CN110346330B - A kind of pH detection method based on responsive thin film material - Google Patents

Abstract

The invention discloses a pH value detection method based on a responsive thin film material. First, the pH value of a buffer solution is adjusted, the responsive thin film material is used as a response element, and the responsive thin film material is soaked with solutions of different pH values; The reflection spectrum of the wet area is used to obtain the reflection characteristic peak wavelength; finally, the origin software is used to fit the curve, and the pH value calculation formula is obtained, which is used to calculate the pH value of the solution to be tested. The material preparation process of the invention adopts emulsion polymerization, the preparation process is simple, energy saving and environmental protection; at the same time, the detection method has high sensitivity, high speed, high precision, the response material can be reused, and the detection result is not affected by the environment, and has a huge application prospect.

Description

A kind of pH detection method based on responsive thin film material

technical field

The invention belongs to the application field of polymer materials, and in particular relates to a pH value detection method based on a responsive thin film material.

Background technique

Photonic crystals are a class of micro-nano structures formed by periodic arrangement of media with different refractive indices in space. According to Bragg's formula, the characteristic peak wavelength of photonic crystal reflection is proportional to the average refractive index and lattice constant. Only by changing the refractive index or lattice constant of the photonic crystal material, the purpose of regulating the structural color of the photonic crystal can be achieved. In recent years, photonic crystal materials have been widely studied, and tens of thousands of related papers have been published. Some studies have combined photonic crystal materials with responsive functional groups to realize the preparation of photonic crystal sensor materials. The color of the photonic crystal material is used as the detection variable, which can be used in the field of chemical substance detection. Considering that carboxyl groups can exhibit different degrees of ionization in different pH environments, combining them with photonic crystal materials may bring new application space for photonic crystal materials in the field of responsive detection.

At present, the commonly used pH detection methods are pH test paper or pH meter. However, pH test strips are disposable and cannot be reused. The pH test paper detection method compares the color with the naked eye to determine the pH value. The judgment result is interfered by the subjective factors of the testing personnel, and is not suitable for people with color weakness and color blindness. In addition, the color of the pH test paper after being dipped in the liquid is not uniform. Usually, the edge area is lighter and the middle area is darker. The selection of the area will affect the judgment result. At the same time, the color of pH test paper is also affected by temperature. Therefore, the detection results of pH test paper are susceptible to interference, and the error is large. The measurement result of the pH meter is relatively accurate, but it is larger in volume and weight than pH test paper, and needs to be cleaned with deionized water, calibrated with various standard pH buffer solutions and other multi-step operations before use. , and the electrode of the pH meter usually needs to be maintained for a long time, and there are certain limitations in the rapid detection of a small amount of samples. Therefore, it is very important to realize the detection of pH value in a convenient, quick and reproducible way through daily use.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a pH value detection method based on a responsive thin film material in view of the deficiencies of the prior art.

The object of the present invention is achieved through the following technical solutions: a pH value detection method based on a responsive thin film material, comprising the following steps:

(1) Adjust the pH value of the buffer solution to obtain a plurality of solutions with different pH values.

(2) using the responsive thin film material as the responsive element, soaking the responsive thin film material with solutions of different pH values obtained in step (1) to obtain wetted thin films corresponding to different pH values;

(3) Collect the reflection spectra of the wetting regions of the wetted film corresponding to different pH values obtained in step (2) in the range of 300-1000 nm, obtain the reflection characteristic peak wavelengths corresponding to different pH values, and fit the reflection characteristic peak wavelengths The relationship curve between the pH value and the pH value is obtained to obtain the pH value calculation formula.

(4) Wet the responsive film material with the solution to be tested, collect the reflection spectrum of the wetted area of the wetted film of the solution to be tested in the range of 300-1000 nm, and obtain the characteristic peak wavelength of reflection corresponding to the solution to be tested. The pH value calculation formula in step (3) calculates the pH value of the solution to be tested.

The responsive film material in the step (2) is obtained by mixing the carboxyl group-containing polymer nanoparticle latex with carbon black particles and silica particles, and then dewatering and drying;

The polymer nano-core-shell particle latex has a three-layer structure, specifically a structure in which one layer of amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent wraps two layers of block copolymer latex; the polymer nano-core-shell particle latex It contains carboxyl group and is prepared by adding amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent technology after block copolymer latex; wherein the volume average diameter of polymer nano-core-shell particles is 100-350nm;

The segment structure expression of the block copolymer latex is: R-AA _n1 -b-St _n2 -bX _n3 -bY _n4 -Z; wherein, R is isopropionic acid group, acetate group, 2-nitrile acetic acid group or 2-aminoacetic acid group; in AA _n1 , AA is methacrylic acid monomer unit or acrylic acid monomer unit, n1 is the average degree of polymerization of AA, n1=10～60; in St _n2 , St is styrene monomer Body unit, n2 is the average degree of polymerization of St, n2=3～10; X In _n3 , X is styrene monomer unit, methyl methacrylate monomer unit, methyl acrylate monomer unit, acrylonitrile monomer unit Or vinylnaphthalene monomer unit, n3 is the average degree of polymerization of X, n3=1000～10000; Y in _n4 , Y is methyl acrylate monomer unit, ethyl acrylate monomer unit, n-butyl acrylate monomer unit, Isobutyl acrylate monomer unit, tert-butyl acrylate monomer unit or isooctyl acrylate monomer unit, n4 is the average degree of polymerization of Y, n4=1500-15000; Z is alkyl dithioester, phenyl dithioester Thioester, benzyldithioester or alkyl trithioester.

Further, the buffer solution in the step (1) is tris-hydrochloric acid buffer, citric acid-sodium citrate buffer, phosphate buffer, acetic acid-sodium acetate buffer or borax-hydrochloric acid buffer .

Further, the responsive thin film material in the step (2) is prepared by the following method:

(3.1) Mix 1-100 parts by weight of polymer nanoparticle latex with 0-10 parts by weight of carbon black particle water dispersion and 0-100 parts by weight of silica water dispersion, and stir for 1 to 60 minutes, to obtain a mixture aqueous dispersion;

(3.2) Dewatering and drying the mixture aqueous dispersion obtained in step (3.1) to obtain a responsive film material.

