Periodic polymer brushes containing biphenyl ester liquid crystal groups, polymer thin films and methods of making the same

Abstract

The application discloses a periodic polymer brush containing a biphenyl ester liquid crystal group, a polymer film and a preparation method thereof. The periodic polymer brush containing the biphenyl ester liquid crystal group comprises a biphenyl ester liquid crystal segment and a polyhydric aliphatic alcohol segment, the two segments are respectively grafted on a norbornene diacid anhydride to form a macromonomer, and through ring-opening metathesis polymerization, the periodic polymer brush with a constant grafting ratio of 1:1 is formed. The polymer contains a classic rod-like biphenyl ester liquid crystal unit, under a series of stimuli given by the environment, the molecular chain can be microphase-separated, and self-assembled to form a long-range ordered structure.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, specifically to a periodic polymer brush containing biphenyl ester liquid crystal groups, a polymer film, and a method for preparing the same. Background Technology

[0002] In the natural environment, many substances can spontaneously form ordered structures; this phenomenon is called self-assembly. In multi-component systems, the self-assembly process can trigger nanoscale phase separation (or microphase separation), and chemists have long been dedicated to constructing desired micro- and nanostructures through microphase separation. Rod-shaped liquid crystal molecules can form various liquid crystal phases and can suppress their own crystallization; introducing them into polymer systems can effectively promote microphase separation.

[0003] The microphase separation cycle in traditional block copolymers (BCPs) depends on the Flory-Huggins parameter (χ) and degree of polymerization (N) between the blocks. Microphase separation in BCPs requires satisfying the χ parameter. N The value is greater than 10.5. Therefore, in order to reduce the feature size to the sub-10 nm scale, a smaller N value is required, which in turn requires BCPs with high χ values. However, the minimum linewidth formed by the self-assembly of block copolymer PS-b-PMMA, which is the "gold standard" for guided self-assembly, is only about 11 nanometers, making it difficult to meet the smaller size requirements. Summary of the Invention

[0004] Based on this, this application provides a periodic polymer brush containing biphenyl ester liquid crystal groups, which has the characteristics of constant grafting ratio and precise molecular structure. At the same time, due to the difference in side chain composition, this type of polymer brush is prone to microphase separation, thereby forming a long-range ordered micro-nano structure.

[0005] A periodic polymer brush containing biphenyl ester liquid crystal groups, the structural formula (I) of which is shown below.

[0006]

[0007] Structural formula (Ⅰ)

[0008] In structural formula (Ⅰ):

[0009] R1 is or ;

[0010] The degree of polymerization n ranges from 50 to 200; m from 1 to 8; p from 2 to 10; k from 8 to 26; a from 6 to 22; and b from 6 to 22.

[0011] The two side chains of the periodic polymer brush containing biphenyl ester liquid crystal groups provided in this application have different properties. The biphenyl ester liquid crystal side chain is a rod-shaped liquid crystal that tends to form a liquid crystal phase under thermal annealing conditions. This provides sufficient driving force for the microphase separation of the polymer brush. The side chain containing R1 has sufficient flexibility, is easy to move and cooperate with the formation of the liquid crystal phase, thereby assisting the occurrence of microphase separation.

[0012] The periodic polymer brush provided in this application, since the period formed by its microphase separation depends only on the length of the side chain, can achieve the formation of a smaller and more precise self-assembled structure simply by adjusting the length of the side chain molecules.

[0013] The periodic polymer brush containing biphenyl ester liquid crystal groups provided in this application has a precise and well-defined periodic structure, which is prone to microphase separation and produces a long-range ordered phase structure with a low defect rate, and has important application prospects in the field of semiconductor lithography.

[0014] Several alternative methods are provided below, but they are not intended as additional limitations on the overall solution above. They are merely further additions or optimizations. Provided there are no technical or logical contradictions, each alternative method can be combined individually with respect to the overall solution above, or multiple alternative methods can be combined with each other.

[0015] Optionally, in structural formula (Ⅰ), the degree of polymerization n ranges from 50 to 150. When the degree of polymerization is 150, the molecular weight is approximately 60,000. More preferably, the degree of polymerization n ranges from 50 to 120.

