A length-controllable polyfluorene-polythiophene block copolymer nanowire and its preparation method

Abstract

The present invention discloses a length-controllable polyfluorene-polythiophene block copolymer nanowire and a preparation method thereof. The structural formula of the polyfluorene-polythiophene block copolymer is shown below: #imgabs0# After annealing, the block copolymer obtains a polyfluorene-polythiophene block copolymer nanowire whose length gradually increases with increasing annealing temperature. The method of the present invention can achieve crystallization self-assembly to prepare nanowires with controllable length and narrow dispersity. By precisely controlling the length and consistency of the nanowires, their physical, chemical and mechanical properties can be optimized. Therefore, the nanowires with controllable length and narrow dispersity can ensure the consistency and predictability of their performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer nanowire preparation, and specifically relates to a length-controllable polyfluorene-polythiophene block copolymer nanowire and its preparation method. Background Art

[0002] Advances in supramolecular chemistry have provided an excellent platform for creating and constructing a wide range of synthetic configurations, from molecular-scale molecular machines to one- or two-dimensional nanostructures of supramolecular polymers, and even macroscopic materials. Furthermore, the size and shape of supramolecular polymers can be controlled by monomer selection, chain structure design, and variations in solvent conditions (e.g., solvent mixtures, pH manipulation, salt concentration, and temperature).

[0003] Amphiphilic block copolymers containing conjugated polymer core-forming blocks are typically assembled in solution to form micelles. However, precise control of the self-assembly process remains a challenge. Active crystallization-driven self-assembly is an efficient seed growth strategy for preparing morphologically pure, low-dispersity one-dimensional fibers and two-dimensional platelets to achieve size control. In addition, for nanowire materials, precise control of the length of the nanowires plays an important role in the physical, chemical, and mechanical properties of the nanowire materials. In addition, how to control the consistency of the length of the nanowires is also a major technical challenge in this field.

[0004] The present invention aims to develop a new nanowire preparation process to solve the above technical challenges in the field. Summary of the Invention

[0005] This invention uses a nickel complex as a catalyst and an active catalyst transfer polymerization method to synthesize polyfluorene-polythiophene conjugated polymers in a one-pot process. By utilizing the crystallization properties of polyfluorene and crystal-driven self-assembly, nanowires with controllable length and narrow dispersion can be formed.

[0006] In one aspect, the present invention provides a length-controllable polyfluorene-polythiophene block copolymer nanowire, wherein the structural formula of the polyfluorene-polythiophene block copolymer is as follows: Where m and n are positive integers that ensure the number average molecular weight of the block copolymer pair is between 10,000 and 50,000. After annealing, the block copolymer produces polyfluorene-polythiophene block copolymer nanowires whose length gradually increases with increasing annealing temperature. Precise control of nanowire length by annealing temperature is crucial for nanowire preparation, as nanowire length can significantly influence its physical, chemical, and mechanical properties. Therefore, the length-controllable polymer nanowires prepared by the present invention essentially achieve precise control over the physical and chemical properties of the nanowires.

[0007] Preferably, the annealing temperature range is 35-60° C. The lower the annealing temperature range, the easier it is to control.

[0008] Preferably, the length of the polyfluorene-polythiophene block copolymer nanowires is 60-2000 nm. It is easy to understand that any length within this range can be achieved, such as 70 nm, 80 nm, 100 nm, 200 nm, 500 nm, 1000 nm, 1500 nm, etc.

[0009] Preferably, the polyfluorene-polythiophene block copolymer nanowires have a polydispersity coefficient Lw / Ln of 1.01-1.04, where Lw represents the weight-average contour length and Ln represents the number-average contour length. The polydispersity coefficient of the nanowires is close to 1, indicating that the assembly consistency is very high, resulting in nanowires of uniform length, which is of great significance for the further development and utilization of nanowires. In addition, the molecular weight distribution of the polyfluorene-polythiophene block copolymer is 1.1-1.3, that is, the molecular weight distribution of the synthesized polymer is also relatively narrow, which lays the foundation for the subsequent synthesis of nanowires with high consistency.

[0010] In another aspect, the present invention provides a method for preparing polyfluorene-polythiophene block copolymer nanowires, comprising the following steps:

[0011] S1. Prepare a polyfluorene-polythiophene block copolymer, the structural formula of which is shown below:

[0012] wherein m and n are positive integers such that the number average molecular weight of the block copolymer pair is between 10,000 and 50,000.

[0013] S2. dissolving the polyfluorene-polythiophene block copolymer in tetrahydrofuran solvent.

