CN115490716A

CN115490716A - Single molecular weight fluorene-azobenzene amphiphilic oligomer precursor, oligomer and self-assembled fiber and preparation method

Info

Publication number: CN115490716A
Application number: CN202210136770.3A
Authority: CN
Inventors: 周年琛; 刘敏; 叶恋东; 王书媛; 张正彪; 张伟; 黄智豪; 朱秀林
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2022-02-15
Filing date: 2022-02-15
Publication date: 2022-12-20
Also published as: WO2023155247A1

Abstract

The invention discloses a single molecular weight fluorene-azobenzene amphiphilic oligomer, a self-assembled fiber and a preparation method thereof, enriches and expands the research of fluorene and azobenzene contained in a main chain, and has guiding significance for the development of the fields of azobenzene and fluorene materials. The single molecular weight oligomer has better product processing performance and physical performance; meanwhile, the method combines an iterative stepwise growth strategy with efficient monovalent copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction and precisely controls the position of azobenzene to precisely synthesize amphiphilic polymers with different sequences, has simple and easy experimental operation, and provides a theoretical basis for precisely researching the relationship between the structure and the performance; the invention precisely controls the internal accumulation and the external appearance of the nano particles from top to bottom in a solution self-assembly mode, and constructs the 1D/2D nano material with special functions; in addition, the chemical reagent used by the method is stable in the air, the operation is simple and convenient, and the efficiency is high.

Description

Single molecular weight fluorene-azobenzene amphiphilic oligomer precursor, oligomer and self-assembled fiber and preparation method

Technical Field

The invention belongs to the fields of monodisperse sequence polymer synthesis and solution self-assembly, and relates to a preparation method and solution self-assembly application of an amphiphilic single molecular weight polymer containing fluorene and azobenzene in different sequence main chains.

Background

The amphiphilic block copolymer can be self-assembled in a selective solvent under the interaction of pi-pi stacking action, hydrogen bonds, hydrophilicity and hydrophobicity and the like by changing the composition, the block concentration, the solvent components, the properties, the temperature and the like, and is used for preparing nano particles with various shapes and sizes. The amphiphilic polymer solution self-assembly not only perfects the theoretical system of solution self-assembly, but also provides value for potential application of polymer nanoparticles in the fields of biomedicine (drug transportation, controllable release and the like), catalysis and pollution control, cosmetics and the like (Nisar, A.; zhuang, J.; wang, X.,Chemistry of Materials 2009, 21, 3745-3751.Zhang, A.; Bai, H.; Li, L.,Chemical Reviews 2015, 115, 9801-9868. Dong, R.; Liu, W.; Hao, J.,Accounts of Chemical Research 2012, 45, 504-513. Govindaraju, T.; Avinash, M. B., Nanoscale 2012, 4, 6102-6117.). Wherein, due to the rigid planar structure of the amphiphilic pi-conjugated polymer,the material is more prone to close packing along the 1D/2D direction in the assembly process, shows anisotropy, and simultaneously shows unique photoelectric characteristics due to strong interaction force and electron mobility. The solution self-assembly of the conjugated polymer provides an effective way for precisely regulating and controlling the ordered accumulation mode of molecules and the photoelectric characteristics generated by the ordered accumulation mode.

Polyfluorene (PF) and its derivatives (PFs), which are one of the conjugated polymers, are highly efficient blue-emitting materials with promising prospects because of their advantages of rigid structure, excellent thermal and chemical stability, easy modification of side chains, high fluorescence quantum efficiency, etc. (Cao, x. Y.; zhou, x. H.; zi, h.; pei, j., macromolecules 2004, 37, 8874-8882. Li, j.; bo, z. S., macromolecules 2004, 37, 2013-2015.); azobenzene is used as a common stimulus response group with light, heat and reduction responses, and can generate reversible cis-trans isomerism under the condition of light irradiation or heating. When the polymer is introduced into the main chain of the polymer, the molecular configuration of the oligomer/polymer can be obviously influenced by light-induced cis-trans isomerization, and a reversible curling/de-curling process is formed. At present, most of amphiphilic solution self-assembly is researched on the basis of narrow-distribution polymers obtained by living polymerization, and has certain limitation, so that amphiphilic oligomers with a single molecular weight and a definite structure are constructed, and self-assembly is cooperatively driven through multiple supermolecule effects, so that the self-assembly method has important significance for accurately regulating and controlling the morphology and performance of polymer nanoparticles. In the prior art, the self-assembly behavior of the solution of sequence isomers with the same composition is researched, and it is found that the sequence of one head and one tail can only form spherical micelles with the increase of the initial concentration, so that amphiphilic polymers with different sequences and single molecular weights need to be researched and developed to accurately regulate the morphology and performance expression of nanoparticles through the self-assembly of the solution.

Disclosure of Invention

In view of the above situation, the present invention provides a preparation method and a solution self-assembly application of a monodisperse amphiphilic polymer containing fluorene and azobenzene in different sequence main chains, wherein a responsive azobenzene unit is introduced into a conjugated polymer chain for solution self-assembly, so as to develop various novel functional 1D/2D nano materials.

Firstly, a series of chemical reactions such as Sonogashira coupling, diazo coupling, nucleophilic substitution, esterification, nitration, reduction and the like are utilized to synthesize fluorene and azobenzene monomers in multiple steps. Nitrifying the C7 position on a fluorene ring, introducing an octyl group into the C9 position, changing Br at the C2 position into alkynyl protected by TBS by adopting a Sonogashira coupling reaction, and reducing nitro at the C7 position into amino by using iron powder to obtain a fluorene monomer with the alkynyl protected by the TBS at one end and the amino at the other end. And introducing TBS protective groups into azobenzene, then carrying out reduction reaction, then carrying out diazo coupling reaction to synthesize an azobenzene intermediate, and then introducing azide sites through nucleophilic substitution and introducing side chains through esterification reaction to obtain an azobenzene monomer with one end being TBS protected alkynyl and the other end being bromine. And then selectively carrying out TBS deprotection or amino or bromine azide reaction, preparing single molecular weight fluorene-azobenzene precise sequence amphiphilic oligomer precursors with azobenzene positioned at different positions of a main chain by utilizing an iterative step-growth strategy and an efficient monovalent copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction, respectively named as 4F-4Azo, 2Azo-4F-2Azo and 4 (F-Azo), and converting the oligomer precursors into amphiphilic oligomers by utilizing trifluoroacetic acid and dilute hydrochloric acid. Relevant tests prove that the method can effectively synthesize the amphiphilic polymer with single molecular weight, the main chain of which contains fluorene and azobenzene, and researches find that the self-assembly behavior of the oligomer solution has dependence on the sequence.

In order to achieve the purpose, the invention adopts the following technical scheme:

a single molecular weight fluorene-azobenzene amphiphilic oligomer precursor has the following structure:

and removing Boc protection from the fluorene-azobenzene amphiphilic oligomer precursor with the single molecular weight to obtain an amino polymer, and salinizing quaternary ammonium to obtain the fluorene-azobenzene amphiphilic oligomer with the single molecular weight. Specifically, a fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight is dissolved in trifluoroacetic acid, the trifluoroacetic acid is removed by rotary evaporation after reaction, and the concentrated solution is put into saturated NaHCO ₃ Precipitating in an aqueous solution, centrifugally drying to obtain a light yellow solid, dissolving in tetrahydrofuran to obtain a clear and transparent solution, then dropwise adding water, and dropwise adding an HCl aqueous solution to realize quaternary ammonium salinization, thereby obtaining the fluorene-azobenzene amphiphilic oligomer with single molecular weight.