Further, the solid content of the aqueous silica dispersion in the step (3.1) is 10-70%, wherein the diameter of the silica particles is 10-350 nm; the aqueous dispersion of carbon black particles in the step (3.1) The solid content is 0.01-10%, and the diameter of the carbon black particles is 5-100 nm.

Further, the polymer nanoparticle latex is prepared by the following method:

(5.1) Dissolve 1-10 parts by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent in 1-100 parts by weight of water with stirring to form an aqueous macromolecular reagent dispersion;

(5.2) Take 1-100 parts by weight of the macromolecular reagent aqueous dispersion obtained in step (5.1) and pour it into the reactor together with 10-10,000 parts by weight of block copolymer latex and 0-100 parts by weight of X; The reactor was heated to 60-80° C., kept stirring, and continued to pass nitrogen and deoxygenate for more than 5 minutes; then, 0-0.1 parts by weight of a water-soluble initiator was added to initiate polymerization for 15-120 minutes to obtain a polymer nanoparticle latex.

Further, the water-soluble initiator in the step (5.2) is azobisisobutyronitrile, azobisisoheptanenitrile, dibenzoyl peroxide, tert-butyl hydroperoxide, potassium persulfate or persulfuric acid Ammonium.

Further, the block copolymer latex is prepared by the following method:

(7.1) 1-10 parts by weight of amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent is stirred and dissolved in 100-10,000 parts by weight of water to form a water phase, and then together with the oil phase consisting of 10-1,000 parts by weight of X Pour into the reactor and stir and mix; raise the temperature of the reactor to 60-80°C, keep stirring, pass nitrogen and deoxygenate for more than 5 minutes, add 0.01-0.2 parts by weight of a water-soluble initiator, and react for 1-20 hours to obtain R-AA _n1 -b-St _n2 -bX _n3 -Z polymer latex;

(7.2) adding 10-1000 parts by weight of Y to the polymer latex obtained in step (7.1), and after reacting for 1-20 hours, then adding 10-1000 parts by weight of Y and 0-30 parts by weight of a crosslinking agent, After continuing the reaction for 1 to 20 hours, the R-AA _n1 -b-St _n2 -bX _n3 -bY _n4 -Z block copolymer latex is obtained.

Further, the water-soluble initiator in the step (7.1) is azobisisobutyronitrile, azobisisoheptanenitrile, dibenzoyl peroxide, tert-butyl hydroperoxide, potassium persulfate or persulfuric acid Ammonium; the crosslinking agent in the step (7.2) is divinylbenzene, 1,4-butanediol diacrylate, dipropylene glycol diacrylate, ethylene glycol diacrylate, 1,6-hexanediol Diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, tripropylene glycol diacrylate or ethylene glycol dimethacrylate.

Further, the general chemical structure of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent is:

Wherein, Z ₁ is an alkylthio group, an alkyl group, a phenyl group or a benzyl group with a carbon number from four to twelve; in Stn2, St is a styrene monomer unit, n2 is the average degree of polymerization of St, n2=3～ 10; In AAn1, AA is methacrylic acid or acrylic acid monomer unit, n1 is the average degree of polymerization of AA, n1=10～60; R is isopropionic acid group, acetate group, 2-nitrile acetate group or 2-amine acetic acid group.

Further, the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent is one of the following chemical structural formulas (I) and (II):

The beneficial effects of the present invention are:

1. The present invention has the characteristics of convenience, speed and high precision, no need to manually compare the color card, and the detection result is not affected by environmental factors such as temperature, and has great application value.

2. The responsive thin film material in the present invention is essentially a photonic crystal material, and the characteristic peak wavelength of reflection of the photonic crystal material is positively correlated with the lattice constant. At the same time, the material contains carboxyl groups inside, which can absorb water, and the internal carboxyl groups increase with the pH value. The osmotic pressure caused by high ionization causes the material to absorb water. The greater the pH value, the greater the degree of ionization of the carboxyl group, the more water absorption, the greater the lattice constant of the photonic crystal material, and the greater the reflection characteristic peak wavelength. Therefore, the reflection characteristic peak wavelength and pH are fitted. The relationship curve between the values and the pH value calculation formula can be used to detect the pH value; the internal carboxyl group content of the material is low (<5wt%), so the amount of the solution to be tested is small, and the material is washed with water after use It can be reused after being cleaned and dried, which is convenient to use and easy to store.

3. The preparation method of polymer nanoparticles in the responsive thin film material in the present invention adopts reversible addition-fragmentation chain transfer emulsion polymerization. This method is energy-saving and environmentally friendly, the process is simple, and the applicable monomers are wide, which is conducive to large-scale promotion. The latex particles are uniform in size and stable in structure.

Description of drawings

1 is a schematic diagram of the GPC curve of the R-AA _n1 -b-St _n2 -b-St _n3 -nBA _n4 -bZ block copolymer latex obtained in Example 1 of the present invention;

2 is a schematic diagram of a transmission electron microscope photograph of the three-layer polymer nano-core-shell particle obtained in Example 1 of the present invention;

Fig. 3 is the visible light reflection spectrum change diagram of the thin film material obtained in Example 1 of the present invention in buffer solutions of different pH values;

Fig. 4 is the reflection characteristic peak wavelength-pH value standard curve of the thin film material obtained in Example 1 of the present invention in buffer solutions of different pH values;

Fig. 5 is the reflection spectrum curve when the thin film material obtained in Example 1 of the present invention detects the pH value of the unknown solution;

FIG. 6 is a graph showing the change of the elongation at break of the film material obtained in Example 2 of the present invention with the content of poly(n-butyl acrylate) in the polymer nanoparticle.

Detailed ways

A pH value detection method based on a responsive thin film material of the present invention comprises the following steps:

(1) Using the responsive thin film material as the response element, adjust the pH value of the buffer solution, and wet the responsive thin film material with the buffer solution; the buffer solution is Tris-HCl buffer solution, citric acid-sodium citrate buffer, phosphate buffer, acetic acid-sodium acetate buffer, or borax-hydrochloric acid buffer.

