Ferroelectric / relaxor ferroelectric liquid crystal polymer as well as preparation method and application thereof

Abstract

The invention provides a ferroelectric / relaxor ferroelectric liquid crystal polymer as well as a preparation method and application thereof, and belongs to the technical field of polymer materials. The invention provides a method for preparing a ferroelectric / relaxor ferroelectric liquid crystal polymer, the molecular structure of a liquid crystal monomer is optimized, and a double bond in the structure provides a polymerizable group; a rigid conjugated structure and a strong polar group in the structure retain the spontaneous polarization characteristic and the nematic phase liquid crystal texture of the ferroelectric liquid crystal. The obtained polymer has high polarization response, low coercive field, stable dielectric response in a wide temperature range and good mechanical flexibility. The polymerization process is simple, the operability is strong, and various types of monomers can be selected, so that the types of ferroelectric polymers can be greatly enriched. The ferroelectric / relaxor ferroelectric liquid crystal polymer has many advantages of ferroelectric macromolecules and can be applied to the fields of flexible actuators, capacitors, phase shifters and the like through integration.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a ferroelectric / relaxor ferroelectric liquid crystal polymer, a preparation method thereof, and an application thereof. Background Art

[0002] Ferroelectric polymers are a type of polymer materials with spontaneous polarization and the polarization direction can be regulated by an external electric field. These materials combine the flexibility and easy processability of polymers with ferroelectricity, and are widely used in flexible electronics, energy storage, sensors and other fields.

[0003] Currently, the main ferroelectric polymers are polyvinylidene fluoride (PVDF) and its copolymers, etc. Polyvinylidene fluoride and its copolymers have high electroactivity and are currently one of the few ferroelectric polymers that can be commercially applied. However, polyvinylidene fluoride and its copolymers are expensive, and the transport process and polymerization process are complex and dangerous. Gas-phase polymerization is required to prepare the polymer, and the polymerization process is complex and uncontrollable, and its coercive field is also relatively high, thus limiting its wide application. Other ferroelectric polymers such as aromatic polyamides can exhibit ferroelectricity under certain conditions, but the polarization intensity is relatively low.

[0004] Therefore, designing and developing new ferroelectric polymers with simple polymerization and processing processes, controllable conditions, strong ferroelectricity and high polarization intensity to expand the types of ferroelectric polymers and further expand their application scope and fields is a scientific problem and technical challenge currently faced. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a ferroelectric / relaxor ferroelectric liquid crystal polymer, a preparation method thereof, and an application thereof. The novel ferroelectric / relaxor ferroelectric liquid crystal polymer of the present invention has a simple polymerization process, strong controllability, is easy to prepare, and has high polarization intensity, low coercive field and high temperature stability.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions: The present invention provides a preparation method of a ferroelectric / relaxor ferroelectric liquid crystal polymer, comprising the following steps: Mixing a polymerizable ferroelectric liquid crystal small molecule, an initiator and an organic solvent for homopolymerization reaction to obtain the ferroelectric / relaxor ferroelectric liquid crystal polymer; Or Mixing a polymerizable ferroelectric liquid crystal small molecule, a monomer containing a double bond, an initiator and an organic solvent for copolymerization reaction to obtain the ferroelectric / relaxor ferroelectric liquid crystal polymer; The polymerizable ferroelectric liquid crystal small molecule in the homopolymerization reaction and the copolymerization reaction has the structure shown in Formula I: Formula I, In Formula I, R1, R2 and R3 are all -H; R4 is -C n H 2n COO-, and the number of carbon atoms in R4 is greater than or equal to 0; R5 has any one of the structures shown by R5-1 to R5-10: , Among R5-1 to R5-10 is the connection site, The monomer containing a double bond includes one or more of ethylene, propylene, vinyl chloride, vinyl acetate, styrene, butadiene, isoprene, chloroprene, acrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, vinyl ether, vinyl pyrrolidone, and divinylbenzene.

[0007] Preferably, the number of carbon atoms in R4 is 0 to 50.

[0008] Preferably, the number of carbon atoms in R4 is 2 to 10.