The invention discloses a preparation method of the fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight, which is one of the following preparation methods:

method one, using TBS-4F-N ₃ And alkyne-4Azo-Br-8Boc as raw materials, carrying out copper-catalyzed azide-alkyne cycloaddition reaction to obtain a fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight, namely 4F-4Azo;

method II, using TBS-4F-N ₃ Carrying out copper-catalyzed azide-alkyne cycloaddition reaction by taking alkyne-2Azo-Br-4Boc as a raw material to obtain alkyne-4F-2Azo-Br-4Boc; then, the alkyne-4F-2Azo-Br-4Boc and TBS-2Azo-N are added ₃ 4Boc is subjected to copper-catalyzed azide-alkyne cycloaddition reaction to obtain a fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight, namely 2Azo-4F-2Azo;

third, the alkyne-F-NH is used ₂ And TBS-Azo-N ₃ Taking-2 Boc as a raw material, carrying out copper-catalyzed azide-alkyne cycloaddition reaction, and then respectively carrying out TBS deprotection or converting amino into azide by using sodium azide to obtain TBS-2 (F-Azo) -N ₃ -4Boc or alkyne-2 (F-Azo) -NH ₂ -4Boc; TBS-2 (F-Azo) -N was added ₃ -4Boc and alkyne-2 (F-Azo) -NH ₂ 4Boc is subjected to copper-catalyzed azide-alkyne cycloaddition reaction to obtain a fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight, namely 4 (F-Azo).

In the invention, cuprous bromide is used as a catalyst of copper-catalyzed azide-alkyne cycloaddition reaction, and pentamethyldiethylenetriamine is used as a ligand; the reaction is carried out for 40 to 50 hours at room temperature.

The invention discloses a self-assembly method of a solution of a fluorene-azobenzene amphiphilic oligomer precursor with a single molecular weight. Further, the self-assembled product of the solution of the fluorene-azobenzene amphiphilic oligomer precursor with the single molecular weight is nano fiber or nanosphere.

The invention discloses a preparation method of a single molecular weight fluorene-azobenzene amphiphilic oligomer self-assembled fiber, which comprises the following steps of dissolving a single molecular weight fluorene-azobenzene amphiphilic oligomer precursor 4F-4Azo in a solvent after deprotection, then adding water and hydrochloric acid, standing to obtain a single molecular weight fluorene-azobenzene amphiphilic oligomer self-assembled fiber which is a nanofiber structure, and further removing the solvent from the solution after standing to obtain the single molecular weight fluorene-azobenzene amphiphilic oligomer nanofiber; this is the first disclosure of the assembly of fluorene-azobenzene polymers into nanofibers.

In the invention, tetrahydrofuran is used as a solvent for dissolving the fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight; the concentration of hydrochloric acid is 1mol/L; the volume ratio of tetrahydrofuran, water and hydrochloric acid is 1:0.5: 0.3-0.4; the mixture is allowed to stand at room temperature for 5 minutes to 24 hours, preferably 2 to 12 hours, and more preferably 8 to 12 hours.

The invention discloses a single molecular weight amphiphilic polymer precursor containing fluorene and azobenzene in a main chain and a polymer thereof, and carries out self-assembly behavior research on the amphiphilic polymer solution, creatively discloses that two-block oligomers are assembled to form long nano fibers, and thicker fibers are formed by tiny winding and stacking; other polymers are assembled to form a spherical structure. Therefore, different polymers can be verified, and the molecular accumulation is different in the assembly process, so that the difference of the appearance of the assembly body is generated.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

1. according to the invention, the azobenzene stimulus responsive group is successfully introduced into the main chain of the polymer to construct a novel amphiphilic polymer containing different functional groups, so that the research on fluorene and azobenzene contained in the main chain is enriched and expanded, and the method has guiding significance on the development of the fields of azobenzene and fluorene materials;

2. the invention combines an iterative stepwise growth strategy with an efficient azide-alkyne cycloaddition (CuAAC) reaction catalyzed by monovalent copper, precisely controls the position of azobenzene to precisely synthesize amphiphilic polymer precursors with different sequences, provides a method for efficiently modularizing and synthesizing amphiphilic polymers with different molecular weights and sequences, and containing fluorene and azobenzene in main chains, and widens the application of the method in the aspect of preparing nano materials by solution self-assembly;

3. when the fluorene-azobenzene amphiphilic oligomer with single molecular weight is self-assembled, the internal accumulation and the external appearance of the nano particles are accurately controlled from top to bottom in a solution self-assembly mode, and a 1D/2D nano material with special functions is constructed;

4. the chemical reagent used in the method is stable in the air, and the reaction operation in the method is simple and convenient, the efficiency is high, and the method is convenient for industrial production.

Drawings

FIG. 1 shows NMR spectra of (a) an azobenzene monomer and (b) a fluorene monomer.

Fig. 2 is a SEC efflux curve of single molecular weight amphiphilic oligomer precursors containing fluorene and azobenzene in different main chains.

FIG. 3 is a MALDI-TOF MS diagram of a single molecular weight amphiphilic oligomer precursor containing fluorene and azobenzene in different main chains.

FIG. 4 shows 4F-4Azo-8NH ₂ In THF/H ₂ TEM image of aggregates formed after completion of assembly in O/HCl.

FIG. 5 shows 4F-4Azo-8NH ₂ In THF/H ₂ TEM and AFM images of aggregates formed after completion of assembly in O/HCl.

FIG. 6 shows 4F-4Azo-8NH ₂ In THF/H ₂ O/HCl medium groupTEM images of the aggregates formed after loading.

FIG. 7 shows 4F-4Azo-8NH ₂ In THF/H ₂ TEM image of aggregates formed after completion of assembly in O/HCl.

FIG. 8 shows 4F-4Azo-8NH ₂ In THF/H ₂ TEM image of aggregates formed after completion of assembly in O/HCl.

FIG. 9 shows 4F-4Azo-8NH ₂ In THF/H ₂ TEM image of aggregates formed after completion of assembly in O/HCl.

FIG. 10 shows 4F-4Azo-8NH ₂ At THF/H ₂ TEM image of aggregates formed after completion of assembly in O/HCl.

FIG. 11 shows 2Azo-4F-2Azo-8NH ₂ In THF/H ₂ TEM image of aggregates formed after completion of assembly in O/HCl.

FIG. 12 shows 4 (F-Azo) -8NH ₂ In THF/H ₂ TEM image of aggregates formed after completion of assembly in O/HCl.

FIG. 13 shows the different oligomers in THF/H ₂ Ultraviolet-visible absorption spectrograms (a-c) and fluorescence emission spectrograms (d-f) of the assembled body solution before and after ultraviolet irradiation and after heating recovery after O/HCl assembly, wherein black lines are before ultraviolet irradiation, red lines are after ultraviolet irradiation, and blue lines are after heating recovery. Assembling conditions are as follows: the solvent ratio is as follows:V _THF :V _H20 :V _{THF (1M)} 0.4; initial concentration: c ₀ =1.0 mg/mL; dropping speed: 0.2 mL/h; temperature: 30 ^o C; stirring speed: 300 r/min.

