CN113861482B - PDMS-based coated sheet SiO 2 Process for preparing a film of a electrochromic material - Google Patents

Abstract

The invention discloses a Polydimethylsiloxane (PDMS) -based coated sheet SiO ₂ Firstly, controlling the preparation condition of a hydrothermal method, controlling the concentration of sodium hydroxide to be 3.5mol/L, and reacting for 3 hours at 180 ℃ to obtain flaky SiO ₂ Cleaning, grinding, then placing into isopropanol, ultrasonic dispersing, then spraying on the surface of glass by using a spray gun to form a layer of particle layer, adding PDMS glue, vacuumizing to remove bubbles, heating, solidifying, removing the film, pre-stretching by 10%, and then performing oxygen plasma treatment for 30 seconds to obtain the mechanochromatic film, wherein the film is based on PDMS coated sheet-shaped SiO ₂ The crack at the interface of the force-induced color film is easier to be unstable and expand to form a cavity when being stretched, and light is reflected and scattered, so that the large transmittance change is generated under the condition of small deformation, and the force-induced color performance of the force-induced color film is greatly improved.

Description

PDMS-based coated sheet SiO 2 Process for preparing a film of a electrochromic material

Technical Field

The invention belongs to a C08 composite material based on an organic polymer compound, in particular to a PDMS-coated flaky SiO-based composite material ₂ Is a method for preparing the mechanochromatic film.

Background

The mechanochromatic material can obtain different response speeds, sensitivities and compressive strengths through different mechanical color-changing structures and materials, and multiple responses are integrated with the mechanical response materials to produce the multifunctional device. The innovative mechanical color-changing materials can meet the requirements of mechanical sensing, dynamic display, intelligent windows, flow monitors, tunable color filters, tunable laser transmitters and other applications. But molecular dye-based mechanochromismMost of the materials have low chemical stability, are decomposed under the action of illumination, and are toxic. The physical color based on the micro-nano structure is also known as structural color without the defects, the structural color widely exists in the natural world, such as feather color of birds and wing color of butterflies, the structural color which responds to mechanical stimulus, namely the mechanochromic structural color, can be prepared by artificial methods such as self-assembly, nano-lithography and the like, has the advantages of stability and innocuity, and has good application prospect. Currently based on PDMS coated SiO ₂ The force-induced color-changing material adopts spherical SiO ₂ Particles, stretched SiO ₂ The crack propagation of the tear between the particle and the PDMS substrate creates a cavity that scatters and refracts light, changing its state from transparent to opaque. However, because the stress field of the crack tip of the spherical gap is passivated, the crack is more difficult to propagate, and larger deformation is needed between the spherical particles and the coated PDMS to tear and create a cavity. PDMS is used to coat spherical SiO in paper Advanced Materials (2015) 27.15:2489-2495, for example ₂ The force-induced color-changing film needs 40-60% deformation to be well switched from transparent state to opaque state. And thus are not sensitive enough to be used in many scenarios.

Disclosure of Invention

The invention provides a method for preparing flaky SiO by a hydrothermal method ₂ Nanoplatelets, then coating the platy SiO with PDMS ₂ A method for constructing a mechanochromatic film to substantially reduce the amount of deformation required to color change. PDMS and SiO without tensile strain ₂ The refractive indexes of the films are similar, no reflection exists at the interface, and the films are in transparent states. For PDMS@SiO ₂ The stretching and color changing process of the electrochromic film can be regarded as that under the plane strain state, under the action of the tensile force, the joint of the PDMS and the silicon dioxide generates cracks due to small binding force, the cracks rapidly expand to generate a cavity, the original transparent state is changed into the opaque state by reflecting scattered light by the cavity, after the strain is released, the elasticity of the PDMS enables the film to shrink back, the cavity disappears, and the original transparent state is returned. As shown in FIG. 1, the interface between spherical silica and PDMS is externally applied to the interface between spherical silica and PDMS in the document Advanced Materials (2015) 27.15:2489-2495The surface of the spherical crack generated by lower tearing is passivated, the surface is difficult to expand, and the crack can be started only by instable expansion of an oversized strain. In the case of nano-sheet silica, as shown in fig. 2, the length-thickness ratio is very large, the stress field intensity factor of the crack tip is much larger, and the crack is easy to unstably expand under smaller strain to generate a cavity, so that a more sensitive force-induced color change effect is generated.

The invention adopts the following technical scheme: preparing flaky SiO by controlling the reaction parameters of a hydrothermal method ₂ Then SiO is added ₂ The method comprises the following steps of:

step 1, placing the glass slide into a hydrothermal reaction kettle, adding 2.5mol/L NaOH solution with the filling rate of 60%, reacting for 3 hours at 180 ℃, taking out the precipitate, cleaning, filtering and drying. At other NaOH concentrations, temperatures or reaction times, high quality nanoplatelets could not be produced.

Step 2, grinding the dried powder, mixing with isopropanol in a mass ratio of 1:10, performing ultrasonic dispersion, cleaning, drying and heating a large whole piece of glass to 60 ℃, putting the dispersion liquid into a spray gun, adding the air compressor pressure to 40kPa for spraying, wherein the spraying distance is 10cm, and the moving speed of the spray gun is 10cms ^-1 And forming a white particle layer on the surface of the glass, and then drying to remove the isopropanol.

And 3, mixing PDMS and a curing agent in a mass ratio of 10:1, uniformly stirring, pouring the mixture onto a white particle layer, spreading the mixture under the action of gravity, placing the mixture into a vacuum drying oven, vacuumizing to remove bubbles, and heating and curing to form a film.