[0016] Optionally, in structural formula (I), m is 4~8; p is 4~8; k is 13~19; a is 12~18; b is 12~18. More preferably, in structural formula (I), m is 6; p is 6; k is 16; a is 15; b is 15.

[0017] This application also provides a method for preparing the periodic polymer brush containing biphenyl ester liquid crystal groups, comprising:

[0018] Step 1: 4,4'-dihydroxybiphenyl undergoes an esterification reaction with fatty acids to obtain a biphenyl ester monomer with one extended chain end;

[0019] Step 2: The biphenyl ester monomer with one chain extended reacts with a haloalcohol through an etherification reaction to obtain the biphenyl ester monomer with chains extended at both ends.

[0020] Step 3: The biphenyl ester monomer with extended chains at both ends undergoes a ring-opening reaction with norborneol olefinic anhydride to obtain a macromolecular monomer grafted at one end.

[0021] Step 4: The macromonomer grafted at one end undergoes an esterification reaction with a fatty alcohol or diglyceride to obtain a macromonomer grafted at both ends.

[0022] Step 5: The macromonomers grafted at both ends undergo ring-opening metathesis reaction under the catalysis of Grubbs catalyst to obtain the periodic polymer brush.

[0023] Optionally, in step 1, the molar ratio of 4,4'-dihydroxybiphenyl to fatty acid is 1~2:1.

[0024] In step 1, the structural formula of 4,4'-dihydroxybiphenyl is shown below:

[0025]

[0026] In step 1, the structural formula of the fatty acid is shown below:

[0027]

[0028] In the structural formula, the value of p ranges from 2 to 10. For example, when p is 6, the fatty acid is octanoic acid.

[0029] Optionally, in step 1, the solvent is tetrahydrofuran, and the ratio of 4,4'-dihydroxybiphenyl to the solvent is 1 mmol: 1.5~2 mL.

[0030] Optionally, in step 1, 4,4'-dihydroxybiphenyl, fatty acid and catalyst are dissolved in a solvent, mixed evenly and then a condensing agent is added, and the reaction is carried out at room temperature for 3 to 5 hours.

[0031] Optionally, in step 1, the catalyst is 4-dimethylaminopyridine (DMPA), the condensing agent is N,N'-diisopropylcarbodiimide (DIC), and the molar ratio of 4,4'-dihydroxybiphenyl, catalyst and condensing agent is 1:0.02~0.04:1~1.2.

[0032] The structural formula of the biphenyl ester monomer with one chain extended end is as follows:

[0033]

[0034] In the structural formula, the value of p ranges from 2 to 10.

[0035] Optionally, in step 2, the molar ratio of the one-end extended biphenyl ester monomer to the haloalcohol is 1:2~5.

[0036] The structural formulas of haloalcohols are as follows:

[0037]

[0038] In the structural formula, m is 1~8, X is a halogen, k is 6, and when X is Br, the haloalcohol is 6-bromohexanol.

[0039] Optionally, in step 2, the solvent is anhydrous acetone, and the ratio of the amount of biphenyl ester monomer with one end extended to the amount of solvent is 1 mmol: 4~6 mL.

[0040] Optionally, in step 2, the one-end extended biphenyl ester monomer, haloalcohol, and potassium carbonate are dissolved in a solvent and refluxed at 70-80°C for 24-48 hours.

[0041] Optionally, in step 2, the molar ratio of the one-end extended biphenyl ester monomer to potassium carbonate is 1:1 to 1.5.

[0042] The structural formula of the biphenyl ester monomer with extended chains at both ends is as follows:

[0043]

[0044] In the structural formula, m is 1~8 and p is 2~10.

[0045] Optionally, in step 3, the molar ratio of the biphenyl ester monomer with extended chains at both ends to norborneol olefinic anhydride is 1:1 to 1.2.

[0046] The structural formula of norborneol enediic anhydride is as follows:

[0047]

[0048] Optionally, in step 3, the biphenyl ester monomer with extended chains at both ends, norborneol olefinic anhydride, and catalyst are dissolved in a solvent and reacted at room temperature for 12-24 hours.