FIG. 14 is an SEM image of a sample prepared by rapid volatilization of different oligomer assembly solutions on a piece of tin foil paper; (a) 4F-4Azo-8NH ₂ ,（b）2Azo-4F-2Azo-8NH ₂ ,（c）4(F-Azo)-8NH ₂ . Assembling conditions are as follows: the solvent ratio is as follows:V _THF :V _H20 :V _{THF (1 M)} 0.4; initial concentration: c ₀ =1.0 mg/mL; dropping speed: 0.2 mL/h; temperature: 30 ^o C; stirring speed: 300 r/min.

Detailed Description

The invention is further described with reference to the following figures and specific embodiments.

Chemical reagent:

2-bromofluorene, aladin;

1-bromooctane, energy-chemical;

tert-butyl dimethylsilylacetylene, aladin;

bis (triphenylphosphine) palladium (II) dichloride, aladin;

cuprous iodide, aladdin;

2-hydroxy-5-nitrobenzyl alcohol, TCI;

t-butyl dimethyl silicon-based protected bromopropyne, aladin;

salicyl alcohol, maire chemical;

Boc-β-alanine, meier chemistry;

dicyclohexylcarbodiimide (DCC), adamas;

4-Dimethylaminopyridine (DMAP), adamas;

tetrabutylammonium fluoride (tetrahydrofuran solution), annaiji;

pentamethyldiethylenetriamine (PMDETA), carbofuran;

cuprous bromide (CuBr), chinese medicine;

sodium azide, aladin;

1, 2-dibromoethane, jiangsu Qiangsheng functional chemistry, inc.;

ammonium chloride, jiangsu Qiangsheng functional chemistry, inc.;

sodium nitrite, jiangsu Qiangsheng functional chemistry, inc.;

sodium bicarbonate, jiangsu Qiangsheng functional chemistry, inc.;

hydrochloric acid, jiangsu Qiangsheng functional chemistry, inc.;

dimethyl sulfoxide, tetrahydrofuran, trichloromethane, methanol, absolute ethyl alcohol, acetone, toluene, n-hexane, ethyl acetate and anhydrous sodium sulfate are all analytically pure, and the chemical reagent company of national drug group is limited.

Testing instruments and conditions:

nuclear magnetic resonance hydrogen spectrum ( ¹ H NMR) with Bruker 300 MHz NMR spectrometer, tetramethylsilane (TMS) as internal standard, CDCl ₃ Or DMSO-d ₆ Is a solvent.

Gel Permeation Chromatography (GPC) was tested on Agilent PL-50;

matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) A Bruker Autoflex III (MALDI-TOF) mass spectrometer equipped with a 150 kHz II laser and a 355 nm nitrogen laser was used.

Ultraviolet-visible (UV-vis) absorption spectra were determined using a Shimadzu UV-2600 spectrophotometer. The light source for the photoresponse test adopts a diode-pumped solid state laser (DPSSL) with model number of LSR532NL-500, wavelength of 365 nm and 435 nm respectively, and intensity of 0.5 mW/cm ² 。

The fluorescence emission spectrum was measured by means of a HITACHI F-4600 type fluorescence spectrophotometer.

Transmission electron microscopy TEM (Hitachi, japan) was carried out using a HITACHI HT7700 instrument at an acceleration voltage of 120 Kv.

A cold field emission scanning electron microscope SEM (Hitachi, japan) was performed using a voltage of HITACHI S-4700, 15 Kv.

AFM was measured in tapping mode (VeecoInstruments inc., nanoscope IV).

The method adopts an azobenzene monomer shown as a formula II and a fluorene monomer shown as a formula III, wherein TBS is tert-butyl dimethylsilane;

the synthetic route of the azobenzene monomer is as follows:

a) Under the condition of stirring, adding n _{2-hydroxy-5-nitrobenzyl alcohol} : n _{TBS protected bromopropyne} : n _{Potassium carbonate} 1-1.2: 2-3, preferably n _{2-hydroxy-5-nitrobenzyl alcohol} : n _{TBS protected bromopropyne} : n _{Potassium carbonate} In a molar ratio of 1: 1.1: 1.5, 2-hydroxy-5-nitrobenzyl alcohol and TBS-protected bromopropyne are reacted under basic conditions12. After hours, intermediate (1) is obtained;

b) With n _{Intermediate (1)} : n _{Iron powder} According to the molar ratio of =1 to 3, firstly dissolving ammonium chloride, then refluxing at 105 ℃ for 1 hour to activate iron powder, adding the intermediate (1), and stirring at 75 ℃ for 12 hours to obtain an intermediate (2);

c) Under the stirring condition, with n _{Intermediate (2)} : n _{Salicylic alcohol} : n _HCl : n _NaNO2 : n _NaOH : n _NaHCO3 =1: 2-3: 3.6-4: 1.2-1.5: 3.5-4: 8-10, preferably n _{Intermediate (2)} : n _{Salicylic alcohol} : n _HCl : n _NaNO2 : n _NaOH : n _NaHCO3 The molar ratio of the intermediate (2) to the intermediate (3) is 1:2: 3.8: 1.2: 3.8: 9, hydrochloric acid and a sodium nitrite aqueous solution are sequentially dripped into the intermediate (2) to generate a diazonium salt solution, and the diazonium salt solution is dripped into a weak base solution containing salicyl alcohol and stirred at room temperature for 12 hours to obtain an intermediate (3);

d) Under the stirring condition, with n _{Intermediate (3)} : n _{Cesium carbonate} : n _{1, 2-dibromoethane} =1: 5-6: 15-20, preferably n _{Intermediate (3)} : n _{Cesium carbonate} : n _{1, 2-dibromoethane} Mixing the intermediate (3) with anhydrous cesium carbonate and 1, 2-dibromoethane at a molar ratio of 1: 5.8: 20, and stirring for 12 hours to obtain an intermediate (4);

e) Under the stirring condition, with n _{Intermediate (4)} : n _{Boc-beta-alanine} : n _DMAP : n _DCC =1: 2-3: 1-1.2: 4-5, preferably n _{Intermediate (4)} : n _{Boc-beta-alanine} : n _DMAP : n _DCC The DCC solution is dissolved by dichloromethane and then is dripped into the intermediate (3) and Boc-βReacting in a mixed solvent of alanine and DMAP for half an hour in an ice water bath, moving to room temperature, and continuously stirring for 12 hours to obtain the azobenzene monomer.

