CN112430898B

CN112430898B - Thermal or solvent dual-stimulus color-change response nanofiber membrane and preparation method and application thereof

Info

Publication number: CN112430898B
Application number: CN202011251932.5A
Authority: CN
Inventors: 李澄; 仵菁菁
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2020-11-11
Filing date: 2020-11-11
Publication date: 2022-06-07
Anticipated expiration: 2040-11-11
Also published as: CN112430898A

Abstract

The invention provides a thermal or solvent dual-stimulus color-change response nanofiber membrane as well as a preparation method and application thereof. The Prussian blue analogue is prepared firstly, and then the Prussian blue analogue and the high molecular compound polyacrylonitrile are subjected to electrostatic spinning to prepare the nano fiber membrane. The inorganic stimulus response color-changing material has the advantages of easy synthesis, low toxicity and high stability, realizes the effective combination of the color-changing material and electrostatic spinning, can directly prepare the composite nanofiber membrane with good self-support and flexibility, and is beneficial to the subsequent application; the obtained fiber membrane has the advantages of quick color response to double stimulation of heat and solvent, good reusability and the like, and can be used in the fields of anti-counterfeiting, secret communication and the like.

Description

Thermal or solvent dual-stimulus color-change response nanofiber membrane and preparation method and application thereof

Technical Field

The invention relates to a thermal or solvent dual stimulus color-changing response nanofiber membrane as well as a preparation method and application thereof, belonging to the field of stimulus color-changing response materials.

Background

The stimulus color change response material refers to a material which generates color change under the action of various chemical or physical stimuli in the external environment. External stimuli for exciting a reversible color transition of a material mainly include light, heat, electricity, moisture, solvents, mechanical forces, acids and bases, and the like. Nowadays, stimulus color-changing response materials have achieved a lot of important achievements, and have shown huge research and application values in the fields of sensors, information storage materials, information display equipment, intelligent windows, safety anti-counterfeiting, rewriting paper and the like.

Chinese patent document CN 107163080A discloses a stimulus response triphenylethylene photochromic material, a synthesis method and application thereof, and the triphenylethylene photochromic material has the advantages of quick photoresponse, good erasability and the like and can be used in the fields of anti-counterfeiting and the like. However, the living environment is complex and changeable, and the single irritant color-changing material is difficult to meet the requirements; the material of the invention relates to organic synthesis, has complicated preparation steps and is not beneficial to environmental protection; in addition, the target product obtained is non-film-like, which greatly limits its practical use. Chinese patent document CN 105670389 a discloses a photochromic material based on spiropyran and AIE molecules, which has reversible optical properties under both ultraviolet light and heat stimuli. However, the organic color-changing material has the problems of high material cost, easy oxidation, poor cycle performance and the like; the material of the invention also relates to organic synthesis, and the preparation steps are complex and not beneficial to environmental protection; and the obtained material is powdery, and a thin film is prepared by means of spin coating and the like, so that the practical use of the material is greatly limited. In comparison, the method has the advantage that the allochroic material which is in a film shape and has multiple stimulus responses is directly prepared by using cheap and low-toxic raw materials in a simple and environment-friendly method.

The electrostatic spinning technology is an advanced technology for preparing the nanofiber membrane developed in recent years, and has the advantages of simplicity, high efficiency, large-scale application and the like. How to effectively combine the color-changing material with the electrostatic spinning technology, the obtained nanofiber membrane can effectively exert the stimulus color-changing responsiveness of the color-changing material, endow the color-changing material with good self-support and flexibility, and promote the application process of the color-changing material, and has important research significance.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a thermal or solvent dual-stimulation color-change response nanofiber membrane and a preparation method and application thereof. The inorganic stimulus response color-changing material has the advantages of easy synthesis, low toxicity and high stability, realizes the effective combination of the color-changing material and electrostatic spinning, can directly prepare the composite nanofiber membrane with good self-support and flexibility, and is beneficial to the subsequent application; the obtained fiber membrane has the advantages of quick color response to double stimuli of heat and solvent, good reusability and the like, and can be used in the fields of anti-counterfeiting, secret communication and the like.