The responsive thin film material is obtained by blending polymer nanoparticles containing carboxyl groups, carbon black particles and silica particles after dewatering and drying. The polymer nanoparticles contain carboxyl groups and are prepared by adding amphiphilic macromolecular reversible addition-fragmentation chain transfer reagents after block copolymer latex. The particles can be stably dispersed in water to form latex, and the average volume average diameter of the particles is 100～350nm. The segment structure expression of the block copolymer latex is: R-AA _n1 -b-St _n2 -bX _n3 -bY _n4 -Z; wherein, R is isopropionic acid group, acetate group, 2-nitrile acetate group or 2-aminoacetic acid group; in AA _n1 , AA is methacrylic acid monomer unit or acrylic acid monomer unit, n1 is the average degree of polymerization of AA, n1=10～60; in St _n2 , St is styrene monomer unit, n2 is the average degree of polymerization of St, n2=3～10; X In _n3 , X is styrene monomer unit, methyl methacrylate monomer unit, methyl acrylate monomer unit, acrylonitrile monomer unit or Vinylnaphthalene monomer unit, n3 is the average degree of polymerization of X, n3=1000～10000; Y in _n4 , Y is methyl acrylate monomer unit, ethyl acrylate monomer unit, n-butyl acrylate monomer unit, acrylic acid Isobutyl ester monomer unit, tert-butyl acrylate monomer unit or isooctyl acrylate monomer unit, n4 is the average degree of polymerization of Y, n4=1500-15000; Z is alkyl dithioester, phenyl disulfide substituted esters, benzyl dithioesters or alkyl trithioesters;

The block copolymer latex is synthesized by reversible addition-fragmentation chain transfer emulsion polymerization, which includes the following steps:

(1.1) 1-10 parts by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent is stirred and dissolved in 100-10,000 parts by weight of water to form a water phase, and then together with the oil phase consisting of 10-1,000 parts by weight X Pour into the reactor and stir to mix. Raise the temperature of the reactor to 60-80°C, keep stirring, pass nitrogen and deoxygenate for more than 5 minutes, add 0.01-0.2 parts by weight of a water-soluble initiator, and react for 1-20 hours to obtain R-AA _n1 -b-St _n2 -bX _n3 -Z polymer latex;

The general chemical structure of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent in the above step (1.1) is:

Wherein, St is a styrene monomer unit, AA is a methacrylic acid or acrylic acid monomer unit, Z ₁ is an alkylthio group, an alkyl group, a phenyl group or a benzyl group with a carbon number from four to twelve, and R is an isopropyl group Acid group, acetate group, 2-nitrile acetate group or 2-aminoacetate group; n1 is the average degree of polymerization of AA, n1=10-60; n2 is the average degree of polymerization of St, n2=3-10.

The water-soluble initiator in the above-mentioned step (1.1) includes but is not limited to azobisisobutyronitrile, azobisisoheptanenitrile, dibenzoyl peroxide, tert-butyl hydroperoxide, potassium persulfate, ammonium persulfate .

(1.2) Add 10-1000 parts by weight of Y to the latex obtained in step (1.1), and after reacting for 1-20 hours, add 10-1000 parts by weight of Y and 0-30 parts by weight of a cross-linking agent, and continue the reaction After 1 to 20 hours, an R- _AAn1 -b- _Stn2 - _bXn3 - _bYn4 -Z block copolymer latex was obtained.

The crosslinking agent in the above step (1.2) includes but is not limited to divinylbenzene, 1,4-butanediol diacrylate, dipropylene glycol diacrylate, ethylene glycol diacrylate, 1,6-hexanediol Diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate.

The steps of preparing polymer nanoparticles by adding amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent technology after block copolymer latex are as follows:

(1.3) Dissolve 1-10 parts by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent in 1-100 parts by weight of water to form an aqueous macromolecular reagent dispersion;

The general chemical structure of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent in the above step (1.3) is:

Wherein, St is a styrene monomer unit, AA is a methacrylic acid or acrylic acid monomer unit, Z ₁ is an alkylthio group, an alkyl group, a phenyl group or a benzyl group with a carbon number from four to twelve, and R is an isopropyl group Acid group, acetate group, 2-nitrile acetate group or 2-aminoacetate group; n1 is the average degree of polymerization of AA, n1=10-60; n2 is the average degree of polymerization of St, n2=3-10.

The chemical structural formula of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent used in the examples of the present invention is:

or

(1.4) Pour 1-100 parts by weight of the aqueous macromolecular reagent dispersion liquid obtained in step (1.3) into the reactor together with 10-10,000 parts by weight of block copolymer latex and 0-100 parts by weight of X; The reactor is heated up to 60-80° C., kept stirring, and nitrogen and oxygen are removed continuously for more than 5 minutes; then 0-0.1 parts by weight of a water-soluble initiator is added, and polymer nanoparticles are obtained after initiating polymerization for 15-120 minutes.

The water-soluble initiator in the above-mentioned step (1.4) includes but is not limited to azobisisobutyronitrile, azobisisoheptanenitrile, dibenzoyl peroxide, tert-butyl hydroperoxide, potassium persulfate, ammonium persulfate .

The responsive thin film material is obtained by blending polymer nanoparticles containing carboxyl groups, carbon black particles and silica particles after dewatering and drying. The steps are:

(1.5) Mix 1-100 parts by weight of polymer nanoparticle latex with 0-10 parts by weight of carbon black particle aqueous dispersion and 0-100 parts by weight of silica aqueous dispersion, and stir for 1-60 minutes to obtain Aqueous dispersion of mixture;

(1.6) Dewatering and drying the aqueous mixture dispersion obtained in step (1.5) to obtain a responsive film material.

The solid content of the silica water dispersion liquid is 10-70%, wherein the diameter of the silica particles is 10-350 nm.

The solid content of the carbon black particle aqueous dispersion is 0.01-10%, wherein the carbon black particle diameter is 5-100 nm.

(2) Detect the reflection spectrum in the range of 300-1000 nm in the wetted area of the responsive film material under different pH values, and use the origin software to fit the standard curve of the reflection characteristic peak wavelength-pH value and the pH value calculation formula; After use, the film material can be washed with water, dried and stored for repeated use;

(3) Wetting the responsive thin film material with a solution of unknown pH value, and detecting the reflection and reflection spectrum of the wetted region of the responsive thin film material. The pH value of the unknown solution can be known by comparing the characteristic peak wavelength of the reflection with the standard curve in (2) and substituting it into the pH value calculation formula;

Monomer conversion for each step was determined gravimetrically.

