Bifuran polyamide with high quantum yield and capable of emitting yellow-green wavelength light as well as preparation method and application of bifuran polyamide

Abstract

The invention belongs to the technical field of fluorescent polymer materials, and particularly discloses bifuran polyamide with high quantum yield and capable of emitting yellow-green wavelength light as well as a preparation method and application of the bifuran polyamide. The method comprises the following steps: dissolving a bifuranoyl chloride monomer in an organic solvent to obtain an organic phase; adding an alkaline aqueous solution into the organic phase to form a phase interface, then adding a diamine monomer, and stirring to carry out an interfacial polymerization reaction; and after the reaction is finished, filtering, precipitating, washing and drying to obtain the bifuran polyamide. The bifuran polyamide is prepared by regulating and controlling the main chain structure and chain rigidity and flexibility of the polymer through a diamine monomer with a specific molecular structure, the emission wavelength of the amorphous bifuran polyamide can reach 540-552 nm under exciting light of 480 nm, red shift is performed to 565-568 nm after crystallization, long-wavelength yellow-green light emission, high-quantum-yield light emission and good biocompatibility are achieved, and the bifuran polyamide can be applied to the field of organic light emitting devices, such as organic light emitting devices, organic light emitting devices, organic light emitting devices, organic light emitting devices, organic light emitting devices, organic light emitting devices, organic light emitting devices and the like. The application of the bio-based polyamide in the field of biological imaging is expanded.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent polymer materials technology, and more specifically, relates to a bifuran polyamide with high quantum yield and emitting yellow-green wavelength light, its preparation method and application. Background Technology

[0002] Fluorescent materials have broad application prospects in fields such as chemical sensing, bioimaging, and optoelectronic devices. Traditional fluorescent materials are mostly based on conjugated systems or heavy metal complexes, which suffer from problems such as complex synthesis, poor biocompatibility, and potential high toxicity. In recent years, non-conjugated cluster-triggered emission (CTE) materials have attracted widespread attention due to their unique luminescence mechanism and good biocompatibility. These materials mainly achieve fluorescence emission by forming luminescent clusters through spatial conjugation of lone pairs of electrons from heteroatoms (such as N, O, and P).

[0003] Polyamides, as an important class of engineering plastics, possess excellent mechanical properties and thermal stability. However, the fluorescence emission of traditional aromatic polyamides (such as PA6T) mainly originates from the aggregation effect of benzene rings and amide groups, resulting in a relatively short emission wavelength (approximately 509 nm) and limited quantum yield. How to achieve long-wavelength emission (especially in the yellow-green light band) and high quantum yield in polyamide materials through molecular structure design, and to expand their applications in the biomedical field, is currently a hot research topic.

[0004] Furan dicarboxylic acid (FDCA) and its derivatives, as renewable bio-based platform compounds, offer new insights for designing novel polyamide materials. Furthermore, the furan ring possesses weaker aromatic stabilization energy and electron-donating effects compared to the benzene ring, potentially allowing for the modulation of the material's fluorescence properties. However, current research on the clustering luminescence properties of bifuran polyamides and their applications in cell imaging remains lacking. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a bifuran polyamide with high quantum yield and yellow-green wavelength emission, along with its preparation method and applications. The bifuran polyamide is prepared through interfacial polymerization of a bifuranyl chloride monomer with a diamine monomer of a specific structure. By utilizing the weak aromatic stabilization energy of the furan ring, the electron-donating effect of oxygen atoms, and the extended conjugated system of bifuran, the HOMO-LUMO band gap is narrowed, achieving long-wavelength yellow-green emission and high quantum yield emission. This overcomes the shortcomings of existing polyamide fluorescent materials, such as short emission wavelength, low quantum yield, and insufficient research on biocompatibility applications.

[0006] To achieve the above objectives, in one aspect of the present invention, a method for preparing bifuran polyamide with high quantum yield and emitting yellow-green wavelength light is provided, comprising: dissolving bifuranyl chloride monomer in an organic solvent to obtain an organic phase; adding an alkaline aqueous solution to the organic phase to form a phase interface, then adding a diamine monomer, stirring to carry out an interfacial polymerization reaction; after the reaction is completed, filtering the precipitate, washing, and drying to obtain bifuran polyamide; wherein the diamine monomer is an aliphatic diamine monomer or an alicyclic diamine monomer.

