CN111443122A - Environment-friendly waterborne polyurethane flexible sensing film and preparation method and application thereof - Google Patents

Abstract

The invention relates to an environment-friendly waterborne polyurethane flexible sensing membrane and a preparation method and application thereof. The environment-friendly waterborne polyurethane flexible sensing membrane comprises a continuous phase membrane matrix, and a solid ionic carrier and an ion exchanger which are embedded in the continuous phase membrane matrix, wherein the continuous phase membrane matrix is waterborne polyurethane, and the solid ionic carrier is a nano compound formed by compounding conductive polymer nano particles rich in functional groups and graphene nano sheets. The environment-friendly waterborne polyurethane flexible sensing membrane is formed by a solution method, can be applied to a sensing membrane in an ion selective electrode, and the corresponding sensing ions are lead ions. The potential sensor assembled by the membrane can be applied to sensitive detection of lead ions, and the lower limit of detection can reachTo 10^‑8In mol/L order, the response time can be as short as several seconds, and the service life can reach at least 4.5 months (18 weeks).

Description

Environment-friendly waterborne polyurethane flexible sensing film and preparation method and application thereof

Technical Field

The invention relates to the technical field of preparation and application of sensing films, in particular to an environment-friendly waterborne polyurethane flexible sensing film and a preparation method and application thereof.

Background

Lead ion as the most serious environmental pollutionOne of the pollutants may cause a series of diseases such as anemia, mental disorder, permanent nerve injury, etc. to human body. Thus, accurate measurement of Pb in the environment²⁺The content of (A) is particularly important for the overall health growth of human beings. And the traditional detection of trace Pb by Atomic Absorption Spectrometry (AAS), inductively coupled plasma mass spectrometry (ICP-MS) and the like²⁺The method has the disadvantages of high equipment cost, need of professional operators and the like, and can only be used for detection under laboratory conditions. But the method of the ion selective electrode can well meet the requirements of outdoor operation and on-line detection of ion concentration by the advantages of simple operation, quick response, low cost, environmental protection, safety, and the like.

Lead ion Selective carriers have been studied mainly at home and abroad on organic compound neutral carriers such as thioethers (Guzinski, M.; L isak, G.; Kupis, J.; Jasinski, A. Bochenska M.; L ead (II); Selective Ionophors for ion-Selective electrons: A review. C.Chim.acta 2013,791:1-12), crown ethers (Kazemi, S.Y.; Shamsur, M.; Sharghi, H. L ead-Selective poly (vinyl chloride) electrically modified base-synthesized surface-treated surface-synthesized aromatic hydrocarbon (III. J. 2009. 19. E.E.; E.E.C.S.E.S.E.S.H.; E.E.E.S.C.S.C.S.C.; E.E.E.E.E.E.E.; E.E.E.C.C.C.S.S.E.; E.E.E.E.S. C.S. E.S.S. C.; E.S. E.E.S. E.S. C.E.E.S. C. Pat. E.E.E.E.; E.S. E.E.E.S. C. 1-3. E.E.E.E. E. E.E.E.E.E.E. C. A. C. A. C.]arene derivative organic Sciences 2006,22(8):1075-²⁺-selective electrode based on electrophoretic polysaccharides films as on-to-electron driver. electrochemical Acta 2017,231: 53-60). However, neutral organic molecular carriers have the disadvantages of complicated synthesis method and the like. More recently inorganic substances such as PbS have also been used as leadIonophore, but plasticized PVC sensor film up to 1mm thick, with a lower detection limit of only 10^-2～10^-4mol/L, narrow detection range, lifetime of 44 days (Ajadi, A.A.; Shuaib, N.M.; Shoukry, A.F. depth profiling X-ray photoelectron spectroscopy and atomic microscopy of Cd (II) -and Pb (II) -selective electrolytes based on nano metallic ions RSC adv.2018,8: 3574) clearly, pure inorganic substances are not the first choice for lead ionophores.

In recent years, tin (IV) tungstate (Khan, A.A.; Alam, M.M.Synthesis, characteristics and analytical applications of a new and novel 'organic' compositional entities as a site exchange and Cd (II) ion-selective membrane electrode: polyannine Sn (IV) longitudinal storage. reaction.Funct.Polymer.2003, 55(3) 277-²⁺A polymeric binder using a fibrous type organic-inorganic hybrid location-exchange material, polypyrole sodium (IV) phosphate. react. Funct. Polymer.2005, 63(2) 119-; khan, m.q.; shaheen, S.Synthesis, chromatography, and electrochemical students of Pb²⁺-selective polypyrrole-Zr (IV) phosphate ion exchange membrane. J. solid State electrochem.2016,20(7) 2079-2091. Inamudin; rangrez, t.a.; mu, N.; ahmad, A.Synthesis and catalysis of poly (3,4-ethylenedioxythiophene) -poly (phenylenesulfonato) (PEDOT: PSS) Zr (IV) monophosphosphosphonate complex exchange, inorganic transition metal such as inorganic transition metal complex exchange, inorganic transition metal complex, ionic transition metal complex, internal, ionic transition metal, organic, chemical, chem, 95(4), 312-323) and the like, through the interaction between the transition metal empty-d orbital and the lone pair electron on the nitrogen atom in the conductive polymer, the formed organic-inorganic complex is used as a lead ion carrier, and the detection lower limit of the electrode can reach 10^-7mol/L, but the selectivity is not ideal enough, to obtain (PEDOT: PSS) -Zr (HPO)₃S)₂For example, many heavy metal ions of divalent and trivalent metals such as Cu: (II, Cd (II), Zn (II), Al (III), Fe (III) and Cr (III) cause certain interference to the detection of Pb (II). In addition to complexing with conducting polymers, transition metal salts are also used as lead ionophores in combination with natural polymers, such as tin (IV) phosphate-poly (gelatin-cl-alginate) nanocomposites, except that the response slope of the electrode is only 20.28mV/dec (Pathania, D.; Thakur, M.; Sharma, G.; Mishra, A.K. tin (IV) phosphate/poly (gelatin-cl-alginate) nanocomposite: catalysis and stabilization of potentiometric sensors for Pb (II). Materials Today Communications 2018,14:282-293), much lower than the Nerstian slope. It can be seen that the performance of the composite carrier is to be improved.

The PVC base membrane has another defect that in the constructed liquid connection ion selection electrode, the target ions cannot be sensitively detected due to the membrane ion current existing on two sides of the membrane, and the lower detection limit of the PVC base membrane is generally only 1 × 10^-6In addition, plasticizers also tend to extract lipid components from the samples being tested, causing the response potential of the sensing membrane to drift and lose selectivity (Mikhelson, k.n. ion-selective electrodes with sensitivity in linear differential concentrations.j.anal.chem).