[0014] S3. Add the tetrahydrofuran solution containing the polyfluorene-polythiophene block copolymer dissolved in step S2 dropwise into the mixed solvent and allow to stand for a period of time to obtain a polyfluorene-polythiophene block copolymer nanowire seed precursor solution.

[0015] S4. Ultrasonic treatment is performed on the nanowire seed precursor solution in step S3 to obtain a polyfluorene-polythiophene block copolymer nanowire seed solution.

[0016] S5. Annealing the nanowire seed solution in step S4 at 35-60° C., and then standing at 25° C. for a period of time to obtain polyfluorene-polythiophene block copolymer nanowires with controllable length.

[0017] Preferably, the mixed solvent consists of chloroform and methanol in a volume ratio of 1:1. The selection of the mixed solvent and the ratio are important for the preparation of nanowires. Experimental results show that a 1:1 volume ratio of chloroform / methanol mixed solvent is crucial for the preparation of nanowire seed precursor solutions.

[0018] Preferably, the annealing time in step 5 is 0.5-2 hours, and the standing time in steps S3 and S5 is 2-4 days.

[0019] Preferably, the ultrasonic treatment in step S4 is performed at 0° C. for 0.5 hours.

[0020] Preferably, the preparation method of the polyfluorene-polythiophene block copolymer in step S1 is as follows, wherein C6H 13 is n-hexyl, and comprises the following steps:

[0021] T1. Add fluorene monomer, lithium chloride and isopropylmagnesium chloride to a reaction vessel. The structural formula of the fluorene monomer is shown below. Evacuate the reaction vessel and fill it with nitrogen to atmospheric pressure. Add tetrahydrofuran solvent and react at -20°C for a period of time. Add nickel complex Ni(acac)2 / dppp and react at 0°C for a period of time to obtain a solution containing a polyfluorene polymer.

[0022] T2. Add thiophene monomer and isopropylmagnesium chloride to another reaction container, evacuate the reaction container and fill it with nitrogen to atmospheric pressure, add tetrahydrofuran solvent, and react at room temperature for a period of time to obtain the thiophene structure shown below; then add the solution containing the polyfluorene polymer in step T1, react at room temperature for a period of time, and then obtain the polyfluorene-polythiophene block copolymer after post-treatment.

[0023]

[0024] Preferably, the post-treatment operation in step T2 is to add diethyl ether to the reaction solution to terminate the reaction, wash the obtained product with diethyl ether 4-5 times, and vacuum dry until the mass remains unchanged.

[0025] The nickel complex Ni(acac)2 / dppp is a commonly used catalyst in the field of polymer synthesis. The synthesis method of the nickel complex catalyst Ni(acac)2 / dppp used in the present invention comprises the following steps: taking a 25mL polymerization bottle, weighing 51.4mg of nickel acetylacetonate and 84.1mg of 1,3-bis(diphenylphosphino)propane (ligand = dppp, Ni(acac)2 / dppp = 1 / 1.02), adding 10mL of tetrahydrofuran under a nitrogen atmosphere, and stirring at room temperature.

[0026] Compared with the prior art, the technical solution provided by the present invention exhibits the following beneficial effects.

[0027] The present invention provides a length-controllable polyfluorene-polythiophene block copolymer nanowire, which can achieve precise control of the nanowire in the length range of 60-1000nm by adjusting the nanowire annealing problem. In addition, the polydispersity coefficient of the prepared nanowire is 1.01-1.04, that is, the prepared nanowire has a narrow dispersity and a high degree of consistency. Therefore, the technical solution provided by the present invention can be used to prepare nanowires with controllable length and narrow dispersity. By precisely controlling the length and consistency of the nanowires, their physical, chemical and mechanical properties can be optimized. Therefore, nanowires with controllable length and narrow dispersity can ensure the consistency and predictability of their performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the gel permeation chromatogram of each polymer involved in Examples 1-5.

[0029] Figure 2 is the hydrogen spectrum of the copolymer prepared in Example 1.

[0030] Figure 3 3 is an SEM image of the copolymer nanowire seeds prepared in Example 6 under mixed solvents in different proportions.

[0031] Figure 4 These are SEM images of copolymer nanowire seeds and copolymer nanowires obtained after treatment at different annealing temperatures. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without paying any creative work. The present invention has many different forms of implementation and should not be construed as limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the present invention to those skilled in the art. The present invention will only be limited by the claims.