The design molecular weight is calculated by the following formula:

Among them, Mn _,th refers to the design value of the molecular weight of the polymer at the end of each step of the reaction, m is the total mass of the monomers added in the step reaction, x is the conversion rate, and [RAFT] is the amphiphilicity added before the reaction starts. The amount of substance of the reversible addition fragmentation chain transfer reagent, Mn _{, RAFT} is the molecular weight of the amphiphilic reversible addition fragmentation chain transfer reagent.

The microstructure of the thin film material was characterized by a Hitachi SU-8010 scanning electron microscope.

The reflection spectrum curve of the thin film material was measured by Shimadzu (SHIMADZU) UV-2450 and Olympus (OLYMPUS) USPM-RU spectrophotometer.

The mechanical tensile properties of the film materials were tested by Zwick/Roell Z020 universal material testing machine.

Molecular weight characterization of the polymers was performed on a Waters 1525-2414-717 gel permeation chromatograph with tetrahydrofuran as the eluent, calibrated against narrow distribution polystyrene standards.

The particle size and particle size distribution measurements of the latex particles were carried out on a Malvern ZETASIZER 3000 HAS particle sizer.

The morphology of polymer latex particles was characterized by JOEL JEMACRO-123 transmission electron microscope, and the test voltage was 80kV.

Example 1:

The first step: 1 part by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent (I) was stirred and dissolved in 1450 parts by weight of water to form an aqueous phase, and then poured together with the oil phase consisting of 120 parts by weight of styrene Stir and mix in the reactor. The temperature of the reactor was raised to 70°C, stirring was maintained, 0.07 parts by weight of potassium persulfate was added after 30 minutes of nitrogen flow, and the R- _AAn1 -b- _Stn2 - _bXn3 -Z polymer latex was obtained after 10 hours of reaction.

The second step: after the first step reaction is completed, add 100 parts by weight of n-butyl acrylate monomer, react for 4.5 hours, then add 120 parts by weight of n-butyl acrylate and 0 parts by weight of 1,4-butanediol Diacrylate, the R- _AAn1 -b- _Stn2 -b- _Stn3 -b- _nBAn4 -Z polymer latex was obtained after the reaction was continued for 5 hours.

The third step: take 1 part by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent (I), stir and dissolve it in 14 parts by weight of water to form an aqueous macromolecular reagent dispersion.

The fourth step: take 6 parts by weight of the macromolecular reagent aqueous dispersion prepared in the third step, and 35 parts by weight of the R-AA _n1 -b-St _n2 -b-St _n3 -b- prepared in the second step The nBA _n4 -Z polymer latex and 0.4 parts by weight of styrene were mixed into the reactor and stirred and mixed. The temperature of the reactor was raised to 70° C., stirring was maintained, 0.005 parts by weight of potassium persulfate was added after 30 minutes of nitrogen flow, and polymer nanoparticles were obtained after 1 hour of reaction.

The fifth step: mixing 10 parts by weight of polymer nanoparticle latex with 4 parts by weight of carbon black particle water dispersion with a solid content of 0.1% and 0.6 parts by weight of a silica water dispersion with a solid content of 30%, Stir for 10 minutes to obtain an aqueous dispersion of the mixture;

The sixth step: the water dispersion of the mixture obtained in the fifth step is evaporated to dryness at 30° C. to obtain a film material.

Step 7: The film is wetted with buffer solutions of different pH values, and the reflection spectrum of the wetted area of the film material in the range of 300-1000 nm is detected, and the origin software is used to fit the standard curve of the characteristic peak wavelength of the reflection, λ-pH value, and pass The origin software automatically fits the pH value calculation formula: pH=0.1256λ-66.7

The eighth step: contact the film material with an unknown pH value solution, detect the reflection spectrum of the wetted area of the film material, compare the characteristic peak wavelength with the standard curve and substitute it into the pH value calculation formula to obtain the corresponding solution pH value.

Test verification: pH value detection is carried out on the five solutions to be tested with the pH meter of Thunder Magnetic Company model PHS-3C, and the pH value detected by the pH meter is compared with the pH value calculated by the pH value calculation formula obtained in the seventh step of the present invention. Yes, the results are shown in Table 1:

Table 1: pH test results

As can be seen from Table 1, the detection result of the pH value detection method based on the responsive film material of the present invention has less error; the present invention is more convenient and quicker than a pH meter, and has higher accuracy than pH test paper.

As shown in Fig. 1, the molecular weight of each block gradually increased during the first and second polymerization steps, proving that a block copolymer was obtained.

As shown in Figure 2, the polymer nano-core-shell particles obtained in the fourth step are distributed in the form of colloidal particles, with an average particle size of about 230 nanometers, good particle morphology, and the particles exhibit an obvious core-shell separation structure. The particles are dyed with ruthenium acid, and the light-colored phase is the inner core of poly(n-butyl acrylate); the dark-colored phase is the polystyrene shell; It is composed of a scission chain transfer agent and contains carboxyl groups, but because the carboxyl group content is too low (<5wt%), it is difficult to directly observe the third layer structure. However, according to the amphiphilicity of the macromolecular reversible addition-fragmentation chain transfer agent, it can be determined that the added agent will be adsorbed on the surface of the block copolymer latex particles to form a very thin carboxyl-based layer. At the same time, the pure block copolymer latex particles do not absorb water after drying. Therefore, according to the water absorption response characteristics of the photonic crystal material in Figure 3, it can be shown that the material also contains a carboxyl base layer, which proves that the surface of the block copolymer latex particles contains carboxyl groups. the third layer structure.

As shown in Figure 3, the thin film material has obvious reflection characteristic peaks, which are characteristic of photonic crystals. As the pH value of the solution increased from 2.3 to 12.7, the characteristic peak of the visible light reflection spectrum of the film material shifted significantly, and the wavelength moved from 560 nm to 640 nm. It can be determined that the material contains carboxyl groups through the absorption of the solution by the film material, and the internal carboxyl group increases with the pH value. The osmotic pressure caused by high ionization causes the material to absorb water. The higher the pH value, the more water absorbed, the greater the lattice constant of the photonic crystal material, and the greater the reflection characteristic peak wavelength.

