CN113788964B

CN113788964B - Preparation method of migration-resistant fluorescent organic silicon elastomer

Info

Publication number: CN113788964B
Application number: CN202111041148.6A
Authority: CN
Inventors: 吴友平; 陈健; 邓建平
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2021-09-06
Filing date: 2021-09-06
Publication date: 2023-03-31
Anticipated expiration: 2041-09-06
Also published as: CN113788964A

Abstract

A preparation method of a migration-resistant fluorescent organic silicon elastomer belongs to the technical field of organic silicon macromolecules. Including the realization of fluorescent substance macromolecules by molecular design. Then, adding the macromolecular fluorescent compound and the organic silicon elastomer base material into the organic good solvent, stirring and ultrasonically dispersing uniformly. And finally, removing the solvent by rotary evaporation, pouring the residual mixture into a mold, and curing and molding to obtain the fluorescent organic silicon elastomer. The invention effectively solves the problems of easy aggregation, crystallization, migration and precipitation of micromolecular chromophore through the large molecular of the fluorescent substance, and the method is simple and convenient and has universality. In addition, the fluorescence emission of the film shows stimulus responsiveness to stress, temperature and partial organic solvent, so that the film has potential application in the field of large-area flexible fluorescent films or sensors.

Description

Preparation method of migration-resistant fluorescent organic silicon elastomer

Technical Field

The invention relates to a preparation method and application of a migration-resistant fluorescent organic silicon elastomer, belonging to the technical field of organic silicon polymers.

Background

The organic silicon elastomer has the advantages of high temperature resistance, low temperature resistance, aging resistance, high flexibility, high chemical inertness, biocompatibility and the like which cannot be compared with and replaced by other carbon-based elastomers, and is widely used in the fields of aerospace, electronic devices, medical health and the like. Especially, the fluorescent organic silicon elastomer has unique photoelectric performance, so that the fluorescent organic silicon elastomer has wide application prospect in the fields of organic light-emitting diodes, fluorescent probes, biochemical sensors and the like.

However, in practical application, it is found that fluorescein in a fluorescent organosilicon device prepared by a common doping method is easy to aggregate, crystallize, migrate and precipitate, so that the defects of uneven fluorescence emission of the material, poor dispersion stability of the fluorescein and the like are caused, and the service life of the material is shortened. And many doped fluorescein has certain toxicity, is harmful to human health after emigration, and limits the application of the fluorescent organic silicon elastomer in the fields of biological medicine and the like. Therefore, in recent years, a method of modifying a fluorescent small molecule to form a covalent bond with an organosilicon matrix is considered to be hot. Polysiloxanes with functional side end groups have a variety of active sites, and the linkage of a fluorophore as a side chain into a silicone rubber matrix through a covalent bond is an effective method for constructing a stable, diverse fluorescent silicone elastomer. For example, the chinese patent application No. CN201910958431.1, entitled "a fluorescent probe for detecting nitrogen monoxide and hydrogen sulfide and a preparation method and application thereof" (application publication No. CN 110698508A) introduces a method for preparing a polysiloxane fluorescent probe by attaching two fluorescent dye groups onto polysiloxane molecules through nucleophilic substitution reaction and amidation reaction with amino polysiloxane using amino as an active reaction point, which shows good stability. In addition, methods for preparing fluorescent silicone elastomers by constructing supramolecular fluorescent probes or triggering the fluorescent properties of materials through structural interactions have also been reported in succession. However, both covalent and non-covalent bonding require harsh or unique construction conditions and have limited preparation methods. Therefore, the experiment intends to add the fluorescent substance into the organic silicon matrix after the fluorescent substance is converted into macromolecules, and the problem that the fluorescein is easy to migrate and separate out is solved as a simpler and more universal method for preparing the fluorescent organic silicon elastomer. Based on aggregation-induced quenching effect or molecular rotation restriction theory, the fluorescence emission of the fluorescence organic silicon film prepared through experiments shows the stimulus responsiveness to stress, temperature and partial organic solvent, so that the fluorescence organic silicon film has potential application in the field of large-area flexible fluorescence films or sensors.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a preparation method of a migration-resistant fluorescent organic silicon elastomer. The fluorescent organic silicon elastomer is obtained by preparing and adding the macromolecular fluorescent compound, and the problems of easy aggregation, crystallization, migration and precipitation of fluorescein in the traditional fluorescent organic silicon elastomer are solved. Compared with the prior art, the method is simple and convenient and has universality, so that the method has potential application in the field of large-area flexible fluorescent films or sensors.