[0033] The synthesis method of the nickel complex catalyst used in the present invention comprises the following steps: taking a 25 mL polymerization bottle, weighing 51.4 mg of nickel acetylacetonate and 84.1 mg of 1,3-bis(diphenylphosphino)propane (ligand = dppp, Ni(acac)2 / dppp = 1 / 1.02), adding 10 mL of tetrahydrofuran under a nitrogen atmosphere, and stirring at room temperature.

[0034] Example 1

[0035] The synthesis route of the polyfluorene-polythiophene block copolymer of the present invention is shown in the figure below. The specific preparation process is as follows: 269 mg (0.5 mmol) of fluorene monomer is added to a 50 mL polymerization bottle. The specific structure of the fluorene monomer is shown in the figure, and the -C6H 13 = represents n-hexyl, 42.4 mg lithium chloride, and then 0.25 ml isopropyl magnesium chloride are added. The polymerization bottle is vacuumed and filled with nitrogen for 3 times. Then 10 mL dry tetrahydrofuran is added and the reaction is carried out at -20 ° C for 2 hours. Under nitrogen environment, 1 mL nickel complex catalyst solution is added, wherein the ratio of fluorene monomer to nickel complex catalyst is 25:1. The reaction is carried out at 0 ° C for 2 hours to obtain polyfluorene polymer. See the attached Figure 1 As shown in the figure, the polyfluorene polymer in this embodiment is poly-1 25 The number average molecular weight of the polyfluorene polymer was 7.68×10 3 , the molecular weight distribution is 1.27.

[0036] 23 mg of hydrophilic thiophene monomer was placed in a 10 mL polymerization bottle. The bottle was vacuumed and filled with nitrogen three times. 1 mL of dry tetrahydrofuran was added, followed by 0.1 mL of isopropylmagnesium chloride. The reaction was allowed to proceed at room temperature for 1 hour. 1 mL of the polymer solution from the previous step was added, and the reaction was continued at room temperature for 2 hours. Ether was added to terminate the reaction. The resulting product was washed with ether 4-5 times and vacuum dried until the mass remained unchanged. The polyfluorene-polythiophene polymer was obtained, with a mass of 43.1 mg. See the attached figure. Figure 1 As shown in the figure, the polyfluorene-polythiophene copolymer described in this embodiment is poly(1 25 -b-2 25 ), the number average molecular weight of the polyfluorene polymer was 15.8×10 3 , molecular weight distribution is 1.25. In addition, see the attached Figure 2 This is the hydrogen spectrum of the prepared copolymer. The figure clearly shows the distribution of hydrogen elements in multiple locations in the copolymer structure, indicating that a copolymer with the following structural formula was prepared.

[0037]

[0038] Example 2,

[0039] The experimental steps were the same as those in Example 1, except that 9.2 mg of hydrophilic thiophene monomer and 0.04 ml of isopropyl magnesium chloride were added, and the mass of the polyfluorene-polythiophene polymer finally prepared was 31.2 mg.

[0040] See attached Figure 1 As shown in the figure, the polyfluorene-polythiophene copolymer described in this embodiment is poly(1 25 -b-210 ), gel permeation chromatography showed that the number average molecular weight of the polyfluorene-polythiophene copolymer was 10.38×10 3 , the molecular weight distribution is 1.23.

[0041] Example 3

[0042] The experimental steps were the same as those in Example 1, except that 27.6 mg of hydrophilic thiophene monomer and 0.12 ml of isopropyl magnesium chloride were added, and the mass of the polyfluorene-polythiophene polymer finally prepared was 47.2 mg.

[0043] See attached Figure 1 As shown in the figure, the polyfluorene-polythiophene copolymer described in this embodiment is poly(1 25 -b-2 30 ), gel permeation chromatography showed that the number average molecular weight of the polyfluorene-polythiophene copolymer was 19.63×10 3 , the molecular weight distribution is 1.13.

[0044] Example 4

[0045] The experimental steps were the same as those in Example 1, except that 64.4 mg of hydrophilic thiophene monomer and 0.28 ml of isopropyl magnesium chloride were added, and the mass of the polyfluorene-polythiophene polymer finally prepared was 82.8 mg.

[0046] See attached Figure 1 As shown in the figure, the polyfluorene-polythiophene copolymer described in this embodiment is poly(1 25 -b-2 70 ), gel permeation chromatography showed that the number average molecular weight of the polyfluorene-polythiophene copolymer was 28.49×10 3 , the molecular weight distribution is 1.13.

[0047] Example 5

[0048] The experimental steps were the same as those in Example 1, except that 73.6 mg of hydrophilic thiophene monomer and 0.31 ml of isopropyl magnesium chloride were added, and the mass of the polyfluorene-polythiophene polymer finally prepared was 90.6 mg.

