Acrylate oligomer and preparation method and application thereof

Abstract

The present invention provides an acrylate oligomer and a preparation method and application thereof. The acrylate oligomer is polymerized by acrylate monomers under the action of 2,4-diphenyl-4-methyl-1-pentene and an initiator; the mass of the 2,4-diphenyl-4-methyl-1-pentene accounts for 1% to 6% of the mass of the acrylate monomer, and the mass of the initiator accounts for 0.2% to 2.5% of the mass of the acrylate monomer. The present invention adopts AMSD to control the polymerization degree of the acrylate monomer, which is green, environmentally friendly and pollution-free. After the polymerization reaction, the residual AMSD in the reaction product can be effectively removed by simple extraction, avoiding its influence on the stability of dimming particles in the SPD device, thereby increasing the stability of the dimming particles in the acrylate oligomer.

Description

Technical Field

[0001] The invention belongs to the technical field of suspended particle devices, and in particular relates to an acrylate oligomer and a preparation method and application thereof. Background Art

[0002] Suspended particle device (SPD for short) is a type of light valve that can change the orientation of internal dimming particles under the action of alternating current (20-110V) to achieve dimming effect. This type of light valve is generally composed of two layers of transparent electrodes and a dimming layer sandwiched between the transparent electrodes. The dimming layer can be either liquid or solid. However, since the liquid dimming layer is prone to leakage and the particles in the liquid dimming layer are prone to agglomeration, which affects the dimming function, SPD with a solid dimming layer has always attracted more attention. Scholars' research on solid-state SPD not only includes the types and synthesis methods of dimming particles, but also involves the state regulation of polymer phase separation systems. In the phase separation system, the continuous phase is a solid matrix polymer, and the discontinuous phase (suspension) in which a number of dimming particles are suspended is distributed in the form of droplets. This structure not only avoids the problem of product liquid leakage, but also effectively inhibits the agglomeration of dimming particles.

[0003] In the phase separation system currently used in SPD, the matrix polymer and the suspension are mainly silicone oil polymer and acrylate oligomer, respectively, and the refractive index of both is about 1.472. The synthesis of silicone oil polymer is generally carried out by double bond chain extension of silicone oil monomer by hydroxyl condensation, and a proper amount of photoinitiator is added to the obtained product to obtain silicone oil prepolymer. Under ultraviolet light irradiation, the prepolymer undergoes polymerization reaction to form silicone oil polymer; while acrylate oligomer is generally obtained by free radical polymerization between acrylate monomers, in which AIBN is used as initiator and thiol is used as chain transfer agent. It is well known that thiol is a type of chain transfer agent with a high chain transfer constant, which is often used to regulate molecular weight in polymerization reactions. However, most thiols have an unpleasant odor and are highly toxic, and their vapors can form explosive mixtures with air. Polymerization reactions that rely on thiol often cause air and soil pollution, which is extremely unfriendly to experimenters and the environment. In addition, the dimming particles in SPD are often polyhalides (RX, where X is a halogen). The thiol groups in the residual thiol in the suspension will react with the halogen in the dimming particles as follows: R—X+H—S—R'→R—S—R'+X - , which causes the dimming particles to decompose. Summary of the invention

[0004] Based on this, the purpose of the present invention is to provide an acrylate oligomer and a preparation method and application thereof. The acrylate oligomer has a small molecular weight, can increase the stability of dimming particles in a suspended particle device, and has a good phase separation state with a benzene silicone oil prepolymer.

[0005] To achieve the above object, the present invention adopts the following technical solution.

[0006] An acrylate oligomer is prepared by polymerizing an acrylate monomer under the action of 2,4-diphenyl-4-methyl-1-pentene (AMSD) and an initiator; the mass of the 2,4-diphenyl-4-methyl-1-pentene accounts for 1% to 6% of the mass of the acrylate monomer, and the mass of the initiator accounts for 0.2% to 2.5% of the mass of the acrylate monomer.

[0007] In some embodiments, the mass of the 2,4-diphenyl-4-methyl-1-pentene accounts for 1% to 4% of the mass of the acrylate monomer, and the mass of the initiator accounts for 0.2% to 1.5% of the mass of the acrylate monomer.

[0008] In some embodiments, the acrylate monomer is selected from one or more of methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, isononyl methacrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and isobutyl acrylate.

