Preparation method of polymer dimming film with passive radiative cooling characteristics

Abstract

The application discloses a preparation method of a polymer light-adjusting film with passive radiation refrigeration characteristics. ‑1 ) just covers the atmospheric transparent window (8-13 mu m), so by reasonable design, selecting non-liquid crystal light-crosslinkable monomers (NLCM) with strong chemical bond vibration in the range, that is, mid-infrared emission monomers, further uniformly mixing the monomers with liquid crystal small molecules, a photoinitiator and spacer particles to form an isotropic liquid, and filling the isotropic liquid into a liquid crystal cell formed by a flexible transparent conductive film, a simple ultraviolet polymerization induced phase separation method is adopted to construct an intelligent polymer light-adjusting film with passive radiation refrigeration characteristics. The novel polymer light-adjusting film shows excellent electro-optic response, displays stable and reversible light switch characteristics, and can effectively actively control the sunlight band by applying a low threshold voltage, so as to control the indoor temperature on demand. In addition, the polymer light-adjusting film obtains a high infrared emissivity in the mid-infrared region, so it has the ability of passive radiation refrigeration, and thus shows great potential in large-scale optical and thermal management.

Description

Technical Field

[0001] This invention discloses a method for preparing a polymer dimming film with passive radiative cooling characteristics, belonging to the field of materials technology. In particular, it relates to a method for constructing a polymer dimming film with passive radiative cooling characteristics by designing non-liquid crystal photocrosslinkable monomers with strong chemical bond vibrations within the atmospheric transparency window (8-13 μm). Background Technology

[0002] Passive radiative coolers can transfer heat to the cold outer space through atmospheric transparent windows (8-13 μm), thus achieving continuous radiative cooling. This is beneficial for addressing the practical problem of global warming and aligns with the trend of low-carbon and environmentally friendly development. The inherent chemical bond vibrations of polymers in the infrared range lead to infrared absorption and emission, thus polymers demonstrate extraordinary potential in the field of radiative cooling.

[0003] In recent years, polymer-dispersed liquid crystals (PDLCs) have achieved remarkable success in dynamic optical modulation for automotive windows, building doors and windows, and projection screens, exhibiting stable optical switching performance. They can optimize indoor light and heat transmission as needed, significantly reducing dependence on air conditioning, lighting, and heaters. However, researchers have neglected the thermal emission effect caused by specific chemical bond vibrations in the infrared region of PDLCs. This invention constructs a polymer dimming film with passive radiative cooling effect by designing and selecting non-liquid crystal photocrosslinked monomers with high emission characteristics in the 8-13 μm range. This film has significant application prospects in large-scale optical and thermal management. Summary of the Invention

[0004] This invention aims to provide a method for preparing a polymer dimming film with passive radiative cooling characteristics. The method includes the following steps:

[0005] (1) Through ingenious molecular design, mid-infrared emitting monomers were selected for constructing polymer dimming films with passive radiation cooling properties.

[0006] (2) The mid-infrared emitting monomer is uniformly mixed with liquid crystal molecules, photoinitiator and spacer particles to form an isotropic liquid.

[0007] (3) Take two flexible transparent conductive films to make a liquid crystal cell, and fill the liquid crystal cell with the above isotropic liquid mixture.

[0008] (4) The polymer dimming film with passive radiation cooling characteristics can be obtained by irradiating the isotropic liquid mixture with ultraviolet light to cause phase separation.

[0009] Furthermore, the mid-infrared emitting unit mentioned in step (1) is located in the infrared fingerprint region (1500-600cm). -1 This region exhibits strong chemical bond vibrations, and coincidentally, it covers the atmospheric transparency window (8-13 μm). Specifically, its chemical structure typically contains functional groups such as CF, C-Cl, CH, CO, CN, and Si-O, and can be a mixture of various structures, as shown in Formula I:

[0010]

[0011] R1 in equation A-1 can be one of the following structures:

[0012]

[0013] The value of 'a' can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 independently.