The technical scheme of the invention is as follows:

the thermal or solvent double-stimulus color change response nanofiber membrane is composed of nanofibers with rough surfaces, the average diameter of the nanofibers is 100-600nm, and the thickness of the nanofiber membrane is 0.1-0.15 mm.

According to the invention, the preferable nano-fiber membrane is prepared by electrostatic spinning of Prussian blue analogue and high molecular compound; the Prussian blue analogue is a Prussian blue analogue with cobalt as a metal ion, the high molecular compound is Polyacrylonitrile (PAN), and the weight-average molecular weight is 150000-200000.

Preferably, the mass ratio of the Prussian blue analogue to the PAN is (0.3-0.7): 1.

the preparation method of the thermal or solvent dual-stimulus color-change response nanofiber membrane comprises the following steps:

(1) preparation of Prussian blue analogue (Co-PBA)

Adding the cobalt acetate aqueous solution into the potassium cobalt cyanide aqueous solution, uniformly mixing, and then reacting for 10-25 h; after the reaction is finished, centrifugally collecting solids, washing and drying to obtain Co-PBA nano particles;

(2) preparation of nanofiber membranes

Fully dispersing Co-PBA nano particles in N, N-dimethylformamide, adding PAN, and uniformly mixing to obtain a spinning solution; then the nano fiber membrane is obtained through electrostatic spinning.

According to the invention, the molar concentration of the cobalt acetate aqueous solution in the step (1) is 0.01-0.05mol/L, and the molar concentration of the potassium cobalt cyanide aqueous solution is 0.005-0.3 mol/L; preferably, the molar concentration of the cobalt acetate aqueous solution is 0.03mol/L, and the molar concentration of the potassium cobalt cyanide aqueous solution is 0.02 mol/L.

Preferably, in step (1), the molar ratio of cobalt acetate to potassium cobalt cyanide is 1-2: 1.

Preferably, in the step (1), the reaction temperature is 20-30 ℃; preferably, the reaction temperature is 25 ℃ and the reaction time is 18 h.

According to the invention, the diameter of the Co-PBA nano-particles obtained in the step (1) is preferably 10-50 nm.

According to the invention, the mass ratio of the Co-PBA nanoparticles, the PAN and the N, N-dimethylformamide in the step (2) is (0.3-0.7): 1: 9.

according to the invention, the weight average molecular weight of the PAN in the step (2) is 150000-200000.

According to the invention, the conditions of the electrostatic spinning in the step (2) are as follows: spinning voltage is 10-20 k V, electrode distance is 150-200 mm, temperature is 25-30 ℃, and relative humidity is 10-15%.

According to the invention, the mass percentage of the Co-PBA in the nanofiber membrane obtained in the step (2) is preferably 60-70%.

The thermal or solvent dual-stimulation color-change response nanofiber membrane is applied to anti-counterfeiting and secret communication.

The double-stimulation color-change response nanofiber disclosed by the invention is uniform in thickness, stable in fiber diameter and uniform in distribution of Co-PBA nanoparticles, the color is respectively changed into blue and purple under the stimulation of heat or a solvent, the color returns to light pink in a natural environment, the color change process can be repeated for more than 20 times, and no obvious color fading exists, so that the fiber membrane has good fatigue resistance.

The invention has the following technical characteristics and beneficial effects:

1. according to the invention, the color-changing material Co-PBA nano particles are effectively combined with the polymer material through electrostatic spinning, so that the color-changing material is uniformly distributed in the nano fibers, and the prepared nano fiber film has good self-supporting and flexibility, is similar to paper and can be used as a functional medium, thereby promoting the application process of the color-changing material; in addition, the method can form a film in a large area, and has strong processability and good application prospect.

