Preparation method of dendritic helical polyphenylenevinylene and chiral fluorescent nanoparticles thereof

Abstract

The application discloses a preparation method of dendritic helical poly (phenylene ethynylene) and chiral fluorescent nanoparticles. The cinnamate is introduced into the dendritic alkyl ether element core point of the side group of poly (phenylene ethynylene) through molecular design, the synthesis steps are simple, the reaction is rapid, the prepared dendritic helical poly (phenylene ethynylene) can control the helical conformation and chiral circularly polarized luminescence properties through solvation, in addition, the dendritic helical poly (phenylene ethynylene) can be self-assembled into various chiral fluorescent nanoparticles, and cross-linking and curing are initiated by ultraviolet irradiation, so that the structure and chirality of the nanoparticles have good stability. The above-mentioned chiral fluorescent nanomaterial has high fluorescence quantum yield, good light and thermal stability, and has good application prospect in the field of chiral optoelectronic materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chiral fluorescent materials, in particular to a dendritic helical poly (phenylacetylene) and a method for preparing chiral fluorescent nanoparticles based thereon. BACKGROUND

[0002] Chiral circularly polarized fluorescent materials have attracted extensive attention in recent years due to their potential applications in three-dimensional optical imaging, information storage encryption and biological probes. Self-assembly strategies are widely used in the construction of chiral fluorescent nanomaterials due to their ability to effectively enhance chiral fluorescent asymmetry factors. At present, obtaining chiral fluorescent materials with high stability is still one of the major challenges. Helical polymers, with their rigid backbone and inherent chirality, can self-assemble into chiral nanostructures with multiple morphologies, including vesicles, nanorings, supramolecular helical fibers, etc. Helical poly (phenylacetylene) is a kind of polyacetylene derivative with highly conjugated main chain. Compared with monosubstituted polyphenylacetylene, it has higher photothermal stability and photoluminescence quantum yield, and becomes an ideal platform for preparing stable chiral fluorescent materials. Photodimerization is of great significance in the synthesis of natural products and drug chemistry. These photodimerization units can be integrated into polymer materials as main chains, side groups or additives. Due to their ability to directly and non-destructively adjust the physical and chemical properties of polymer structures, photodimerization has been widely used in materials science in recent years. However, the photodimerization group modified in the polymer obviously has more free movement space than in the crystal. The random collision of photodimerization group can meet the above reaction conditions at a certain moment in space and time, which significantly reduces the design difficulty of introducing reactive groups, but the appropriate structure can still significantly accelerate the photodimerization reaction speed or improve the dimerization reaction degree, and provides a new opportunity for the regulation of photodimerization reaction of polymer groups. Based on the spatial requirements of photodimerization, the selectivity of intramolecular adjacent side groups, intramolecular non-adjacent side groups and intermolecular reactions can be manipulated by structure design, and different scale polymer materials can be obtained respectively. SUMMARY

[0003] The present application aims to prepare chiral fluorescent materials with stable structure and chirality; a preparation method of dendritic helical polyphenylacetylene and chiral fluorescent nanoparticles thereof is developed. The dendritic helical polyphenylacetylene developed by the present application can regulate the helical conformation and circularly polarized fluorescence of the polymer through solvation, has high fluorescence quantum yield, good light and thermal stability, and can be self-assembled into various chiral fluorescent nanoparticles, including dense spheres, loose spheres and nanobowls, etc. The cinnamate element is introduced into the side group dendritic alkoxy ether element core point, and after appropriate ultraviolet irradiation, the photo-cyclization reaction is initiated and the nanometer assembly is cross-linked and solidified, so that the supramolecular structure and chirality of the nanoparticles have good stability to the environment. The present technology lays a foundation for developing helical polymers suitable for harsh environmental conditions such as high temperature and strong light irradiation, and provides an effective strategy for supporting helical polymers to prepare chiral and morphology-stable stimulus-responsive chiral fluorescent nanoparticles through photo-crosslinking, especially the strategy allows the preparation of various morphological nanostructures with opposite fluorescent optical activity from one helical polymer.

[0004] One of the objects of the present application is to provide a dendritic alkoxy ether modified helical polyphenylacetylene, which has a polyphenylacetylene backbone, a dendritic alkoxy ether modified with cinnamate as a side group, and a propylamino alcohol as a linking element.

[0005] As an embodiment of the present application, the dendritic alkoxy ether modified helical polyphenylacetylene has the following structural formula:

[0006]

[0007] Preferably, the dendritic polyphenylacetylene used has a degree of polymerization n = 50-1000.