2010,65(2):112-116)。

In order to avoid the above disadvantages of PVC films, some base films with little or no Plasticizer are proposed to be used in ion selective electrodes, and the problems of polyimide (Cha, G.S.; PVC.B. polymer-Plasticizer-selective Membrane) such as polyethylene-acrylate copolymer (1) (281-285), room temperature vulcanized rubber (Oh, B.K.; Kim, C.Y.; L ee, H.J.; Rho, K. L.; Cha G.S.; Nam, H.one-polyolefin rubber-coated ceramic-conductive films, Anal.Chem.1996,68(3), 2. for example, 2. C.S.; No. 2. F.; polyacrylic acid copolymer, 14, 10.7, and poly-acrylate copolymer (1, 14, 7, 14, 23, 24, 14, 23, 24, 14, 23, 21, 23, 7, eight.

Therefore, the plasticizer-free all-solid-state sensing membrane electrode with high response speed and stable response potential is not realized at present. The research on how to find a sensing membrane material which is non-toxic, environment-friendly and can tolerate the embedding of active component particles from a plurality of organic materials so as to realize the stable detection of lead ions is not reported.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides an environment-friendly waterborne polyurethane flexible sensing membrane as well as a preparation method and application thereof.

The purpose of the invention can be realized by the following technical scheme:

the first technical scheme is as follows:

provided is a solid ionic carrier which is a nano-composite formed by compounding conductive polymer nano-particles rich in functional groups and graphene nano-sheets.

Further, the solid ionophore is a lead ionophore.

In the solid ionophore, the weight ratio of the conductive polymer to the graphene is 90/10-99.9/0.1, and the preferable ratio is 98/2-99/1.

Preferably, the solid ionophore may be a polyaniline/graphene nanocomposite.

In the nano composite formed by compounding the conductive polymer nano particles rich in functional groups and the graphene nano sheets, the conductive polymer is a lead ion carrier, but the electronic conduction capability, particularly the ion conduction capability, of the conductive polymer is limited, the graphene sheets dispersed in the conductive polymer nano particles can realize both electronic conduction and ion conduction, and a bridge can be built for the conduction among the conductive polymer particles, so that the electric signal conduction performance among the carrier particles is greatly increased, the electric signal conduction function of the solid carrier is endowed, and the response and feedback of electric signals are facilitated. On the other hand, planar graphene also contributes to particle preventionSoft agglomeration of the granular conductive polymer, further separation of the nanoparticles, finer level dispersion, and finally functional group-NH on its molecular chain₂、-NH-、OH-、-SO₃H, etc. are sufficiently exposed. The synergistic effect between the conduction function and the fine dispersion structure achieves the sensitive response function of the nano composite to lead ions. The schematic diagram of the aggregate structure of such solid ionophores is shown in fig. 1.

That is, the active functional group in the ionic carrier is easier to expose, and the complexing site of the solid carrier is undoubtedly enhanced, so that the complexing function of the solid carrier is enhanced; on the other hand, in the process of selective complexation between the ion carrier and target ions, the graphene in the compound can provide and enhance the electron conduction and ion conduction capability of the ion carrier and the conversion between the electron conduction and the ion conduction capability, and promote the complexation between the carrier and ions, so that the problem of difficulty in carrier transfer in the existing all-solid sensing membrane is solved, the potential response of the electrode of the solid ion carrier applying the technical scheme is more stable compared with other all-solid membrane ion selection electrodes, and meanwhile, the response time is obviously shorter than that of other all-solid membrane ion selection electrodes.

The second technical scheme is as follows:

preparation method for providing the solid ionophore

A method for preparing a solid ionophore: the preparation method comprises the following steps of carrying out chemical oxidative polymerization on graphene nanosheets, conductive polymer monomers and conductive polymer monomers containing multiple functional groups, so that the conductive polymer monomers and the conductive polymer monomers containing the multiple functional groups are polymerized on the graphene nanosheets in situ to form a nano-composite, namely a solid ionic carrier, consisting of the conductive polymer nanoparticles rich in the functional groups and the graphene nanosheets.

The preparation method of the solid ionophore specifically comprises the following steps:

mixing the graphene nanosheets, the conductive polymer monomer and the conductive polymer monomer containing various functional groups, stirring, performing ultrasonic treatment, adding an oxidant, performing polymerization reaction under the condition of water bath, performing centrifugal treatment after the reaction is finished, and washing the obtained product to obtain a nano compound, namely the solid ionic carrier, which is composed of the conductive polymer nanoparticles rich in the functional groups and the graphene nanosheets.

Further, the graphene nanosheet and the conductive polymer monomer are mixed firstly and then subjected to ultrasonic treatment, and then the conductive polymer monomer containing multiple functional groups is added and mixed.

Further, mixing graphite and a conductive polymer monomer, performing ultrasonic treatment to obtain a blending system of the graphene nanosheet and the conductive polymer monomer, and then adding the conductive polymer monomer containing multiple functional groups for mixing.

The blending system of the graphene nanosheets and the conductive polymer monomer is equivalent to a mixing system of the graphene nanosheets and the conductive polymer monomer.

Further, the conductive polymer monomer is selected from one or more of aniline, methylaniline, ethylaniline, propylaniline, N-methylaniline, N-ethylaniline or N-propylaniline.

The conductive polymer monomer is used as a polymerization monomer and also used as a liquid-phase ultrasonic medium.

Further, the conductive polymer monomer containing multiple functional groups is an aniline derivative containing one or more of amino groups, sulfonic acid groups, hydroxyl groups or alkoxy groups, and has the following structural general formula:

in the formula, R₁And R₂Each independently selected from-H, -NH₂、-OH、-SO₃H、-OCH₃or-OCH₂CH₃；

The conductive polymer monomer having various functional groups is preferably as follows:

the oxidant is selected from ammonium persulfate or ferric trichloride.

The oxidant is added in the form of being prepared in an acid solution, and the acid solution for preparing the oxidant solution can be selected from 0.5-1 mol/L hydrochloric acid, nitric acid, sulfuric acid, perchloric acid and the like.

When the oxidant is selected from ammonium persulfate, the molar concentration of the ammonium persulfate is 50 mmol/L-500 mmol/L, and the molar concentration of the ammonium persulfate is preferably 100-300 mmol/L.

When the oxidant is selected from ferric trichloride, the molar concentration of the ferric trichloride is 100 mmol/L-500 mmol/L, and the molar concentration of the ferric trichloride is preferably 200-300 mmol/L.

The molar ratio of the oxidant to the comonomer is 1/2-3/1, preferably 1/1, and the molar weight of the comonomer is the sum of the molar weight of the conductive polymer monomer and the molar weight of the conductive polymer monomer containing various functional groups.