[0007] Preferably, the aliphatic diamine monomer is 1,6-hexanediamine, 1,8-octanediamine, or 1,10-decanediamine, and the alicyclic diamine is piperazine or 4,4'-bipiperidine.

[0008] Preferably, the alkaline aqueous solution is a KOH aqueous solution; the alkaline aqueous solution has a concentration of 0.5-2 mol / L.

[0009] Preferably, the molar ratio of the bifuranyl chloride monomer to the diamine monomer is 1:1.

[0010] Preferably, the stirring time for the interfacial polymerization reaction is 20 to 30 hours.

[0011] Preferably, the bifuranyl chloride monomer is prepared by refluxing bifuranic acid with excess thionyl chloride under the action of a catalyst, followed by post-treatment to obtain the bifuranyl chloride monomer.

[0012] Preferably, the catalyst is N,N-dimethylformamide, and the amount of N,N-dimethylformamide added is 0.5%-0.8% of the mass of the bifurandicarboxylic acid; the reflux reaction time is 3-8 hours.

[0013] In another aspect of the present invention, a bifuran polyamide prepared according to any one of the above-described preparation methods is provided, wherein when the diamine monomer is an aliphatic diamine monomer, the prepared bifuran polyamide is an amorphous polymer, and the maximum emission wavelength under 480 nm excitation light is in the range of 540 to 568 nm; when the diamine monomer is an alicyclic diamine monomer, the prepared bifuran polyamide is a crystalline polymer, and the maximum emission wavelength under 480 nm excitation light is in the range of 565 to 568 nm.

[0014] Preferably, the bifuran polyamide prepared when the diamine monomer is 1,10-decanediamine has a good effect on Fe. 3+ It exhibits a fluorescence quenching response.

[0015] In another aspect of the invention, the use of bifuran polyamide prepared according to any one of the above methods in the preparation of bioimaging fluorescent probes is provided.

[0016] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: 1. This invention is the first to synthesize a series of bifuran polyamides by reacting bifuranyl chloride with a diamine monomer of a specific structure via interfacial polymerization. By introducing the bifuran structure into the polyamide backbone and utilizing the weak aromatic stabilization energy of the furan ring, the electron-donating effect of the oxygen atom, and the extended conjugated system of bifuran, the HOMO-LUMO band gap is effectively narrowed, achieving a systematic redshift of the emission wavelength and successfully obtaining yellow-green fluorescent materials with emission wavelengths in the range of 540–568 nm. Furthermore, the polymer with a rigid-flexible balanced molecular structure obtained by introducing a diamine monomer of a specific structure exhibits excellent quantum yield. At the same time, the bifuran polyamides prepared by this invention have low cytotoxicity.

[0017] 2. In this invention, the preferred aliphatic diamine monomers are 1,6-hexanediamine, 1,8-octanediamine, or 1,10-decanediamine, and the alicyclic diamines are piperazine or 4,4'-bipiperidine. When the polyamide is amorphous, the maximum emission wavelength is in the range of 540-568 nm under 480 nm excitation light. When the polyamide is crystalline, the maximum emission wavelength is in the range of 565-568 nm under 480 nm excitation light, thus achieving yellow-green luminescence.

[0018] 3. The bifuran polyamide prepared by the present invention preferably using 1,10-decanediamine as the diamine monomer is soluble in hexafluoroisopropanol and has an absolute quantum yield of up to 70.5%, setting a new record for cluster luminescent materials; the quantum yield of the crystalline polymer in the solid state is also much higher than that of similar materials.

[0019] 4. The present invention preferably uses 1,10-decanediamine as the diamine monomer to prepare the bifuran polyamide, which is effective against Fe. 3+ It exhibits a fluorescence quenching response, which enables ion detection; at the same time, it elucidates the mechanism by which crystallization improves luminescence efficiency by reducing quenching defects and suppressing non-radiative vibrations.

[0020] 5. The bifuran polyamide prepared by this invention has been successfully applied to live cell cytoplasmic staining due to its bright yellow-green fluorescence and excellent biocompatibility, demonstrating its great application potential in the field of biomedical visualization and expanding the application boundaries of bio-based polyamides. Attached Figure Description

[0021] Figure 1 These are the XRD curves of the polymers prepared according to embodiments of the present invention; wherein, Figure 1(a) shows the XRD curves of monofuran polyamides PAF6, PAF8, and PAF10; (b) shows the XRD curve of monofuran polyimide PAFPE; (c) shows the XRD curve of monofuran polyimide PAFBPE; (d) shows the XRD curves of difuran polyamides PABF6, PABF8, and PABF10; (e) shows the XRD curve of difuran polyimide PABFPE; and (f) shows the XRD curve of difuran polyimide PABFBPE.