[0009] In some embodiments, the initiator is selected from azobisisobutyronitrile (AIBN).

[0010] In some embodiments, the number average molecular weight of the acrylate oligomer is 1,000 to 6,000.

[0011] The present invention also provides a method for preparing the above-mentioned acrylate oligomer, comprising the following steps: (1) dispersing the acrylate monomer in toluene, and adding the initiator and chain transfer agent 2,4-diphenyl-4-methyl-1-pentene thereto to fully dissolve the monomers to obtain a precursor solution; (2) continuously passing nitrogen into the reaction system, and then heating the reaction system to 45° C. to 70° C. to react for 12 h to 24 h; (3) rotary evaporating the product obtained in step (2) to discharge the volatile solvent and additional products; (4) slowly dripping an organic solvent with a polarity greater than toluene into the rotary evaporation product to obtain an emulsion; (5) standing the emulsion, and collecting the lower transparent liquid after the emulsion is separated into layers; and (6) rotary evaporating the transparent liquid again to obtain the acrylate oligomer.

[0012] In some embodiments, rotary evaporation is performed at 100° C. in step (3) and / or step (6).

[0013] In some embodiments, the organic solvent is selected from one or more of benzene, butanol, n-propanol, ethanol, tetrahydrofuran, isopropanol, acetone, methanol, and ethylene glycol; preferably, the organic solvent is selected from one or both of ethanol and methanol.

[0014] The present invention also provides the use of the acrylate oligomer as described above or the acrylate oligomer prepared by the preparation method as described above in a device for preparing suspended particles.

[0015] The present invention also provides a suspended particle device (SPD), comprising two layers of transparent electrodes and a dimming layer arranged between the two layers of transparent electrodes, wherein the dimming layer comprises the acrylate oligomer as described above or the acrylate oligomer prepared by the preparation method as described above.

[0016] In view of the defect that the synthesis of suspension in SPD device generally uses mercaptan as chain transfer agent which has high environmental pollution and great influence on the stability of dimming particles, the present invention proposes to use novel molecular weight regulator AMSD to control the polymerization degree of acrylate monomer. After the polymerization reaction, the residual AMSD in the reaction product can be effectively removed by simple extraction to avoid its influence on the stability of the dimming particles in the SPD device, thereby increasing the stability of the dimming particles in the acrylate oligomer. In addition, the yellowing index of the acrylate oligomer (suspension) is significantly reduced, and the refractive index is close to that of the phenyl silicone oil polymer (matrix polymer). The two can form a phase separation film with excellent light transmittance, so that the SPD device can show good dimming behavior.

[0017] The preparation method of the acrylate oligomer of the present invention is green, environmentally friendly and pollution-free, and can effectively promote the development and marketization of SPD devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The results of transparency testing in the visible light region of the transparent film prepared from the acrylate oligomer and the benzene silicone oil polymer in Example 1 are shown.

[0019] Figure 2 This is a SEM image of the transparent film prepared from the acrylate oligomer and the benzene silicone oil polymer in Example 1.

[0020] Figure 3 This is the transmittance test result of the SPD device prepared with the acrylate oligomer in Example 1. DETAILED DESCRIPTION

[0021] The experimental methods in the following examples of the present invention, where no specific conditions are specified, are usually carried out under conventional conditions or under conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0022] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0023] The terms "including" and "having" and any variations thereof of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment comprising a series of steps is not limited to the listed steps or modules, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products or equipment.

[0024] In the present invention, the term "multiple" refers to two or more than two. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0025] The following describes the invention in conjunction with specific embodiments.

[0026] Example 1

[0027] This embodiment provides an acrylate oligomer, which is prepared by the following method:

[0028] 1. Weigh 28.44 g (0.2 mol) of butyl methacrylate and add it into a two-necked flask containing 100 mL of toluene. Stir magnetically for 15 min.