[0008] Preferably, the substituent R of the dendritic polyphenylacetylene used is a lower alkyl group. The lower alkyl group is a C1-C6 alkyl group, such as methyl, ethyl, etc.

[0009] Preferably, the chiral amino alcohol has an R-type or S-type chiral configuration. * represents the connection site.

[0010] Preferably, the oligomeric alkoxy ether has a degree of polymerization m = 1-4.

[0011] The dendritic alkoxy ether modified helical polyphenylacetylene of the present application can provide circularly polarized luminescence; can be cross-linked by light irradiation. Moreover, the dendritic alkoxy ether modified helical polyphenylacetylene of the present application can form two opposite helical conformations in different solvents according to the polarity of the solvent at high temperature, and retain the induced conformation at room temperature. It also has the ability to maintain stable chiral optical properties at high temperature or strong light irradiation.

[0012] The application also relates to a preparation method of the dendritic alkoxyl ether modified helical poly (phenylenevinylene), which comprises the following steps: synthesizing a poly (phenylenevinylene) precursor functionalized with a pentafluorophenol active ester, and combining the poly (phenylenevinylene) precursor with a dendritic macromolecule modified with a cinnamate through an amidation reaction to obtain the dendritic alkoxyl ether modified helical poly (phenylenevinylene).

[0013] As a preferred technical scheme of the application, the preparation method of the dendritic helical poly (phenylenevinylene) comprises the following steps:

[0014] S1, compound B The polymer C is obtained through a polymerization reaction under the catalysis of tetraphenyl tin and tungsten hexachloride n = 50-1000;

[0015] S2, compound C and compound D The polymer A is obtained through an amidation reaction The dendritic alkoxyl ether modified helical poly (phenylenevinylene), compound D has the structural formula: and m = 1-4, R is a lower alkyl group, and the chiral configuration of the chiral amino alcohol is R-type or S-type. The lower alkyl group is a C1-C6 alkyl group, such as a methyl group and an ethyl group.

[0016] Preferably, in step S1, the polymerization reaction is carried out in toluene.

[0017] Preferably, in step S1, the molar ratios of compound B to tetraphenyl tin and tungsten hexachloride are 1:5-50 and 1:10-1:100 respectively, and the reaction temperature is 80-100 DEG C.

[0018] Preferably, in step S2, the reaction is an amidation reaction in the presence of an organic base.

[0019] Preferably, in step S2, the molar ratio of the polymerization unit of compound C to compound D is 1:1.5-5.

[0020] The second object of the application is to provide a self-assembled aggregate (chiral fluorescent nanometer assembly) and a preparation method thereof. The self-assembled aggregate is obtained by adding a poor solvent to a solution containing the dendritic alkoxyl ether modified helical poly (phenylenevinylene), and inducing self-assembly through a nanometer precipitation method.

[0021] Preferably, the selective organic solvent selected for the solution of the dendritic alkoxyl ether modified helical poly (phenylenevinylene) is a polar protic solvent, such as MeOH and ethanol.

[0022] Preferably, the poor solvent is water.

[0023] Preferably, the solution of the dendronized alkoxyl ether modified helical poly(phenylene ethynylene) further contains a good solvent, which is a polar aprotic solvent, such as THF, DMF, DMSO, etc.

[0024] Preferably, the volume ratio of the selective organic solvent, the good solvent and the poor solvent is 1:(0-4):(0.5-19).

[0025] Preferably, in the solution of the dendronized alkoxyl ether modified helical poly(phenylene ethynylene), the mass fraction of the dendronized alkoxyl ether modified helical poly(phenylene ethynylene) is 0.01-0.5wt%.

[0026] In some specific embodiments, the dendronized alkoxyl ether modified helical poly(phenylene ethynylene) is dissolved in an organic solvent and water is added to the solution, which can self-assemble to form spherical or bowl-shaped nanoparticles.

[0027] The third object of the present application is to provide a photo-crosslinking method of the dendronized poly(phenylene ethynylene) nano-assembly and a photo-crosslinked nanoparticle; the photo-crosslinked nanoparticle is obtained by photo-irradiation of the self-assembled aggregate to induce a photo-cyclization reaction between cinnamate esters.

