator is azobisisobutyronitrile, and the heating temperature is 60-70 ℃, 60 ℃, 65 ℃ and 70 ℃.

In a specific embodiment, the amount of the initiator added is 0.8 to 1.5 wt%, such as specifically 0.9 wt%, 1.0 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt% of the total mass of the monomers.

In a specific embodiment, the crosslinking agent is divinylbenzene.

In a specific embodiment, the amount of the crosslinking agent added is 8 to 12% of the total volume of the monomers, such as 8%, 9%, 10%, 12%.

The embodiment of the application also provides the pH response type porous adsorption material prepared by the preparation method.

In a specific embodiment, the pH response type porous adsorption material has a connected multi-stage pore structure, wherein the average pore diameter of large pores is 4.0-20.0 μm, and the average pore diameter of small pores is 0.5-3.5 μm.

In a specific embodiment, the pH-responsive porous adsorbent material has adsorption properties.

In one embodiment as shown in fig. 1, the pH-responsive porous adsorbent material has reversible pH-responsive properties.

The pH response type porous adsorption material has different adsorption capacities in water with different pH conditions, and the mechanism is as follows: in the pH response type porous adsorption material, a PDEAEMA or DEAEMA molecular structure unit simultaneously has a hydrophilic tertiary amino group and a hydrophobic alkyl group, and the tertiary amino group has protonation and deprotonation effects under different pH environments, so that the porous adsorption material has pH response adsorption characteristics. Specifically, under the condition that the pH is less than the pKa, the tertiary amino group in the pH response type porous adsorption material is subjected to protonation reaction, so that the pH response type porous adsorption material has stronger hydrophilicity.

The embodiment of the invention also provides application of the pH response type porous adsorption material in the field of adsorption and separation.

In a specific embodiment, the pH response type porous adsorption material is used in the fields of oil spill recovery, oil product water removal, industrial acid-containing wastewater treatment and the like.

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

Synthesis of polyethylene glycol-b-polystyrene diblock copolymers (PEO-b-PS) of three different chain lengths:

1) preparation of bromine-terminated polyethylene glycol macroinitiator:

adding a proper amount of anhydrous dichloromethane, 1mmol of polyethylene glycol and 2mmol of triethylamine into a reaction container, placing the reaction container in an ice bath, then dropwise adding 2mmol of 2-bromoisobutyryl bromide into the reaction container for reaction, firstly reacting under the condition of the ice bath, and then reacting at room temperature of 25 ℃; after the reaction is finished, adding saturated sodium bicarbonate solution and deionized water into the reaction solution for extraction for three times, adding anhydrous magnesium sulfate into an organic layer, drying the organic layer overnight, filtering, carrying out rotary evaporation on the filtrate to remove excess solvent, precipitating the obtained reaction concentrated solution for a plurality of times by using ethyl glacial ether, centrifuging, and carrying out vacuum drying at 30 ℃ for 24 hours to obtain the bromine-terminated polyethylene glycol macroinitiator;

2) according to the raw material ratios and polymerization reaction time shown in Table 1, the bromine-terminated polyethylene glycol macroinitiator (PEO-Br) in step 1) was dissolved in styrene (St), and then copper chloride powder and tris [ (2-pyridyl) methyl group were added]Adding a mixed solution of amine (TPMA), styrene and dimethylformamide into a reaction vessel; vacuumizing the reactor, introducing inert gas, hermetically stirring uniformly, adding a styrene solution of stannous octoate, and carrying out polymerization reaction at 110 ℃; after the reaction is finished, the solution is diluted by dichloromethane solution, the catalyst and the solvent are removed, petroleum ether with the temperature of 75 ℃ is used for precipitation, and vacuum drying is carried out at the temperature of 60 ℃ to respectively obtain three polyethylene glycol-b-polystyrene diblock copolymers PEO with different chain lengths₄₃-b-PS₄₁、PEO₄₃-b-PS₇₈And PEO₄₃-b-PS₁₃₀The molecular weight and the hydrophilic-lipophilic balance (HLB) are shown in Table 2.