The technical scheme of the invention is as follows:

a preparation method of a migration-resistant fluorescent organic silicon elastomer comprises the following steps:

(1) Designing a small molecular fluorescent unit with an active reaction point, and carrying out an ester forming reaction, a nucleophilic substitution reaction or an amidation reaction with a functionalized molecule containing an olefin double bond to obtain a polymerizable fluorescent molecular structure containing the double bond;

(2) Adding a polymerizable fluorescent molecular structure containing double bonds, a chain transfer agent, an initiator and an organic solvent into N ₂ Under protection, reacting for 3-36 h at 50-80 ℃ (preferably 70 ℃), precipitating with methanol, centrifuging, and drying to obtain macromolecular fluorescent compound;

(3) And (3) dissolving the macromolecular fluorescent compound prepared in the step (2) and the base material (including the functionalized polysiloxane, the cross-linking agent and the catalyst) of the organic silicon elastomer into an organic good solvent, stirring and ultrasonically mixing uniformly, removing the solvent by rotary evaporation, pouring the residual mixture into a mold, and curing and molding to obtain the fluorescent organic silicon elastomer.

The silicone elastomer substrate may be various silicone rubbers, such as a dehydration condensation-curing type silicone elastomer, an addition-type vulcanized silicone elastomer, a peroxide-curing type silicone elastomer, and the like, and the silicone elastomer substrate raw material (including a functionalized polysiloxane, a crosslinking agent, and a catalyst) is crosslinked to serve as the silicone elastomer substrate.

According to the present invention, in step (1), the reactive site may be one of an amino group, a hydroxyl group or a bromine substituent, and preferably, the reactive site is a hydroxyl group or an amino group; in the step (1), the small molecule fluorescent unit can be one or more fluorescent molecules based on pi aromatic chromophores such as benzene, fluorene, naphthalene, anthracene, phenanthrene and pyrene, such as tetraphenylethylene, carbazole, naphthalimide, dansylamide, rhodamine and 2,3,4, 5-tetraphenyl silole, preferably, the small molecule fluorescent unit is tetraphenylethylene.

Preferably, in step (1), the functionalized molecule containing an olefinic double bond may be an olefin containing a carboxyl, hydroxyl or acid chloride substituent, preferably acryloyl chloride.

Preferably, in step (2), the chain transfer agent is one of xanthates such as isobutyronitrile-based dithiobenzoate, methyl 2-propionate-O-ethyl xanthate or diisopropyl xanthogen disulfide.

According to the present invention, in the step (2), the molar ratio of the polymerizable fluorescent molecular structure containing a double bond, the chain transfer agent and the initiator is preferably from 100.

Preferably, according to the invention, in step (2), the organic solvent is preferably selected from 1, 4-dioxane.

Preferably, in step (3), the functionalized polysiloxane is polysiloxane containing one or more functional groups of mercapto, hydroxyl or vinyl.

According to the invention, in step (3), the cross-linking agent is polysiloxane or small molecule containing sulfhydryl, vinyl or silicon hydrogen bond, preferably tetravinyltetramethylcyclotetrasiloxane, tetramethyldivinyldisiloxane, siloxane containing Si-H bond or D-limonene.

Preferably, in step (3), the catalyst is a platinum complex, an ether compound or a tin compound.

Preferably, in step (3), the mass ratio of the macromolecular fluorescent compound to the silicone elastomer substrate is 1. Preferably, the mass ratio of the macromolecular fluorescent compound to the silicone elastomer substrate is 1.

According to the present invention, in the step (3), the good organic solvent is one or a mixture of any two or more of tetrahydrofuran, dichloromethane, and chloroform. Preferably, the good organic solvent is tetrahydrofuran.

The fluorescent organic silicon elastomer is applied to a large-area flexible fluorescent film or a sensor for detecting stress, temperature and part of organic solvents such as toluene.

Compared with the prior art, the invention has the advantages that: the invention adds the fluorescent substance after the macromolecule is changed into the organic silicon matrix, thereby having more convenience and universality and effectively solving the problem of migration and precipitation of the fluorescent substance. And by means of the macro-molecule, the aggregation-induced emission or enhancement effect of the fluorescent unit can be fully exerted, so that the luminous intensity of the organic silicon elastomer prepared by the method is greatly increased, strong fluorescence can be emitted under the condition that the doping quality is one thousandth, the raw materials are saved, and the manufacturing cost is reduced. Therefore, the method of the invention is more advantageous in the application of large-area fluorescent films or sensors.