[0049] See attached Figure 1 As shown in the figure, the polyfluorene-polythiophene copolymer described in this embodiment is poly(1 25 -b-2 80 ), gel permeation chromatography showed that the number average molecular weight of the polyfluorene-polythiophene copolymer was 35.45×10 3 , the molecular weight distribution is 1.12.

[0050] Example 6

[0051] The experimental steps were the same as those in Example 1, except that 110.4 mg of hydrophilic thiophene monomer and 0.48 ml of isopropyl magnesium chloride were added, and the mass of the polyfluorene-polythiophene polymer finally prepared was 116.7 mg.

[0052] See attached Figure 1 As shown in the figure, the polyfluorene-polythiophene copolymer described in this embodiment is poly(1 25 -b-2 120 ), gel permeation chromatography showed that the number average molecular weight of the polyfluorene-polythiophene copolymer was 47.46×10 3 , the molecular weight distribution is 1.14.

[0053] Figure 1 The polyfluorene polymer and the polyfluorene-polythiophene polymer prepared in Examples 1-7 are shown together, and their gel chromatograms are arranged from right to left.

[0054] Example 7,

[0055] 60 mg of the polyfluorene-polythiophene copolymer prepared in Example 1 was dissolved in 10 mL of tetrahydrofuran to obtain a copolymer solution. 30 uL of the copolymer solution was dripped into a culture bottle containing 1 mL of a chloroform / methanol mixed solvent. The mouth of the culture bottle was then covered with a rubber septum. After standing for 3 days, the solution was examined using a SEM. The volume ratios of chloroform and methanol were set to 10:0, 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9, and 0:10, respectively. 10:0 means that the solvent used was pure chloroform solvent, and 0:10 means that the solvent used was pure methanol solvent. See Appendix Figure 3 It is known that Figure 3 The results of the copolymer nanowire seed precursors obtained under the above 11 solvent conditions are shown in a sequence from top to bottom and from left to right. As can be seen, no assembly was observed when pure chloroform was used. When the chloroform / methanol ratio was set to 9:1 and 8:2, some less obvious assembly was observed. When the chloroform / methanol ratio was set to 7:3 and 6:4, some self-assembly was observed, but the assembled morphology was irregular nanospheres. When the chloroform / methanol ratio was set to 5:5, a distinct elongated nanowire structure with uniform width was formed, indicating an ideal nanowire seed precursor. When the chloroform / methanol ratio was set to 4:6, the nanowire structure was not obvious, and a small amount of nanospheres appeared. When the chloroform / methanol ratio was set to 3:7, 2:8, 1:9, and 0:10, nanospheres appeared. In summary, when the ratio of chloroform / methanol in the solvent is set to 5:5, it can be seen that a well-structured copolymer nanoseed precursor solution is prepared.

[0056] Example 8

[0057] The nanoseed precursor solution of Example 7 was ultrasonically treated at 0°C for 0.5 h to obtain a polyfluorene-polythiophene block copolymer nanowire seed solution. Figure 4 The prepared seeds had a nanometer length of 82 nm and a polydispersity coefficient (Lw / Ln) of 1.04. 1 mL of the polyfluorene-polythiophene block copolymer nanowire seed solution was transferred to six culture flasks, capped with rubber septa, and annealed for 1 hour in oil baths at different temperatures (35, 40, 45, 55, and 60°C). After annealing, the flasks were transferred to a 25°C oil bath and allowed to stand for 3 days. The samples from each flask were then examined by scanning electron microscopy (SEM). It can be clearly seen that when the annealing temperature is 35°C, the resulting copolymer nanowires are 340 nm and have a polydispersity index (Lw / Ln) of 1.03; when the annealing temperature is 40°C, the resulting copolymer nanowires are 520 nm and have a polydispersity index (Lw / Ln) of 1.03; when the annealing temperature is 45°C, the resulting copolymer nanowires are 640 nm and have a polydispersity index (Lw / Ln) of 1.01; when the annealing temperature is 55°C, the resulting copolymer nanowires are 1500 nm and have a polydispersity index (Lw / Ln) of 1.04; and when the annealing temperature is 60°C, the resulting copolymer nanowires are 1900 nm and have a polydispersity index (Lw / Ln) of 1.05. It can be seen that after annealing the block copolymer, polyfluorene-polythiophene block copolymer nanowires are obtained, whose length gradually increases with increasing annealing temperature. Moreover, the polydispersity coefficient Lw / Ln of these nanowires is close to 1 and the dispersion is narrow, indicating good consistency, which is of great significance for the subsequent physical, chemical and / or mechanical properties of the nanowires in functional materials.