[0029] 2. Add 0.2 g AIBN and 0.6 g AMSD to the flask and continue stirring for 15 min;

[0030] 3. Introduce nitrogen from one side of the flask, extend the nitrogen outlet below the liquid surface, keep a pinhole on the other side, and continue bubbling for 30 minutes;

[0031] 4. Place the flask in a 70°C oil bath and react for 12 hours, continuously introducing nitrogen during the reaction;

[0032] 5. The obtained product was subjected to rotary evaporation at 100°C. After the rotary evaporation product was cooled to room temperature, 50 g of anhydrous ethanol was added thereto and the mixture was stirred and mixed to obtain an emulsion;

[0033] 6. After the emulsion was allowed to stand for 2 hours, the clear liquid was taken out and subjected to rotary evaporation at 100°C again to obtain the target product, acrylate oligomer (labeled as S-1).

[0034] The refractive index of S-1 was measured by Abbe refractometer to be about 1.4710; the number average molecular weight of S-1 was measured by GPC to be about 2650; it was mixed with a benzene silicone oil polymer (matrix polymer) prepared according to US Patent (US2006 / 045574), and a transparent film was obtained by coating and photocuring, and the transparency of the film in the visible light region was more than 80% ( Figure 1 ); SEM observation of the film revealed that it had an excellent phase separation state, i.e., the suspended droplets were approximately 2-10 μm in size and were evenly distributed in the matrix polymer ( Figure 2 ).

[0035] S-1 was mixed with dimming particles prepared according to Japanese patent (WO2010-092954), and an SPD device was prepared according to the SPD device preparation method provided in the patent. It can be seen that when the obtained device is in the initial state, its transmittance in the visible light region is about 20%, and when an AC voltage of 110V is applied to it, its transmittance rises to 60% ( Figure 3 ).

[0036] Example 2

[0037] This embodiment provides an acrylate oligomer. In the preparation method of the acrylate oligomer, except that 28.44 g (0.2 mol) of butyl methacrylate is replaced by 5.01 g (0.05 mol) of methyl methacrylate and 38.16 g (0.15 mol) of lauryl methacrylate, the rest is the same as in Example 1. The acrylate oligomer is labeled S-2.

[0038] The refractive index of S-2 was measured to be about 1.4736 using an Abbe refractometer. The number average molecular weight of S-1 was measured to be about 3047 using GPC. The SPD device made using S-2 had an initial visible light transmittance of about 20%, and when an AC voltage of 110V was applied to it, its transmittance increased to 55%.

[0039] Example 3

[0040] This embodiment provides an acrylate oligomer, and in the preparation method of the acrylate oligomer, except that 50g of anhydrous ethanol is replaced by 50g of methanol, the rest is the same as in Embodiment 1. The acrylate oligomer is labeled S-3.

[0041] The refractive index of S-3 measured by Abbe refractometer is about 1.4728; the number average molecular weight of S-3 measured by GPC is about 2330; the SPD device made of S-3 has an initial visible light transmittance of about 20%, and when an AC voltage of 110V is applied to it, its transmittance rises to 65%.

[0042] Comparative Example 1

[0043] This comparative example provides an acrylate oligomer, which is prepared by the following method:

[0044] 1. Weigh 28.44 g (0.2 mol) of butyl methacrylate and add it into a two-necked flask containing 100 mL of toluene. Stir magnetically for 15 min.

[0045] 2. Add 0.2 g of AIBN to the flask and stir for 15 minutes to fully dissolve it;

[0046] 3. Introduce nitrogen from one side of the flask, extend the nitrogen outlet below the liquid surface, keep a pinhole on the other side, continue bubbling for 30 minutes, and then cut off the nitrogen inlet;

[0047] 4. Inject 4 g of ethanethiol into the flask through the pinhole, stir for 10 min, then place the flask in a 70°C oil bath and react for 12 h;

[0048] 5. The obtained product was subjected to rotary evaporation at 100°C. After the rotary evaporation product was cooled to room temperature, 50 g of anhydrous ethanol was added thereto and the mixture was stirred and mixed to obtain an emulsion;

[0049] 6. After the emulsion was allowed to stand for 2 hours, the clear liquid was taken out and subjected to rotary evaporation at 100°C again to obtain the target product, acrylate oligomer. The acrylate oligomer is labeled S-4.

[0050] The refractive index of S-4 measured by Abbe refractometer is about 1.4721; the number average molecular weight of S-4 measured by GPC is about 2290; the SPD device made of S-4 has an initial visible light transmittance of about 16%, and when an AC voltage of 110V is applied to it, its transmittance rises to 59%.