[0009] Preferably, the molar ratio of the polymerizable ferroelectric liquid crystal small molecule to the monomer containing a double bond is (0.1 to 1):(0.9 to 0), and the molar amount of the monomer containing a double bond is not 0.

[0010] Preferably, the temperature of the homopolymerization reaction and the copolymerization reaction is independently 40 to 120 °C, and the time is independently 2 to 20 h.

[0011] Preferably, the mass equivalent ratio of the polymerizable ferroelectric liquid crystal small molecule to the initiator during the homopolymerization reaction is 1:0.005 to 0.02.

[0012] Preferably, the mass equivalent ratio of the reaction monomer to the initiator during the copolymerization reaction is 1:0.005 to 0.02, and the reaction monomer includes the polymerizable ferroelectric liquid crystal small molecule and the monomer containing a double bond.

[0013] Preferably, the initiator in the homopolymerization reaction and the copolymerization reaction independently includes one or more of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, and diisopropylbenzene peroxide.

[0014] The present invention also provides a ferroelectric / relaxor ferroelectric liquid crystal polymer prepared by the preparation method described in the above technical solution.

[0015] The present invention also provides the application of the ferroelectric / relaxor ferroelectric liquid crystal polymer described in the above technical solution in the field of flexible electronic devices.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for preparing a ferroelectric / relaxor ferroelectric liquid crystal polymer, which optimizes the molecular structure. In its structure, strong polar dipole groups retain the spontaneous polarization characteristics of ferroelectric polymers, and the dipole groups are easily polarized in response to an electric field and form ferroelectric domains, further enhancing polarization. The dielectric relaxation phenomenon is significant in a wide temperature range (ΔT > exceeding 100 °C), and it has high polarization response, relaxation stability within a wide temperature range, and excellent mechanical flexibility. At the same time, it has a low coercive field and the typical texture of nematic liquid crystals. The polymerization process is strongly controllable and easy to prepare, thus enriching the types of ferroelectric polymers.

[0017] The present invention also provides the application of the ferroelectric / relaxor ferroelectric liquid crystal polymer in the field of flexible electronic devices, which has great potential for application as artificial muscles. It can be integrated and applied to the field of flexible actuators, and can also be applied to devices or fields such as high-frequency capacitors, pulsed power systems, flexible electronic devices, high-temperature energy storage, tunable light refraction devices, phase shifters, electrocaloric, piezoelectric / thermoelectric response, and dielectric regulation devices (such as flexible transistor gate dielectrics), etc., and has a wide range of application fields and potential. Description of the Drawings

[0018] Figure 1 is the 1H NMR spectrum of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 1; Figure 2 is the DSC diagram of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 1; Figure 3 is the physical picture of the ferroelectric / relaxor ferroelectric liquid crystal polymer film in Example 1; Figure 4 is the texture diagram of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 1 under a polarized light microscope; Figure 5 is the polarization-electric field hysteresis loop of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 1; Figure 6 is the dielectric spectrum of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 1; Figure 7 is the dielectric spectrum of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 2; Figure 8 is the polarization-electric field hysteresis loop of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 2; Figure 9 is the dielectric spectrum of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 3; Figure 10 is the polarization-electric field hysteresis loop of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 3; Figure 11 is the dielectric spectrum of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 4; Figure 12 is the polarization - electric field hysteresis loop of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 4; Figure 13 is the polarization - electric field hysteresis loop of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 5. Detailed implementation manners