Further, the temperature of the polymerization reaction is 0-50 ℃, preferably 10 ℃, and the time of the polymerization reaction is 6-48 hours, preferably 24 hours.

Further, the preparation method of the solid ionophore directly takes graphite as an initial raw material to prepare, and specifically comprises the following steps:

1) preparation of expanded graphite using a thermal expansion process: and uniformly scattering graphite into a stainless steel disc in a high-temperature muffle furnace, and taking out after a certain time. And (3) placing the graphite on a temperature-resistant experiment table, covering the experiment table with a cover, cooling to be close to room temperature, and then placing the graphite in a dryer filled with blue silica gel for cooling to obtain the expanded graphite.

2) Preparing graphene nanosheets by using expanded graphite through a liquid phase stripping method: dispersing the expanded graphite obtained in the step 1) in a conductive polymer monomer according to a certain amount, taking the conductive polymer monomer as a liquid phase medium, performing ultrasonic treatment at a certain frequency and power for a certain time, performing centrifugal separation, and removing redundant conductive polymer monomer.

3) And (2) preparing a solid ionic carrier by using an in-situ chemical oxidation polymerization method, namely centrifuging the graphene subjected to ultrasonic treatment in the step 2) at a high speed for a certain time to ensure that all graphene nano sheets can be settled, checking whether graphene is contained in the supernatant by using an ultraviolet spectrophotometer during the period, if so, prolonging the centrifugation time, and if not, stopping the centrifugation, carefully sucking the redundant supernatant until the residual conductive polymer monomer in the bottle reaches a set amount, adding the conductive polymer monomer containing multiple functional groups, stirring for several minutes by strong magnetic force, immediately transferring to a water bath for ultrasonic treatment, immediately dropping a certain amount of oxidant solution into the blending system at a dropping speed of 1 drop/3 s, finishing dropping for about 40min, transferring to a magnetic stirrer, stirring and reacting in the water bath at a certain temperature for a certain time to obtain a dark black suspension, centrifuging at 4000rpm for at least 90min, repeatedly washing the obtained product for 5-6 times by 1 mol/L HCl to remove byproducts, finally transferring the obtained nano composite of the lead ionic carrier into a surface dish, freeze-drying for 48h to constant weight, and calculating the weight yield of the conductive polymer and the nano composite in a nano composite.

The graphite is natural crystalline flake graphite or expandable graphite, and preferably expandable graphite.

The expansion process of the graphite is different according to the graphite raw materials, the thermal expansion temperature of the graphite is generally 600-1200 ℃, the preferred temperature and time are 950 ℃, and the expansion time is tens of seconds.

When the expanded graphite is subjected to liquid phase stripping, the expanded graphite needs to be subjected to ultrasonic treatment, and the solid content of the graphite during ultrasonic treatment is below 2mg/m L, preferably below 1mg/m L, and most preferably below 0.5mg/m L.

The ultrasound is selected from water bath ultrasound or needle ultrasound, the process conditions of the water bath ultrasound are ultrasound for 24h to 72h under the acoustic frequency of 40kHz to 60kHz and the acoustic power of 50W to 200W, and ultrasound for 48h under 180W is preferred; the needle type ultrasound process conditions are 20kHz sound frequency and 200W to 600W sound power, ultrasound lasts for 2h to 6h, and ultrasound lasts for 3h under 400W is preferred.

The centrifugation condition after the ultrasonic treatment is that the centrifugation is carried out for 20min to 90min at 5000rpm to 2000rpm, and the centrifugation is preferably carried out for 90min at 3000 rpm.

By using the preparation method of the solid-state ionophore, the actual yield and the actual weight percentage calculation formula of graphene in the solid-state ionophore are derived in detail as follows:

since the oxidizing agent is added in the form of a solution formulated in an acid, i.e. a polymerization systemIs carried out under acidic condition, the added acid is sulfate radical which is a reaction by-product when ammonium persulfate is used as an oxidizing agent, and the whole polymerization system is kept acidic along with the removal of the acid in the polymerization process, so that the generated conductive polymer is in a doped state, and the doping protonic acid of the conductive polymer is determined by an acid medium. The specific acid anion to be incorporated depends on the acid used. Thus, the yield Y of the conductive polymer_CPThe calculation formula is as follows:

Y_CP＝(W_Total–W_G)/W_T…………………………….(1)

W_Total: total weight of the resulting nanocomposite

W_G: graphene input weight

W_T: theoretical weight of doped conducting polymer

Actual weight ratio R of conductive polymer to graphene in solid ionophore_CP/GThe calculation formula is as follows:

R_CP/G＝(W_Total–WG)/W_G…………………………….(2)

the third technical scheme is as follows:

provides an environment-friendly waterborne polyurethane flexible sensing film without plasticizer

The plasticizer-free environment-friendly waterborne polyurethane flexible sensing film comprises a continuous phase film matrix, and a solid ionic carrier and an ion exchanger embedded in the continuous phase film matrix, wherein the continuous phase film matrix is Waterborne Polyurethane (WPU), and the solid ionic carrier is a nano compound formed by compounding conductive polymer nano particles rich in functional groups and graphene nano sheets.

The solid ionophore can be prepared by the above technical scheme two as described in the above technical scheme one.

The content of the solid ionophore is 1 wt% to 8 wt%, preferably 3 wt%. The solid ionophore is mainly used for lead ionophores.

The ion exchanger is selected from one of NaTPB, NaFTPB, KTClPB or KClTPB and the like.

The content of the ion exchanger is 0 to 10 weight percent, and 3 weight percent is preferred.

The water-based polyurethane is water-dispersed polyurethane or water-based polyurethane without organic solvent, and can be one or a mixture of more of polyurethane water-based emulsion, vinyl polyurethane water-based emulsion or polyisocyanate water-based emulsion.

The WPU base film is environment-friendly and non-toxic, has excellent flexibility and moderate elasticity, can enable the mechanical property of the WPU base film to completely meet the use requirement of an electrode film without using any plasticizer, and can tolerate the situation that a small amount of nano-particles or even micro-particles are embedded in the WPU base film and still maintain a good compact structure without generating defects. The base membrane can block transmembrane ion circulation on two sides of the membrane so that the lower detection limit of the base membrane breaks through 10 of a PVC membrane ion electrode^-6The bottleneck of mol/L. the plasticizer-free environment-friendly waterborne polyurethane flexible sensing film can also obtain a calibration-free ion selective electrode, and the response potential curve of the flexible sensing film does not drift in 2 months of use.