[0014] R2 and R3 mentioned in formulas A-2 and A-3 include -CF3, -CHF2 or -CF2CH3; wherein the values ​​of b, c, d and e are independently 0, 1, 2, 3, 4 or 5.

[0015] In equations A-4 and A-5, the values ​​of f and g are independently 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14.

[0016] Furthermore, the liquid crystal molecules in step (2) are any one of commercial liquid crystals such as 5CB, E7, E8, and SLC1717.

[0017] Furthermore, in step (2), the photoinitiator is one of Irgacure 651 or other similar photoinitiators.

[0018] Furthermore, in step (2), the spacer particles are any one of diameters from 0 to 100 μm.

[0019] Furthermore, in step (2), the content of photoinitiator Irgacure 651 is 1 to 5 wt.% of the NLCM mass, and the content of spacer particles is 0.2 to 1 wt.% of the total mass.

[0020] Furthermore, in step (3), the conductive layer of the flexible transparent conductive film is any one of indium tin oxide (ITO), fluorine-doped tin dioxide coating (FTO), aluminum-doped zinc oxide coating (AZO), nano silver, metal mesh, or conductive polymer, and its resistance is 50 to 150 Ω.

[0021] Furthermore, in step (3), the substrate material of the flexible transparent conductive film is any one of polyethylene terephthalate (PET), polyimide (PI), polyethylene naphthalate (PEN), polyethylene (PE), etc.

[0022] Furthermore, the ultraviolet light intensity in step (4) is 4–20 mW / cm². 2 The illumination time is 5 to 30 minutes.

[0023] Furthermore, the polymer film has stable and reversible optical switching characteristics, and can effectively control the solar radiation band with a low threshold voltage. At the same time, it has a high infrared emissivity in the mid-infrared region and has the ability to passively radiatively cool.

[0024] The present invention has the following technical effects:

[0025] This invention can stably and actively regulate the transmittance of sunlight using a relatively low voltage, thereby controlling indoor temperature as needed. Simultaneously, this invention possesses passive radiative cooling characteristics, enabling continuous heat exchange with the cold universe through an atmospheric transparent window within the 8-13μm range by absorbing and emitting electromagnetic waves. It has enormous development potential in fields such as building energy conservation, photovoltaic cooling, energy harvesting, and human body heat management. Attached Figure Description

[0026] Figure 1 The curve showing the transmittance of the radiation-cooled polymer film in Example 1 as a function of voltage is shown.

[0027] Figure 2 These are photographs of the radiation-cooled polymer film in Example 1 before and after being energized;

[0028] Figure 3 The infrared emission spectrum of the radiation-cooled polymer film in Example 1;

[0029] Figure 4 This is a comparison image of infrared imagers of the radiation-cooled polymer film and the low-emission Al foil in Example 1. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.

[0031] Example 1

[0032] Raw materials: Cyclohexyl methacrylate (CHMA), hexafluorobutyl methacrylate (HFMA), polyethylene glycol diacrylate 600 (PEGDA 600), commercial liquid crystal mixture E7, photoinitiator Irgacure 651, and 30μm spacer particles. The preparation process is as follows:

[0033] First, CHMA (2g), HFMA (2g), PEGDA 600 (1g), commercial mixed liquid crystal E7 (5g), photoinitiator Irgacure 651 (0.15g), and spacer particles (0.05g) were placed in a 20mL sample vial and vigorously shaken for 30 minutes to form a homogeneous isotropic liquid. Then, two 10cm*10cm PET transparent conductive films were used to construct a liquid crystal cell. The liquid was filled into the liquid crystal cell and subjected to light intensity of 6mW / cm². 2 Irradiation with ultraviolet light for 10 minutes causes polymerization-induced phase separation to form a polymer film with passive radiation cooling properties.