[0028] Preferably, the solution of the dendronized poly(phenylene ethynylene) nano-assembly is irradiated with ultraviolet light to induce a photo-dimerization reaction between cinnamate esters, thereby realizing photo-crosslinking of the nano-assembly.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] 1) The present application provides a preparation method of dendronized poly(phenylene ethynylene), which is prepared by molecular design and synthesis, i.e., first, a polymer precursor functionalized with a pentafluorophenol active ester is synthesized, and then the dendronized poly(phenylene ethynylene) is successfully prepared by amide reaction and combination with a dendronized macromolecule, which has the advantages of simple steps, rapid reaction, and good application prospect of the prepared dendronized poly(phenylene ethynylene) in the field of fluorescence sensing, etc.

[0031] 2) The alkoxyl ether dendronized poly(phenylene ethynylene) prepared in the present application introduces cinnamate esters at the dendronized alkoxyl ether element core point, which endows this kind of temperature-sensitive dendronized poly(phenylene ethynylene) with photo-dimerization characteristics. The helical conformation, fluorescence optical activity and self-assembly behavior of the poly(phenylene ethynylene) can be regulated by solvation, and the crosslinked assembly can be prepared by photo-irradiation to induce a photo-cyclization reaction; the present method has the advantages of simple preparation and high stability of structure and optical performance. BRIEF DESCRIPTION OF DRAWINGS

[0032] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments with reference to the following drawings:

[0033] Figure 1 is a polymer C1 H NMR spectra;

[0034] Figure 2 H NMR spectra of polymer C; 19 F NMR spectra;

[0035] Figure 3 F NMR spectra of polymer A; 1 H NMR spectra;

[0036] Figure 4 H NMR spectra of polymer A; 13 C NMR spectra;

[0037] Figure 5 Circular dichroism spectra of polymer A in toluene (a) and DMSO (b) at 80 °C for different time;

[0038] Figure 6 Chiroptical fluorescence spectra of polymer A after high temperature treatment in DMSO (blue line) or toluene (red line) and then transferred to DMSO solution at room temperature;

[0039] Figure 7 Hydrodynamic radius distribution of polymer A in different solvents;

[0040] Figure 8 Atomic force microscopy images of self-assemblies of polymer A in different solvents; (a) methanol solution, and solvent ratio is (b) v MeOH THF water = 1 / 0 / 4, (c) v MeOH THF water = 1 / 1 / 4, (d) v MeOH THF water = 1 / 1 / 19 mixed solution, scale bar is 100 nm;

[0041] Figure 9 UV / Vis spectra of polymer A under different UV irradiation time;

[0042] Figure 10 Nanoparticles prepared from polymer A, (a) main chain molar ellipticity at different time after transferred to toluene solution and heated to 100 °C, and (b) fluorescence spectra at different temperature in aqueous solution;

[0043] Figure 11 Circular dichroism spectra (a) and fluorescence spectra (b) of nanoparticles prepared from polymer A under different UV irradiation time. DETAILED DESCRIPTION ​​​​​​

[0044] The present application will be described in detail below with reference to the embodiments and drawings. The following embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be pointed out that those skilled in the art can make several adjustments and improvements without departing from the concept of the present application. These are within the scope of protection of the present application.

[0045] Example 1, synthesis of dendronized helical polydibenzotriazine

[0046] In this embodiment, dendronized helical polydibenzotriazine is prepared using the following synthesis route:

[0047]

[0048] Specifically, the following steps are included:

[0049] Compound B is subjected to polymerization reaction under the catalysis of tetraphenyltin and tungsten hexachloride to obtain polymer C; wherein, compound B is synthesized according to reference (Angew. Chem. Int. Ed., 2022, 134, e202115070);

[0050] The polymerization reaction is carried out in toluene, and the molar ratios of compound B to tetraphenyltin and tungsten hexachloride are 1:10 and 1:50, respectively, and the reaction temperature is 100°C.

[0051] Polymer C and compound D to obtain polymer A, i.e., the dendronized alkoxy ether modified helical polydibenzotriazine.

[0052] The reaction is an amidation reaction in the presence of organic base triethylamine, and the molar ratio of the polymerization unit of polymer C to compound D is 1:5. The reaction solvent is tetrahydrofuran, and the reaction temperature is 40°C.

[0053] wherein, compound D can be synthesized according to the following route (reference (J. Colloid Interface Sci. 2025, 667, 928-940)):

[0054]

[0055] Specific steps include:

[0056] Compound E is subjected to esterification reaction with N-tert-butoxycarbonyl-D-propanol in the presence of coupling agent 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and catalyst 4-dimethylaminopyridine to obtain compound F, wherein compound E is synthesized according to reference (Macromolecules 2020, 53, 10866-10873).