[0019] The present invention provides a preparation method of a ferroelectric / relaxor ferroelectric liquid crystal polymer, comprising the following steps: Mix a polymerizable ferroelectric liquid crystal small molecule, an initiator and an organic solvent and carry out a homopolymerization reaction to obtain the ferroelectric / relaxor ferroelectric liquid crystal polymer; Or Mix a polymerizable ferroelectric liquid crystal small molecule, a double - bond - containing monomer, an initiator and an organic solvent and carry out a copolymerization reaction to obtain the ferroelectric / relaxor ferroelectric liquid crystal polymer; In the homopolymerization reaction and the copolymerization reaction, the polymerizable ferroelectric liquid crystal small molecule has the structure shown in Formula I: Formula I In Formula I, R1, R2 and R3 are all - H; R4 is - C n H 2n COO -, and the number of carbon atoms in R4 is greater than or equal to 0; R5 has any one of the structures shown in R5 - 1 to R5 - 10: , Among R5 - 1 to R5 - 10 is the connection site, The double - bond - containing monomer includes one or more of ethylene, propylene, vinyl chloride, vinyl acetate, styrene, butadiene, isoprene, chloroprene, acrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, vinyl ether, vinyl pyrrolidone and divinylbenzene.

[0020] In the present invention, unless otherwise specified, the raw materials used are commercially available products in the art or prepared by conventional methods in the art.

[0021] The present invention mixes a polymerizable ferroelectric liquid crystal small molecule, an initiator and an organic solvent and carries out a homopolymerization reaction to obtain the ferroelectric / relaxor ferroelectric liquid crystal polymer. At this time, the obtained ferroelectric / relaxor ferroelectric liquid crystal polymer is a homopolymer.

[0022] In the present invention, R1, R2 and R3 are all - H.

[0023] In the present invention, the number of carbon atoms in R4 is preferably 0 to 50, more preferably 2 to 10, and specifically can be 2, 3, 4, 5, 6, 7, 8, 9 or 10, that is, R4 is -C2H4COO-, -C3H6COO-, -C4H8COO-, -C5H 10 COO-, -C6H 12 COO-, -C7H 14 COO-, -C8H 16 COO-, C9H 18 COO- or -C 10 H 20 COO-. When R4 is -C6H 12 COO-, the polymerizable ferroelectric liquid crystal small molecule is 4-((4-nitrophenoxy)carbonyl)phenyl-2-((6-(acryloyloxy)hexyl)oxy)-4-methoxybenzoate, CAS: 2610074-98-9. When R4 is -C8H 16 COO-, C9H 18 COO- or -C 10 H 20 COO-. Taking R4 being -C8H 16 COO- as an example, the preparation principle of the polymerizable ferroelectric liquid crystal small molecule (i.e., the polymerizable ferroelectric liquid crystal small molecule 2 in the examples of the present invention) is shown in the following formula: .

[0024] In the present invention, the reaction principle of the homopolymerization reaction is shown in Formula II: Formula II, In Formula II, n is 10 to 10000.

[0025] In the present invention, the temperature of the homopolymerization reaction is preferably 40 to 120 °C, and specifically can be 40, 50, 60, 70 or 80 °C. The time is preferably 2 to 20 h, and specifically can be 8, 10, 12, 14, 16, 18 or 20 h.

[0026] In the present invention, during the homopolymerization reaction, the mass equivalent ratio of the polymerizable ferroelectric liquid crystal small molecule to the initiator is preferably 1:0.005 to 0.02, and specifically can be 1:0.005, 1:0.01, 1:0.015 or 1:0.02.

[0027] In the present invention, the initiator preferably includes one or more of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate and diisopropylbenzene peroxide.

[0028] In the present invention, the organic solvent preferably includes one or more of chloroform, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide. There is no special limitation on the amount of the organic solvent in the present invention, as long as the raw materials can be mixed evenly.

[0029] In the present invention, preferably, after mixing the polymerizable ferroelectric liquid crystal small molecule, the initiator, and the organic solvent, a "freezing - evacuation - thawing" cycle operation is carried out using nitrogen, and then the obtained mixture is placed in an oil bath and heated with stirring to carry out the homopolymerization reaction.

[0030] After the homopolymerization reaction is completed, in the present invention, preferably, the obtained product is naturally cooled to room temperature, the obtained mixture is precipitated into methanol, then the solid is collected by filtration, and then successively purified by filtration and dried to obtain the ferroelectric / relaxor ferroelectric liquid crystal polymer.

[0031] In the present invention, the drying is preferably vacuum drying. The temperature of the vacuum drying is preferably 40 - 60 °C, specifically it can be 40, 50, or 60 °C, and the time is preferably 8 - 16 h, specifically it can be 8, 10, 12, 14, or 16 h.