2. The Co-PBA nano-particles of the color-changing material have high stability, and the preparation method is simple, green and environment-friendly and has low toxicity. The invention effectively realizes the combination of the color-changing material and electrostatic spinning by adopting an electrostatic spinning method, not only obtains the nanofiber membrane with good self-support and flexibility, and fully exerts the function of Co-PBA stimulating color-changing response, but also exerts the synergistic effect between Co-PBA and PAN to further improve the stimulating color-changing response performance. According to the invention, the polymer PAN with a specific molecular weight is used as a spinning polymer to be compounded with the Co-PBA nanoparticles, and compared with other polymers, the composite nanofiber membrane with good self-supporting property, flexibility and more excellent stimulus discoloration response performance can be obtained smoothly, so that the subsequent application is facilitated; meanwhile, the Co-PBA nano particles with specific addition amount are adopted, so that the fibrous membrane with good form, self-support and flexibility is obtained, and the synergistic effect with PAN is exerted, and the stimulus color change response performance of the fibrous membrane is further improved. In addition, the invention adopts specific electrostatic spinning conditions, is favorable for obtaining a fiber membrane with good form, self-support and flexibility, and is favorable for exerting the synergistic action between Co-PBA and PAN.

3. The dual stimulus color change response nanofiber has the advantages of uniform thickness, stable fiber diameter and uniform distribution of Co-PBA. The fiber membrane has the advantages of quick color response to double stimulation of heat or solvent, good reusability and the like, and can be used in the fields of anti-counterfeiting, secret communication and the like; the fiber membrane of the invention respectively turns blue and purple in color under the stimulation of heat or solvent ethanol, and returns to light pink in natural environment; and the color change process can be repeated for more than 20 times without obvious color decline, which shows that the fiber membrane has good fatigue resistance.

4. The fiber film has flexibility and self-supporting property, and can be designed into an anti-counterfeiting label for checking the authenticity of products; the fiber film has a printable function and can be used for anti-counterfeiting files; the fiber film can also be used as 'paper' to record information for secret communication, the information can be automatically erased, and the fiber film can be repeatedly used.

Description of the drawings:

FIG. 1 is a scanning electron microscope photograph of the Co-PBA obtained in example 1.

FIG. 2 is an X-ray diffraction pattern of Co-PBA obtained in example 1.

FIG. 3 is a Fourier transform infrared spectrum of Co-PBA obtained in example 1.

FIG. 4 is a scanning electron microscope photograph of Co-PBA/PAN obtained in example 1.

FIG. 5 is an X-ray diffraction pattern of Co-PBA/PAN obtained in example 1.

FIG. 6 is a Fourier transform infrared spectrum of Co-PBA/PAN obtained in example 1.

FIG. 7 is a scanning electron microscope photograph of Co-PBA/PAN obtained in example 2.

FIG. 8 is a scanning electron microscope photograph of Co-PBA/PAN obtained in example 3.

FIG. 9 is an optical photograph of Co-PBA/PAN obtained in comparative example 1.

FIG. 10 is an optical photograph of Co-PBA/PAN (left) obtained in example 1 and Co-PBA/PVP (right) obtained in comparative example 2 in water.

FIG. 11 is a comparative graph of optical photographs of the fiber films prepared in example 1, example 2 and example 3 heated at different temperatures.

FIG. 12 is a graph of the UV-VIS diffuse reflectance spectra of the fiber films prepared in example 1 at various temperatures.

Fig. 13 is a spectrum of absorbance change of the fiber membrane prepared in example 1 cyclically used under thermal stimulation.

FIG. 14 is a comparative graph of optical photographs of dropping different solvents on the fiber films prepared in example 1, example 2 and example 3.

FIG. 15 is a UV-VIS diffuse reflectance spectrum of the fiber film prepared in example 1 when exposed to various solvents.

FIG. 16 is a spectrum of absorbance change of the fiber membrane prepared in example 1 in cyclic use under stimulation of solvent.

Fig. 17 is a graph of a fibrous film prepared in example 1 designed as a security label for checking the authenticity of a product.

Fig. 18 is a graph of characters printed by an ink-jet printer for a security document from the fiber film prepared in example 1.

Fig. 19 is a photograph of a digital camera showing a reversible pattern of thermal stimulation of the fiber membrane prepared in example 1.