The synthetic route of the fluorene monomer is as follows:

a) Reacting 2-bromofluorene in a mixed solution of nitric acid and 1, 2-dichloroethane for 1 hour, and pouring into ice methanol to obtain an intermediate (1);

b) Under the stirring condition, the n is _{Intermediate (1)} :n _{1-bromooctane} 1 to 3, preferably n _{Intermediate (1)} :n _{1-bromooctane} (ii) =1 molar ratio, KOH and DMSO are mixed, and the intermediate (1) and 1-bromooctane are added and stirred at room temperature for 12 hours to obtain an intermediate (2);

c) Under the protection of argon, with n _PdCl2(pph3)2 :n _CuI :n _{TBS protected alkynyl} :n _{Intermediate (2)} 2 to 5, preferably n _PdCl2(pph3)2 :n _CuI :n _{TBS protected alkynyl} :

n

_{Intermediate (2)} 1,2, in toluene and triethylamine in a molar ratio of 1;

d) With n _{Intermediate (3)} :n _{Iron powder} According to the molar ratio of = 1;

in the invention, tetrahydrofuran solution of tetrabutylammonium fluoride (TBAF) is used for removing a protecting group TBS, so as to realize deprotection of fluorene monomer and azobenzene monomer; converting amino or bromine into an azide group by using sodium azide to realize the azide reaction of a fluorene monomer and an azobenzene monomer; the schematic is as follows:

a) TBS deprotection of fluorene monomer/azobenzene: with n _{Fluorene monomer/azobenzene monomer} : n _{Deprotection reagents} 3 to 6, preferably n _{Fluorene monomer/azobenzene monomer} : n _{Deprotection reagents} And (3) removing TBS protecting groups according to a molar ratio of =1 to 5 to obtain the alkynyl fluorene monomer/azobenzene monomer, wherein the deprotection reagent is tetrabutylammonium fluoride, the solvent is anhydrous tetrahydrofuran, and the reaction condition is stirring at room temperature for 30 minutes.

b) Nitridizing fluorene monomer: stirring in ice water bath with n _{Fluorene monomer} : n _{Hydrochloric acid} : n _{Sodium nitrite} 1.6 to 3.8, preferably n _{Fluorene monomer} : n _{Hydrochloric acid} : n _{Sodium nitrite} According to the molar ratio of = 1.6; then n is added _{Fluorene monomer} :n _{Sodium azide} According to the molar ratio of =1 and 2, adding sodium azide (2 eq) into a diazonium salt solution, and continuously stirring at 0-5 ℃ for post-treatment to obtain a fluorene azide monomer;

azobenzene azidation reaction: under the stirring condition, the n is _{Azobenzene monomer} :n _{Sodium azide} 3 to 5, preferably n =1 _{Azobenzene monomer} :n _{Sodium azide} In a molar ratio of =1, the azobenzene monomer and sodium azide are stirred in a DMF solvent at 80 ℃ for 12 hours, and then the azobenzene monomer is treated to obtain the azidobenzene monomer.

Taking the deprotected and azidated monomers as raw materials to synthesize fluorene-azobenzene amphiphilic oligomer precursors with different sequences and single molecular weights, and specifically, obtaining the fluorene-azobenzene amphiphilic oligomer precursors with different sequences and single molecular weights by utilizing step-by-step growth and efficient azide-alkyne cycloaddition (CuAAC) reaction catalyzed by cuprous, wherein n is the ratio of n to n _{Azide compound} :n _{Alkynyl group-containing compound} 1.2 to 1.5, preferably n _{Azide compound} :n _{Alkynyl group-containing compound} Carrying out CuAAC reaction at a molar ratio of = 1.2, and synthesizing amphiphilic fluorene-azobenzene oligomer precursors with single molecular weight and different sequences. Wherein the catalyst is cuprous bromide with catalytic amount, the ligand is pentamethyldiethylenetriamine, the solvent is tetrahydrofuran, and the oxygen removal tube sealing reaction is carried out for 48 hours. And then the amphiphilic fluorene-azobenzene oligomer precursor side chains with single molecular weight accurate sequence, in which azobenzene is positioned at different positions of the main chain, are subjected to de-Boc protection to synthesize amphiphilic oligomers with different sequences. With n _{Oligomer precursor} :n _{Trifluoroacetic acid} =1: 10-30, preferably n _{Oligomer precursor} :n _{Trifluoroacetic acid} In a molar ratio of 1: 10, the oligomer precursor is dissolved in trifluoroacetic acid, reacted at room temperature for 12 h, then most of the trifluoroacetic acid is removed by rotary evaporation, and then saturated NaHCO is used ₃ Dissolving in waterAdjusting the pH value to be neutral, and centrifugally drying to obtain the oligomer with the azobenzene side chain being amino. Then dilute hydrochloric acid is added into the tetrahydrofuran solution of the oligomer with the side chain being amino, so that the amino can be converted into quaternary ammonium salt to become an amphiphilic oligomer, and the solution self-assembly can be carried out. Specifically, deionized water is dripped into tetrahydrofuran solution of an oligomer, and then quantitative 1.0 mol/L diluted HCl is dripped into a mixed solvent to convert amino into hydrophilic quaternary ammonium salt so as to drive the solution to self-assemble. The specific experimental operation is that 1.0 mL tetrahydrofuran solution of oligomer with concentration of 1.0 mg/mL is put into an ampoule bottle at 30 DEG C ^o C, firstly dripping 0.5 mL of Milli-Q water into the solution, then continuously dripping 0.4 mL of 1.0 mol/L diluted HCl, slowly stirring at 300 r/min, and after the assembly is finished, sealing the ampoule bottle and standing at room temperature for storage to obtain an assembled product.

The first embodiment is as follows: synthesis of azobenzene donors

1. Synthesis of azobenzene intermediate (1):

2-hydroxy-5-nitrobenzyl alcohol (1.0 g, 5.91 mmol), potassium carbonate (1.23 g, 8.87 mmol) were weighed into a 100 mL single-neck round-bottom flask, TBS protected bromopropyne (1.51 g, 6.51 mmol) and 35 mL acetone were added, and the temperature was raised to 70% ^o And C, heating and refluxing, performing suction filtration after TLC tracking reaction, washing with a large amount of acetone, concentrating the filtrate, and performing vacuum drying to obtain 1.53 g of a light yellow solid target product.

2. Synthesis of azobenzene intermediate (2):

in a 50 mL single neck round bottom flask, ammonium chloride (2.16 g, 40.48 mmol) was dissolved in a small amount of water and iron powder (0.70 g, 12.46 mmol) 105 was added ^o Heating, refluxing and activating for 1 h under C, and cooling to 75 ^o C. Intermediate (1) (1.0 g, 3.12 mmol) dissolved in 14 mL of ethanol was then added slowly to the reaction and monitored by TLC for follow-up until the reaction was complete. Spreading a layer of diatomite on a Buchner funnel, filtering the reaction solution to remove iron powder, rotary evaporating the filtrate, and adding BExtraction of ethyl acetate and saturated brine was carried out, the organic phase was collected and purified by column chromatography (petroleum ether: ethyl acetate = 2).

3. Synthesis of azobenzene intermediate (3):

diazotization reaction: intermediate (2) (200.0 mg, 0.69 mmol) was weighed and dissolved in 1.0 mL of methanol, and after dropwise addition of a dilute HCl solution (230. Mu.L, 2.61 mmol) in an ice-water bath, naNO was further added dropwise ₂ (53.54 mg, 0.78 mmol) of aqueous solution, stirring for 1 h and then adding urea and excess NaNO conventionally ₂ Reacting to obtain a diazonium salt solution;

coupling reaction: salicylic alcohol (161.86 mg, 1.31 mmol) and NaOH (107.17 mg, 2.68 mmol) were weighed into 30 mL of water, and NaHCO was added after complete dissolution ₃ (537.84 mg, 6.40 mmol) is adjusted to pH 9, the diazonium salt solution is dripped into the solution under the condition of ice-water bath for reaction for 2 h, then the reaction is continued for 12 h at room temperature, and after the completion of the reaction, the solution is filtered by suction filtration and purified by column chromatography (petroleum ether: ethyl acetate = 1), and 170.00 mg of yellow target product is obtained after spin-drying.