And (3) structural characterization of the polymer: make itMolecular Structure analysis of the Polymer, deuterated chloroform (CDCl), on a Bruker Avance III HD 500MHz NMR spectrometer₃) As a deuterated solvent, the test was performed at room temperature; the number average molecular weight Mn and molecular weight distribution (Mw/Mn) of the block copolymer were measured using a gel permeation chromatograph. The column was calibrated with polyethylene glycol (PEG) standards and the eluent was Dimethylformamide (DMF). The test temperature was 40 ℃ and the flow rate was 0.6 ml/min.

TABLE 1 formulation and polymerization time of polyethylene glycol-b-polystyrene diblock copolymer

TABLE 2 molecular weight and hydrophilic-lipophilic balance (HLB) of polyethylene glycol-b-polystyrene diblock copolymer

Examples 1 to 10

Referring to the types and addition amounts of the pH-responsive monomer and the polyethylene glycol-b-polystyrene diblock copolymer shown in table 3, the polyethylene glycol-b-polystyrene diblock copolymer and azobisisobutyronitrile were dissolved in the pH-responsive monomer/styrene and divinylbenzene, the amount of azobisisobutyronitrile was 1 wt% of the total mass of the monomers, and the content of the crosslinking agent divinylbenzene DVB was 10% of the total volume of the monomers; then dropwise adding 0.09mol/L calcium chloride aqueous solution into the organic phase containing the monomer, the stabilizer and the initiator at a homogenizing speed of 6000rpm to form a high internal phase emulsion, and then placing the high internal phase emulsion in a 60 ℃ drying oven for reaction, wherein the volume fraction of the calcium chloride aqueous solution is 90% based on the total volume of the high internal phase emulsion; and (3) Soxhlet extracting and washing the polymerized monolithic material with water and ethanol respectively, and drying in vacuum at 60 ℃ to obtain the pH response type porous adsorption material, wherein the performance parameters of the pH response type porous adsorption material are shown in Table 3.

TABLE 3 formulations and Material Properties of examples 1-10

In Table 3, D and D are the average pore diameters of the macropores and the interconnected pores, respectively, and O is the sample opening degree (N.d)²/4·D²And N is the average number of the communicating holes on the wall of the macroporous hole. The average pore diameter of the material is the diameter of about 150 pores as measured by ImageJ analysis software and is given by the formula d_Average＝d_{Measurement averaging}×2/(3^1/2) And correcting the data.

The microstructure of the material is tested by a table type scanning electron microscope, a small amount of section parts of the material are taken and placed on a sample table paved with conductive adhesive, after gold spraying treatment, the material is placed into the scanning electron microscope for observation and shooting, and the accelerating voltage is set to be 5 kV. SEM images of the pH-responsive porous adsorption materials prepared in examples 1 to 3 are respectively shown in FIG. 2(a), FIG. 2(b) and FIG. 2(c), and it can be seen from FIG. 2 that when the amount of the polyethylene glycol-b-polystyrene diblock copolymer is low, the obtained product basically has a closed pore structure, and latex particles with a particle size of 650 to 700nm exist in the closed pore structure (an inset in FIG. 2 (a)). This is due to the presence of small oil-in-water emulsion droplets in the system, which, after polymerization, results in the formation of latex particles on the pore walls. With the increase of the amount of the polyethylene glycol-b-polystyrene diblock copolymer in the system to 5.96 wt%, the stable emulsion droplets become smaller, resulting in the reduction of the macroporous diameter of the obtained product from 13.9 +/-5.7 mu m to 8.3 +/-3.3 mu m; meanwhile, the water-oil interface of the HIPE becomes thin, so that the aperture ratio of the product is effectively improved (figure 2 (b)). When the amount of the polyethylene glycol-b-polystyrene diblock copolymer in the system was further increased to 15 wt% (fig. 2(c)), the macroporous diameter of the resulting product was further decreased, but the opening of the material was instead decreased from 5.3% to 1.8%.