The technical scheme is as follows:

provides a method for preparing an environment-friendly waterborne polyurethane flexible sensing film without a plasticizer

Firstly, carrying out ultrasonic dispersion on a solid ion carrier and an ion exchanger in an organic phase, then adding the solid ion carrier and the ion exchanger into a certain amount of aqueous polyurethane emulsion in batches, finally forming a film by a solution method, drying for a certain time at a certain temperature, and removing the film by buoyancy in water to obtain the plasticizer-free aqueous polyurethane flexible sensing film.

The solution method film forming can adopt a method of solution casting film forming and a method of solution wire rod scraping film forming, and preferably the wire rod scraping film forming.

The film forming and drying temperature is 0-100 ℃, and preferably 50 ℃.

The film-forming drying time is 1 min-48 h, preferably 24 h.

The technical scheme is as follows:

provides application of plasticizer-free environment-friendly waterborne polyurethane flexible sensing film

The plasticizer-free environment-friendly waterborne polyurethane flexible sensing film is applied to a sensing film in an ion selective electrode, and corresponding sensing ions are lead ions. Or be assembled on a potential sensor to be applied to the detection of lead ions.

The internal filling liquid used in the ion selective electrode is 1.00 × 10^-5～1.00×10^-2mol/L Pb(NO₃)₂Solutions, preferably 1.00 × 10^-4mol/L。

The preparation solution used in the ion selective electrode was 1.00 × 10^-5～1.00×10^-2mol/L Pb(NO₃)₂Solutions, preferably 1.00 × 10^-4mol/L, the preparation time is 1 to 3 days, preferably 1 day.

The specific operation that the plasticizer-free environment-friendly waterborne polyurethane flexible sensing film has an excellent lead ion sensing effect is as follows: preparing a certain amount of Pb (NO) with a certain concentration₃)₂And (3) inserting the prepared electrode into a standard solution, taking the Shanghai Lei magnet 232-01 single-salt bridge saturated calomel electrode as an external reference electrode, and testing the response potential of the WPU sensing membrane by adopting a PXSJ-216F type ion meter produced by Shanghai Lei magnet company. The electrochemical cell structure is as follows:

Ag|AgCl|10^-4mol/L Pb(NO₃)₂| WPU sensing film | sample solution | saturated KNO₃Salt bridge | Hg₂Cl₂|Hg。

The technical scheme is six:

the lead ion selective electrode is provided, and the environment-friendly water-based polyurethane flexible sensing film without the plasticizer is used as the sensing film in the technical scheme V.

The invention has the following benefits:

a very small amount of graphene nanosheets are introduced into conductive polymer (such as copolyalniline) nanoparticles, so that the graphene nanosheets are dispersed in the conductive polymer nanoparticles, and a bridge is built for electronic conduction and ionic conduction among particles. Due to the specific fine composite structure and the synergistic effect of the two, when the nano composite is used as a lead ion carrier, not only can the functional groups on the molecular chain of the conductive polymer be more effectively exposed, but also the sensitive response function to lead ions can be further improved. The sensor is embedded into a water-based polyurethane base film without a plasticizer, and the constructed all-solid-state sensing film can also obtain the functions of electronic conduction and ion conduction, so that the potential response of the electrode is more stable and the response speed is faster compared with other solid-state film ion-selective electrodes. The method retains the inherent advantages of the non-plasticized solid sensing membrane, overcomes the common defect of unstable potential response reading of the solid sensing membrane, and is expected to be developed into a new generation of lead ion selective electrode following the conventional plasticized PVC base membrane.

The waterborne polyurethane without the plasticizer is used as a film matrix material, so that the defects of the traditional plasticized PVC base film are overcome, and the waterborne polyurethane has excellent environmental friendliness compared with other non-plasticized PVC films. The waterborne polyurethane is an environment-friendly high polymer material which is expected to replace toxic organic solvent system polyurethane and developed in recent years, is a binary colloid system formed by uniformly dispersing polyurethane nanoparticles in a water system, and has the advantages of no free isocyanate group (-NCO), low VOC content, easiness in cleaning, non-flammability and the like. The flexible and elastic sensing film can be obtained by using the self-prepared polyurethane as a sensing film substrate and embedding active components such as an ionophore and the like into the sensing film substrate by virtue of the excellent film-forming property of the waterborne polyurethane. The method not only widens the application field of the waterborne polyurethane, but also develops a new class of environment-friendly base film materials for the sensing film, and makes the preparation of the sensing film step on a new step of removing the organic solvent. Related studies have not been reported.

Compared with the lead ion selective electrode reported in the prior art, the lead ion selective electrode taking the conductive polymer/graphene nano composite as the carrier has the following advantages:

(1) the conductive polymer/graphene nano-composite has the advantages of simple synthesis method, high yield and rich monomer sources, and compared with the traditional neutral molecular carrier, the conductive polymer/graphene nano-composite has low price and is embedded in the sensing membrane in a solid state and not easy to run off;

(2) compared with the lower detection limit of a plasticized PVC membrane electrode, the lower detection limit of the lead ion selective electrode is expanded by 2 orders of magnitude to 10^-8moThe membrane has the l/L grade, the response potential is stable, the response time is extremely short and generally does not exceed 8s, and the potential stability is obviously superior to other all-solid-state membranes reported.

(3) The plasticizer-free environment-friendly water-based polyurethane flexible sensing film serving as the lead ion selective electrode is a long-life calibration-free electrode, the response potential curve of the electrode does not drift in 2-month use, and the service life of the electrode can reach at least 4.5 months (18 weeks).

Drawings

FIG. 1 is a schematic diagram of the aggregate structure of a lead ionophore nanocomposite;

FIG. 2 is the ultraviolet absorption spectrum and the Tyndall phenomenon of the graphene nanosheet obtained by ultrasonic treatment in example 4;

FIG. 3 is the infrared absorption spectrum of the polyaniline/graphene nanocomposite obtained in examples 6 and 7;

FIG. 4 is a scanning electron micrograph of the polyaniline/graphene nanocomposite obtained in example 6;

FIG. 5 is a potential response curve of a sensing membrane electrode prepared in example 11 to lead ions;

FIG. 6 is a graph showing the potential response of a sensing membrane electrode prepared in example 12 to lead ions;

FIG. 7 is a graph showing the potential response of a sensing membrane electrode prepared in example 13 to lead ions;

FIG. 8 is the response time of the sensing membrane electrode prepared in example 11 to the potential of lead ions;

FIG. 9 is the pH window of the sensor film electrode prepared in example 11;

FIG. 10 is a potential response curve of the sensor film electrode prepared in example 11 for the first 8 weeks;

FIG. 11 is an electrochemical impedance spectrum of a sensor film electrode prepared in example 11;

FIG. 12 is an equivalent circuit diagram used in the simulation of the EIS;

FIG. 13 is a thermogravimetric plot of a primary sensing film;

FIG. 14 thermogravimetric curves of the modulated and used sensing film;

FIG. 15 SEM-EDX spectra of the inner liquid-filled side of the sensing membrane.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Examples 1-2 preparation of expanded graphite by thermal expansion method

Example 1

Weighing 0.5g of graphite in a ceramic crucible, scattering the graphite in a disc placed in a muffle furnace at 800 ℃, taking out after 20s, placing on a temperature-resistant experiment table, covering the experiment table with a cover, cooling to room temperature, placing in a dryer filled with blue silica gel, cooling to obtain expanded graphite, weighing, measuring the volume, and calculating the expansion rate to be 365m L/g.