[0049] Optionally, in step 3, the solvent is anhydrous dichloromethane (DCM), and the ratio of the amount of biphenyl ester monomer extended at both ends to the amount of solvent is 1 mmol: 5~6 mL.

[0050] Optionally, in step 3, the catalyst is 4-dimethylaminopyridine (DMAP), and the molar ratio of the biphenyl ester monomers extended at both ends to the catalyst is 1:0.3~0.5.

[0051] The structural formula of the macromolecular monomer grafted at one end is as follows:

[0052]

[0053] Optionally, in step 4, the molar ratio of the macromonomer grafted at one end to the fatty alcohol is 1:1~2, and the molar ratio of the macromonomer grafted at one end to the diglyceride is 1:1~2.

[0054] In step 4, the structural formula of the di-fatty acid glyceride is as follows:

[0055]

[0056] In the structural formula, a is 6~22; b is 6~22.

[0057] Optionally, in step 4, after the macromonomer grafted at one end, catalyst, condensing agent and solvent are mixed evenly, fatty alcohol is added and reacted at room temperature for 12-24 hours.

[0058] Optionally, in step 4, the solvent is anhydrous dichloromethane (DCM), and the ratio of the amount of the macromonomer grafted at one end to the amount of solvent is 1 mmol: 1~2 mL.

[0059] Optionally, in the steps, the catalyst is 4-dimethylaminopyridine (DMAP), the condensing agent is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDCI), and the molar ratio of the one-end grafted macromonomer, catalyst and condensing agent is 1:0.3~0.5:1~1.5.

[0060] The structural formulas of the macromonomers grafted at both ends are as follows:

[0061]

[0062] In the formula, R1 is or ;

[0063] m is 1~8; p is 2~10; k is 8~26; a is 4~15; b is 4~15.

[0064] Optionally, in step 5, the molar ratio of the macromonomer grafted at both ends to the Grubbs catalyst is 50-200:1. More preferably, the molar ratio of the macromonomer grafted at both ends to the Grubbs catalyst is 50-150:1. Even more preferably, the molar ratio of the macromonomer grafted at both ends to the Grubbs catalyst is 50-120:1.

[0065] Optionally, in step 5, the catalyst is a third-generation Grubbs catalyst, with the following structural formula:

[0066] .

[0067] Optionally, in step 5, the macromolecular monomers and catalysts grafted at both ends are dissolved in tetrahydrofuran to prepare solutions, and the solutions are mixed and reacted at room temperature for 1.5 to 2.5 hours.

[0068] Optionally, the concentration of the macromonomer solution grafted at both ends is 40-60 mmol / mL, and the concentration of the catalyst solution is 5-9 mmol / mL.

[0069] Optionally, in step 5, vinyl ether is added to terminate the reaction after the reaction is complete.

[0070] The fatty acid used in step 1 is octanoic acid, the haloalcohol used in step 2 is 6-bromohexanol, and the fatty alcohol used in step 4 is octadecyl alcohol. The reaction equations for each step are as follows:

[0071] Step 1, as shown in reaction R-1, 4,4'-dihydroxybiphenyl undergoes an esterification reaction with n-octanoic acid to obtain a biphenyl ester monomer with one extended chain end (BP-1).

[0072]

[0073] R-1

[0074] Step 2, as shown in reaction R-2, BP-1 reacts with 6-bromohexanol via the Williamson etherification reaction to obtain biphenyl ester monomers with extended chains at both ends (BP-2).

[0075]

[0076] R-2

[0077] Step 3, as shown in reaction R-3, BP-2 undergoes a ring-opening reaction with norborneol edanediol to obtain a macromolecular monomer (Nb-BP-COOH) grafted at one end.

[0078]

[0079] R-3

[0080] Step 4, as shown in reaction R-4, Nb-BP-COOH undergoes an esterification reaction with octadecyl alcohol (OCT) to obtain a macromonomer (BP-OCT) grafted at both ends.

[0081]

[0082] R-4

[0083] Step 5, as shown in reaction R-5, BP-OCT undergoes a ring-opening metathesis polymerization reaction to obtain a periodic polymer brush (P(BP-OCT)) containing biphenyl ester liquid crystal groups, as shown in the following structural formula.