[0058] The present invention uses the above-described embodiments to illustrate the detailed process flow of the present invention. However, the present invention is not limited to the above-described detailed process flow, that is, it does not mean that the present invention must rely on the above-described detailed process flow to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements of various raw materials in the products of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A length-controllable polyfluorene-polythiophene block copolymer nanowire, characterized in that: The structural formula of the polyfluorene-polythiophene block copolymer is shown below: ； wherein m and n are positive integers such that the number average molecular weight of the block copolymer pair is between 10,000 and 50,000; After the block copolymer is annealed, a polyfluorene-polythiophene block copolymer nanowire is obtained, the length of which gradually increases as the annealing temperature rises.

2. The polyfluorene-polythiophene block copolymer nanowire according to claim 1, characterized in that: The annealing temperature range is 35-60°C.

3. The polyfluorene-polythiophene block copolymer nanowire according to claim 1, characterized in that: The length of the polyfluorene-polythiophene block copolymer nanowire is 70-2000 nm.

4. The polyfluorene-polythiophene block copolymer nanowire according to claim 1, characterized in that: The polydispersity coefficient Lw / Ln of the polyfluorene-polythiophene block copolymer nanowires is 1.01-1.04, wherein Lw represents the weight-average contour length and Ln represents the number-average contour length; the molecular weight distribution of the polyfluorene-polythiophene block copolymer is 1.1-1.

3.

5. The method for preparing the polyfluorene-polythiophene block copolymer nanowires according to any one of claims 1 to 4, comprising the following steps: S1. Prepare a polyfluorene-polythiophene block copolymer, the structural formula of which is shown below: ， wherein m and n are positive integers such that the number average molecular weight of the block copolymer pair is between 10,000 and 50,000; S2, dissolving the polyfluorene-polythiophene block copolymer in tetrahydrofuran solvent; S3, adding the tetrahydrofuran solution containing the polyfluorene-polythiophene block copolymer dissolved in step S2 dropwise into the mixed solvent and allowing the mixture to stand for a period of time to obtain a polyfluorene-polythiophene block copolymer nanowire seed precursor solution; S4, ultrasonically treating the nanowire seed precursor solution in step S3 to obtain a polyfluorene-polythiophene block copolymer nanowire seed solution; S5. Annealing the nanowire seed solution in step S4 at 35-60° C., and then standing at 25° C. for a period of time to obtain polyfluorene-polythiophene block copolymer nanowires with controllable length.

6. The method for preparing polyfluorene-polythiophene block copolymer nanowires according to claim 5, characterized in that: The mixed solvent consists of chloroform and methanol, and the volume ratio of chloroform to methanol is 1:

1.

7. The method for preparing polyfluorene-polythiophene block copolymer nanowires according to claim 5, characterized in that: The annealing time in step 5 is 0.5-2 hours, and the standing time in steps S3 and S5 is 2-4 days.

8. The method for preparing polyfluorene-polythiophene block copolymer nanowires according to claim 5, characterized in that: The ultrasonic treatment in step S4 was performed at 0°C for 0.5 hours.

9. The method for preparing polyfluorene-polythiophene block copolymer nanowires according to claim 5, characterized in that: The preparation method of the polyfluorene-polythiophene block copolymer in step S1 is as follows, wherein C6H 13 is n-hexyl, and comprises the following steps: T1. Adding a fluorene monomer, lithium chloride, and isopropylmagnesium chloride to a reaction vessel, wherein the fluorene monomer has the structural formula shown below, evacuating the reaction vessel and filling it with nitrogen to atmospheric pressure, adding tetrahydrofuran solvent, and reacting at -20°C for a period of time, adding a nickel complex catalyst Ni(acac)2 / dppp, and reacting at 0°C for a period of time to obtain a solution containing a polyfluorene polymer; T2, adding thiophene monomer and isopropylmagnesium chloride to another reaction container, evacuating the reaction container and filling it with nitrogen to atmospheric pressure, adding tetrahydrofuran solvent, and reacting at room temperature for a period of time to obtain the thiophene structure shown below; then adding the solution containing the polyfluorene polymer in step T1, reacting at room temperature for a period of time, and then performing post-treatment to obtain the polyfluorene-polythiophene block copolymer; 。 10. The method for preparing polyfluorene-polythiophene block copolymer nanowires according to claim 9, characterized in that: The post-treatment operation in step T2 is to add diethyl ether to the reaction solution to terminate the reaction, wash the obtained product with diethyl ether 4-5 times, and vacuum dry until the mass remains unchanged.

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