As shown in Figure 4, there is a quantitative correlation between the characteristic peak wavelength of the reflection of the film material and the pH value of the solution. As the pH value of the solution increases, the characteristic peak wavelength increases. This curve can be used as a standard curve, and the pH value calculation formula obtained by fitting is: pH=0.1256×wavelength-66.7.

As shown in Figure 5, the characteristic peak wavelength of the wetted area between the film material and the solution with unknown pH value is 609 nm, and the pH value of the solution is 9.8 obtained by substituting it into the pH value calculation formula.

Example 2:

The first step: 2 parts by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent (I) is stirred and dissolved in 5000 parts by weight of water to form an aqueous phase, and then poured together with the oil phase composed of 500 parts by weight of styrene. into the reactor with stirring. The temperature of the reactor was raised to 70°C, stirring was maintained, 0.15 parts by weight of potassium persulfate was added after 30 minutes of nitrogen flow, and the R- _AAn1 -b- _Stn2 - _bXn3 -Z polymer latex was obtained after 9.5 hours of reaction.

The second step: after the first step reaction is completed, add 340 parts by weight of n-butyl acrylate monomer, react for 5.5 hours, then add 430 parts by weight of n-butyl acrylate and 10 parts by weight of 1,4-butanediol Diacrylate, the R- _AAn1 -b- _Stn2 -b- _Stn3 -b- _nBAn4 -Z polymer latex was obtained after the reaction was continued for 6 hours.

The third step: take 2 parts by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent (I), stir and dissolve it in 56 parts by weight of water to form an aqueous macromolecular reagent dispersion.

The fourth step: take 24 parts by weight of the macromolecular reagent aqueous dispersion prepared in the third step, and 75 parts by weight of the R-AA _n1 -b-St _n2 -b-St _n3 -b- prepared in the second step The nBA _n4 -Z polymer latex and 0.8 parts by weight of styrene were mixed into the reactor and stirred for mixing. The temperature of the reactor was raised to 70° C., stirring was maintained, and 0.01 part by weight of potassium persulfate was added after 30 minutes of nitrogen flow, and polymer nanoparticles were obtained after 1.5 hours of reaction.

The fifth step: mixing 10 parts by weight of polymer nanoparticle latex with 1 part by weight of carbon black particle water dispersion with a solid content of 0.04% and 1 part by weight of a silica water dispersion with a solid content of 20%, Stir for 20 minutes to obtain a mixture aqueous dispersion;

The sixth step: the water dispersion of the mixture obtained in the fifth step is evaporated to dryness at 35° C. to obtain a film material.

Step 7: The film is wetted with buffer solutions of different pH values, and the reflection spectrum of the wetted area of the film material in the range of 300-1000 nm is detected, and the origin software is used to fit the reflection characteristic peak wavelength-pH value standard curve. The software automatically fitted the pH value calculation formula.

The eighth step: contact the film material with an unknown pH value solution, detect the reflection spectrum of the film material, and compare the reflection characteristic peak wavelength with the standard curve and substitute it into the pH value calculation formula to obtain the corresponding solution pH value.

As shown in Figure 6, the mechanical properties of the film material can be adjusted according to the actual application. With the content of poly(n-butyl acrylate) in the polymer nanoparticles from 52% to 68%, the elongation at break can increase from 20% to 96%.

The molecular weight of each block gradually increases during the first and second polymerization steps, which proves that a block copolymer is obtained.

The polymer nano-core-shell particles obtained in the fourth step are distributed in the form of colloidal particles, the average particle size is about 250 nanometers, the particle shape is good, and the particles show an obvious core-shell separation structure. There should be a third layer on the outer surface of the particles, which is composed of amphiphilic macromolecular reversible addition-fragmentation chain transfer reagents adsorbed on the particle surface, and contains carboxyl groups, but because the carboxyl group content is too low (<5wt%), it is difficult to directly observe The third layer structure. However, according to the amphiphilicity of the macromolecular reversible addition-fragmentation chain transfer agent, it can be determined that the added agent will be adsorbed on the surface of the block copolymer latex particles to form a very thin carboxyl-based layer. At the same time, the pure block copolymer latex particles do not absorb water after drying, so the water absorption response characteristics of the photonic crystal material can indicate that the material also contains a carboxyl layer, which proves that there is a third layer containing carboxyl groups on the surface of the block copolymer latex particles. structure.

Example 3:

The first step: 5 parts by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent (I) was stirred and dissolved in 9000 parts by weight of water to form an aqueous phase, and then poured together with the oil phase composed of 1000 parts by weight of styrene. into the reactor with stirring. The temperature of the reactor was raised to 70°C, stirring was maintained, 0.2 parts by weight of potassium persulfate was added after 30 minutes of nitrogen flow, and the R- _AAn1 -b- _Stn2 - _bXn3 -Z polymer latex was obtained after 9.5 hours of reaction.

The second step: after the first step reaction is completed, add 850 parts by weight of n-butyl acrylate monomer, react for 5.5 hours, then add 1000 parts by weight of n-butyl acrylate and 30 parts by weight of 1,4-butanediol Diacrylate, the R- _AAn1 -b- _Stn2 -b- _Stn3 -b- _nBAn4 -Z polymer latex was obtained after the reaction was continued for 7 hours.

The third step: take 10 parts by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent (II), stir and dissolve it in 98 parts by weight of water to form an aqueous macromolecular reagent dispersion.

The fourth step: take 1 part by weight of the macromolecular reagent aqueous dispersion prepared in the third step, and 10 parts by weight of the R-AA _n1 -b-St _n2 -b-St _n3 -b- prepared in the second step The nBA _n4 -Z polymer latex and 0 parts by weight of styrene were mixed into the reactor and stirred for mixing. The temperature of the reactor was raised to 70° C., stirring was maintained, and 0 parts by weight of potassium persulfate was added after 30 minutes of nitrogen flow, and polymer nanoparticles were obtained after 1 hour of reaction.

Step 5: Mix 90 parts by weight of polymer nanoparticle latex with 3 parts by weight of a 0.3% carbon black particle water dispersion and 10 parts by weight of a 70% silica water dispersion, and stir. Treated for 20 minutes to obtain a mixture aqueous dispersion;

The sixth step: the water dispersion of the mixture obtained in the fifth step is evaporated to dryness at 50° C. to obtain a film material.