[0084]

[0085] R-5

[0086] In the formula, the degree of polymerization n ranges from 50 to 150.

[0087] This application also provides a polymer film prepared using the aforementioned periodic polymer brush containing biphenyl ester liquid crystal groups.

[0088] This application also provides a method for preparing the polymer film, wherein the periodic polymer brush containing biphenyl ester liquid crystal groups is dissolved in toluene, the resulting solution is coated on a carrier, and the polymer film is obtained by thermal annealing. The specific conditions for thermal annealing are: heating to 80~85℃, holding at that temperature for 6~12h, and cooling at a rate of 10~20℃ / min.

[0089] The concentration of the periodic polymer brush containing biphenyl ester liquid crystal groups in the solution is 10~20 mg / mL.

[0090] The specific conditions for the heat annealing are: heating to 80~85℃, holding at that temperature for 10~12h, and cooling at a rate of 10~15℃ / min.

[0091] The method for synthesizing a periodic polymer brush containing biphenyl ester liquid crystal groups provided in this application involves first designing a macromolecular monomer with 1:1 bimolecular side chains, and then polymerizing it to obtain a polymer structure with periodicity and the same 1:1 side chain ratio. In modern chip manufacturing processes, the periodic polymer brush provided in this application can be used as a self-assembly material to form a nanoscale vertical layered structure under thermal annealing conditions. This structure can be used to manufacture oriented self-assembled photolithography templates with nanoscale regular patterns, or to form nanoporous structures as low dielectric constant insulating materials. It has important application prospects in microelectronics manufacturing, semiconductor photolithography and other fields. Attached Figure Description

[0092] Figure 1 It is BP-1 in Embodiment 1 of this application. 1 H NMR spectrum;

[0093] Figure 2 It is BP-2 in Embodiment 1 of this application. 1 H NMR spectrum;

[0094] Figure 3 It is the Nb-BP-COOH in Example 1 of this application. 1 H NMR spectrum;

[0095] Figure 4 It is the BP-OCT in Embodiment 1 of this application. 1 H NMR spectrum;

[0096] Figure 5 It is P(BP-OCT) in Embodiment 1 of this application. 1 H NMR spectrum;

[0097] Figure 6 It is BP-1 in Embodiment 2 of this application. 1 H NMR spectrum;

[0098] Figure 7It is BP-2 in Embodiment 2 of this application. 1 H NMR spectrum;

[0099] Figure 8 It is Nb-BP-COOH in Example 2 of this application. 1 H NMR spectrum;

[0100] Figure 9 It is the BP-OCT in Embodiment 2 of this application. 1 H NMR spectrum;

[0101] Figure 10 It is P(BP-OCT) in Embodiment 2 of this application. 1 H NMR spectrum;

[0102] Figure 11 It is P(BP-GD) in Embodiment 3 of this application. 1 H NMR spectrum;

[0103] Figure 12 This is the GPC curve of P(BP-OCT) in Embodiment 1 of this application;

[0104] Figure 13 This is the GPC curve of P(BP-OCT) in Embodiment 2 of this application;

[0105] Figure 14 This is the GPC curve of P(BP-GD) in Embodiment 3 of this application;

[0106] Figure 15a This is the AFM pattern of the polymer film in this application;

[0107] Figure 15b yes Figure 15a Cross-sectional view of the polymer film;

[0108] Figure 16 This is the AFM pattern of the polymer film in this application;

[0109] Figure 17 This is the AFM image (after smoothing) of the polymer film in this application. Detailed Implementation

[0110] The preparation method of this application will be described in detail below with reference to the accompanying drawings and embodiments.

[0111] Example 1: Preparation of a periodic polymer brush

[0112] A method for preparing a periodic polymer brush containing biphenyl ester liquid crystal groups includes the following steps:

[0113] (1) Preparation of monomer BP-1 (i.e., one-end extended biphenyl ester monomer)

[0114] In a 250 mL round-bottom flask, 50 mmol of 4,4'-dihydroxybiphenyl, 50 mmol of octanoic acid, 2 mmol of 4-dimethylaminopyridine, and a stir bar were added. The mixture was dissolved in 100 mL of anhydrous tetrahydrofuran (THF). After stirring for 10 minutes at room temperature under a nitrogen atmosphere, 50 mmol of N,N'-diisopropylcarbodiimide was added, resulting in a white precipitate. Stirring was continued for 3 hours. After the reaction was complete, the white precipitate was removed by filtration. The filtrate was purified by column chromatography (eluent was chloroform) to obtain a white granular product. NMR characterization is shown below. Figure 1 Its structural formula is as follows:

[0115] .