[0057] The esterification reaction was carried out in dichloromethane solution, the molar ratio of compound E, N-tert-butoxycarbonyl-D-alaninol, coupling agent and catalyst was 1:0.8:1.5:0.2, and the reaction temperature was 0°C.

[0058] Subsequently, the deprotection reaction of compound F in acidic environment was carried out, and after the reaction was completed, the organic phase was washed with saturated aqueous sodium bicarbonate solution to obtain compound D.

[0059] The deprotection reaction was carried out in a mixed solution of dichloromethane and trifluoroacetic acid with a volume ratio of 4:1, and the compound concentration was 0.1 g mL -1 , and the reaction temperature was 0°C.

[0060] The key intermediates and the desired product were characterized by NMR, and the molecular weight of the polymer was measured by GPC, which was summarized in Table 1, and the specific details were provided in Figures 1 to 4 .

[0061] Table 1 Polymerization conditions and results of dendritic polyphenylacetylene

[0062]

[0063] Example 2, photophysical properties

[0064] In this example, polymer A has good solubility in various solvents and exhibits excellent circularly polarized luminescence performance. When it is dissolved in DMSO and toluene respectively, the fluorescence quantum yields are 45% and 28% respectively, and the first Cotton signal peak intensity at 397 nm in the circular dichroism spectrum is about 2.8×10 4 deg cm 2 dmol -1 , indicating that the main chain conformation of the dendritic polyphenylacetylene is independent of the polarity of the solvent at room temperature. Subsequently, the temperature of the polymer solution was raised to 80°C and maintained for different times, then lowered to room temperature and subjected to CD testing. With the extension of the high-temperature annealing time, the CD signal intensity of the toluene solution gradually increased and reached a maximum of about -9×10 4 deg cm 2 dmol -1 , while in the high-polarity solvent DMSO, the CD signal of the polymer was reversed with the extension of time, and the Cotton signal intensity finally increased to about 9×10 4 deg cm 2 dmol -1 after 48 h. The above results show that the dendritic polyphenylacetylene can be induced to dominant right-handed helical conformation and left-handed helical conformation respectively after high-temperature annealing treatment in low-polarity solvent toluene or high-polarity solvent DMSO Figure 5). The CPL signal direction of these polymer solutions is consistent with the CD signal, and g lum The maximum values are all close to + / - 1 x 10 -3 ( Figure 6 )。

[0065] Example 3, Self-assembly properties

[0066] In this example, by virtue of the remarkable radial amphiphilicity of the dendronized helical polydiacetylene, poor solvent water was added to the MeOH solution of the above dendronized polydiacetylene A, and self-assembly was induced by a nanoprecipitation method. DLS showed that chiral nanoparticles with a hydrodynamic radius of about 110 nm were formed in the polymer solution with a solvent ratio of v MeOH / v water = 1 / 4. Notably, when a small amount of good solvent THF was introduced into the above solution (v MeOH / v THF / v water = 1 / 1 / 4), the hydrodynamic radius of the nanoparticles increased significantly to 154 nm. While further increasing the content of poor solvent water (v MeOH / v THF / v water = 1 / 1 / 19), the hydrodynamic radius of the nanoparticles decreased to 86 nm Figure 7 ). Atomic force microscopy was used to characterize the morphology of the above aggregates Figure 8 ).

[0067] Example 4, Photocrosslinking behavior of dendronized polydiacetylene

[0068] In this example, dendronized helical polydiacetylene A was self-assembled into nanoparticles in a mixed solution of water and methanol with a volume ratio of 4 to 1. Subsequently, the nanoparticle solution was irradiated with ultraviolet light with a wavelength of 365 nm and an irradiation intensity of 12 mW cm -2 , and the photodimerization reaction within the aggregates formed by dendronized polydiacetylene A was studied by UV-Vis spectroscopy Figure 9 ). As the irradiation time was prolonged, the absorption peak at 305 nm attributed to the color group of cinnamate ester was significantly reduced, indicating that efficient photodimerization reaction occurred. The degree of dimerization x increased rapidly with the extension of the irradiation time, and reached about 62% at 30 min, and further extension of the irradiation time did not lead to significant improvement in the degree of dimerization. This indicates that the photocrosslinking of self-assembled nanoparticles has been successfully achieved.