Step 7: The film is wetted with buffer solutions of different pH values, and the reflection spectrum of the wetted area of the film material in the range of 300-1000 nm is detected, and the origin software is used to fit the reflection characteristic peak wavelength-pH value standard curve. The software automatically fitted the pH value calculation formula.

The eighth step: contact the film material with an unknown pH value solution, detect the reflection spectrum of the film material, and compare the reflection characteristic peak wavelength with the standard curve and substitute it into the pH value calculation formula to obtain the corresponding solution pH value.

The molecular weight of each block gradually increases during the first and second polymerization steps, which proves that a block copolymer is obtained.

The polymer nano-core-shell particles obtained in the fourth step are distributed in the form of colloidal particles, the average particle size is about 190 nanometers, the particle shape is good, and the particles show an obvious core-shell separation structure. There should be a third layer on the outer surface of the particles, which is composed of amphiphilic macromolecular reversible addition-fragmentation chain transfer reagents adsorbed on the particle surface, and contains carboxyl groups, but because the carboxyl group content is too low (<5wt%), it is difficult to directly observe The third layer structure. However, according to the amphiphilicity of the macromolecular reversible addition-fragmentation chain transfer agent, it can be determined that the added agent will be adsorbed on the surface of the block copolymer latex particles to form a very thin carboxyl-based layer. At the same time, the pure block copolymer latex particles do not absorb water after drying, so the water absorption response characteristics of the photonic crystal material can indicate that the material also contains a carboxyl layer, which proves that there is a third layer containing carboxyl groups on the surface of the block copolymer latex particles. structure.

Example 4:

The first step: 1 part by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent (I) is stirred and dissolved in 100 parts by weight of water to form an aqueous phase, and then poured together with the oil phase consisting of 600 parts by weight of styrene. into the reactor with stirring. The temperature of the reactor was raised to 70°C, stirring was maintained, 0.1 part by weight of potassium persulfate was added after 40 minutes of nitrogen flow, and the R-AA _n1 -b-St _n2 -bX _n3 -Z polymer latex was obtained after 8 hours of reaction.

The second step: after the first step reaction is completed, add 10 parts by weight of n-butyl acrylate monomer, and after 6.5 hours of reaction, add 1000 parts by weight of n-butyl acrylate and 30 parts by weight of 1,4-butanediol Diacrylate, the R- _AAn1 -b- _Stn2 -b- _Stn3 -b- _nBAn4 -Z polymer latex was obtained after the reaction was continued for 7 hours.

The third step: take 10 parts by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent (I), stir and dissolve it in 100 parts by weight of water to form an aqueous macromolecular reagent dispersion.

The fourth step: take 57 parts by weight of the macromolecular reagent aqueous dispersion prepared in the third step, and 350 parts by weight of the R-AA _n1 -b-St _n2 -b-St _n3 -b- prepared in the second step The nBA _n4 -Z polymer latex and 13 parts by weight of styrene were mixed into the reactor and stirred and mixed. The temperature of the reactor was raised to 70° C., stirring was maintained, 0.02 parts by weight of potassium persulfate was added after 30 minutes of nitrogen flow, and polymer nanoparticles were obtained after 1.5 hours of reaction.

The fifth step: mixing 80 parts by weight of polymer nanoparticle latex with 9.5 parts by weight of carbon black particle water dispersion with a solid content of 10% and 0 part by weight of a silica water dispersion with a solid content of 20%, Stir for 20 minutes to obtain a mixture aqueous dispersion;

The sixth step: the water dispersion of the mixture obtained in the fifth step is evaporated to dryness at 40° C. to obtain a film material.

Step 7: The film is wetted with buffer solutions of different pH values, and the reflection spectrum of the wetted area of the film material in the range of 300-1000 nm is detected, and the origin software is used to fit the reflection characteristic peak wavelength-pH value standard curve. The software automatically fitted the pH value calculation formula.

The eighth step: contact the film material with an unknown pH value solution, detect the reflection spectrum of the film material, and compare the reflection characteristic peak wavelength with the standard curve and substitute it into the pH value calculation formula to obtain the corresponding solution pH value.

The molecular weight of each block gradually increases during the first and second polymerization steps, which proves that a block copolymer is obtained.

The polymer nano-core-shell particles obtained in the fourth step are distributed in the form of colloidal particles, the average particle size is about 270 nanometers, the particle shape is good, and the particles show an obvious core-shell separation structure. There should be a third layer on the outer surface of the particles, which is composed of amphiphilic macromolecular reversible addition-fragmentation chain transfer reagents adsorbed on the particle surface, and contains carboxyl groups, but because the carboxyl group content is too low (<5wt%), it is difficult to directly observe The third layer structure. However, according to the amphiphilicity of the macromolecular reversible addition-fragmentation chain transfer agent, it can be determined that the added agent will be adsorbed on the surface of the block copolymer latex particles to form a very thin carboxyl-based layer. At the same time, the pure block copolymer latex particles do not absorb water after drying, so the water absorption response characteristics of the photonic crystal material can indicate that the material also contains a carboxyl layer, which proves that there is a third layer containing carboxyl groups on the surface of the block copolymer latex particles. structure.

Example 5:

The first step: 3 parts by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent (I) was stirred and dissolved in 6900 parts by weight of water to form an aqueous phase, and then poured together with the oil phase consisting of 10 parts by weight of styrene. into the reactor with stirring. The temperature of the reactor was raised to 70°C, stirring was maintained, 0.09 parts by weight of potassium persulfate was added after 30 minutes of nitrogen flow, and the R-AA _n1 -b-St _n2 -bX _n3 -Z polymer latex was obtained after 7.5 hours of reaction.

The second step: after the first step reaction is completed, add 1000 parts by weight of n-butyl acrylate monomer, react for 5.5 hours, then add 10 parts by weight of n-butyl acrylate and 0 parts by weight of 1,4-butanediol Diacrylate, the R- _AAn1 -b- _Stn2 -b- _Stn3 -b- _nBAn4 -Z polymer latex was obtained after the reaction was continued for 6 hours.

The third step: take 3 parts by weight of the amphiphilic macromolecular reversible addition-fragmentation chain transfer reagent (I), stir and dissolve it in 80 parts by weight of water to form an aqueous macromolecular reagent dispersion.