[0116] (2) Preparation of monomer BP-2 (i.e., biphenyl ester monomer with extended chains at both ends)

[0117] In a 250 mL round-bottom flask, BP-1 (10 mmol), 6-bromohexanol (20.0 mmol), potassium carbonate (10 mmol), and a stir bar were added and dissolved in 40 mL of acetone. The reaction mixture was refluxed at 75 °C for 24 h. After the reaction was complete, the potassium carbonate was removed by filtration. The crude product was purified by column chromatography using hexane:ethyl acetate as the eluent (1:5, v / v). The NMR characterization of the product is shown in [reference needed]. Figure 2 Its structural formula is as follows:

[0118]

[0119] (3) Preparation of monomer Nb-BP-COOH (i.e., macromonomer grafted at one end)

[0120] BP-2 (10 mmol), norbornene adipic anhydride (10 mmol), 4-dimethylaminopyridine (5 mmol), and a stir bar were added to a 100 mL round-bottom flask and dissolved in 50 mL of anhydrous dichloromethane. The reaction was carried out at room temperature for 12 h. After the reaction was completed, the crude product was purified by column chromatography using hexane:ethyl acetate as the eluent (1:3, v / v). The NMR characterization of the product is shown in [reference needed]. Figure 3 Its structural formula is as follows:

[0121]

[0122] (4) Preparation of monomer BP-OCT (i.e., macromonomer grafted at both ends)

[0123] In a 100 mL round-bottom flask, Nb-BP-COOH (10 mmol), 4-dimethylaminopyridine catalyst (3 mmol), and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (10 mmol) were added and dissolved in 10 mL of anhydrous dichloromethane. After 10 minutes, 10 mmol of octadecyl alcohol was added, and the reaction was carried out at room temperature for 12 h. After the reaction was completed, the crude product was purified by column chromatography using n-hexane:ethyl acetate = 1:5 (v / v). The NMR characterization of the product is shown in [reference needed]. Figure 4 Its structural formula is as follows:

[0124]

[0125] (5) Preparation of polymer P (BP-OCT) (i.e., periodic polymer brush containing biphenyl ester liquid crystal groups)

[0126] Prepare 1 mL of 50 mmol / mL BP-OCT solution (tetrahydrofuran solvent) and a certain volume of 7 mmol / mL G3 catalyst solution (tetrahydrofuran solvent) in a glove box. Add 0.047 mL of G3 catalyst solution to the BP-OCT solution to make the molar ratio of catalyst G3 (i.e., Grubbs third-generation catalyst) to monomer BP-OCT 1:150. After reacting at room temperature for 2 hours, the reaction was terminated by adding vinyl diethyl ether. The reaction solution was centrifuged with ice-cold methanol, and the supernatant was removed to obtain polymer P (BP-OCT). The NMR characterization of the product is shown in [reference needed]. Figure 5 GPC curves are shown below. Figure 12 .

[0127] Example 2: Preparation of periodic polymer brushes

[0128] A method for preparing a periodic polymer brush containing biphenyl ester liquid crystal groups includes the following steps:

[0129] (1) Preparation of monomer BP-1

[0130] In a 250 mL round-bottom flask, 100 mmol of 4,4'-dihydroxybiphenyl, 50 mmol of octanoic acid, 2 mmol of 4-dimethylaminopyridine, and a stir bar were added. The mixture was dissolved in 150 mL of anhydrous tetrahydrofuran (THF). After stirring for 10 minutes at room temperature under a nitrogen atmosphere, 120 mmol of N,N'-diisopropylcarbodiimide was added, resulting in a white precipitate. Stirring was continued for 5 hours. After the reaction was complete, the white precipitate was removed by filtration. The filtrate was purified by column chromatography (eluent was chloroform) to obtain a white granular product. NMR characterization is shown below. Figure 6 Its structural formula is as follows:

[0131]

[0132] (2) Preparation of monomer BP-2

[0133] In a 250 mL round-bottom flask, BP-1 (10 mmol), 6-bromohexanol (50 mmol), potassium carbonate (15 mmol), and a stir bar were added and dissolved in 60 mL of acetone. The reaction mixture was refluxed at 75 °C for 48 h. After the reaction was complete, the potassium carbonate was removed by filtration, and the crude product was purified by column chromatography using hexane:ethyl acetate as the eluent. The NMR characterization of the product is shown in [reference needed]. Figure 7 Its structural formula is as follows:

[0134]

[0135] (3) Preparation of monomer Nb-BP-COOH

[0136] BP-2 (10 mmol), norbornene adipic anhydride (12 mmol), 4-dimethylaminopyridine (5 mmol), and a stir bar were added to a 100 mL round-bottom flask and dissolved in 60 mL of anhydrous dichloromethane. The reaction was carried out at room temperature for 24 h. After the reaction was completed, the crude product was purified by column chromatography using n-hexane:ethyl acetate as the eluent. The NMR characterization of the product is shown in [reference needed]. Figure 8 Its structural formula is as follows:

[0137]

[0138] (4) Preparation of monomeric BP-OCT

[0139] In a 100 mL round-bottom flask, Nb-BP-COOH (10 mmol), 4-dimethylaminopyridine catalyst (5 mmol), and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (15 mmol) were added and dissolved in 20 mL of anhydrous dichloromethane. After 10 minutes, 20 mmol of octadecyl alcohol was added, and the reaction was carried out at room temperature for 24 h. After the reaction was completed, the crude product was purified by column chromatography using n-hexane:ethyl acetate as the eluent. The NMR characterization of the product is shown in [reference needed]. Figure 9 Its structural formula is as follows:

[0140]

[0141] (5) Preparation of polymer P (BP-OCT)

[0142] Prepare 1 mL of 50 mmol / mL BP-OCT solution (tetrahydrofuran solvent) and a certain volume of 7 mmol / mL G3 catalyst solution (tetrahydrofuran solvent) in a glove box. Add 0.141 mL of G3 catalyst solution to the BP-OCT solution to make the molar ratio of catalyst G3 to monomer BP-OCT 1:50. After reacting at room temperature for 2 hours, the reaction was terminated by adding vinyl diethyl ether. The reaction solution was centrifuged with ice-cold methanol, and the supernatant was removed to obtain polymer P(BP-OCT). The NMR characterization of the product is shown in [reference needed]. Figure 10 See GPC curve. Figure 13 .

[0143] Example 3: Preparation of Periodic Polymer Brushes

[0144] In this embodiment, octadecyl alcohol in the raw materials for preparing the macromonomer in Example 1 was replaced with glyceryl distearate, while the remaining raw materials and preparation method were the same as in Example 1. The NMR characterization of the obtained polymer in this embodiment is shown in [reference needed]. Figure 11 GPC curves are shown below. Figure 14 Its structural formula is as follows:

[0145]

[0146] Morphological characterization of polymer films for performance characterization

[0147] In this embodiment, the periodic polymer brush containing biphenyl ester liquid crystal groups prepared in Example 1 (i.e., polymer P(BP-OCT)) was dissolved in toluene (10 mg / mL), spin-coated onto a clean silicon wafer, and annealed at 80°C for 12 hours in an oven, followed by a cooling rate of 10°C / min to obtain an ordered layered structure with AFM as shown in the figure. Figure 15a , Figure 15b and Figure 16 As shown.

[0148] AFM uses a probe to scan the sample surface, allowing direct observation of the height variations of the surface layered structure. Figure 15a In the diagram, the lighter-colored areas are shorter, containing multiple discretely distributed darker areas. The darker areas are taller, and the lighter and darker areas correspond to different layers. The lighter-colored areas are layers closer to the surface. The topmost layer has a porous structure due to insufficient filling material, allowing observation of deeper layers. See also... Figure 15b The corresponding cross-sectional images show that the height difference between the dark and light areas is uniform, indicating that a layered structure parallel to the substrate has been formed. The height difference between each layer is about 15nm, and the phase separation half-cycle is about 7.5nm, which meets the requirements of sub-10nm structure in advanced lithography manufacturing.