Drawings

FIG. 1 is a graph showing fluorescence emission curves of fluorescent silicone elastomer films with different tetraphenylethylene acrylate polymer (TPE-P) contents obtained in example 1; the inset is a fluorescent photograph of fluorescent silicone elastomer films of different tetraphenylethylene acrylate polymer (TPE-P) content under 365nm uv lamp illumination.

FIG. 2 is a graph showing the change in the ratio (A/Ao) of the absorption value at 360nm to the initial absorption value during immersion in (a) n-hexane and (b) tetrahydrofuran, with respect to the immersion time, of a 1wt% fluorescent silicone elastomer film obtained in example 1.

FIG. 3 is a graph showing the change in the fluorescence intensity at the peak position in 10 stretch recovery processes of a 1wt% fluorescent silicone elastomer film obtained in example 1.

FIG. 4 is a graph showing the change in the peak fluorescence intensity of the 1wt% fluorescent silicone elastomer film prepared in example 1 during 10 cycles of heating from 0 ℃ to 100 ℃ and then cooling to 0 ℃.

FIG. 5 is a graph showing the change in peak intensity during 10 cycles of swelling in saturated toluene vapor and then air-drying the 1wt% fluorescent silicone elastomer film obtained in example 1.

FIG. 6 is a graph of the fluorescence emission of fluorescent silicone elastomer films of different polyvinylcarbazole contents obtained in example 2; the inset is a fluorescent photograph of fluorescent silicone elastomer films with different polyvinylcarbazole contents under 365nm ultraviolet lamp irradiation.

Detailed Description

The present invention will be specifically explained with reference to specific examples. It is to be understood that the following examples are for further illustration of the present invention and are not to be construed as limiting the scope of the invention. The invention is not limited to the embodiments described herein, but is capable of numerous modifications and variations within the spirit and scope of the invention.

Example 1:

(1) Synthesis of polymerizable small molecule fluorescent unit in this example:

in a 100mL three-necked flask washed and dried, monohydroxytetraphenylethylene (TPE-OH, 1.0g, 2.87mmol) and triethylamine (0.544mL, 4.305mmol) were dissolved in 40mL of dichloromethane, placed in a cold water bath, and a solution of acryloyl chloride (0.354mL, 4.305mmol) in dichloromethane (20 mL) was slowly dropped under a nitrogen atmosphere. The reaction mixture was stirred for 3min in a cold water bath and then stirred at reflux at room temperature for 2h. The reaction solution was transferred to a 125mL separatory funnel, washed 3 times with 15mL water, twice with 20mL saturated brine, and the organic phase was concentrated to 2-3mL by rotary evaporation. Separating by column chromatography (silica gel 200-300 mesh), using mixed solvent of dichloromethane and petroleum ether (8/1, V/V) as eluent, evaporating to dryness by rotation, and drying in vacuum oven at 35 deg.C to constant weight to obtain tetraphenylethylene acrylate monomer (TPE-M) with yield of about 80%.

The synthetic route of the polymerizable small-molecule fluorescent unit in the embodiment is as follows:

(2) Synthesis of macromolecular fluorescent Compounds in this example:

0.4g (0.001 mol) of tetraphenylethylene acrylate monomer and 1.64mg (0.01 mmol) of azobisisobutyronitrile as an initiator were weighed and placed in a 10mL Schlenk reaction tube, and 11.05mg (0.05 mmol) of the chain transfer agent, isobutyronitrile-dithiobenzoate, was weighed and dissolved in 2mL of 1,4 dioxane, and injected into the Schlenk reaction tube, stirred and sonicated. Three times through liquid nitrogen freezing, vacuumizing, argon filling and unfreezing, and then stirring and reacting for 36 hours at 70 ℃ under the nitrogen atmosphere. Stopping the reaction, cooling to room temperature, dropwise adding the reaction liquid into 60mL of cold methanol, and continuously stirring to obtain white precipitate at 10000 r.min ^-1 Centrifuging for 10min. Then THF dissolving, cold methanol precipitation, centrifugal separation and purification are carried out once. The product is dried in a vacuum oven at 45 ℃ to constant weight,tetraphenylethylene acrylate polymer (TPE-P) was obtained in about 80% yield.