The fourth step: take 0 parts by weight of the macromolecular reagent aqueous dispersion prepared in the third step, and 160 parts by weight of the R-AA _n1 -b-St _n2 -b-St _n3 -b- prepared in the second step The nBA _n4 -Z polymer latex and 0.9 parts by weight of styrene were mixed into the reactor and stirred and mixed. The temperature of the reactor was raised to 70° C., stirring was maintained, and 0.01 parts by weight of potassium persulfate was added after 30 minutes of nitrogen flow, and polymer nanoparticles were obtained after 1 hour of reaction.

Step 5: Mix 79 parts by weight of polymer nanoparticle latex with 0 parts by weight of 0.8% carbon black particle water dispersion and 100 parts by weight of 10% silica water dispersion, stir Treated for 30 minutes to obtain a mixture aqueous dispersion;

The sixth step: the water dispersion of the mixture obtained in the fifth step is evaporated to dryness at 55° C. to obtain a film material.

Step 7: The film is wetted with buffer solutions of different pH values, and the reflection spectrum of the wetted area of the film material in the range of 300-1000 nm is detected, and the origin software is used to fit the reflection characteristic peak wavelength-pH value standard curve. The software automatically fitted the pH value calculation formula.

The eighth step: contact the film material with an unknown pH value solution, detect the reflection spectrum of the film material, and compare the reflection characteristic peak wavelength with the standard curve and substitute it into the pH value calculation formula to obtain the corresponding solution pH value.

The molecular weight of each block gradually increases during the first and second polymerization steps, which proves that a block copolymer is obtained.

The polymer nano-core-shell particles obtained in the fourth step are distributed in the form of colloidal particles, the average particle size is about 180 nanometers, the particle shape is good, and the particles show an obvious core-shell separation structure. There should be a third layer on the outer surface of the particles, which is composed of amphiphilic macromolecular reversible addition-fragmentation chain transfer reagents adsorbed on the particle surface, and contains carboxyl groups, but because the carboxyl group content is too low (<5wt%), it is difficult to directly observe The third layer structure. However, according to the amphiphilicity of the macromolecular reversible addition-fragmentation chain transfer agent, it can be determined that the added agent will be adsorbed on the surface of the block copolymer latex particles to form a very thin carboxyl-based layer. At the same time, the pure block copolymer latex particles do not absorb water after drying, so the water absorption response characteristics of the photonic crystal material can indicate that the material also contains a carboxyl layer, which proves that there is a third layer containing carboxyl groups on the surface of the block copolymer latex particles. structure.

The segment structure expression of the block copolymer latex in the embodiment of the present invention is: R-AAn1-b-Stn2-b-Xn3-b-Yn4-Z; wherein, R is an isopropionic acid group, an acetate group, a 2- Nitrile acetate group or 2-aminoacetic acid group, the above-mentioned groups have similar properties and can play a similar effect; in AAn1, AA is a methacrylic acid monomer unit or an acrylic acid monomer unit, and the above monomer units are hydrophilic mono The body unit has similar properties and can have similar effects. n1 is the average degree of polymerization of AA, n1=10～60; in Stn2, St is the styrene monomer unit, n2 is the average degree of polymerization of St, n2=3～10 In Xn3, X is styrene monomer unit, methyl methacrylate monomer unit, methyl acrylate monomer unit, acrylonitrile monomer unit or vinyl naphthalene monomer unit. To a similar effect, n3 is the average degree of polymerization of X, n3=1000～10000; in Yn4, Y is methyl acrylate monomer unit, ethyl acrylate monomer unit, n-butyl acrylate monomer unit, isobutyl acrylate monomer unit body unit, tert-butyl acrylate monomer unit or isooctyl acrylate monomer unit, the above-mentioned monomer units have similar properties and can play a similar effect, n4 is the average degree of polymerization of Y, n4=1500～15000; Z is an alkyl group Dithioester, phenyldithioester, benzyldithioester or alkyl trithioester, the above-mentioned groups have similar properties and can have similar effects.

The water-soluble initiators used in the embodiments of the present invention include but are not limited to azobisisobutyronitrile, azobisisoheptanenitrile, dibenzoyl peroxide, tert-butyl hydroperoxide, potassium persulfate, ammonium persulfate, The above compounds have similar properties and can have similar effects.

The crosslinking agents used in the embodiments of the present invention include but are not limited to divinylbenzene, 1,4-butanediol diacrylate, dipropylene glycol diacrylate, ethylene glycol diacrylate, 1,6-hexanediol diacrylate Acrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, the above-mentioned compounds have similar properties and can have similar effects.

The aqueous surfactants used in the embodiments of the present invention include, but are not limited to, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, polyethylene glycol, Tween 80, alkyl glycosides, cocoic acid diethanolamide, Ethoxylated sodium alkyl sulfate, lauramidopropyl betaine, the above compounds have similar properties and can have similar effects.

The buffer solution used in the embodiment of the present invention is tris-hydrochloric acid buffer, citric acid-sodium citrate buffer, phosphate buffer, acetic acid-sodium acetate buffer or borax-hydrochloric acid buffer. similar, with similar effects.

Claims (9)

1. A pH value detection method based on a responsive film material is characterized by comprising the following steps:

(1) adjusting the pH value of the buffer solution to obtain a plurality of solutions with different pH values;

(2) soaking the responsive film material by using the solutions with different pH values obtained in the step (1) by using the responsive film material as a response element to obtain soaked films corresponding to different pH values;

(3) acquiring the reflection spectrum of the wetted area of the wetted film corresponding to different pH values in the range of 300-1000 nm obtained in the step (2), obtaining the reflection characteristic peak wavelength corresponding to different pH values, and fitting a relation curve between the reflection characteristic peak wavelength and the pH value to obtain a pH value calculation formula;