4. Synthesis of azobenzene intermediate (4):

anhydrous cesium carbonate (1.71 g, 25 mmol) is weighed into a 50 mL single-neck round-bottom flask, 1, 2-dibromoethane (16 mL, 86.02 mmol) and 17 mL acetonitrile are added and mixed thoroughly, and the temperature is raised to 65% ^o Intermediate (3) (1.71 g, 4.34 mmol) was weighed into a round bottom flask and followed by TLC until the reaction was complete. Cesium carbonate was removed by suction filtration, purified by column chromatography (petroleum ether: ethyl acetate = 1), and spin-dried to give 2.18 g of an orange-yellow target product.

5. Synthesis of azobenzene donor:

weighing the intermediate (4) (150.00 mg, 0.28 mmol), boc-βAlanine (117.32 mg, 0.62 mmol), DMAP (34.45 mg, 0.28 mmol) was dissolved in 6 mL of dichloromethane. EDCI (230.72 mg, 1.12 mmol) is dissolved in 2 mL dichloromethane, the solution is dripped into the system under the condition of ice-water bath, after 0.5 h reaction, the solution is shifted to normal temperature for further reaction, after TLC tracking monitoring reaction, dichloromethane and saturated saline solution are extracted, an organic phase is collected, rotary evaporation drying is carried out, column chromatography (petroleum ether: ethyl acetate = 1) is carried out for purification, and 225.00 mg orange yellow target product which is TBS-Azo-Br-2Boc is obtained after rotary drying.

The obtained azobenzene monomer is characterized by a nuclear magnetic resonance hydrogen spectrum, and the spectrogram is shown in figure 1a, which shows that the monomer purity is high.

TBS-Azo-Br-2Boc (66.92 mg, 1.03 mmol) and sodium azide (133.9 mg,2.06 mmol) were dissolved in 5 mL DMF at 80 ^o The reaction was stirred for 12 h under C and the TLC plates were followed until the reaction was complete. After cooling to room temperature, extraction was carried out with ethyl acetate, washed with saturated brine three times, the organic phase was collected, dried, rotary evaporated, concentrated and dried to give an orange-yellow sticky substance (63.46 mg) TBS-Azo-N ₃ -2Boc, yield about 99.0%.

TBS-Azo-Br-2Boc (200 mg, 0.23 mmol) was dissolved in 10 mL anhydrous THF, TBAF solution (300. Mu.L, 1.14 mmol) was added thereto, stirred at room temperature for 0.5 h, monitored by TLC follow-up, tetrahydrofuran was removed by rotary evaporation until the reaction was completed, extraction was performed using ethyl acetate, washed three times with saturated brine, the organic phase was collected and dried, and rotary evaporation was concentrated and dried to obtain a brown solid (171.29 mg) alkyne-Azo-Br-2Boc with a yield of about 98.5%.

To a 10 mL Schlenk tube was added TBS-Azo-N dissolved in 5 mL anhydrous oxygen-free THF ₃ -2Boc (85.69 mg, 0.11 mmol) and alkyne-Azo-Br-2Boc (117.00 mg, 0.15 mmol) were added, PMDETA (26.69 mg, 0.15 mmol) and CuBr (14.63 mg, 0.11 mmol) were added, oxygen sealed by pumping three times with argon, after 48 h reaction at room temperature, tetrahydrofuran was removed by rotary evaporation, extraction was performed using ethyl acetate, three times with saturated brine, the organic phase was collected and dried, purified by column chromatography (silica gel, eluent:V _PE /V _EA = 1/4). The product was concentrated by rotary evaporation and dried in vacuo to give TBS-2Azo-Br-4Boc (TBS-2 Azo-Br) as an orange-red paste (150.56 mg) in about 92.1% yield. ¹ H NMR (300 MHz, CDCl ₃ ) δ7.94 (s, 1H), 7.81 (tt, J = 7.1, 2.5 Hz, 8H), 7.09 (dd, J = 13.3, 8.6 Hz, 2H), 6.86 (d, J = 8.8 Hz, 2H), 5.30 (s, 2H), 5.23-5.11 (m, 6H), 5.07 (s, 4H), 4.75 (d, J = 13.1 Hz, 4H), 4.43 (t, J = 4.9 Hz, 2H), 4.31 (t, J = 6.0 Hz, 2H), 3.67-3.55 (m, 5H), 3.37-3.25 (m, 8H), 2.51 (qd, J = 6.4, 1.8 Hz, 8H), 1.31 (d, J = 7.0 Hz, 38H), 0.79 (s, 9H)。

TBS-2Azo-Br-4Boc (1.01 mmol) and sodium azide (2.02 mmol) were dissolved in 5 mL DMF at 80 ^o The reaction was stirred for 12 h under C and the TLC plates were followed until the reaction was complete. Cooling to room temperature, extracting with ethyl acetate, washing with saturated salt water for three times, collecting organic phase, drying, rotary steaming, concentrating, and drying to obtain TBS-2Azo-N ₃ -4Boc。

TBS-2Azo-Br-4Boc (0.22 mmol) was dissolved in 10 mL of anhydrous THF, TBAF solution (2.26 mmol) was added thereto, the mixture was stirred at room temperature for 0.5 h, and TLC-follow-up was performed until the reaction was completed, tetrahydrofuran was removed by rotary evaporation, extraction was performed with ethyl acetate, washing was performed with saturated brine three times, the organic phase was collected and dried, and after rotary evaporation and concentration, alkyne-2Azo-Br-4Boc was obtained.

Using the same parameters as TBS-2Azo-Br-4Boc, TBS-2Azo-N was added ₃ -4Boc and alkyne-2Azo-Br-4Boc was subjected to the "CuAAC" click reaction to give TBS-4Azo-Br-8Boc (TBS-4 Azo-Br). ¹ H NMR (300 MHz, CDCl ₃ ) δ 8.01 (s, 3H), 7.95-7.68 (m, 16H), 7.24-7.04 (m, 5H), 6.96 (t, J = 7.1 Hz, 4H), 5.52-5.04 (m, 28H), 4.96-4.80 (m, 9H), 4.61-4.23 (m, 8H), 4.21-3.57 (m, 5H), 3.41 (s, 16H), 2.61 (q, J = 7.0, 5.6 Hz, 16H), 1.41 (d, J = 6.9 Hz, 73H), 0.89 (s, 9H), 0.09 (d, J = 7.5 Hz, 5H)。

TBS-4Azo-Br-8Boc (0.22 mmol) was dissolved in 10 mL of anhydrous THF, TBAF solution (2.27 mmol) was added thereto, the mixture was stirred at room temperature for 0.5 h, and TLC-follow-up was performed until the reaction was completed, tetrahydrofuran was removed by rotary evaporation, extraction was performed with ethyl acetate, washing was performed with saturated brine three times, the organic phase was collected and dried, and after rotary evaporation and concentration, the organic phase was dried to obtain alkyne-4Azo-Br-8Boc.

Example two: and (3) synthesizing a fluorene donor.

1. Synthesis of fluorene intermediate (1):

nitric acid (10 mL) and 1, 2-dichloroethane (80 mL) were stirred uniformly for 10 min, 2-bromofluorene (10.00 g,41.15 mmol) was added and stirring was continued for 1 h, after completion of the TLC monitoring reaction, the precipitate was precipitated with ice methanol, collected by suction filtration and dried to obtain 10.61 g of the target product.