[0069] Example 5, Photothermal stability of crosslinked chiral fluorescent nanoparticles

[0070] In this example, the crosslinked chiral fluorescent nanoparticles prepared in Example 4 were transferred into toluene solution, and the photothermal stability of their chiral and fluorescent emission properties were investigated. After 6 h of high temperature treatment, the Cotton signal of the crosslinked chiral fluorescent nanoparticles transferred into toluene solution remained about 9 x 10 4 deg cm 2 dmol -1 This indicates that even under high temperature conditions of 100 °C, the photo-crosslinked dendronized polyphenylacetylene nanoparticles can still maintain a stable helical conformation. Figure 10 a). While the fluorescence spectra show that the photo-crosslinked nanoparticle aqueous solution has similar intensity of fluorescence emission intensity Figure 10 b) in the temperature range of 10 to 80 °C. While the photo-crosslinked nanoparticles further experienced different light times measured almost coincided CD spectra and fluorescence spectra Figure 11 ) indicates that the helical conformation and fluorescence emission properties of the photo-crosslinked nanoparticles have good light stability.

[0071] The above describes specific embodiments of the present application. It should be understood that the present application is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or changes within the scope of the claims, which does not affect the essential content of the present application.

Claims

1. A dendronized poly(phenyleneethynylene) modified with alkoxyl ethers, characterized in that, The polymer takes polyphenylenevinylene as a main chain, takes dendronized alkyl ether modified with cinnamate as a side group, and takes propanolamine as a connecting unit; the structural formula of the dendronized alkyl ether modified helical polyphenylenevinylene is as follows: ， wherein n = 50-1000, m = 1-4, R is lower alkyl, * indicates the point of attachment, and the chiral configuration of the chiral amino alcohol is R - of the type S - of the type The helical polyphenylenevinylene forms two opposite helical conformations in different solvents according to the polarity of the solvents and high temperature induction, and retains the conformation induced at high temperature at room temperature.

2. A method of preparing a dendronized poly(phenyleneethynylene) modified with a polyalkoxyether according to claim 1, characterized in that, First, a polyphenylenevinylene polymer precursor functionalized with pentafluorophenol active ester is synthesized, and then the helical polyphenylenevinylene modified with dendronized alkyl ether is obtained by amide reaction with dendronized macromolecules modified with cinnamate; the method comprises the following steps: S1, compound B The polymerization reaction was carried out under the catalysis of tetraphenyl tin and tungsten hexachloride to obtain polymer C n = 50-1000; S2, compound C and compound D amide reaction to obtain polymer A i.e. the dendronized alkoxy ether modified spirobifluorene; compound D structural formula, m = 1-4, R is lower alkyl, the chiral configuration of the chiral amino alcohol is R - type or S - type.

3. The method of preparing a dendronized alkoxyether-modified spirobifluorene according to claim 2, characterized in that, In step S1, the polymerization reaction is carried out in toluene; And / or, the molar ratio of compound B to tetraphenyltin and tungsten hexachloride is 1:5-50 and 1:10-1:100, respectively, and the reaction temperature is 80-100°C.

4. The method for preparing dendritic alkoxy ether-modified helical polydiphenylacetylene according to claim 2, characterized in that, In step S2, the reaction is an amide reaction in the presence of an organic base. And / or, the molar ratio of the polymerization unit of compound C to compound D is 1:1.5-5.

5. A self-assembled aggregate, characterized in that, An undesirable solvent is added to a solution containing the helical polyphenylenevinylene modified with dendronized alkyl ether as claimed in claim 1, and a self-assembled aggregate is obtained by inducing self-assembly through a nanometer precipitation method.

6. The self-assembled aggregate according to claim 5, wherein, The solution of the helical polyphenylenevinylene modified with dendronized alkyl ether further contains a selective organic solvent, and the selective organic solvent is a polar protic solvent; And / or, the undesirable solvent is water; And / or, the solution of the helical polyphenylenevinylene modified with dendronized alkyl ether further contains a good solvent, and the good solvent is a polar aprotic solvent; and the volume ratio of the selective organic solvent, the good solvent and the undesirable solvent is 1:(0-4):(0.5-19).

7. The self-assembled aggregate according to claim 5 or 6, characterized in that, In the solution of the helical polyphenylenevinylene modified with dendronized alkyl ether, the mass fraction of the helical polyphenylenevinylene modified with dendronized alkyl ether is 0.01-0.5wt%.

8. Photocrosslinked nanoparticles, characterized in that, The self-assembled aggregate as claimed in claim 5 is irradiated to initiate a photo-cyclization reaction between cinnamates, and the photo-crosslinked nanoparticles are obtained.

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