[0032] In the present invention, the polymerizable ferroelectric liquid crystal small molecule, the double bond-containing monomer, the initiator, and the organic solvent are mixed to carry out a copolymerization reaction to obtain the ferroelectric / relaxor ferroelectric liquid crystal polymer. At this time, the obtained ferroelectric / relaxor ferroelectric liquid crystal polymer is a copolymer. The double bond-containing monomer includes one or more of ethylene, propylene, vinyl chloride, vinyl acetate, styrene, butadiene, isoprene, chloroprene, acrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, vinyl ether, vinyl pyrrolidone, and divinylbenzene.

[0033] In the present invention, the molar ratio of the polymerizable ferroelectric liquid crystal small molecule to the double bond-containing monomer during the copolymerization reaction is preferably (0.1 - 1) : (0.9 - 0), specifically it can be 0.8 : 0.2, 0.7 : 0.3, or 0.5 : 0.5.

[0034] In the present invention, the mass equivalent ratio of the reaction monomer to the initiator during the copolymerization reaction is preferably 1 : 0.005 - 0.02, specifically it can be 1 : 0.005, 1 : 0.01, 1 : 0.015, or 1 : 0.02. The reaction monomer includes the polymerizable ferroelectric liquid crystal small molecule and the double bond-containing monomer.

[0035] In the present invention, the parameters of the copolymerization reaction are preferably the same as those of the homopolymerization reaction, which will not be elaborated here.

[0036] In the present invention, the reaction principle of the copolymerization reaction is shown in Formula III: Formula III R in formula III 13 includes one or more of vinyl, propenyl, vinyl chloride group, vinyl acetate group, styryl, butadienyl, isoprenyl, chloroprene group, acrylic group, methyl acrylate group, methyl methacrylate group, acrylonitrile group, vinyl ether group, vinyl pyrrolidone group and divinylphenyl group.

[0037] The present invention also provides a ferroelectric / relaxor ferroelectric liquid crystal polymer prepared by the preparation method described in the above technical solution. When the ferroelectric / relaxor ferroelectric liquid crystal polymer is a homopolymer, the ferroelectric / relaxor ferroelectric liquid crystal polymer has a structure shown in formula IV: Formula IV In formula IV, n is 10 to 10,000, preferably 100 to 800; When the ferroelectric / relaxor ferroelectric liquid crystal polymer is a copolymer, the ferroelectric / relaxor ferroelectric liquid crystal polymer has a structure shown in formula V: Formula V In formula V, a is 0.1 to 1, and the a refers to the molar ratio of the polymerizable ferroelectric liquid crystal small molecule to the double bond-containing monomer; R in formula V 13 includes one or more of vinyl, propenyl, vinyl chloride group, vinyl acetate group, styryl, butadienyl, isoprenyl, chloroprene group, acrylic group, methyl acrylate group, methyl methacrylate group, acrylonitrile group, vinyl ether group, vinyl pyrrolidone group and divinylphenyl group.

[0038] R in formulas IV and V 1~ R5 is preferably the same as that in formula I and will not be elaborated here.

[0039] The present invention also provides the application of the ferroelectric / relaxor ferroelectric liquid crystal polymer described in the above technical solution in the field of flexible electronic devices.

[0040] The ferroelectric / relaxor ferroelectric liquid crystal polymer of the present invention has great potential for application as artificial muscles, can be integrated into the field of flexible actuators, and can also be applied to devices or fields such as high-frequency capacitors, pulse power systems, flexible electronic devices, high-temperature energy storage, tunable light refraction devices, phase shifters, electrocaloric effect, piezoelectric / thermoelectric response, and dielectric regulation devices (flexible transistor gate dielectrics, etc.), and has a wide range of application fields and potential.