2. Synthesis of fluorene intermediate (2):

ground KOH (10.00 g,178.50 mmol) was mixed well with DMSO (50 mL) for 10 min. Then intermediate (1) (5.00 g,17.30 mmol) was added and stirring continued for 20 min. 1-bromooctane (6.64 mL,37.80 mmol) was then added and stirred for 12 h. After TLC monitoring the reaction was completed, extraction was performed in dichloromethane, dried, concentrated by rotary evaporation, purified by column chromatography (petroleum ether: ethyl acetate = 64) and dried to obtain 8.16 g of the target product.

3. Synthesis of fluorene intermediate (3):

intermediate (2) (256.50 mg, 0.50 mmol) was dissolved in 10 mL of a mixed solvent of triethylamine and anhydrous toluene (1). Followed by the sequential addition of PdCl ₂ (pph ₃ ) ₂ (14.10 mg, 0.02 mmol), cuI (7.60 mg, 0.04 mmol), TBS protected alkynyl (168.00 mg, 1.20 mmol), 80 ^o Stirring for 12 h at the temperature of C. After the completion of the TLC monitoring reaction, extraction was performed in dichloromethane, dried, concentrated by rotary evaporation, purified by column chromatography (petroleum ether: ethyl acetate = 32) and dried to obtain 202.00 mg of the target product.

4. Synthesis of fluorene donor:

ammonium chloride (280.08 mg,5.24 mmol) was dissolved in water and iron powder (68.41 mg,1.22 mmol) was added at 105 ^o Activating for 1 h under C, and cooling to 75 deg.C ^o C. Intermediate (3) (200.00 mg,0.35 mmol) in absolute ethanol was then added and reacted for 12 h. After TLC monitoring reaction, a layer of diatomite is paved for suction filtration, rotary evaporation filtrate is extracted in dichloromethane again, drying, rotary evaporation concentration, column chromatography (petroleum ether: ethyl acetate = 32) purification and rotary drying are carried out, and 80.00 mg of target product is obtained.

The obtained fluorene monomer is characterized by nuclear magnetic resonance hydrogen spectrum, and the spectrogram is shown in figure 1b, which shows that the monomer purity is high.

TBS-4F-NH ₂ The following:

diazotization reaction: the fluorene donor TBS-4F-NH ₂ (0.40 mmol) was dissolved in 5 mL of ethyl acetate, and then an aqueous hydrochloric acid solution (3.6 eq), naNO was added dropwise ₂ Adding urea and NaNO after stirring the aqueous solution (1.2 eq) for 1 hour in an ice-water bath ₂ Reacting to obtain a diazo solution; adding NaN ₃ (51.74 mg, 0.80 mmol) of an aqueous solution was added dropwise to the above diazo solution; stirring for 1 h in an ice water bath, pouring the reaction solution into water after the reaction is finished, extracting with ethyl acetate, drying, performing rotary evaporation concentration, purifying by column chromatography (petroleum ether: dichloromethane = 8), and performing rotary drying to obtain TBS-4F-N ₃ 。

Example three: synthesis of 4F-4Azo

Firstly, carrying out nitridization on tetra-substituted fluorene by using sodium azide, and carrying out TBS removal on tetra-substituted azobenzene by using tetrahydrofuran solution of tetrabutylammonium fluoride. To a 10 mL Schlenk tube was added TBS-4F-N dissolved in 30 mL anhydrous oxygen-free THF ₃ (322.00 mg, 0.17 mmol) and alkyne-4Azo-Br-8Boc (162.50 mg, 0.06 mmol) were added, PMDETA (28.65 mg, 0.17 mmol) and CuBr (15.78 mg, 0.11 mmol) were added, the tube was sealed by removing oxygen by pumping argon three times, after reaction at room temperature for 48 hours, tetrahydrofuran was removed by rotary evaporation, extraction was performed using ethyl acetate and saturated saline, the organic phase was collected and dried, and purified by column chromatography (silica gel, eluent:V _PE /V _THF = 1/2). The product was concentrated by rotary evaporation and dried to give an orange-red solid (213.56 mg) with a yield of about 79.8%. ¹ H NMR (300 MHz, CDCl ₃ ) δ8.52-8.19 (m, 5H), 8.16-7.61 (m, 43H), 7.57-7.39 (m, 2H), 7.25-7.03 (m, 4H), 6.97 (d, J = 7.2 Hz, 6H), 5.53-4.97 (m, 32H), 4.95-4.74 (m, 7H), 4.61-4.34 (m, 8H), 3.40 (q, J= 5.9 Hz, 16H), 2.61 (qt, J = 6.3, 3.0 Hz, 16H), 1.81 (s, 14H), 1.42 (d, J = 9.5 Hz, 86H), 1.32-0.93 (m, 102H), 0.92-0.51 (m, 44H), 0.24 (s, 5H), 0.07 (s, 4H)。

EXAMPLE Synthesis of tetra 2Azo-4F-2Azo

To a 20 mL schlenk tube was added TBS-4F-N dissolved in 30 mL anhydrous oxygen-free THF ₃ (500.00 mg, 0.26 mmol) and alkyne-2Azo-Br-4Boc (459.92 mg, 0.31 mmol), then PMDETA (107.45 mg, 0.62 mmol) and CuBr (74.11 mg, 0.52 mmol) are respectively added into the mixture, argon is pumped into the mixture for three times to remove oxygen and seal the tube, the mixture reacts for 48 hours at room temperature and then is extracted, and the TBS-4F-2Azo-Br-4Boc is obtained after column chromatography purification and drying; TBS deprotection of TBS-4F-2Azo-Br-4Boc using TBAF gave alkyne-4F-2Azo-Br-4Boc, as above.

To a 20 mL schlenk tube were added alkyne-4F-2Azo-Br-4Boc (530.00 mg, 0.16 mmol) and TBS-2Azo-N dissolved in 10 mL anhydrous oxygen-free THF ₃ -4Boc (1070.00 mg, 0.69 mmol), followed by PMDETA (168.00 mg, 0.97 mmol) and CuBr (57.4 mg, 0.40 mmol), purging with argon three times to remove oxygen, reaction at room temperature for 48 h, removal of tetrahydrofuran by rotary evaporation, extraction with ethyl acetate, washing with saturated brine three times, collection of the organic phase for drying, purification by column chromatography (silica gel, eluent:V _PE /V _THF = 1/1). The product was rotary evaporated and concentrated and dried to give an orange red solid (533.30 mg) with a yield of about 68.5%. ¹ H NMR (300 MHz, CDCl ₃ ) δ8.42-8.15 (m, 6H), 8.11-7.63 (m, 43H), 7.24-7.04 (m, 5H), 6.98 (t, J = 8.4 Hz, 4H), 5.53-5.20 (m, 18H), 5.17 (d, J = 4.8 Hz, 12H), 4.99-4.73 (m, 11H), 4.55 (d, J = 10.7 Hz, 8H), 3.43 (dd, J = 11.2, 5.9 Hz, 16H), 2.62 (qd, J = 6.7, 5.9, 2.8 Hz, 16H), 1.73 (s, 15H), 1.51-1.33 (m, 72H), 1.17 (d, J = 53.2 Hz, 88H), 0.89 (s, 10H), 0.87-0.52 (m, 39H), 0.08 (d, J = 8.0 Hz, 7H)。

EXAMPLE five 4 Synthesis of (F-Azo) oligomer

alkyne-F-NH ₂ The following:

to a 25 mL schlenk tube was added TBS-Azo-N dissolved in 15 mL anhydrous oxygen-free THF ₃ -2Boc (969.00 mg, 1.14 mmol) and alkyne-F-NH ₂ (590.00 mg, 1.37 mmol), PMDETA (297.38 mg, 1.72 mmol) and CuBr (164.11 mg, 1.14 mmol) were added, the tube was sealed by purging with argon three times, and after reaction for 48 hours at room temperature, TBS- (Azo-F) -Br-2Boc was obtained by extraction, purification and drying by column chromatography, and TBS deprotection using TBAF or amino conversion to azide using sodium azide was carried out in the same manner as described above using this macromolecule as a repeating unit, 2 (F-Azo) was synthesized by stepwise growth, and 4 (F-Azo) was prepared using 2 (F-Azo).