[0022] Figure 2 This is a comparison of the emission wavelengths of bifuran polyamide films with different structures in Examples 2-6 and Comparative Examples 2-6 under ultraviolet light.

[0023] Figure 3 The graphs (a) and (b) show the quantum yield of polyamides with different structures in HFIP in Examples 2-5, Comparative Examples 2-5, and Comparative Examples 7-8 of this invention as a function of concentration.

[0024] Figure 4 The fluorescence spectrum of the effect of different metal ions on the luminescence performance of PABF10 solution in Example 4 of the present invention is shown. Figure 4 (a) shows the fluorescence emission spectra of systems containing different metal ions, and the inset shows the emission spectra of solutions containing the corresponding ions. (b) shows the fluorescence emission spectra of Fe at different concentrations. 3+ The fluorescence emission spectrum of the system exists, (c) is Fe 3+ The detection curve (d) is the UV-Vis absorption spectrum of the system with different metal ions.

[0025] Figure 5 This is the PL spectrum of 0.001 mg / ml PABF10 in DMSO solution according to the present invention. Figure 5 (a) represents the heating state and (b) represents the cooling state, where λex = 330 nm.

[0026] Figure 6 This is a cytotoxicity diagram (MTT assay) of PABFPE on 4T1, HeLa, and B16-F10 cells in Example 5 of the present invention.

[0027] Figure 7 This is a confocal laser scanning microscope (CLSM) image of 4T1 cell cytoplasm staining by PABFPE in Example 5 of this invention, wherein... Figure 5 (ac) and (df) are confocal laser scanning microscope images stained using the same method. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] To achieve the above objectives, the technical solution of the present invention is as follows: First, this invention provides a method for preparing bifuran polyamide with high quantum yield and emitting yellow-green long-wavelength light, comprising the following steps: (1) Interfacial polymerization reaction: The bifuranyl chloride monomer is dissolved in an organic solvent to obtain an organic phase; an alkaline aqueous solution is slowly added to the obtained organic phase solution to form a phase interface; then the diamine monomer dissolved in the alkaline aqueous solution is slowly added along the wall of the container, and the resulting mixture is vigorously stirred to carry out the interfacial polymerization reaction.

[0030] (2) Post-processing: After the reaction is completed, the precipitate in the reaction system is filtered, and the residue is washed and dried in sequence to obtain bifuran polyamide.

[0031] Preferably, the aliphatic diamine monomer is 1,6-hexanediamine, 1,8-octanediamine, or 1,10-decanediamine; the alicyclic diamine is piperazine or 4,4'-bipiperidine.

[0032] Preferably, the concentration of the bifuranyl chloride monomer in the resulting organic phase solution is 100 mg / ml, and the organic solvent is anhydrous, inert, and capable of dissolving the monomer but not reacting with the acyl chloride group, such as dichloromethane or chloroform.

[0033] Preferably, the alkaline aqueous solution in step (1) is a KOH aqueous solution with a concentration of 0.5-2 mol / L, more preferably 1 mol / L, to neutralize reaction byproducts and catalyze the polymerization reaction. Preferably, the molar ratio of bifuranyl chloride monomer to diamine monomer is 1:1.

[0034] Preferably, the interfacial polymerization reaction is carried out with stirring for 20–30 hours at room temperature. Preferably, the washing process specifically includes washing with deionized water and an organic solvent, wherein the organic solvent is methanol or dichloromethane.

[0035] Preferably, the bifuranyl chloride monomer in this invention is highly reactive and easily deactivated, and is prepared by the following method: Under reflux condensation conditions, difurandicarboxylic acid is added to a reaction vessel, placed in an ice-water bath, and excess thionyl chloride and catalyst are added. The mixture is heated to oil bath temperature under stirring and refluxed for 3-8 hours. After the reaction, excess thionyl chloride is removed by rotary evaporation to obtain difuranyl chloride monomer. The molar ratio of difurandicarboxylic acid to thionyl chloride is 1:(4~10) (acid:thionyl chloride), or even higher. The catalyst is DMF, used in an amount of 0.5%-0.8% of the mass of difurandicarboxylic acid.