The synthetic route of the macromolecular fluorescent compound in this example is as follows:

(3) The preparation of the fluorescent silicone elastomer in this example:

in a 100mL dry single-neck flask with jujube arc magnetons, 11mg of tetraphenylethylene acrylate polymer (TPE-P) was added dissolved in 22mL of tetrahydrofuran, stirred well and sonicated. Weighing 11g of organic silicon elastomer substrate raw materials, including 10g of component A (platinum complex of functional polysiloxane containing vinyl and divinyl tetramethyl disiloxane in a structural unit) and 1g of component B (siloxane containing Si-H bonds, functional polysiloxane containing vinyl and tetravinyl tetramethyl cyclotetrasiloxane), adding into a single-neck flask, fully stirring and ultrasonically dispersing uniformly, and carrying out reduced pressure rotary evaporation to remove tetrahydrofuran. And (3) casting 1mL of the residual mixture into a customized tetrafluoroethylene mold, removing bubbles in vacuum at room temperature, and heating to 120 ℃ under normal pressure to perform crosslinking curing for 1h to obtain the fluorescent organic silicon elastomer film. And changing the mass ratio of the tetraphenylethylene acrylate polymer (TPE-P) to the organic silicon elastomer base material to prepare the fluorescent organic silicon elastomer films with different tetraphenylethylene acrylate polymer (TPE-P) contents. The fluorescence emission curves of the fluorescent silicone elastomer films with different tetraphenyl ethylene acrylate polymer (TPE-P) contents are tested by using a fluorescence spectrophotometer, and the specific results are shown in figure 1; the inset is a fluorescent photograph of fluorescent silicone elastomer films of different tetraphenylethylene acrylate polymer (TPE-P) content under 365nm uv lamp.

The migration-resistant precipitation performance of the prepared 1wt% fluorescent organic silicon elastomer film is characterized by an organic solvent soaking method, and a quantifiable ultraviolet-visible light absorption spectrum is selected as a characterization means. The change of the ratio (A/Ao) of the absorption value of the silicone elastomer film at 360nm to the initial absorption value in the soaking process with the soaking time was plotted, and the result is shown in FIG. 2. It can be seen that the film maintained a higher absorbance during the soaking process because the entanglement of the macromolecular chains and their restriction to molecular motion reduced the migration of the fluorescent species. The feasibility of solving the problem of migration of the fluorescent material by the large-molecular fluorescent material is verified.

Based on the theory of limited intramolecular rotation and the AIE effect of tetraphenylethylene units, the fluorescence emission of the fluorescent silicone elastomer film prepared in the embodiment shows the stimulus responsiveness to stress, temperature and part of organic solvents, so that the fluorescent silicone elastomer film has potential application in the field of large-area flexible fluorescent sensors. A 1wt% fluorescent silicone elastomer film was selected for stimulus responsiveness studies. First, stretching affects the concentration or aggregation state of the macromolecular fluorescent compound in the film, so that the change in the fluorescence emission property of the film in 10 stretch recovery processes was tested, and the result is shown in fig. 3. When the film is stretched to 150%, the fluorescence emission intensity is weakened, and after the film is recovered, the fluorescence emission intensity is basically recovered, so that good reversibility is shown. Secondly, the molecular motion is affected by the temperature, and as shown in FIG. 4, when the temperature of the film is increased from 0 ℃ to 100 ℃, the molecular motion ability is increased, the energy consumed by the rotation is increased, and the fluorescence intensity is sharply reduced. And reversible switching of fluorescence emission can be achieved by changing the temperature 10 times repeatedly. FIG. 5 shows the response of the film to toluene vapor. The dried film was left to stand in toluene vapor and the fluorescence of the film was quenched. The reason is that toluene molecules can penetrate into the PDMS cross-linked network, and the toluene molecules are used as a good solvent of the macromolecular fluorescent compound, so that the chain segment of the macromolecular fluorescent compound is gradually stretched, the intramolecular rotation of the fluorescent unit is promoted, and the non-radiative energy is increased. After the film dried, it substantially returned to the original fluorescence intensity.

Example 2

(1) Synthesis of macromolecular fluorescent Compound in this example:

1g (0.005 mol) of vinylcarbazole and 24.6mg (0.15 mmol) of azobisisobutyronitrile as an initiator are weighed into a 10mL Schlenk reaction tube, 27mg (0.1 mmol) of the chain transfer agent diisopropyl disulfide xanthate is weighed into a

2mL

1,4 dioxane, injected into the Schlenk reaction tube, stirred and sonicated. By passingFreezing by liquid nitrogen, vacuumizing, filling argon, unfreezing for three times, and then stirring and reacting for 3 hours at 70 ℃ under the nitrogen atmosphere. Stopping reaction, cooling to room temperature, adding a small amount of 1,4 dioxane dissolved product, and stirring uniformly. The reaction solution is added into 60mL of cold methanol drop by drop and stirred continuously to obtain white precipitate, 10000 r.min ^-1 Centrifuging for 10min. Then THF dissolution, cold methanol precipitation, centrifugal separation and purification are carried out once. The product is dried in a vacuum oven at 45 ℃ to constant weight to obtain polyvinylcarbazole, and the yield is about 90%.