Example 2

The other conditions were the same as in example 1, except that a muffle furnace at 1200 ℃ was used, and the expansion ratio was 331m L/g.

Example 3-5 preparation of graphene nanoplate by ultrasonic method

Example 3

Adding 13mg of graphite and 20m L aniline into a glass test tube, performing rod type ultrasonic treatment at 40% power by using a JY92-IIN ultrasonic cell crusher (650W, 20-25 kHz), stopping ultrasonic treatment for 1s every 3s, and performing ultrasonic treatment for 1h in total to obtain graphene dispersion liquid with the appearance like ink, wherein the ultraviolet spectrum of the graphene dispersion liquid can obviously absorb light waves with the wavelength of 660nm, but a small amount of particles can be observed to settle after standing overnight.

Example 4

The other conditions were the same as example 3, except that an SK3300HP ultrasonic cleaner (180W,53kHz) was used, and ultrasonic cleaning was carried out in a water bath at a power of 180W for 48 hours. The graphene dispersion liquid with the appearance like ink is obtained, the ultraviolet spectrum of the graphene dispersion liquid generates obvious absorption on light waves with the wavelength of 660nm, and basically no precipitate is generated after standing overnight. The ultraviolet spectrum of the obtained graphene dispersion liquid after 5-time dilution is shown in figure 2, the Tyndall photo is shown in an inset of figure 2, and a scattering light path cannot be observed due to high graphene concentration.

Example 5

The other conditions were the same as in example 4, but 13mg of graphite was soaked in 20m L aniline for 4 weeks before sonication, and the resulting graphene dispersion was more stable.

Example 6 in situ polymerization 1

Prepared by the method of example 4Centrifuging the graphene dispersion liquid for 90min at 3000rpm, gradually sucking and removing a supernatant liquid to ensure that the weight of the residual substances in the bottle is just 757.8mg to obtain a mixed liquid of 13mg of graphene and 744.8mg of aniline, quickly adding 100m L1 mol/L mol HCl solution of 378.4mg of o-aminophenol sulfonic acid prepared in advance into the mixed liquid, immediately transferring the mixed liquid into a water bath ultrasonic wave (53kHz,180W, 100%) after strongly magnetic stirring for 5min, immediately dropping 1 mol/3 s of 1 mol/L0.2 mol/L ammonium persulfate in 1 mol/L HCl acid aqueous solution, finishing dropping 40min, transferring the mixed liquid into a magnetic stirrer, stirring for 24h in a water bath, after the reaction is finished, repeatedly washing by using 1 mol/L HCl to remove by-products, centrifugally separating and removing the supernatant liquid, finally transferring the obtained polyaniline/graphene nano composite to a surface dish, freeze-drying for 48h to constant weight to obtain probe powder of the polyaniline/graphene nano composite, wherein the polymerization yield is 50.21%, the mass ratio of the polyaniline to the graphene nano composite is about 9.73 × 10, and the conductivity of the tetrapolymer composite is about 3973.2^-2S/cm。

The infrared spectrum of the resulting composite is shown in fig. 3 as the absorption spectrum labeled "ultrasound aniline copolymer/graphene nanocomposite". 2800 to 3400cm in a high-band region^-1A broad absorption peak appears in the range, which is an-NH-stretching vibration absorption peak of amino and imino, particularly 3200cm^-1A small distinct absorption peak based on the broad absorption peak was observed indicating significant exposure of the amino groups in the copolymer. 2950cm at a slightly lower band^-1Also appear as weaker peak-CH-characteristic absorption peak. Combined 1580, 1500cm^-1Typical vibration characteristic peaks of the benzene ring skeleton correspond to stretching vibration of a quinoid (C ═ C) and a benzene (C-C) in a molecular chain of the copolymer, respectively, and illustrate formation of the aniline copolymer.

The scanning electron micrograph of the resulting composite is shown in FIG. 4. It can be seen that the copolymerized aniline particles of submicron level formed by the agglomeration of the primary particles of nanometer level are attached to the graphene nanosheets, and particularly, the particles of the copolymerized aniline particles are hidden and visible between the layers of the graphene nanosheets, so that a composite structure coated with the graphene wafers is formed.

Example 7 in situ polymerization 2 raw, un-sonicated aniline control experiment

Centrifuging the graphene dispersion liquid obtained by stripping in the example 4 at 3000rpm for 90min, completely removing supernatant liquid to ensure that only the graphite subjected to ultrasonic treatment remains in a bottle, supplementing fresh aniline 0.73m L, and quickly adding 100m L1 mol/L mol HCl solution of 378.4mg o-aminophenol sulfonic acid prepared in advance into the bottle, wherein the rest operations are the same as the example 6, finally, freeze-drying the mixture for 48h to constant weight to obtain the powder of the copolyalniline/graphene nano composite, wherein the polymerization yield is 40.62%, the mass ratio of the copolyalniline to the graphene is 98:2, and the conductivity of the composite measured by a powder tabletting four-probe method is 3.06 × 10^-3S/cm. 1/32 for the resulting composite was only interpolymerized with aniline monomer that underwent sonication. The infrared spectrum of the resulting composite is shown in fig. 3 as the absorption spectrum of the "pristine aniline copolymer/graphene nanocomposite". Compared with the absorption spectrum of the ultrasonic aniline copolymer/graphene nano composite, the biggest difference is 3200cm^-1The small nearby absorption peaks are attenuated, indicating a reduced exposure of the amino groups in the copolymer.

Example 8 in situ polymerization 3

6.5mg of graphite and 20m of L m of ethylaniline were placed in a glass test tube, subjected to ultrasonic bath for 48 hours under a power of 180W using an SK3300HP ultrasonic cleaner (180W,53kHz), the resulting dispersion was centrifuged at 3000rpm for 90 minutes, and the supernatant was gradually removed by pipetting to give a weight of just 998.3mg of the remaining material in the bottle, to obtain a blend of 6.3mg of graphene and 992mg of ethylaniline, 246mg of o-methoxyaniline previously prepared at 100m L1 mol/L HNO₃The solution was added rapidly and the subsequent polymerization procedure was the same as in example 6 to obtain the copolyalniline/graphene nanocomposite powder with a polymerization yield of 45.98% and a mass ratio of copolyalniline to graphene of about 99: 1.