[0036] Secondly, the present invention provides a bifuran polyamide obtained according to the above preparation method.

[0037] The bifuran polyamide emits green to yellowish-green light in the range of 540–568 nm under 480 nm excitation light. In particular, when the polymer is a crystalline polymer (such as that synthesized from piperazine or 4,4'-bipiperidine), its maximum emission wavelength is further red-shifted to 565–568 nm, emitting bright yellowish-green light.

[0038] Bifuran polyamides prepared with 1,10-decanediamine as the diamine monomer exhibit a quantum yield of up to 70.5% in hexafluoroisopropanol (HFIP) solvent, a value superior to other cluster luminescent materials currently studied. In the solid state, crystalline bifuran polyamides achieve a quantum yield of 3.99%, significantly higher than that of amorphous films.

[0039] The bifuran polyamide prepared when the diamine monomer is 1,10-decanediamine has a good effect on Fe. 3+ It exhibits a fluorescence quenching response.

[0040] Finally, this invention provides the application of the above-mentioned bifuran polyamide in the preparation of bioimaging fluorescent probes.

[0041] The following are specific examples: Example 1: Synthesis of bifuranyl chloride monomer (BFDCl): 300 mg of bifurandicarboxylic acid was added to a 500 ml round-bottom flask equipped with a magnetic stirrer. The flask was placed in an ice-water bath, and excess thionyl chloride was added while stirring. 0.5% (by weight of) DMF catalyst (1.5 mg) of bifurandicarboxylic acid was added using a pipette. The ice-water bath was removed, and the mixture was refluxed in an oil bath for 5 h. After the reaction was complete, excess thionyl chloride was removed by rotary evaporation to obtain 325 mg of bifuranyl chloride monomer (BFDCl), with a yield of 93.0%.

[0042] Example 2: Synthesis of bifuran polyamide PABF6 (interfacial polymerization): In a 50 ml round-bottom flask equipped with a magnetic flask, 300 mg of bifuranyl chloride (1.16 mmol) prepared in Example 2 was dissolved in 3 ml of dichloromethane. A 1 M aqueous solution of KOH (0.9 ml) was slowly added along the flask wall to the resulting solution to induce phase separation. 134.8 mg (1.16 mmol) of 1,6-hexanediamine was dissolved in 1 mol / L KOH (2.7 ml) and then slowly added along the wall to the above system. The resulting mixture was vigorously stirred for 24 hours to initiate the polymerization reaction. After the reaction was complete, the precipitate was filtered off, and the residue was washed successively with water, methanol, and dichloromethane, and dried to obtain poly(hexamethylene bifuranamide), denoted as PABF6. XRD characterization showed that the polymer was amorphous.

[0043] Example 3: Synthesis of bifuran polyamide PABF8: The diamine monomer was replaced with 1,8-octanediamine (1.16 mmol), and the remaining procedures were the same as in Example 1 to synthesize poly(octamethylene bifuranamide), denoted as PABF8. XRD characterization showed that the polymer was amorphous.

[0044] Example 4: Synthesis of bifuran polyamide PABF10: The diamine monomer was replaced with 1,10-decanediamine (1.16 mmol), and the remaining procedures were the same as in Example 2 to synthesize poly(decamethylene bifuranamide), denoted as PABF10. XRD characterization showed that the polymer was amorphous.

[0045] Example 5: Synthesis of crystalline bifuran polyamide PABFPE: The diamine monomer was replaced with piperazine (1.16 mmol), and the remaining procedures were the same as in Example 2, to synthesize poly(piperazine-1,4-diyl-2,2'-bifuran-5,5'-dicarbonyl), denoted as PABFPE. XRD characterization showed that the polymer was crystalline.

[0046] Example 6: Synthesis of crystalline bifuran polyamide PABFBPE: The diamine monomer was replaced with 4,4'-bipiperidine (1.16 mmol), and the remaining procedures were the same as in Example 2, to synthesize poly(4,4'-bipiperidine-1,1'-diyl-2,2'-bifuran-5,5'-dicarbonyl), denoted as PABFBPE. This polymer is crystalline. XRD characterization confirmed that the polymer is crystalline.