[0149] By adjusting the polymer solution concentration to 20 mg / mL, vertical layered structures (such as...) can be observed in some areas over a large scale. Figure 16 and Figure 17 As shown in the figure, this is because the increase in film thickness makes the film surface more inclined to the polymer bulk state, and the presence of parallel and perpendicular layers further proves the generation of layered phase.

[0150] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered to be within the scope of this specification. When technical features of different embodiments are embodied in the same drawing, it can be regarded as the drawing also disclosing examples of combinations of the various embodiments involved.

[0151] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the patent protection scope of this application should be determined by the appended claims.

Claims

1. A periodic polymer brush containing a biphenyl ester liquid crystal group, characterized in that, The structural formula (I) of the periodic polymer brush is shown below, The structural formula (I) In the structural formula (I), R1is or ; The value range of the polymerization degree n is 50-200; m is 1-8; p is 2-10; k is 8-26; a is 6-22; and b is 6-22.

2. The periodic polymer brush containing biphenyl ester liquid crystal groups according to claim 1, wherein, In the structural formula (I), the value range of the polymerization degree n is 50-150.

3. A preparation method of the periodic polymer brush containing a biphenyl ester liquid crystal group according to claim 1 or 2, comprising: Step 1, esterification reaction of 4,4'-dihydroxybiphenyl and fatty acid to obtain a biphenyl ester monomer with chain extension at one end; Step 2, etherification reaction of the biphenyl ester monomer with chain extension at one end and halogenated alcohol to obtain a biphenyl ester monomer with chain extension at both ends; Step 3, ring-opening reaction of the biphenyl ester monomer with chain extension at both ends and norbornene anhydride to obtain a macromonomer grafted at one end; Step 4, esterification reaction of the macromonomer grafted at one end and fatty alcohol or glycerol difatty acid ester to obtain a macromonomer grafted at both ends; Step 5, ring-opening metathesis reaction of the macromonomer grafted at both ends under the catalysis of Grubbs catalyst to obtain the periodic polymer brush.

4. The method for preparing a periodic polymer brush containing a biphenyl ester liquid crystal group according to claim 3, characterized by, In step 1, the molar ratio of 4,4'-dihydroxybiphenyl and fatty acid is 1-2:

1.

5. The method of preparing a periodic polymer brush containing a biphenyl ester liquid crystal group according to claim 3, wherein In step 2, the molar ratio of the biphenyl ester monomer with chain extension at one end and halogenated alcohol is 1:2-5.

6. The method of preparing a periodic polymer brush containing a biphenyl ester liquid crystal group according to claim 3, wherein In step 3, the molar ratio of the biphenyl ester monomer with chain extension at both ends and norbornene anhydride is 1:1-2.

7. The method of preparing a periodic polymer brush containing a biphenyl ester liquid crystal group according to claim 3, wherein In step 4, the molar ratio of the macromonomer grafted at one end and fatty alcohol is 1:1-2, and the molar ratio of the macromonomer grafted at one end and glycerol difatty acid ester is 1:1-2.

8. The method for preparing the periodic polymer brush containing biphenyl ester liquid crystal groups as described in claim 3, characterized in that, In step 5, the molar ratio of the macromonomer grafted at both ends and Grubbs catalyst is 50-200:

1.

9. A polymer film, characterized by, The periodic polymer brush containing a biphenyl ester liquid crystal group is prepared by using the periodic polymer brush containing a biphenyl ester liquid crystal group according to claim 1 or 2.

10. The method for preparing the polymer film according to claim 9, characterized in that, The periodic polymer brush containing a biphenyl ester liquid crystal group is dissolved in toluene, the obtained solution is coated on a carrier, and the periodic polymer brush containing a biphenyl ester liquid crystal group is obtained by heat annealing, wherein the specific conditions of the heat annealing are as follows: heating to 80-85℃, holding for 6-12h, and cooling at a speed of 10-20℃ / min.

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