[0041] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] Example 1 1 g of polymerizable ferroelectric liquid crystal small molecule 1 (CAS: 2610074-98-9), 0.01 g of azobisisobutyronitrile (the mass equivalent ratio of polymerizable ferroelectric liquid crystal small molecule 1 to azobisisobutyronitrile is 1:0.01), and 3 mL of chloroform were added to a Schlenk flask. The "freezing - pumping - thawing" cycle operation was carried out three times using nitrogen. Then, the Schlenk flask was placed in an oil bath (80 °C) and heated with stirring for 8 h for homopolymerization reaction. After turning off the heating and cooling to room temperature, the mixed solution was poured into 50 mL of methanol to precipitate the polymer. The solid was filtered and collected, and then purified by precipitation three times. The purified solid was dried in a vacuum drying oven at 40 °C for 12 h to obtain 0.5 g of ferroelectric / relaxor ferroelectric liquid crystal polymer, with a yield of 50% and a purity of 98%. Among them, polymerizable ferroelectric liquid crystal small molecule 1 has the structure shown in Formula I. In Formula I, R1, R2, and R3 are all -H, R4 is -C6H 12 COO-, R5 is R5-1, and the ferroelectric / relaxor ferroelectric liquid crystal polymer is a homopolymer.

[0043] Example 2 1 g of polymerizable ferroelectric liquid crystal small molecule 2, 0.02 g of azobisisobutyronitrile (the mass equivalent ratio of polymerizable ferroelectric liquid crystal small molecule 2 to azobisisobutyronitrile is 1:0.02), and 15 mL of N,N-dimethylformamide were added to a Schlenk flask. The "freezing - pumping - thawing" cycle operation was carried out three times using nitrogen. Then, the Schlenk flask was placed in an oil bath (80 °C) and heated with stirring for 10 h for homopolymerization reaction. After turning off the heating and cooling to room temperature, the mixed solution was poured into 200 mL of methanol to precipitate the polymer. The solid was filtered and collected, and then purified by precipitation three times. The purified solid was dried in a vacuum drying oven at 40 °C for 12 h to obtain 0.6 g of ferroelectric / relaxor ferroelectric liquid crystal polymer, with a yield of 60% and a purity of 98%. Among them, polymerizable ferroelectric liquid crystal small molecule 2 has the structure shown in Formula I. In Formula I, R1, R2, and R3 are all -H, R4 is -C8H 16 COO-, R5 is R5-1, and the ferroelectric / relaxor ferroelectric liquid crystal polymer is a homopolymer.

[0044] The preparation method of polymerizable ferroelectric liquid crystal small molecule 2 is as follows: 2-Hydroxy-4-methoxybenzaldehyde, potassium carbonate, and 8-bromo-1-octanol were dissolved in N,N-dimethylformamide (DMF) at a feed molar ratio of 1.65:3.3:2. The mixed solution was heated to 60 °C and stirred vigorously overnight to obtain intermediate A1. A1 and triethylamine were dissolved in anhydrous dichloromethane at a feed molar ratio of 2:3, and the mixture was stirred in an ice bath for 5 min. Acryloyl chloride was added dropwise to obtain intermediate A2. Sodium dihydrogen phosphate, sodium chlorite, and A2 were stirred well at 0 °C in a mixture of dimethyl sulfoxide (DMSO) / deionized water with a volume ratio of 4 / 3 at a feed molar ratio of 4:3.5:1. Subsequently, the temperature was raised to room temperature and stirred for 6 h. After adjusting the pH, intermediate A3 was obtained. A3, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 4-dimethylaminopyridine were dissolved in dichloromethane at a feed molar ratio of 1:1:1.5:0.05 and reacted for 15 h. After recrystallization to remove impurities, the polymerizable ferroelectric liquid crystal small molecule 2 was obtained.