[0047] Comparative Example 1: Synthesis of the monofuranyl chloride monomer FDCl: 300 mg of difurandicarboxylic acid was added to a 500 ml flask equipped with a magnetic stirrer. The flask was placed in an ice-water bath, and excess thionyl chloride was added while stirring. 0.5% (by weight of difurandicarboxylic acid) of DMF catalyst (1.5 mg) was added using a pipette. The mixture was refluxed in an oil bath for 5 h. After the reaction was complete, excess thionyl chloride was removed by rotary evaporation to obtain monofuranyl chloride (FDCl) (346 mg, yield 93.4%).

[0048] Comparative Example 2: Synthesis of monofuran polyamide PAF6 (interfacial polymerization): In a 50 ml round-bottom flask equipped with a magnetic flask, 300 mg of monofuranyl chloride (1.16 mmol) prepared in Comparative Example 1 was dissolved in 3 ml of dichloromethane. A 1 M aqueous solution of KOH (0.9 ml) was slowly added along the flask wall to the resulting solution to induce phase separation. 134.8 mg (1.16 mmol) of 1,6-hexanediamine was dissolved in 1 mol / L KOH (2.7 ml) and then slowly added along the wall to the above system. The resulting mixture was stirred vigorously for 24 hours. After the reaction was complete, the precipitate was filtered off, and the residue was washed successively with water, methanol, and dichloromethane, and dried to obtain poly(hexamethylene furanamide), denoted as PAF6. XRD characterization showed that the polymer was amorphous.

[0049] Comparative Example 3: Synthesis of monofuran polyamide PAF8: The diamine monomer was replaced with 1,8-octanediamine (1.16 mmol), and the remaining procedures were the same as in Comparative Example 2, to synthesize poly(octamethylene furanamide), denoted as PAF8. XRD characterization showed that the polymer was amorphous.

[0050] Comparative Example 4: Synthesis of monofuran polyamide PAF10: The diamine monomer was replaced with 1,10-decanediamine (1.16 mmol), and the remaining procedures were the same as in Comparative Example 2, to synthesize poly(decaethylenedifuranamide), denoted as PAF10. XRD characterization showed that the polymer was amorphous.

[0051] Comparative Example 5: Synthesis of crystalline bifuran polyamide PAFPE: The diamine monomer was replaced with piperazine (1.16 mmol), and the remaining procedures were the same as in Comparative Example 2, to synthesize poly(piperazine-1,4-diyl-2,5-furandicarbonyl), denoted as PAFPE. XRD characterization showed that the polymer was crystalline.

[0052] Comparative Example 6: Synthesis of crystalline bifuran polyamide PAFBPE: The diamine monomer was replaced with 4,4'-bipiperidine (1.16 mmol), and the remaining procedures were the same as in Comparative Example 2, to synthesize poly(4,4'-bipiperidine-1,1'-diyl-2,2'-furan-5,5'-dicarbonyl), denoted as PAFBPE. XRD characterization showed that the polymer was crystalline.

[0053] Comparative Example 7: Synthesis of bifuran polyamide PABF12: The diamine monomer was replaced with 1,12-dodecyldiamine (1.16 mmol), and the rest of the operation was the same as in Comparative Example 2, to synthesize poly(dodecylmethylenefuranamide), denoted as PABF12.

[0054] Product characterization: XRD test; XRD tests were performed on the polymers prepared in Examples 2-6 and Comparative Examples 2-6, and the results are as follows: Figure 1 As shown, the XRD curves of PAF6, PAF8, PAF10, PABF6, PABF8, and PABF10 show only a broad peak at 2θ≈22°, indicating that they are amorphous polymers. In contrast, PAFPE, PAFBPE, PABFPE, and PABFBPE all exhibit sharp crystallization peaks, with crystallinity as high as 68.8%, 38.2%, 78.6%, and 55.0%, respectively. The polyamides obtained by introducing alicyclic monomers suppress intramolecular hydrogen bonds, which are detrimental to crystallization, and promote the formation of intermolecular hydrogen bonds. Simultaneously, their rigidity forces the molecular chains to extend, which is conducive to orderly stacking, thus leading to crystallization. Furthermore, bifurans have better geometric symmetry, structural elongation, and π-π stacking ability than monofurans, resulting in a more regular and compact arrangement of molecular chains in the crystal lattice, thereby improving the degree of crystallization (i.e., crystallinity).