Example 9 in situ polymerization 4

15mg of graphite and 20m of L N-methylaniline were placed in a glass test tube, sonicated in a water bath for 48h at 180W power using an SK3300HP sonicator (180W,53kHz), the resulting dispersion was centrifuged at 3000rpm for 90min, the supernatant was gradually aspirated off so that the weight of the remaining material in the bottle was exactly 998.3mg, yielding a total of 6.3mg of graphene and 992mg of ethylanilineMixing 346.4mg m-aminobenzenesulfonic acid prepared in advance with 100m L0.5.5 mol/L H₂SO₄The solution was added rapidly and the subsequent polymerization procedure was the same as in example 6 to obtain a powder of the copolyalniline/graphene nanocomposite with a polymerization yield of 67.81% and a mass ratio of copolyalniline to graphene of about 94: 6.

Example 10 in situ polymerization 5

The graphene dispersion obtained by stripping after soaking for 4 weeks in example 5 was subjected to in-situ polymerization as in example 6, but the obtained copolyalniline/graphene composite was not dried any more after being washed, but was dispersed in a mixed medium of 64.5m L ethanol and water in a volume ratio of 1: 1.

Examples 11-12 preparation of sensing films from composite powders

Weighing 30.6mg of the copolyalniline/graphene nanocomposite obtained in example 6 and example 7 respectively, placing the weighed composite in a weighing bottle, adding a 3m L blend solvent of ethanol and water (volume ratio 1:1), performing water bath ultrasound (60kHz, 100%) for 30min, then strongly stirring the mixture for 10min at 800rpm by using a homogenizer, then transferring the mixture to water bath ultrasound (60kHz, 100%) for 10min, circulating the above steps for 5 times, measuring an aqueous polyurethane (R974) solution with a solid content of 35%, placing the aqueous polyurethane (R974) solution for 2.6m L into another weighing bottle, strongly stirring the aqueous polyurethane (R97rpm) solution by using a homogenizer at 800rpm, slowly adding the nanocomposite dispersion liquid, adding 200 mu L once, strongly stirring the aqueous polyurethane solution while adding, wherein the time interval is 20min each time, stirring the aqueous polyurethane solution for about 150min totally, pouring all the casting solution onto an OPP film, using a RK stamp press and a 100 mu m bar to scrape the film into an oven at 50 ℃ for 24h, taking out, naturally cooling the wet film to about 3cm, drying the film in clear water, and taking out the film with a thickness of about 46 to 44 mu m and drying the film.

EXAMPLE 13 preparation of sensing membranes from Complex dispersions

Weighing 3m L of the graphene dispersion liquid prepared in the example 10 into a weighing bottle, strongly stirring the graphene dispersion liquid for 10min at 800rpm by using a homogenizer, transferring the graphene dispersion liquid into a water bath at 60kHz and under 100% power for 10min, and carrying out ultrasonic processing on the graphene dispersion liquid for 5 times in this way, and then blending the graphene dispersion liquid with polyurethane, wherein the specific operation is the same as that of the examples 10-11, and the thickness of the obtained film is 30-38 mu m.

Examples 14-16 Assembly of lead ion electrodes

The sensor films obtained in examples 11 to 13 were cut into disks 12mm in diameter, adhered to the ends of plastic tubes with glue, and after they were naturally dried, 10 pieces of adhesive were inserted into the tubes^-4mol/L lead nitrate solution 10^-4The response performance of the lead nitrate/L can be tested after being modulated for 24 hours and activated, and detailed results are shown in fig. 5-7. it can be seen that when the copolyalniline/graphene nanocomposite in example 6 is used as a carrier, the minimum value of the lower electrode detection limit is 10^-8mol/L，Pb²⁺Activity linear range 10^-2.27～10^{- 7.98}M, the response slope is 27.84 mV/dec; when the copolyalniline/graphene nanocomposite in example 9 is used as a carrier, the lower limit of electrode detection is 10^-6.31mol/L，Pb²⁺Activity linear range 10^-1.59～10^-6.31M, the response slope is 32.99 mV/dec; when the copolyalniline/graphene nanocomposite in example 9 is used as a carrier, the lower limit of electrode detection is 10^-6.82mol/L，Pb²⁺Activity linear range 10^-2.27～10^-6.82M, the response slope is 29.43 mV/dec;

it can be seen that, comparing the sensing membranes prepared from the nanocomposite lead ion carriers prepared in examples 6 and 7, it is found that the nanocomposite carrier obtained by in-situ copolymerization of the monomers left after the graphite ultrasonication is easier to obtain a more excellent lower detection limit and a more ideal Nernstian slope than the nanocomposite carrier obtained from the original monomers without being subjected to ultrasonication, and thus there is more chance that the monomers subjected to the common ultrasonication interact with the graphite and the graphene. The monomer is easier to wet graphite and even insert into graphite layers according to moderate surface tension and similar benzene ring pi planes in the ultrasonic process, in the process that the graphite is subjected to ultrasonic stripping, the graphite enters a certain non-equilibrium state at a certain moment under the action of strong sound wave power, slight opening trend exists among graphite sheet layers, at the moment, monomer molecules wetted on the graphite molecules can be inserted into graphene planes while the monomer molecules are still in the graphite, and thus, the monomer molecules are adsorbed on the graphite layers by virtue of pi-pi action while graphite stripping is promotedThe graphene-based plane is easy to nucleate and grow on the surface of graphene when the monomer is subjected to subsequent copolymerization, so that the two components are easy to be hybridized and compounded with each other, a deeper and finer composite structure is finally achieved, more functional groups in the copolyalniline are promoted to be exposed, the effect of sensing target ions is exerted, and the infrared spectrum is 3200cm^-1This is evidenced by the apparent enhancement of the absorption peaks on the left and right representing amino groups. And the original monomer is added after the graphite is subjected to ultrasonic treatment, the monomer molecules and the graphene do not have sufficient effect, and the polymerization of the monomer molecules and the graphene is more likely to occur in a water phase to perform isolated nucleation growth. Therefore, fresh monomers that have not been subjected to ultrasound with graphite cannot achieve a fine composite structure.

Example 17 response time of electrodes

The response time of an electrode refers to the time that the electrode takes from contacting the test solution to obtaining a relatively stable value. The potential response of the sensing membrane electrode prepared in example 11 in six different concentrations of lead solution versus time is shown in fig. 8. It can be seen that for 10^-2～10^-8The response time of the electrode is not more than 10s in mol/L lead solution.