TBS- (Azo-F) -Br-2Boc (0.22 mmol) was dissolved in 10 mL of anhydrous THF, TBAF solution (0.44 mmol) was added thereto, the mixture was stirred at room temperature for 0.5 h, followed by TLC monitoring until the reaction was completed, tetrahydrofuran was removed by rotary evaporation, extraction was performed with ethyl acetate, washing was performed with saturated brine three times, the organic phase was collected and dried, and after rotary evaporation concentration, alkyne- (Azo-F) -Br-2Boc was obtained.

TBS- (Azo-F) -Br-2Boc (1.01 mmol) and sodium azide (2.02 mmol) were dissolved in 5 mL DMF at 80 ^o The reaction was stirred for 12 h under C and the TLC plates were followed until the reaction was complete. After cooling to room temperature, extraction was performed with ethyl acetate, washed with saturated brine three times, the organic phase was collected, dried, rotary evaporated, concentrated and dried to obtain TBS- (Azo-F) -N ₃ -2Boc。

To a 25 mL schlenk tube was added TBS- (Azo-F) -N dissolved in 15 mL anhydrous oxygen-free THF ₃ -2Boc (1.14 mmol) and alkyne- (Azo-F) -Br-2Boc (1.37 mmol), then PMDETA (1.72 mmol) and CuBr (1.14 mmol) are added, then argon is pumped and filled three times to remove oxygen and seal the tube, reaction is carried out for 48 h at room temperature, extraction is carried out, column chromatography purification and drying are carried out, and TBS-2 (Azo-F) -Br-2Boc is prepared.

TBS-2 (Azo-F) -Br-2Boc (0.22 mmol) was dissolved in 10 mL anhydrous THF, TBAF solution (0.44 mmol) was added thereto, stirred at room temperature for 0.5 h, followed by TLC monitoring, tetrahydrofuran was removed by rotary evaporation, extraction was performed with ethyl acetate, washed with saturated brine three times, the organic phase was collected and dried, and rotary evaporation was concentrated and then dried to obtain alkyne-2 (Azo-F) -Br-2Boc.

TBS-2 (Azo-F) -Br-2Boc (1.01 mmol) and sodium azide (2.02 mmol) were dissolved in 5 mL DMF at 80 ^o The reaction was stirred for 12 h under C and the TLC plates were followed until the reaction was complete. Cooling to room temperature, extracting with ethyl acetate, washing with saturated salt water for three times, collecting organic phase, drying, rotary steaming, concentrating, and drying to obtain TBS-2 (Azo-F) -N ₃ -2Boc。

To a 50 mL schlenk tube was added TBS-2 (F-Azo) -N dissolved in 30 mL anhydrous oxygen-free THF ₃ -4Boc (304.10 mg, 0.12 mmol) and alkyne-2 (F-Azo) -NH ₂ -4Boc (383.10 mg, 0.16 mmol), followed by PMDETA (41.60 mg, 0.24 mmol) and CuBr (17.20 mg, 0.12 mmol), purging with argon three times to remove oxygen, reaction at room temperature for 48 h, removal of tetrahydrofuran by rotary evaporation, extraction with ethyl acetate, washing with saturated brine three times, collection of the organic phase for drying, purification by column chromatography (silica gel, eluent:V _PE /V _THF = 1/1). The product was concentrated by rotary evaporation and dried to give an orange-red solid (358.50 mg) with a yield of about 61.4%, abbreviated as 4 (F-Azo). ¹ H NMR (300 MHz, CDCl ₃ ) δ8.22 (d, J = 10.7 Hz, 8H), 7.87 (dt, J = 40.2, 31.5 Hz, 39H), 7.00 (d, J = 9.7 Hz, 9H), 5.56-5.17 (m, 25H), 5.01 (s, 9H), 4.87 (d, J = 24.9 Hz, 12H), 4.55 (s, 8H), 3.43 (s, 16H), 2.62 (s, 16H), 2.04 (dd, J = 17.4, 10.0 Hz, 20H), 1.54-1.36 (m, 105H), 1.34-0.94 (m, 154H), 0.96-0.51 (m, 76H), 0.08 (d, J = 6.7 Hz, 12H)。

The single molecular weight polymer precursors with different backbones containing fluorene and azobenzene obtained above were characterized by SEC efflux curve and MALDI-TOF MS chart, as shown in FIG. 2 and FIG. 3.

EXAMPLE six deprotection of Boc

4F-4Azo (260.00 mg) was dissolved in 1mL of trifluoroacetic acid, reacted at room temperature for 12 hours, then the trifluoroacetic acid was removed by rotary evaporation, and the concentrated solution was placed in saturated NaHCO ₃ Precipitating in water solution, and centrifugally drying to obtain light yellow solid 4F-4Azo-8NH ₂ 。2Azo-4F-2Azo-8NH ₂ And 4 (F-Azo) -8NH ₂ The method for removing Boc from the side chain is the same as that of 4F-4Azo-8NH ₂ 。

EXAMPLE seven

1.0 mL of 1.0 mg/mL 4F-4Azo-8NH was taken ₂ In a 5.0 mL ampoule, at 30 ℃ first 0.5 mL of Milli-Q water (dropping rate: 0.2 mL/h) was added to the solution, then 0.4 mL of 1.0 mol/L aqueous HCl solution (dropping rate: 0.2 mL/h) was added dropwise with stirring at 300 r/min, and after completion of the addition, the ampoule was sealed and allowed to stand at room temperature for 12 hours, and FIG. 4 is a TEM photograph after standing, and many nanofibers can be clearly observed. The height of these fine fibers was characterized by AFM, and was about 9.8 nm, as shown in FIG. 5. 4F-4Azo-8NH is calculated by theoretical simulation ₂ The length of the main chain in the most stable state is 11.7 nm, the actual measured value is close to the theoretical calculated value, and the 4F-4Azo-8NH is shown ₂ The solution assembled assembly is monolayer supported.

Example eight

The amount of aqueous HCl solution used in example seven was adjusted to 0.3mL, the remainder was unchanged, and the assembly is shown in FIG. 6.

The amount of Milli-Q water used in example seven was adjusted to 1mL, with the remainder unchanged, and the assembly is shown in FIG. 7.

The concentration of the aqueous HCl solution of example seven was adjusted to 2 mol/L, the remainder being unchanged, and the assembly is shown in FIG. 8.

The room temperature was adjusted to 2 hours in example seven, and the rest was unchanged, and the assembly was shown in FIG. 9.

The room temperature was adjusted to 24 hours for example seven, the rest was unchanged and the assembly is shown in figure 10.

Example nine

4F-4Azo-8NH from EXAMPLE VII ₂ Replacement by 2Azo-4F-2Azo-8NH ₂ Otherwise, the assembly is shown in FIG. 11.