Fig. 20 is a photograph of a digital camera with the fiber membrane prepared in example 1 showing ethanol written as ink.

Detailed Description

The present invention will be further described with reference to the following examples, but is not limited thereto.

In the examples, the starting materials used were, unless otherwise specified, conventional ones, and the apparatus and method used were, unless otherwise specified, conventional ones.

Example 1

A preparation method of a thermal or solvent dual-stimulus color-change response nanofiber membrane comprises the following steps:

(1) preparation of Co-PBA

149.5mg of cobalt acetate tetrahydrate is dissolved in 20mL of deionized water to obtain a cobalt acetate aqueous solution; 133mg of potassium cobalt cyanide was dissolved in 20mL of deionized water to obtain an aqueous solution of potassium cobalt cyanide. Adding the cobalt acetate aqueous solution into a potassium cobalt cyanide aqueous solution, stirring for 3min under magnetic stirring, uniformly mixing, and placing the mixed solution in a water bath at 25 ℃ for aging for 18 h; after the reaction is finished, the solid is collected by centrifugal separation and washed by water for three times, and then the Co-PBA nano-particles are obtained after drying at 70 ℃.

(2) Preparation of the spinning dope

Uniformly dispersing 0.35g of Co-PBA nano-particles prepared in the step (1) in a 4.5g N N-dimethylformamide solution, adding 0.5g of PAN, stirring for 12h, and uniformly mixing to obtain a spinning solution; wherein the weight average molecular weight of PAN is 150000;

(3) preparation of nanofiber membranes

Performing electrostatic spinning on the spinning solution obtained in the step (2), wherein the spinning conditions are as follows: spinning voltage is 16kV, electrode distance is 180mm, temperature is 30 ℃, and relative humidity is 10%, so that the nanofiber membrane, Co-PBA/PAN for short is obtained. The thickness of the nanofiber membrane is 0.1-0.15 mm.

An SEM photograph of the Co-PBA prepared in this example 1 is shown in fig. 1, which shows that the Co-PBA prepared in this example has an irregular morphology, and the diameter of the particles is 10 to 50 nm.

The X-ray diffraction spectrum of the Co-PBA prepared in this example 1 is shown in fig. 2, and as can be seen from fig. 2, the X-ray diffraction data of the Co-PBA prepared in this example is better matched with the simulated data, thus proving that the Co-PBA is successfully prepared in this example.

The Fourier transform infrared spectrogram of the Co-PBA prepared in the example 1 is shown in FIG. 3, and as can be seen from FIG. 3, the Co-PBA was successfully prepared in the example.

An SEM photograph of the Co-PBA/PAN prepared in the example 1 is shown in FIG. 4, and it can be seen from FIG. 4 that the Co-PBA/PAN nanofibers prepared in the example have uniform diameter and average diameter of 500 nm.

The X-ray diffraction pattern of the Co-PBA/PAN prepared in the example 1 is shown in FIG. 5, and as can be seen from FIG. 5, the Co-PBA/PAN prepared in the example still maintains the PBA structure.

The Fourier transform infrared spectrogram of the Co-PBA/PAN prepared in the example 1 is shown in FIG. 6, and as can be seen from FIG. 6, the Co-PBA/PAN prepared in the example 1 still maintains the active functional groups of the PBA.

Example 2

A method for preparing a thermal or solvent dual-stimulus color-change response nanofiber membrane, as described in example 1, except that: the adding amount of the Co-PBA in the step (2) is 0.25 g; the other steps and conditions were the same as in example 1.

An SEM photograph of the Co-PBA/PAN prepared in the example 2 is shown in FIG. 7, and it can be seen from FIG. 7 that the Co-PBA/PAN nanofibers prepared in the example 2 have uniform diameter and an average diameter of 350 nm.

Example 3

A method for preparing a thermal or solvent dual-stimulus color-change response nanofiber membrane, as described in example 1, except that: the adding amount of the Co-PBA in the step (2) is 0.15 g; the other steps and conditions were the same as in example 1.