Example 18pH Window

The potential response of the sensing membrane electrode prepared in example 11 in two lead solutions with different concentrations is related to the pH value as shown in FIG. 9. it can be seen that the potential response is 1.0 × 10^-3And 1.0 × 10^-4In the pH range to be considered, the potential response of the electrode of two lead standard solutions of mol/L is divided into three stages, wherein the middle section 5.0-7.0 is a horizontal line, the potential change with the pH is small and corresponds to 1.0 × 10^-3mol/L and 1.0 × 10^-4The potential reading values of the two lead standard solutions of mol/L are respectively in the ranges of-54.8 mV to-56.2 mV and-83.9 mV to-84.4 mV, the fluctuation ranges are respectively 1.4mV and 0.5 mV., and the pH potential platform window of the electrode is 5.0-7.0.

EXAMPLE 19 electrode Selectivity

The selectivity of the electrode to lead ions was evaluated by a modified separate solution method, so that a non-biased selectivity coefficient could be obtained. 13 possible interfering ions were selected, and a separate electrode pair of 13 rods was used for each interferenceThe specific potential difference of i ion and j ion corresponding to the potential response curve of each interference ion is read by adopting an equipotential processing method when the extrapolated activity is 1 mol/L

Substituting into formula (3) to calculate the selection coefficient. The selection coefficients thus determined are listed in table 1. Therefore, the electrode has better anti-interference capability on divalent ions and certain anti-interference capability on monovalent ions.

TABLE 1 Selectivity coefficients of lead ion-selective electrodes

EXAMPLE 20 service life of the electrode

The service life of the electrode is evaluated by electric polarity energy parameters such as the response slope, linear range, response time, and detection lower limit of the electrode. According to IUPAC regulations, an electrode is considered to be failed when the response slope for evaluating electrode life is less than 95% of the initial electrode test parameters. The electrodes were tested twice a week for the first month, once a week for the second month, and once every two weeks for the third month and thereafter. After each test, the electrode is washed, the internal filling liquid is poured out, and the electrode is placed in a cool and dry place for storage. Refill 10 for lower wheel test^-4The potential response curve parameters of the sensing membrane electrode prepared in the example 11 during the investigation period are shown in Table 2. it can be seen that the electrode can maintain good lead ion linear response in the investigated 22 weeks, the lower detection limit is basically unchanged, especially the response slope in the first 18 weeks is close to the Nernst slope, and especially, the response curve in the first 8 weeks has almost no change (FIG. 10), not only the slope is changed almostThere was almost no degradation cracking, and even the response potential at each concentration point in its linear range did not drift, so that the entire response curve was fixed at the response potential level at the initial stage. This property confers on the electrode a calibration-free capability, and ion-selective electrodes capable of sustaining for 2 months without calibration have not been reported.

Table 2 change of potential response curve at each stage of sensor film electrode prepared in example 11

EXAMPLE 21 application of the electrode

The actual samples were taken from tap water in the laboratories of the ecological buildings of the university of Tongji, 10 months of rainwater in Shanghai City, and river water under the administrative road and bridge in the Yanpu area of Shanghai city, respectively. The actual samples were filtered using a 0.22 μm filter to remove insoluble solid particles from the water prior to testing. The pH of all three water samples was near neutral. The lead content of the pretreated sample and the contents of other common metal ions were measured by an Agilent ICPMS7700 inductively coupled plasma mass spectrometer, and the results are shown in Table 3. It can be seen that the lead content of three actual water samples ranges from several ppb to tens of ppb. Because the concentration of lead ions is too low, the response potential of the electrode adopting the direct potential method is not in a linear range, and the lead content cannot be accurately detected.

TABLE 3 pH of three actual water samples and several metal ion contents (mol/L)

Then, the three actual water samples are subjected to the labeling recovery experiment, and the samples are accurately transferred into the sample 1.00 × 10 in the sample 40m L^-3Lead marking solution of 200 mu L mol/L is shaken up to obtain lead content of 5.00 × 10^-6Adding a standard water sample of mol/L passing the electrode of the invention through 1.00 × 10^-4modulating and activating for 24 hours in mol/L lead standard solution, washing with ultrapure water to a stable potential, directly measuring the lead content of three standard water samples, and repeatedly testing each water sample for 3 times, wherein each timeAnd repeatedly cleaning the tested electrode for 5-6 times by using ultrapure water, and recovering or approaching the potential to the initial potential and then using the electrode for the next test. The results of such tests are shown in Table 4. Therefore, the recovery rate of each water sample measured by the direct potentiometry is within the range of 93-107%, and the test accuracy and precision are better.

TABLE 4 lead content (mol/L) recovery experiments using lead ion selective electrodes to test three actual spiked water samples

Example 22EIS testing

The sensing membrane electrode prepared in example 11 was used as a working electrode, a platinum electrode was used as a counter electrode, and a saturated calomel electrode was used as a reference electrode to form a three-electrode system of 1.0 × 10^-4Performing Electrochemical Impedance Spectroscopy (EIS) measurement after the open-circuit potential in the lead nitrate solution of mol/L is stabilized, wherein the measured voltage amplitude is 5mV, the frequency is 0.01 Hz-100 kHz, the Bode diagram and the Nyquist diagram are shown in FIG. 11, fitting the EIS diagram by Zsimpwin software according to the equivalent circuit shown in FIG. 12, and the parameters used in the fitting are that the thickness of the sensing film is about 35 mu m, the effective radius of the sensing film is 0.8cm, and the effective area is 2cm²The parameter of each element obtained by fitting is that the series resistance Rs is 2.45 × 10⁴Ω/cm²Membrane resistance R_bIs 1.59 × 10⁶Ω/cm²Conductivity 1.3 × 10^-9S/cm, geometric capacitance C_gIs 1.25 × 10^-10F/cm²Warburg impedance coefficient 6.67 × 10⁴Ω·s^-1/2. Therefore, the graphene in the composite carrier has an ion and electron conduction function, so that the conduction capability of the membrane is obviously improved, and the ion selective electrode is endowed with excellent potential response performance.