4F-4Azo-8NH from EXAMPLE VII ₂ Replacement by 4 (F-Azo) -8NH ₂ Otherwise, the assembly is shown in FIG. 12.

Example ten

The above-mentioned assembled assembly solution was subjected to 365 nm ultraviolet light (intensity of 0.5 mW/cm) ² ) The irradiation is carried out, the whole process is carried out in a dark environment, and except ultraviolet light, no light with other wavelengths exists. And after the TEM sample is irradiated for a certain time, preparing the TEM sample in a dark environment, wrapping the TEM sample by using tinfoil paper after the sample preparation is finished, and storing the TEM sample in a dark place. The ultraviolet absorption spectrum and the fluorescence emission spectrum of the oligomer assembly solution with different sequences in the azobenzene photoisomerization process are studied by using 365 nm ultraviolet irradiation or heating mode, and the ultraviolet absorption and fluorescence emission changes and the photoresponse of the oligomer assembly are studied, as shown in fig. 13. It can be clearly observed that the intensity of the trans-absorption peak at 350 nm is obviously reduced and the fluorescence emission intensity is obviously increased after the ultraviolet light irradiation, because azobenzene is converted from a trans-configuration to a cis-configuration in the ultraviolet light irradiation process, the non-planar cis-configuration destroys the pi-pi plane accumulation of azobenzene, aggregates are dissociated, and the fluorescence intensity is enhanced. When the azobenzene is heated and recovered, the azobenzene is converted from a cis configuration to a trans configuration with better planarity, the intensity of a trans absorption peak at 350 nm is increased, and the fluorescence emission intensity is reduced. Meanwhile, the influence of the morphology of the azobenzene photoisomerization alignment polymer assembly can be observed, under the ultraviolet illumination, the stacking is hindered by the non-planar cis-configuration of azobenzene, and the assembly in the initial state of fiber and sphere is dissociated.

EXAMPLE eleven

Dropping the assembled assembly solution on clean tin foil paper, and rapidly draining the solvent in a vacuum oven at 30 deg.C to obtain a sample for SEM test, wherein the test results are shown in FIG. 14 (a-c), and are similar to those of TEM, 4F-4Azo-8NH ₂ For crimping wound long fibres, 2Azo-4F-2Azo-8NH ₂ 、4(F-Azo)-8NH ₂ Are packed spherical particles.

The above results fully indicate that fine adjustment on the polymer molecular level, such as sequence, can significantly affect the internal aggregation state of the aggregates and the morphology of the final assembly. The original driving force of individuals in nature comes from assembly, while the self-assembly of the amphiphilic polymer solution is an important class in the assembly, and various influencing factors are assembled under the interaction force to form various morphological assemblies, so that the amphiphilic polymer solution has potential application in the fields of biomedicine, chemistry, environment and the like. However, the research on the relationship between the sequence and the self-assembly behavior of the solution has been very little, and there are only few reports on the polymer containing azobenzene and fluorene in its main chain and its properties, and only studies on supramolecular chirality, photo-orientation, reduction-induced fluorescence, screening of single-walled carbon nanotubes and nanowires have been made. According to the invention, azobenzene stimulus-responsive groups are successfully introduced into the main chain of the polymer to construct a novel amphiphilic polymer containing different functional groups, so that the research on fluorene and azobenzene contained in the main chain is enriched and expanded, and the method has guiding significance for the development of the fields of azobenzene materials and fluorene materials. Meanwhile, the internal accumulation and the external appearance of the nano particles are accurately controlled from top to bottom for the first time in a solution self-assembly mode, so that the fluorene-azobenzene amphiphilic oligomer nano fiber with single molecular weight is obtained, and the 1D/2D nano material with special functions is constructed.

Claims

1. A single molecular weight fluorene-azobenzene amphiphilic oligomer precursor has the following structure:

。

2. a single molecular weight fluorene-azobenzene amphiphilic oligomer, which is obtained by removing Boc protection from the single molecular weight fluorene-azobenzene amphiphilic oligomer of claim 1 and then carrying out quaternization.

3. The amphiphilic fluorene-azobenzene oligomer of claim 2, wherein the Boc protection is removed with trifluoroacetic acid; quaternization is carried out with hydrochloric acid.

4. The method for preparing the fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight as claimed in claim 1, is one of the following preparation methods:

method one, using TBS-4F-N ₃ And alkyne-4Azo-Br-8Boc as raw materials, carrying out copper-catalyzed azide-alkyne cycloaddition reaction to obtain a fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight;

method II, TBS-4F-N ₃ Carrying out copper-catalyzed azide-alkyne cycloaddition reaction by taking alkyne-2Azo-Br-4Boc as a raw material to obtain alkyne-4F-2Azo-Br-4Boc; then the alkyne-4F-2Azo-Br-4Boc and TBS-2Azo-N are added ₃ 4Boc is subjected to copper-catalyzed azide-alkyne cycloaddition reaction to obtain a fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight;

third, the alkyne-F-NH is used ₂ And TBS-Azo-N ₃ Taking-2 Boc as a raw material, carrying out copper-catalyzed azide-alkyne cycloaddition reaction, and then respectively carrying out TBS deprotection or converting amino into azide by using sodium azide to obtain TBS-2 (F-Azo) -N ₃ -4Boc or alkyne-2 (F-Azo) -NH ₂ -4Boc; then adding TBS-2 (F-Azo) -N ₃ -4Boc and alkyne-2 (F-Azo) -NH ₂ 4Boc is subjected to copper-catalyzed azide-alkyne cycloaddition reaction to obtain the fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight.

5. The preparation method of the fluorene-azobenzene amphiphilic oligomer precursor with single molecular weight according to claim 4, wherein the catalyst for the copper-catalyzed azide-alkyne cycloaddition reaction is cuprous bromide, and the ligand is pentamethyldiethylenetriamine; the reaction is carried out for 40 to 50 hours at room temperature.

6. The self-assembly method of the solution of the single molecular weight fluorene-azobenzene amphiphilic oligomer precursor as claimed in claim 1, wherein the method comprises the steps of deprotecting the single molecular weight fluorene-azobenzene amphiphilic oligomer precursor, dissolving the deprotected single molecular weight fluorene-azobenzene amphiphilic oligomer precursor in a solvent, adding water and hydrochloric acid, and standing to realize the self-assembly of the solution of the single molecular weight fluorene-azobenzene amphiphilic oligomer precursor.

7. A preparation method of a single molecular weight fluorene-azobenzene amphiphilic oligomer self-assembly fiber is characterized by comprising the following steps of dissolving a single molecular weight fluorene-azobenzene amphiphilic oligomer precursor 4F-4Azo in a solvent after deprotection, then adding water and hydrochloric acid, and standing to obtain the single molecular weight fluorene-azobenzene amphiphilic oligomer self-assembly fiber.

8. The process according to claim 6 or 7, characterized in that the solvent is tetrahydrofuran; the concentration of hydrochloric acid is 1mol/L; the volume ratio of tetrahydrofuran, water and hydrochloric acid is 1:0.5: 0.3-0.4; standing for 5 minutes to 24 hours at room temperature.

9. The self-assembled fiber of the single molecular weight fluorene-azobenzene amphiphilic oligomer prepared by the method of claim 7.

10. Use of the single molecular weight fluorene-azobenzene amphiphilic oligomer precursor according to claim 1 or the single molecular weight fluorene-azobenzene amphiphilic oligomer according to claim 2 in the preparation of nanofibers.