An SEM photograph of the Co-PBA/PAN prepared in the example 3 is shown in FIG. 8, and it can be seen from FIG. 8 that the Co-PBA/PAN nanofibers prepared in the example 3 have uniform diameter and an average diameter of 200 nm.

Comparative example 1

A method of making a nanofiber membrane as described in example 1, except that: the adding amount of the Co-PBA in the step (2) is 0.4 g; the other steps and conditions were the same as in example 1.

The optical photograph of the Co-PBA/PAN prepared in the comparative example 1 is shown in FIG. 9, and it can be seen from FIG. 9 that the fiber membrane prepared in the comparative example 1 has many spots on the surface and is unusable; as is evident from the above, the amount of Co-PBA to be added in the present invention needs to be appropriate.

Comparative example 2

A method of making a nanofiber membrane as described in example 1, except that: replacing PAN in the step (2) with 0.5g of polyethylene pyrrolidone with the weight-average molecular weight of 130 ten thousand; the other steps and conditions were the same as in example 1. The obtained nanofiber membrane is called Co-PBA/PVP for short.

Optical photographs of Co-PBA/PAN (left) prepared in example 1 and Co-PBA/PVP (right) prepared in comparative example 2 in water are shown in FIG. 10, and it can be seen from FIG. 10 that Co-PBA/PAN can exist stably in water and is suitable for various environments; Co-PBA/PVP can be dissolved in water, and the practical use is limited. The specificity and importance of the spun polymer PAN of the invention is demonstrated by the above.

Test example 1

The nanofiber membranes prepared in example 1, example 2 and example 3 were placed on a heating plate for heating, and three fiber membranes with different Co-PBA contents were photographed at the same temperature, respectively, to compare the difference of the thermochromic colors of the fiber membranes, as shown in fig. 11. As can be seen from FIG. 11, the higher the Co-PBA content of the fiber film heated at the same temperature, the darker the color change of the fiber film, and the color of the film gradually changed from pink to blue with the increase of the temperature.

Test example 2

The nanofiber membrane prepared in experimental example 1 was subjected to uv-vis diffuse reflectance spectrum test, as shown in fig. 12.

As can be seen from FIG. 12, the wavelength of the maximum absorption peak changes from 500nm to 540-640nm with increasing temperature; indicating that the coordination number of Co (II) loses two coordinated water molecules with the increase of temperature is changed from 6 to 4.

Test example 3

The fiber membrane prepared in example 1 was subjected to a repeated heating-cooling process, and then tested for fatigue by uv-vis diffuse reflectance spectroscopy, as shown in fig. 13.

As can be seen from FIG. 13, the fibrous membrane was repeatedly used for more than 20 times without significant color fading, indicating that it had good fatigue resistance.

Test example 4

Solvent was dropped on the fiber membranes prepared in example 1, example 2 and example 3, and three fiber membranes with different Co-PBA contents were photographed in the same solvent, respectively, to compare the difference of color change caused by the solvent of the fiber membranes, as shown in fig. 14.

As can be seen from fig. 14, the color of the fiber film changed more deeply when the same solvent was added dropwise to the fiber film, as the Co-PBA content was higher.

Test example 5

The fiber film prepared in experimental example 1 was dropped with different solvents and then subjected to uv-vis diffuse reflectance spectrum test, as shown in fig. 15.

As can be seen from FIG. 15, the strongest absorption peak position was about 500nm when the fiber membrane was exposed to water and methanol, respectively, indicating that the coordination environment of Co (II) was not changed. When the nanofiber membrane was exposed to acetonitrile, acetone and ethanol, the absorption peak position of the product changed significantly, with the strongest absorption red-shifted to about 600 nm. The results show that when Co-PBA is contacted with a solvent, the solvent molecules can coordinate with Co (ii) instead of water molecules, or some water molecules in Co-PBA can be released into the environment due to the strong binding ability between Co (ii) and water molecules, so that the coordination number of Co (ii) decreases from 6 to 5 or 4.

Test example 6

The fiber membrane prepared in example 1 was subjected to a repeated write-erase process with ethanol, and then tested for fatigue by uv-visible diffuse reflectance spectroscopy, as shown in fig. 16.