Example 23 TG testing

5.20mg of the primary sensor film prepared in example 11 and 2.77mg of the conditioned and used sensor film were weighed, respectively, and their thermogravimetric curves TG and DTG were measured at a temperature rising rate of 10 ℃/min in a synthetic air atmosphere, and the results are shown in FIG. 13 and FIG. 14. The analysis of DTG shows that the primary film is basically free from equilibrium hygroscopic water peaks, which indicates that the surface and the inside of the base film do not contain water, and the base film can prove to be difficult to absorb water and can block water from penetrating, namely can effectively block ion flow. The main peak of the maximum decomposition rate is 341 ℃ at high temperature, 2-4 shoulder peaks are arranged on the main peak, which is the characteristic expression of the multi-component aliphatic polyurethane, each degradation peak is corresponding to the degradation of one chain link component until all soft segments and hard segments in a polyurethane molecular chain are completely degraded at 600 ℃, only graphene and partial aniline copolymer in the active carrier compound are remained, and the residual coke content is about 0.9 wt%. However, although the maximum thermal decomposition rate of the thermogravimetric curve of the sensing film subjected to lead ion modulation and lead ion response curve test is-1.5 wt%/° c without any change, the thermal stability of the sensing film is obviously improved, and the weight loss peak attributed to soft segment degradation at about 214 ℃ basically disappears, the initial decomposition temperature is improved to 291 ℃ from about 161 ℃, the temperature at the maximum thermal decomposition rate is improved to 356 ℃ from 341 ℃, the temperature is respectively improved by 130 ℃ and 15 ℃, the residual coke content is also improved to 2.8 wt% from 0.9 wt%, and the residual coke content is increased by 3.1 times. Meanwhile, multiple degradation peaks tend to be fused, the peak width becomes narrow and small, the spike shape becomes sharp, and the improvement of the possible thermal performance and the increase of the residual weight are reflected by the fact that lead salt enters a membrane phase. It can be seen that after the sensing film is contacted with the lead ion solution, the active carrier on the sensing film can introduce the lead ions in the solution into the sensing film through complexation and anchor the lead ions in the sensing film.

Example 24 SEM-EDX testing

An electrode constructed in example 14 was taken, after which it was passed through 1.0 × 10^-4Preparing mol/L lead standard solution and processing the solution by 1.0 × 10^{- 8}mol/L～1.0×10^-1After the response curve of the mol/L lead standard solution is tested, the electrode is dismantled, the sensing film at the center is cut off after the electrode is dried in the air, and the content of lead on the surface of the sensing film is analyzed by a scanning electron microscope-X ray energy dispersion spectrometer (SEM-EDX)SEM-EDX energy spectra on the inner liquid-filled side see FIG. 15, where it can be seen that in addition to having C, N and O elements from the WPU material (Table 5), the presence of lead element was detected, and 4 absorption peaks at 2.4keV, 9.2keV, 10.5keV and 14.7keV, respectively, reflect 4 electron energy level differences of lead element, with a content of around 0.16 wt%^-4The phenomenon is more obvious on the sample side of the sensing film, the lead content of the surface fluctuates with the position of the surface of the film bombarded by the electron beam, the lead content is in the range of 0.35-1.69 wt% and is obviously higher than the inner side.

TABLE 5 SEM-EDX test of the content of each element in the lead ion sensing film

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims (10)

1. The environment-friendly waterborne polyurethane flexible sensing membrane is characterized by comprising a continuous phase membrane matrix, and a solid ionic carrier and an ion exchanger embedded in the continuous phase membrane matrix, wherein the continuous phase membrane matrix is waterborne polyurethane, and the solid ionic carrier is a nano compound formed by compounding conductive polymer nano particles rich in functional groups and graphene nano sheets.

2. The environment-friendly waterborne polyurethane flexible sensing film according to claim 1, wherein the solid ionophore is a lead ionophore, and the weight ratio of the conductive polymer to the graphene in the solid ionophore is 90/10-99.9/0.1, preferably 98/2-99/1;

the conductive polymer is prepared by polymerizing a conductive polymer monomer with a conductive polymer monomer having various functional groups,

the conductive polymer monomer is selected from one or more of aniline, methylaniline, ethylaniline, propylaniline, N-methylaniline, N-ethylaniline or N-propylaniline;

the conductive polymer monomer containing multiple functional groups is an aniline derivative containing one or more of amino groups, sulfonic acid groups, hydroxyl groups or alkoxy groups, and has the following structural general formula:

in the formula, R₁And R₂Each independently selected from-H, -NH₂、-OH、-SO₃H、-OCH₃or-OCH₂CH₃；

The conductive polymer monomer having various functional groups is preferably as follows:

3. the flexible sensing membrane of claim 1, wherein the content of the solid ionophore is 1 wt% to 8 wt%, preferably 3 wt%, and the solid ionophore is used as a lead ionophore.

4. The environment-friendly waterborne polyurethane flexible sensing membrane according to claim 1, wherein the ion exchanger is selected from one of NaTPB, NaFTPB, KTClPB or KClTPB, and the content of the ion exchanger is 0-10 wt%, preferably 3 wt%.

5. The flexible sensing film of claim 1, wherein the aqueous polyurethane is water-dispersible polyurethane or water-based polyurethane without organic solvent, and is selected from one or more of polyurethane aqueous emulsion, vinyl polyurethane aqueous emulsion, and polyisocyanate aqueous emulsion.

6. The preparation method of the environment-friendly aqueous polyurethane flexible sensing membrane of any one of claims 1 to 5, wherein the method comprises the steps of firstly carrying out ultrasonic dispersion on a solid ion carrier and an ion exchanger in an organic phase, then adding the solid ion carrier and the ion exchanger into an aqueous polyurethane emulsion in batches, finally forming a membrane by a solution method, and drying and removing the membrane to obtain the environment-friendly aqueous polyurethane flexible sensing membrane without a plasticizer.

7. The preparation method of the environment-friendly waterborne polyurethane flexible sensing film according to claim 6, wherein the solution method is a method of casting and film forming by solution or scraping by a solution wire rod, the film forming drying temperature is 0-100 ℃, preferably 50 ℃, and the film forming drying time is 1 min-48 h, preferably 24 h.

8. The use of the environmentally friendly aqueous polyurethane flexible sensor film according to any one of claims 1 to 5, wherein the plasticizer-free environmentally friendly aqueous polyurethane flexible sensor film is used as a sensor film in an ion selective electrode, and the corresponding sensor ions are lead ions, or are assembled in a potential sensor for detection of lead ions.

9. A lead ion selective electrode, characterized in that the environment-friendly aqueous polyurethane flexible sensing film of any one of claims 1 to 5 is used as a sensing film.

10. According to the rightThe lead ion selective electrode according to claim 9, wherein the internal filling solution used in the ion selective electrode is 1.00 × 10^-5～1.00×10^-2mol/L Pb(NO₃)₂Solutions, preferably 1.00 × 10^-4mol/L；

The preparation solution used in the ion selective electrode was 1.00 × 10^-5～1.00×10^-2mol/L Pb(NO₃)₂Solutions, preferably 1.00 × 10^-4mol/L, the preparation time is 1 to 3 days, preferably 1 day.

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