[0055] Performance Test Example 1: Photophysical Performance Test Fluorescence spectroscopy was performed on the bifuran polyamide films prepared in Examples 2-6 and the monofuran polyamide films prepared in Comparative Examples 2-6. Figure 2As shown, under 480 nm excitation light, the optimal emission wavelengths of polyamide films with different structures are: PABF6, PABF8, and PABF10 are 540 nm, 547 nm, and 552 nm, respectively, exhibiting green to yellowish-green light; the optimal emission wavelengths of crystalline PABFPE and PABFBPE are 565 nm and 568 nm, respectively, showing a significant redshift compared to the amorphous samples, emitting bright yellowish-green light; while the optimal emission wavelengths of PAF6, PAF8, and PAF10 are 521 nm, 528 nm, and 534 nm, respectively, exhibiting green light; the optimal emission wavelengths of crystalline PAFPE and PAFBPE are 558 nm and 561 nm, respectively, exhibiting yellowish-green light. The polyamides prepared in this invention introduce furan / bifuran groups, which, due to their low aromatic stabilization energy and the electron-donating effect of oxygen atoms, narrow the band gap, leading to a redshift; increasing the alkyl chain length (i.e., selecting diamine monomers with specific structures) improves the chain segment flexibility, further redshifting the polyamides by stabilizing the excited state. Crystalline polymers containing piperazine structures (PAFPE, PABFBPE, etc.) exhibit the most significant redshift (558-568 nm), which stems from the synergistic effect of intramolecular charge transfer and ordered crystalline stacking, minimizing the excited-state energy. Therefore, this invention, for the first time, synthesizes a series of bifuran polyamides by reacting bifuranyl chloride with a diamine monomer of a specific structure via interfacial polymerization, achieving a systematic redshift of the emission wavelength and successfully obtaining yellow-green fluorescent materials with emission wavelengths in the range of 540–568 nm.

[0056] Performance Test Example 2: Quantum Yield Test Different polyamide structures from Examples 2-5, Comparative Examples 2-5, and Comparative Examples 7-8 were dissolved in hexafluoroisopropanol (HFIP) to prepare solutions with different concentration gradients, and their absolute quantum yields (QY) were tested. Figure 3(a) shows that the overall quantum yield (QY) of polyamides with different structures first increases and then decreases with increasing concentration. Higher concentration promotes the formation of interchain luminescent clusters and enhances radiative transitions. However, excessively high concentrations increase non-radiative energy transfer, leading to the formation of dense aggregates and quenching. When the maximum quantum yield is reached, the concentrations of monofuran PAF6 / PAF8 / PAF10 / PAFPE are 8.5, 3.8, 1.7, and 2.4 μM, respectively, and the concentrations of bifuran PABF6 / PABF8 / PABF10 / PABF12 / PABFPE are 1.7, 0.3, 0.2, 0.1, and 2.4 μM, respectively. Furthermore, the PABF10 prepared in Example 4 can achieve a maximum QY of 70.5% at the optimal concentration (0.2 μM), setting a new record for cluster luminescent materials. The quantum yield of the solid-state crystalline polymer is also much higher than that of similar materials. This indicates that molecular structure significantly affects QY and the optimal concentration: from monofuran to bifuran, the density of luminescent groups and the contribution of heteroatoms increase, intrachain clusters are more easily formed, the optimal concentration decreases, and high-concentration quenching occurs earlier. In bifurans, medium-length intrachain clusters are abundant and quenching is minimal, exhibiting an inverted U-shaped trend, indicating that the rigid-flexible balance plays a decisive role in fluorescence performance. Figure 3 As shown in (b), the QY trend of the thin film is consistent with that of the solution, but the absolute value is significantly reduced. In solution, the chain segments have greater freedom of movement, allowing for the adaptive formation of the optimal luminescent configuration; in the solid state, the conformation is frozen, resulting in higher efficiency in the transfer of nonradiative energy to the quenching center. The QY of PABFPE and PAFPE films reaches 3.99% and 3.58%, respectively, far exceeding others. This is attributed to their high crystallinity locking the luminescent configuration, suppressing nonradiative transitions, and enhancing spatial n-π* interactions. Therefore, the polyamide of this invention significantly enhances the quantum yield of the material by eliminating excessive intramolecular hydrogen bond binding, regulating the aggregated structure, and improving crystallinity and chain regularity.