[0045] Example 3 The polymerizable ferroelectric liquid crystal small molecule 3 (3 g), azobisisobutyronitrile (0.015 g, the mass equivalent ratio of the polymerizable ferroelectric liquid crystal small molecule 3 to azobisisobutyronitrile was 1:0.005), and 9 mL of chloroform were added to a Schlenk flask. The "freezing-pumping-thawing" cycle operation was carried out three times using nitrogen. Then, the Schlenk flask was placed in an oil bath (80 °C) and heated and stirred for 12 h for homopolymerization reaction. After turning off the heating and cooling to room temperature, the mixed solution was poured into 150 mL of methanol to precipitate the polymer. The solid was filtered and collected, and then purified by precipitation three times. The purified solid was dried in a vacuum drying oven at 40 °C for 12 h to obtain 1.8 g of ferroelectric / relaxor ferroelectric liquid crystal polymer with a yield of 60% and a purity of 97%. Among them, the polymerizable ferroelectric liquid crystal small molecule 3 has the structure shown in Formula I. In Formula I, R1, R2, and R3 are all -H, R4 is -C9H 18 COO-, R5 is R5-1, and the ferroelectric / relaxor ferroelectric liquid crystal polymer is a homopolymer.

[0046] The preparation method of the polymerizable ferroelectric liquid crystal small molecule 3 is as follows: 2-Hydroxy-4-methoxybenzaldehyde, potassium carbonate, and 9-bromo-1-nonanol were dissolved in N,N-dimethylformamide according to a molar feed ratio of 1.65:3.3:2. The mixed solution was heated to 60 °C and stirred vigorously overnight to obtain intermediate A4. A4 and triethylamine were dissolved in anhydrous dichloromethane according to a molar feed ratio of 2:3, and the mixture was stirred in an ice bath for 5 min. Acryloyl chloride was added dropwise to obtain intermediate A5. Sodium dihydrogen phosphate, sodium chlorite, and A5 were stirred well at 0 °C in a mixture of dimethyl sulfoxide / deionized water with a volume ratio of 4 / 3 according to a molar feed ratio of 4:3.5:1. Subsequently, the temperature was raised to room temperature and stirred for 6 h. After adjusting the pH, intermediate A6 was obtained. A6, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 4-dimethylaminopyridine were dissolved in dichloromethane and reacted for 15 h according to a molar feed ratio of 1:1:1.5:0.05. After recrystallization to remove impurities, the polymerizable ferroelectric liquid crystal small molecule 3 was obtained.

[0047] Example 4 The polymerizable ferroelectric liquid crystal small molecule 4 (3 g), azobisisobutyronitrile (0.015 g, the mass equivalent ratio of the polymerizable ferroelectric liquid crystal small molecule 4 to azobisisobutyronitrile was 1:0.005), and 9 mL of chloroform were added to a Schlenk flask. The Schlenk flask was subjected to three "freezing-pumping-thawing" cycles using nitrogen. Then, the Schlenk flask was placed in an oil bath (80 °C) and heated and stirred for 16 h for homopolymerization reaction. After turning off the heating and cooling to room temperature, the mixed solution was poured into 50 mL of methanol to precipitate the polymer. The solid was filtered and collected, and then purified by precipitation three times. The purified solid was dried in a vacuum drying oven at 40 °C for 12 h to obtain 1.7 g of ferroelectric / relaxor ferroelectric liquid crystal polymer with a yield of 56% and a purity of 98%. Among them, the polymerizable ferroelectric liquid crystal small molecule 4 has the structure shown in Formula I. In Formula I, R1, R2, and R3 are all -H, R4 is -C 10 H 20 COO-, R5 is R5-1, and the ferroelectric / relaxor ferroelectric liquid crystal polymer is a homopolymer.

[0048] The preparation method of the polymerizable ferroelectric liquid crystal small molecule 4 is as follows: 2-Hydroxy-4-methoxybenzaldehyde, potassium carbonate, and 10-bromo-1-decanol were dissolved in N,N-dimethylformamide in a molar ratio of 1.65:3.3:2. The mixed solution was heated to 60 °C and stirred vigorously overnight to obtain intermediate A1. A1 and triethylamine were dissolved in anhydrous dichloromethane in a molar ratio of 2:3, and the mixture was stirred in an ice bath for 5 min. Acryloyl chloride was added dropwise to obtain intermediate A2. Sodium dihydrogen phosphate, sodium chlorite, and A2 were stirred well at 0 °C in a mixture of dimethyl sulfoxide / deionized water with a volume ratio of 4 / 3 in a molar ratio of 4:3.5:1. Subsequently, the temperature was raised to room temperature and stirred for 6 h. After adjusting the pH, intermediate A3 was obtained. A3, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and 4-dimethylaminopyridine were dissolved in dichloromethane in a molar ratio of 1:1:1.5:0.05 and reacted for 15 h. After recrystallization to remove impurities, the polymerizable ferroelectric liquid crystal small molecule 4 was obtained.