And 4, taking out and stripping the film, pre-stretching the film by 10% on a clamp, and performing oxygen plasma treatment to form wrinkles to obtain the mechanochromatic film.

The beneficial effects are that: the invention provides a PDMS-coated sheet SiO-based material ₂ The constructed electrochromic film reduces the visible light transmittance of 550nm from 74% to 44% when the tensile deformation amount is increased from 10% to 20%, and the equivalent condition is based on spherical coating of spherical SiO based on PDMS ₂ The transmittance of the constructed electrochromic film can only be reduced from 62 percentThe strength and the color change performance are improved by 6 times by 57 percent.

Drawings

FIG. 1 PDMS coated spherical SiO ₂ Is a schematic diagram of the principle of force-induced color change;

FIG. 2 PDMS coated platelet SiO ₂ Is a schematic diagram of the principle of force-induced color change;

FIG. 3 sheet SiO ₂ Scanning electron microscope pictures;

FIG. 4 PDMS coated platelet SiO ₂ A force-induced color film scanning electron microscope picture;

FIG. 5 PDMS coated platelet SiO ₂ Is formed by coating spherical SiO with PDMS ₂ The visible light transmittance of the force-induced color film is changed under different stretching deformation rates;

FIG. 6 PDMS coated platelet SiO ₂ The color-changing effect of the force-induced color-changing film is not stretched (left) and stretched (right).

Detailed Description

The invention will be further explained with reference to examples and figures.

Example 1:

step 1, sequentially cleaning commercial glass slides (with the size of 25.4X76.2X1 mm) in ultrasonic bath by using ethanol and deionized water, putting the cleaned commercial glass slides into a polytetrafluoroethylene reaction kettle, adding 60mL of 2.5mol/L sodium hydroxide solution, screwing the reaction kettle, putting the reaction kettle into a preheated blast drying box at 180 ℃ for 3 hours, taking out the reaction kettle, and cooling to room temperature in air. Removing the rest glass slide, washing with deionized water, sequentially washing the precipitate with deionized water and ethanol, centrifuging for 5 times, and drying at 70deg.C for 240min to obtain final product sheet SiO ₂ . Prepared flake SiO flakes ₂ As shown in fig. 3, 1 micron in length and about 50 nanometers in thickness.

Step 2, siO will be obtained ₂ Grinding fully, mixing the powder into uniform white fine particles, mixing the powder with isopropanol in a mass ratio of 1:10, and performing ultrasonic dispersion for 2 hours. Cleaning and drying large glass, heating to 60deg.C, rapidly adding dispersion into spray gun, and air-pressingThe compressor pressure is increased to 40kPa, spraying is carried out, the spraying distance is 10cm, and the moving speed of the spray gun is 10cms ^-1 And forming a white particle layer on the surface of the glass, and then drying to remove the isopropanol.

And 3, mixing PDMS and a curing agent in a mass ratio of 10:1, uniformly stirring, placing a mold on glass to block the flow of PDMS liquid, slowly pouring the PDMS on a white particle layer, flowing under the action of gravity, spreading to a thickness of about 2mm, placing in a vacuum drying oven, vacuumizing to remove bubbles, and curing at 70 ℃ for 6 hours to form a film. Film-coated sheet-shaped SiO ₂ As shown in FIG. 4, a sheet-like SiO can be seen ₂ Compounded in PDMS.

And 4, taking out and stripping the film, cutting the film into strips, pre-stretching the strips by 10% on a customized clamp, performing oxygen plasma treatment, wherein the radio frequency power is 90W, the oxygen flow rate is 100mL/min, and treating the strips for 30s to form wrinkles on the surface, thus obtaining the mechanochromatic film. The effect of the mechanochromism is shown in fig. 5, and the visible light transmittance is greatly reduced when the stretching ratio is changed from 10% to 20%. It can be seen that after stretching the film, as shown in fig. 6, it changes from transparent to opaque, strain is released, and the film changes back to transparent again.

The foregoing is only a preferred embodiment of the invention, it being noted that: it will be apparent to those skilled in the art that modifications may be made without departing from the principles of the invention, and such modifications are intended to be within the scope of the invention.

Claims (1)

1. PDMS-based coated sheet SiO ₂ The preparation method of the mechanochromatic film is characterized in that flaky SiO is obtained by controlling hydrothermal reaction parameters ₂ Then coating with PDMS, pre-stretching, and performing oxygen plasma treatment to obtain wrinkles, thereby obtaining the mechanochromatic film, which comprises the following steps:

step 1, placing the cleaned glass slide into a hydrothermal reaction kettle, adding NaOH solution with the concentration of 2.5mol/L, reacting for 2 hours at 180 ℃, cleaning, filtering and drying the precipitate at the bottom of the reaction kettle to obtain sheet-shaped SiO with the length of 1 micrometer and the thickness of 50nm ₂ ；

Step 2, flaky SiO is prepared ₂ Mixing with isopropanol at a mass ratio of 1:10, ultrasonic dispersing, cleaning and drying large whole glass, heating to 60deg.C, placing the dispersion into a spray gun, adding air compressor pressure to 40kPa, spraying at a spray distance of 10cm and a spray gun moving speed of 10cms ^-1 Forming a white particle layer on the surface of the glass, and then drying to remove isopropanol;

step 3, mixing PDMS and a curing agent in a mass ratio of 10:1, uniformly stirring, pouring the mixture onto a white particle layer, spreading the mixture under the action of gravity, placing the mixture into a vacuum drying oven, vacuumizing to remove bubbles, and heating and curing to form a film;

and 4, taking out and stripping the film, pre-stretching the film by 10% on a clamp, and performing oxygen plasma treatment to form wrinkles to obtain the mechanochromatic film.

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