[0057] Performance Test Example 4: The Influence of Metal Ions on the Luminescence Properties of Polyamide Clusters To verify that amide clusters depend on dipole-dipole interactions, the dissociation effect of metal ions was investigated. Taking PABF10 in Example 4 as an example, the effect of metal ions on the luminescence performance of PABF10 was tested. Figure 4 The fluorescence spectra of the effect of different metal ions on the luminescence properties of PABF10 solution in Example 4 of this invention are shown below: Figure 5 In (a), 50 μM of different metal ions were added to PABF10 solution, and Fe³⁺ was found to increase. + It exhibits a significant and highly selective quenching effect on fluorescence, an effect not found in other ions; further, the study explored the role of PABF10 as a Fe³⁺ quencher. + The performance of fluorescent probes, such as Figure 5 The middle (bc) shows the relationship with Fe³ +As the concentration (10-200 μM) increased, the fluorescence intensity gradually decreased, and the quenching data conformed to the Stern-Volmer equation (Ksv=0.08973, R²=0.987); and as... Figure 5 The ultraviolet absorption spectrum of (d) shows that only Fe³ + The appearance of a new absorption band at 400-600 nm indicates that Fe³ + It can effectively coordinate to the carbonyl group and dissociate the amide cluster, leading to fluorescence quenching. Therefore, the bifuran polyamide prepared when the diamine monomer is 1,10-decanediamine has a strong effect on Fe... 3+ It exhibits a fluorescence quenching response.

[0058] Performance Test Example 5: The Effect of Temperature on the Luminescence Properties of Polyamide Clusters Taking PABF10 in Example 4 as an example, the effect of temperature on the luminescence performance of PABF10 was tested. Figure 5 The temperature-dependent photoluminescence spectrum of the PABF10 solution in Example 4 is shown. Figure 5 The excitation and emission spectra of 0.001 mg / ml PABF10 in DMSO solution (λex = 330 nm) are shown below. Figure 5 As shown in (a), as the temperature rises from 10℃ to 80℃, the PL intensity gradually decreases, and the emission peak redshifts from 364 nm to 368 nm; from Figure 5 As shown in (b), the spectrum is reversibly recovered after cooling, and different emission wavelengths (470-515 nm) correspond to different luminescent centers. The results indicate that the cluster structure in dilute solutions is less affected by polymer conformation, demonstrating its potential for application in biological cells.

[0059] Performance Test Example 6: Cytotoxicity Test (MTT Method): Using PABFPE prepared in Example 5 as the test subject, 4T1 cells, HeLa cells, and B16-F10 cells were selected to evaluate its cytotoxicity. Cells were seeded in 96-well plates, and after adhesion, different concentrations of PABFPE solution (0.2–1.4 mg / mL) were added and incubated for 24 hours. MTT solution was then added, and after 4 hours of culture, lysis buffer was added. Absorbance was measured using a microplate reader, and cell viability was calculated. The results showed that the survival rate of the three cancer cell types was higher than 90% at all tested concentrations. Particularly in the concentration range of 0.2–1.2 mg / mL, PABFPE even showed a proliferative effect on 4T1 cells and HeLa cells.

[0060] The cytotoxicity experiments conducted using PABFPE (containing a six-membered ring structure) as an example have confirmed its excellent biocompatibility. Since PABF6, PABF8, and PABF10 share the same bifuranamide backbone and amide cluster luminescence mechanism, and PABFBPE shares the same six-membered ring rigid structural unit, these compounds exhibit high homology with PABFPE in molecular composition. Therefore, this series of bifuran polyamide compounds (including PABF6, PABF8, PABF10, and PABFBPE) all exhibit low cytotoxicity and are suitable for use in the biomedical field.

[0061] Performance Test Example 7: Cell Imaging Experiment Using PABFPE prepared in Example 5 as the test subject, 4T1 cells were seeded in confocal culture dishes and cultured overnight. After washing with PBS, a PABFPE solution with a concentration of 0.8 mg / mL was added, and the cells were incubated for 24 hours. After washing with PBS again, the cells were observed under a laser confocal microscope at an excitation wavelength of 488 nm. The results showed that the cytoplasm of 4T1 cells exhibited strong yellow-green fluorescence, indicating that PABFPE was efficiently taken up by the cells and uniformly stained, making it an excellent bioimaging probe.