As can be seen in FIG. 16, the fibrous membrane was able to be used repeatedly for more than 20 times without significant color fading, indicating that it had good fatigue resistance.

Test example 7

The fibrous film prepared in example 1 was designed into a character label for an anti-counterfeit display. The color change process under heat and ethanol stimulation was recorded by a digital camera as shown in fig. 17.

As can be seen from fig. 17, the color of the character label changes from pink to blue and purple respectively under the stimulation of heat and ethanol. And the color is restored to the original state after being cooled or dried in the natural environment. It is stated that the authenticity of the product can be identified by a simple external stimulus.

Test example 8

The fiber film prepared in example 1 was printed with a letter by an ink jet printer to make an anti-counterfeit display. The color change process under heat and ethanol stimulation was recorded by a digital camera as shown in fig. 18.

As can be seen from fig. 18, the color of the fiber membrane changed from pink to blue and purple respectively under the stimulation of heat and ethanol. And the color is restored to the original state after being cooled or dried in the natural environment. The fiber film has a printable function, and the authenticity of the document can be identified through simple external stimulation.

Test example 9

The fibrous membrane prepared in example 1 was placed on a hot template with a hollow pattern, and a pattern formed by the fibrous membrane under thermal stimulation was shown. The color change process was recorded by a digital camera as shown in fig. 19.

As can be seen from fig. 19, the pattern can appear in the same position of the same film under thermal stimulation through different templates, when the film is placed in a natural environment, Co (ii) coordinates with water molecules in the air, the color returns to the original state, and the pattern disappears; with the increase of the using times, the color of the pattern is not obviously attenuated, and the pattern is clear and has high resolution, which shows that the fiber film has erasability and good fatigue resistance.

Test example 10

Writing was performed on the fiber membrane prepared in example 1 using a brush pen dipped with ethanol, and the process was recorded by a digital camera, as shown in fig. 20.

As can be seen from fig. 20, writing can be performed repeatedly on the same position of the same film, and the pattern disappears when the ethanol volatilizes; with the increase of the use times, the color is not obviously attenuated, and the clear text resolution is high, which indicates that the fiber film has erasability and good fatigue resistance.

Claims

1. The application of the thermal or solvent dual-stimulus color-change response nanofiber membrane in anti-counterfeiting and secret communication;

the thermal or solvent dual-stimulus color change response nanofiber membrane is composed of nanofibers with rough surfaces, the average diameter of the nanofibers is 100-600nm, and the thickness of the nanofiber membrane is 0.1-0.15 mm;

(1) preparation of Prussian blue analogue (Co-PBA)

Adding a cobalt acetate aqueous solution into a potassium cobalt cyanide aqueous solution, uniformly mixing, and then reacting for 10-25 h; after the reaction is finished, centrifugally collecting solids, washing and drying to obtain Co-PBA nanoparticles;

the molar concentration of the cobalt acetate aqueous solution is 0.01-0.05mol/L, and the molar concentration of the potassium cobalt cyanide aqueous solution is 0.005-0.3 mol/L; the molar ratio of the cobalt acetate to the potassium cobalt cyanide is 1-2: 1; the reaction temperature is 20-30 ℃; the diameter of the obtained Co-PBA nano-particles is 10-50 nm;

(2) preparation of nanofiber membranes

Fully dispersing Co-PBA nano particles in N, N-dimethylformamide, adding PAN, and uniformly mixing to obtain a spinning solution; then carrying out electrostatic spinning to obtain a nanofiber membrane;

the weight average molecular weight of the PAN is 150000-200000; the mass ratio of the Co-PBA nanoparticles to the PAN to the N, N-dimethylformamide is (0.3-0.7): 1: 9; the electrostatic spinning conditions are as follows: spinning voltage is 10-20 k V, electrode distance is 150-200 mm, temperature is 25-30 ℃, and relative humidity is 10-15%; in the obtained nanofiber membrane, the mass percentage of Co-PBA is 60-70%.