[0051] The yellowing index of the acrylate oligomers in the above examples and comparative examples when used in SPD and the stability of the dimming particles in the SPD device were tested. The test method is as follows:

[0052] 1. Yellowing index: The acrylate oligomers in the examples and comparative examples were phase-separated with the phenyl silicone oil polymer (base polymer) prepared according to U.S. Patent (US2006 / 045574) at a mass ratio of 1:2, and the phase-separated system was sandwiched between two layers of PET film material with a thickness of 100 μm, and a transparent film was obtained by photocuring; the yellowing index (b* value) of the film was tested using a Haze-gard haze meter, and the b* value of the two layers of PET film material without sandwiching was deducted to obtain the b* value of the phase-separated system.

[0053] 2. Stability of dimming particles: The iodine sulfate dimming particles are dispersed in the acrylic ester oligomer in the embodiment and the comparative example at a mass fraction of 1% by stirring and ultrasonically to obtain a dimming particle suspension; the suspension is placed in a glass bottle, and the bottle is filled with nitrogen and sealed, and then placed in a double 85 test box for testing; a small amount of samples from the glass bottle are extracted in stages (12 hours), and the bottle is re-filled with nitrogen and sealed to continue testing; the particle morphology in the extracted staged samples is detected by SEM, and its changes are observed to obtain the particle stability time.

[0054] The test results are shown in Table 1:

[0055] Table 1

[0056] Group Yellowing Index Stability time Example 1 0.06 ＞96h Example 2 0.03 ＞96h Example 3 0.02 ＞96h Comparative Example 1 0.63 24h

[0057] The above results show that the yellowing index of the acrylate oligomers of the present invention (Examples 1 to 3) is significantly lower than that of Comparative Example 1, and the stability of the dimming particles in the prepared SPD device is significantly improved.

[0058] In summary, the present invention uses a novel molecular weight regulator AMSD to control the degree of polymerization of the acrylate monomer, which can effectively increase the stability of the dimming particles in the acrylate oligomer, and the preparation method is environmentally friendly and pollution-free.

[0059] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A suspended particle device, comprising two layers of transparent electrodes and a dimming layer disposed between the two layers of transparent electrodes, characterized in that: The dimming layer comprises an acrylate oligomer; The acrylate oligomer is polymerized by acrylate monomers under the action of 2,4-diphenyl-4-methyl-1-pentene and an initiator; the mass of the 2,4-diphenyl-4-methyl-1-pentene accounts for 1% to 6% of the mass of the acrylate monomer, and the mass of the initiator accounts for 0.2% to 2.5% of the mass of the acrylate monomer; The acrylic acid ester monomer is selected from one or more of methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, isononyl methacrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and isobutyl acrylate; The number average molecular weight of the acrylate oligomer is 1000-6000.

2. A suspended particle device as claimed in claim 1, characterized in that: The mass of the 2,4-diphenyl-4-methyl-1-pentene accounts for 1% to 4% of the mass of the acrylic ester monomer, and the mass of the initiator accounts for 0.2% to 1.5% of the mass of the acrylic ester monomer.

3. A suspended particle device as claimed in claim 1, characterized in that: The initiator is selected from azobisisobutyronitrile.

4. A suspended particle device according to any one of claims 1 to 3, characterized in that: The preparation method of the acrylic ester oligomer comprises the following steps: (1) dispersing the acrylic ester monomer in toluene, and adding the initiator and the chain transfer agent 2,4-diphenyl-4-methyl-1-pentene thereto to fully dissolve the monomers to obtain a precursor solution; (2) continuously passing nitrogen into the reaction system, and then heating the reaction system to 45° C. to 70° C. to react for 12 h to 24 h; (3) rotary evaporating the product obtained in step (2) to discharge the volatile solvent and the additional product; (4) slowly dripping an organic solvent with a polarity greater than toluene into the rotary evaporation product to obtain an emulsion; (5) standing the emulsion for separation, and collecting the lower transparent liquid; (6) rotary evaporating the transparent liquid again to obtain the acrylic ester oligomer.

5. A suspended particle device as claimed in claim 4, characterized in that: The organic solvent is selected from one or more of benzene, butanol, n-propanol, ethanol, tetrahydrofuran, isopropanol, acetone, methanol, and ethylene glycol.

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