[0049] Example 5 The polymerizable ferroelectric liquid crystal small molecule 1 (0.009 mol, 5.0686 g), the double bond-containing monomer styrene (0.001 mol, 0.1042 g), azobisisobutyronitrile (0.1034 g, the mass equivalent ratio of the sum of the masses of the polymerizable ferroelectric liquid crystal small molecule 1 and styrene to azobisisobutyronitrile is 1:0.02), and 15 mL of chloroform were added to a Schlenk flask. The "freezing-pumping-thawing" cycle operation was carried out three times using nitrogen. Then the Schlenk flask was placed in an oil bath (70 °C) and heated and stirred for 16 h for copolymerization reaction. After turning off the heating and cooling to room temperature, the mixed solution was poured into 200 mL of methanol to precipitate the polymer. The solid was filtered and collected, and then purified by precipitation three times. The purified solid was dried in a vacuum drying oven at 40 °C for 12 h to obtain 3.2 g of ferroelectric / relaxor ferroelectric liquid crystal polymer with a yield of 62% and a purity of 98%. Among them, the polymerizable ferroelectric liquid crystal small molecule 1 has the structure shown in Formula I. In Formula I, R1, R2, and R3 are all -H, R4 is -C6H 12 COO-, R5 is R5-1, and the ferroelectric / relaxor ferroelectric liquid crystal polymer is a copolymer with the structure shown in Formula V, and a is 0.9.

[0050] Figure 1 is the 1H NMR spectrum (400 MHz, deuterated chloroform) of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 1. It can be seen that the compound with the structure shown in Formula I was prepared in the present invention.

[0051] Figure 2 is the DSC diagram of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 1. It can be seen that its glass transition temperature is 48 °C.

[0052] Figure 3It is a physical picture of the ferroelectric / relaxor ferroelectric liquid crystal polymer film of Example 1.

[0053] Figure 4 It is the texture diagram of the ferroelectric / relaxor ferroelectric liquid crystal polymer of Example 1 under a polarized light microscope. It can be seen that the ferroelectric / relaxor ferroelectric liquid crystal polymer of the present invention exhibits the texture diagram of a typical nematic liquid crystal polymer.

[0054] Figure 5 It is the polarization-electric field hysteresis loop of the ferroelectric / relaxor ferroelectric liquid crystal polymer of Example 1. It can be seen that the ferroelectric / relaxor ferroelectric liquid crystal polymer of the present invention exhibits the hysteresis loop of a typical ferroelectric polymer under an electric field of 38 MV / m.

[0055] Figure 6 It is the dielectric spectrum diagram of the ferroelectric / relaxor ferroelectric liquid crystal polymer of Example 1. It can be seen that there is a significant dielectric relaxation phenomenon in a wide temperature range above 100 °C, that is, as the frequency increases, the dielectric peak shifts towards higher temperatures.

[0056] Figure 7 It is the dielectric spectrum diagram of the ferroelectric / relaxor ferroelectric liquid crystal polymer of Example 2. It can be seen that there is a significant dielectric relaxation phenomenon in a wide temperature range above 100 °C.

[0057] Figure 8 It is the polarization-electric field hysteresis loop of the ferroelectric / relaxor ferroelectric liquid crystal polymer of Example 2. It can be seen that the ferroelectric / relaxor ferroelectric liquid crystal polymer of the present invention exhibits the hysteresis loop of a typical ferroelectric polymer.

[0058] Figure 9 It is the dielectric spectrum diagram of the ferroelectric / relaxor ferroelectric liquid crystal polymer of Example 3. It can be seen that there is a significant dielectric relaxation phenomenon in a wide temperature range above 100 °C.