The SEM characterization results are consistent with the data in table 3, and the sample prepared in example 1 has a closed cell structure, and it is not possible to count interconnected pores and calculate the opening degree; the pore structure of the sample obtained in example 6 had collapse with an excessively large diameter, and the diameters of macropores and interconnected pores thereof could not be counted.

The surface contact angles of the samples prepared in examples 4, 8-10 in different pH environments were tested.

The surface wetting properties of the samples were tested by optical contact angle measurement. Before testing, the sample surface was polished smooth and an acid-base solution was formulated with pH 1 and 11. The test was performed at room temperature using a volume of 2 μ L of acid or base solution in the test, and the test was repeated three times for each sample.

In FIG. 3 are the contact angles (WCA) of water drops of different pH after the surface of the samples prepared in examples 4, 8-10 has stabilized (5 min). The sample of example 4 containing 30% DMAEMA monomer did not exhibit significant pH responsiveness due to the lower content of the responsive monomer, and the contact angles of water droplets at pH 1 and 11 on the sample surface were not much different, 62.8 ± 1.3 ° and 60.5 ± 2.5 °, respectively. Example 8 samples containing 30% DEAEMA had contact angles for water droplets of different pH of 64.8 ± 0.4 ° (pH 1) and 91.7 ± 2.5 ° (pH 11), respectively, which were slightly larger than the samples of example 4, which correlates with the intrinsic hydropathic and hydrophobic properties of PDMAEMA and PDEAEMA. While investigating the effect of pH-responsive monomer content on the surface wettability behavior of the samples, for the sample of example 9, when a water drop of pH 1 was applied to the material surface, the water drop gradually spread over the surface of the sample, and the WCA of the water drop of pH 11 was about 29.7 + -1.1 deg. at the material surface after five minutes, while the WCA of the water drop of pH 11 was 43.4 + -0.2 deg. at the surface of the polymer material. Increasing the DEAEMA content to 70% (example 10) showed strong hydrophilicity, with the test water droplets at pH 1 and 11, the droplet spread and deformed on the surface with WCA less than 30 °. The above results show that as the responsive monomer content increases from 30% to 70%, the hydrophilicity of the material gradually increases.

The graph of the adsorption amount qt and the time t of the PDEAEMA co-St based pH response type porous adsorption material prepared in the example 10 in the aqueous solutions with different pH values is shown in FIG. 4: the adsorption capacity of the porous adsorption material to the aqueous solution with the pH value of 1 within 1 hour is 5.6 +/-0.7 g/g, and the adsorption capacity to the aqueous solution with the pH value of 11 is 2.3 +/-0.4 g/g.

The adsorption cycle performance of the PDEAEMA co-St based pH-responsive porous adsorption material prepared in example 10 was tested by the following method: and centrifuging the adsorbed material, washing with weak base water to deprotonate the surface of the material, drying to recover the adsorption capacity, and performing cyclic adsorption. The material can be washed with ethanol before drying, so as to accelerate the drying speed. The results of the adsorption cycle test for the solution having pH 1 are shown in fig. 5, and it can be seen that the porous adsorbent material has the characteristics of good response reversibility and recyclability.

In conclusion, the invention takes polyethylene glycol-b-polystyrene two-block copolymer as a stabilizer, pH response type monomers DMAEMA or DEAEMA and St jointly form an oil phase, and the pH response type porous adsorption material is prepared through a W/O HIPE template. The method has the advantages that the intrinsic characteristic that the length of the molecular chain segment of the polyethylene glycol-b-polystyrene diblock copolymer is adjustable and the characteristic that the hydrophobic segment enhances the hydrophobicity and viscosity of the oil phase are utilized, so that the stability of the high internal phase emulsion taking DMAEMA or DEAEMA as the oil phase is effectively improved on the premise of less addition amount; the pH response type porous adsorption material prepared by the synthesis system has the characteristics of uniform pore channel structure, high pH response type monomer content, sensitive response to external pH and good response reversible cyclicity, and can be applied to the field of adsorption separation.

Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.