[0062] This invention confirms through confocal laser scanning microscopy that PABFPE can effectively stain the cytoplasm of 4T1 cells, demonstrating excellent cell imaging capabilities. Given that PABF6, PABF8, PABF10, and PABFBPE share the same bifuranamide luminescent backbone as PABFPE and all utilize the same cluster luminescence mechanism for fluorescence imaging, their molecular structural differences lie only in the length of the alkyl chain or the introduction of alicyclic units, without altering their fundamental ability to penetrate the cell membrane and generate stable fluorescence signals in the cytoplasm. Therefore, PABF6, PABF8, PABF10, and PABFBPE are also suitable for cell imaging experiments.

[0063] In summary, the bifuran polyamide prepared by this invention has excellent biocompatibility and bright yellow-green fluorescence properties, enabling its successful application in live cell cytoplasm staining. This demonstrates its great application potential in the field of biomedical visualization and expands the application boundaries of bio-based polyamides.

[0064] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations. The above-described embodiments are merely preferred embodiments given to fully illustrate this invention, and their scope of protection is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on this invention are all within the scope of protection of this invention.

Claims

1. A method for preparing a bifuran polyamide with high quantum yield and emitting yellow-green wavelength light, characterized in that, include: The bifuranyl chloride monomer was dissolved in an organic solvent to obtain an organic phase; An alkaline aqueous solution is added to the organic phase to form a phase interface, and then a diamine monomer is added and stirred to carry out an interfacial polymerization reaction. After the reaction is completed, the precipitate is filtered, washed, and dried to obtain bifuran polyamide. The diamine monomer is an aliphatic diamine monomer or an alicyclic diamine monomer.

2. The method for preparing bifuran polyamide with high quantum yield and emitting yellow-green wavelength light according to claim 1, characterized in that, The aliphatic diamine monomer is 1,6-hexanediamine, 1,8-octanediamine, or 1,10-decanediamine; the alicyclic diamine is piperazine or 4,4'-bipiperidine.

3. The method for preparing bifuran polyamide with high quantum yield and emitting yellow-green wavelength light according to claim 1, characterized in that, The alkaline aqueous solution is a KOH aqueous solution; the alkaline aqueous solution has a concentration of 0.5-2 mol / L.

4. The method for preparing bifuran polyamide with high quantum yield and emitting yellow-green wavelength light according to claim 1, characterized in that, The molar ratio of the bifuranyl chloride monomer to the diamine monomer is 1:

1.

5. The method for preparing bifuran polyamide with high quantum yield and emitting yellow-green wavelength light according to claim 1, characterized in that, The interfacial polymerization reaction was carried out by stirring for 20 to 30 hours.

6. The method for preparing bifuran polyamide with high quantum yield and emitting yellow-green wavelength light according to claim 1, wherein the bifuranyl chloride monomer is prepared by: reacting bifuran dicarboxylic acid with excess thionyl chloride under reflux in the presence of a catalyst, and then obtaining the bifuranyl chloride monomer through post-treatment.

7. The method for preparing bifuran polyamide with high quantum yield and emitting yellow-green wavelength light according to claim 6, wherein the catalyst is N,N-dimethylformamide, the amount of N,N-dimethylformamide added is 0.5%-0.8% of the mass of bifuran dicarboxylic acid; and the reflux reaction time is 3-8 hours.

8. A bifuran polyamide prepared by the method according to any one of claims 1-7, characterized in that, When the diamine monomer is an aliphatic diamine monomer, the prepared bifuran polyamide is an amorphous polymer, and the maximum emission wavelength is in the range of 540-568 nm under 480 nm excitation light; when the diamine monomer is an alicyclic diamine monomer, the prepared bifuran polyamide is a crystalline polymer, and the maximum emission wavelength is in the range of 565-568 nm under 480 nm excitation light.

9. The bifuran polyamide prepared by the method according to claim 8, characterized in that, The bifuran polyamide prepared when the diamine monomer is 1,10-decanediamine has a positive effect on Fe. 3+ It exhibits a fluorescence quenching response.

10. The application of a bifuran polyamide prepared by the method according to any one of claims 1-7 in the preparation of a bioimaging fluorescent probe.

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