[0059] Figure 10 It is the polarization-electric field hysteresis loop of the ferroelectric / relaxor ferroelectric liquid crystal polymer of Example 3. It can be seen that the ferroelectric / relaxor ferroelectric liquid crystal polymer of the present invention exhibits the hysteresis loop of a typical ferroelectric polymer.

[0060] Figure 11 It is the dielectric spectrum diagram of the ferroelectric / relaxor ferroelectric liquid crystal polymer of Example 4. It can be seen that there is a significant dielectric relaxation phenomenon in a wide temperature range above 100 °C.

[0061] Figure 12 It is the polarization-electric field hysteresis loop of the ferroelectric / relaxor ferroelectric liquid crystal polymer of Example 4. It can be seen that the ferroelectric / relaxor ferroelectric liquid crystal polymer of the present invention exhibits the hysteresis loop of a typical ferroelectric polymer.

[0062] Figure 13It is the polarization-electric field hysteresis loop of the ferroelectric / relaxor ferroelectric liquid crystal polymer in Example 5. It can be seen that the ferroelectric / relaxor ferroelectric liquid crystal polymer of the present invention exhibits the hysteresis loop of a typical ferroelectric polymer.

[0063] The above are only the preferred embodiments of the present invention and do not impose any formal restrictions on the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a ferroelectric / relaxor ferroelectric liquid crystal polymer, characterized in that, It includes the following steps: Mix the polymerizable ferroelectric liquid crystal small molecule, initiator and organic solvent and carry out a homopolymerization reaction to obtain the ferroelectric / relaxor ferroelectric liquid crystal polymer; Or Mix the polymerizable ferroelectric liquid crystal small molecule, monomer containing double bond, initiator and organic solvent and carry out a copolymerization reaction to obtain the ferroelectric / relaxor ferroelectric liquid crystal polymer; In the homopolymerization reaction and copolymerization reaction, the polymerizable ferroelectric liquid crystal small molecule has the structure shown in Formula I: Formula I, In Formula I, R1, R2 and R3 are all -H; R4 is -C n H 2n COO-, and the number of carbon atoms in R4 is greater than or equal to 0; R5 has any one of the structures shown in R5-1 to R5-10: ， Among R5-1 to R5-10 are connection sites The monomer containing double bond includes one or more of ethylene, propylene, vinyl chloride, vinyl acetate, styrene, butadiene, isoprene, chloroprene, acrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, vinyl ether, vinyl pyrrolidone and divinylbenzene.

2. The preparation method according to claim 1, characterized in that, The number of carbon atoms in R4 is 0 to 50.

3. The preparation method according to claim 2, wherein, The number of carbon atoms in R4 is 2 to 10.

4. The preparation method according to claim 1, wherein During the copolymerization reaction, the molar ratio of the polymerizable ferroelectric liquid crystal small molecule to the monomer containing double bond is (0.1 to 1):(0.9 to 0), and the molar amount of the monomer containing double bond is not 0.

5. The preparation method according to claim 1, characterized in that, The temperature of the homopolymerization reaction and copolymerization reaction is independently 40 to 120 °C, and the time is independently 2 to 20 h.

6. The preparation method according to claim 1, characterized in that, During the homopolymerization reaction, the mass equivalent ratio of the polymerizable ferroelectric liquid crystal small molecule to the initiator is 1:0.005 to 0.

02.

7. The preparation method according to claim 1, wherein During the copolymerization reaction, the mass equivalent ratio of the reaction monomers to the initiator is 1:0.005 to 0.02, and the reaction monomers include the polymerizable ferroelectric liquid crystal small molecule and the monomer containing double bond.

8. The preparation method according to claim 1, characterized in that, The initiators in the homopolymerization reaction and copolymerization reaction independently include one or more of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate and diisopropylbenzene peroxide.

9. The ferroelectric / relaxor ferroelectric liquid crystal polymer prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the ferroelectric / relaxor ferroelectric liquid crystal polymer according to claim 9 in the field of flexible electronic devices.

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