[0034] Example 2

[0035] Cyclohexyl methacrylate (CHMA), 2-(perfluorohexyl)ethyl methacrylate (TFOMA), polyethylene glycol diacrylate 600 (PEGDA 600), commercial liquid crystal mixture E7, photoinitiator Irgacure 651, and 30 μm spacer particles. The preparation process is shown below:

[0036] First, CHMA (2g), TFOMA (2g), PEGDA 600 (1g), commercial mixed liquid crystal E7 (5g), photoinitiator Irgacure 651 (0.15g), and spacer particles (0.05g) were placed in a 20mL sample vial and vigorously shaken for 30 minutes to form a homogeneous isotropic liquid. Then, two 10cm*10cm PET transparent conductive films were used to construct a liquid crystal cell. The liquid was filled into the cell and subjected to light intensity of 6mW / cm². 2 Irradiation with ultraviolet light for 10 minutes causes polymerization-induced phase separation to form a polymer film with passive radiation cooling properties.

Claims

1. A method for preparing a polymer dimming film with passive radiative cooling properties, characterized in that, The method involves selectively choosing a non-liquid crystal photocrosslinkable monomer (NLCM) with strong chemical bond vibrations within an atmospheric transparency window range of 8-13 μm, i.e., a mid-infrared emitting monomer, and combining it with liquid crystal small molecules. A polymer dimming film is then constructed using ultraviolet light-induced phase separation to achieve passive radiative cooling and optical modulation. The method includes the following steps: (1) Select mid-infrared emitting monomers for constructing polymer dimming films with passive radiation cooling properties; (2) The mid-infrared emitting monomer is uniformly mixed with liquid crystal molecules, photoinitiator and spacer particles to form an isotropic liquid; (3) Take two flexible transparent conductive films to make a liquid crystal cell, and fill the liquid crystal cell with the above isotropic liquid mixture; (4) The polymer dimming film with passive radiation cooling characteristics can be obtained by causing phase separation of the isotropic liquid mixture by ultraviolet light irradiation; The mid-infrared emitting element mentioned in step (1) is located in the infrared fingerprint region at 1500-600cm. -1 It exhibits strong chemical bond vibrations, and this region happens to cover the atmospheric transparency window of 8-13 μm; The mid-infrared emitting monomers are cyclohexyl methacrylate, hexafluorobutyl methacrylate, and polyethylene glycol diacrylate 600.

2. The method for preparing the polymer dimming film with passive radiative cooling characteristics as described in claim 1, characterized in that, In step (2), the content of photoinitiator Irgacure651 is 1-5 wt.% of the NLCM mass, and the content of spacer particles is 0.2-1 wt.% of the total mass.

3. The method for preparing the polymer dimming film with passive radiative cooling characteristics as described in claim 1, characterized in that, In step (3), the conductive layer of the flexible transparent conductive film is any one of indium tin oxide (ITO) coating, fluorine-doped tin dioxide (FTO) coating, aluminum-doped zinc oxide (AZO) coating, nano silver, metal mesh, or conductive polymer, and its resistance is 50~150Ω.

4. The method for preparing the polymer dimming film with passive radiative cooling characteristics as described in claim 3, characterized in that, The substrate material of the flexible transparent conductive film is any one of polyethylene terephthalate (PET), polyimide (PI), polyethylene naphthalate (PEN), and polyethylene (PE).

5. The method for preparing the polymer dimming film with passive radiative cooling characteristics as described in claim 1, characterized in that, In step (4), the ultraviolet light intensity is 4~20mW / cm². 2 The illumination time is 5~30 minutes.

6. The method for preparing the polymer dimming film with passive radiative cooling characteristics as described in claim 1, characterized in that, The polymer dimming film has stable and reversible optical switching characteristics, and can effectively control the solar light band with a low threshold voltage. At the same time, it has a high infrared emissivity in the mid-infrared region and has the ability to passively radiatively cool.

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