(4) soaking the responsive film material with a solution to be detected, collecting the reflection spectrum of the soaking area of the soaked film of the solution to be detected in the range of 300-1000 nm wave band, obtaining the reflection characteristic peak wavelength corresponding to the solution to be detected, and calculating to obtain the pH value of the solution to be detected through the pH value calculation formula in the step (3);

the responsive film material in the step (2) is obtained by mixing polymer nanoparticle latex containing carboxyl, carbon black particles and silica particles, removing water and drying;

the polymer nano core-shell particle latex is of a three-layer structure, in particular to a structure that a layer of amphiphilic macromolecule reversible addition fragmentation chain transfer reagent wraps two layers of block copolymer latex; the polymer nano core-shell particle latex contains carboxyl, and is prepared by adding amphiphilic macromolecule reversible addition fragmentation chain transfer reagent after block copolymer latex; wherein the volume average diameter of the polymer nano core-shell particles is 100-350 nm;

the chain segment structure expression of the block copolymer latex is as follows: R-AA_n1-b-St_n2-b-X_n3-b-Y_n4-Z; wherein R is an isopropanoyl group, an acetoxy group, a 2-nitriloacetic acid group or a 2-aminoacetoxy group; AA_n1Wherein AA is a methacrylic acid monomer unit or an acrylic acid monomer unit, n1 is the average polymerization degree of AA, and n1 is 10-60; st_n2Wherein St is a styrene monomer unit, n2 is the average polymerization degree of St, and n2 is 3-10; x_n3Wherein X is a styrene monomer unit, a methyl methacrylate monomer unit, a methyl acrylate monomer unit, an acrylonitrile monomer unit or a vinyl naphthalene monomer unit, n3 is the average polymerization degree of X, and n3 is 1000-10000; y is_n4Wherein Y is a methyl acrylate monomer unit, an ethyl acrylate monomer unit, an n-butyl acrylate monomer unit, an isobutyl acrylate monomer unit, a tert-butyl acrylate monomer unit or an isooctyl acrylate monomer unit, n4 is the average polymerization degree of Y, and n4 is 1500-; z is an alkyl dithioester, phenyl dithioester, benzyl dithioester or alkyl trithioester;

the chemical structural general formula of the amphiphilic macromolecule reversible addition fragmentation chain transfer reagent is as follows:

wherein Z is₁Alkylthio, alkyl, phenyl or benzyl with the number of carbon atoms from four to twelve; st in Stn2 is a styrene monomer unit, n2 is the average polymerization degree of St, and n2 is 3-10; in AAn1, AA is a methacrylic acid or acrylic acid monomer unit, n1 is the average polymerization degree of AA, and n1 is 10-60; r is isopropyl, acetoxy, 2-nitriloacetic acid or 2-amino acetoxy.

2. The method for detecting the pH value based on the responsive thin film material of claim 1, wherein the buffer solution in the step (1) is a tris-hydroxymethyl aminomethane-hydrochloric acid buffer solution, a citric acid-sodium citrate buffer solution, a phosphate buffer solution, an acetic acid-sodium acetate buffer solution or a borax-hydrochloric acid buffer solution.

3. The method for detecting pH value based on responsive film material of claim 1, wherein the responsive film material in step (2) is prepared by the following method:

(3.1) mixing 1-100 parts by weight of polymer nanoparticle latex, 1-10 parts by weight of carbon black particle aqueous dispersion and 0.6-100 parts by weight of silica aqueous dispersion, and stirring for 1-60 minutes to obtain mixture aqueous dispersion;

and (3.2) dewatering and drying the mixture aqueous dispersion obtained in the step (3.1) to obtain the responsive film material.

4. The method for detecting pH value based on responsive film material of claim 3, wherein the solid content of the silica aqueous dispersion in the step (3.1) is 10-70%, wherein the diameter of the silica particle is 10-350 nm; the solid content of the carbon black particle water dispersion liquid in the step (3.1) is 0.01-10%, wherein the diameter of the carbon black particle is 5-100 nm.

5. The pH detection method based on the responsive film material according to claim 1, wherein the polymer nanoparticle latex is prepared by the following method:

(5.1) stirring and dissolving 1-10 parts by weight of amphiphilic macromolecular reversible addition fragmentation chain transfer reagent in 1-100 parts by weight of water to form macromolecular reagent aqueous dispersion;

(5.2) pouring 1-100 parts by weight of the macromolecular reagent aqueous dispersion obtained in the step (5.1), 10-10000 parts by weight of block copolymer latex and 0-100 parts by weight of X into a reactor; heating the reactor to 60-80 ℃, keeping stirring, and continuously introducing nitrogen to remove oxygen for more than 5 minutes; and then adding 0-0.1 part by weight of water-soluble initiator to initiate polymerization for 15-120 minutes to obtain the polymer nanoparticle latex.

6. The method for detecting pH value based on responsive thin film material of claim 5, wherein the water-soluble initiator in step (5.2) is azobisisobutyronitrile, azobisisoheptonitrile, dibenzoyl peroxide, tert-butyl hydroperoxide, potassium persulfate or ammonium persulfate.

7. The pH detection method based on the responsive film material as claimed in claim 1, wherein the block copolymer latex is prepared by the following method:

(7.1) stirring and dissolving 1-10 parts by weight of amphiphilic macromolecular reversible addition fragmentation chain transfer reagent in 100-10000 parts by weight of water to form a water phase, and pouring the water phase and an oil phase consisting of 10-1000 parts by weight of X into a reactor to be stirred and mixed; heating the reactor to 60-80 ℃, keeping stirring, introducing nitrogen to remove oxygen for more than 5 minutes, adding 0.01-0.2 part by weight of water-soluble initiator, reacting for 1-20 hours to obtain R-AA_n1-b-St_n2-b-X_n3-a Z polymer latex;

(7.2) adding 10-1000 parts by weight of Y into the polymer latex obtained in the step (7.1), reacting for 1-20 hours, then adding 10-1000 parts by weight of Y and 0-30 parts by weight of cross-linking agent, and continuing to react for 1-20 hours to obtain R-AA_n1-b-St_n2-b-X_n3-b-Y_n4-Z block copolymer latex.

8. The method for detecting pH value based on responsive thin film material of claim 7, wherein the water-soluble initiator in step (7.1) is azobisisobutyronitrile, azobisisoheptonitrile, dibenzoyl peroxide, tert-butyl hydroperoxide, potassium persulfate or ammonium persulfate; the cross-linking agent in the step (7.2) is divinylbenzene, 1, 4-butanediol diacrylate, dipropylene glycol diacrylate, ethylene glycol diacrylate, 1, 6-hexanediol diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate or ethylene glycol dimethacrylate.

9. The pH detection method based on the responsive thin film material as claimed in claim 1, wherein the amphiphilic macromolecular reversible addition fragmentation chain transfer reagent is one of the following chemical structural formulas (I) and (II):

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