(2) The preparation of the fluorescent silicone elastomer in this example:

in a 100mL dry single-neck flask containing zizyphus coruscule, 11mg polyvinylcarbazole was added and dissolved in 22mL tetrahydrofuran, and the mixture was stirred well and sonicated. Weighing 11g of organic silicon elastomer base material which comprises 10g of component A (platinum complex of vinyl-containing functional polysiloxane and divinyl tetramethyl disiloxane in a structural unit) and 1g of component B (siloxane containing Si-H bonds, vinyl-containing functional polysiloxane and tetravinyl tetramethyl cyclotetrasiloxane), adding into a single-neck flask, fully stirring and ultrasonically dispersing uniformly, and carrying out reduced pressure rotary evaporation to remove tetrahydrofuran. And (3) casting 1mL of the residual mixture into a customized tetrafluoroethylene mold, removing bubbles in vacuum at room temperature, and heating to 120 ℃ under normal pressure to perform crosslinking curing for 1h to obtain the fluorescent organic silicon elastomer film. Changing the mass ratio of the polyvinylcarbazole to the organosilicon elastomer substrate to prepare the fluorescent organosilicon elastomer films with different polyvinylcarbazole contents. A fluorescence spectrophotometer is used for testing the fluorescence emission curves of the fluorescent organic silicon elastomer films with different polyvinyl carbazole contents, and the specific result is shown in figure 6; the inset is a fluorescent photograph of fluorescent silicone elastomer films with different polyvinylcarbazole contents under 365nm ultraviolet lamp irradiation.

Claims

1. The application of the migration-resistant fluorescent organic silicon elastomer is applied to the field of flexible fluorescent films or sensors which need to respond to stress, temperature and stimulation of partial organic solvents;

the preparation method of the migration-resistant fluorescent silicone elastomer comprises the following steps:

(2) Adding a polymerizable fluorescent molecular structure containing double bonds, a chain transfer agent, an initiator and an organic solvent into N ₂ Reacting for 3-36 h at 50-80 ℃ under protection, and obtaining a macromolecular fluorescent compound through methanol precipitation, centrifugal separation and drying;

(3) Dissolving the macromolecular fluorescent compound prepared in the step (2) and the base material of the organic silicon elastomer into an organic good solvent, stirring and ultrasonically mixing uniformly, removing the solvent by rotary evaporation, pouring the residual mixture into a mold, and curing and molding to obtain the fluorescent organic silicon elastomer; wherein the raw materials of the organosilicon elastomer substrate comprise functionalized polysiloxane, a cross-linking agent and a catalyst, and the organosilicon elastomer substrate is used as an organosilicon elastomer matrix after cross-linking.

2. Use according to claim 1, wherein the fluorescent silicone elastomer comprises a silicone elastomer matrix in which a macromolecular fluorescent compound is homogeneously dispersed.

3. The use according to claim 1, wherein in step (1), the reactive sites are one of amino, hydroxyl or bromo substituents; in the step (1), the small molecule fluorescent unit is one or more fluorescent molecules of pi aromatic chromophores based on benzene, fluorene, naphthalene, anthracene, phenanthrene and pyrene; the functionalized molecule containing the olefin double bond is olefin containing carboxyl, hydroxyl or acyl chloride substituent.

4. The use according to claim 1, wherein in step (2), the chain transfer agent is one of isobutyronitrile-based dithiobenzoate, methyl 2-propionate-O-ethyl xanthate or diisopropyl xanthogen disulfide; in the step (2), the organic solvent is selected from 1, 4-dioxane.

5. The use according to claim 1, wherein in step (2), the molar ratio between the polymerizable fluorescent molecular structure containing double bonds, the chain transfer agent and the initiator is from 1 to 10.

6. The use according to claim 1, wherein in the step (3), the functionalized polysiloxane is polysiloxane containing one or more functional groups of mercapto, hydroxyl or vinyl; the cross-linking agent is polysiloxane or D-limonene containing sulfydryl, vinyl or silicon hydrogen bonds; the catalyst is a platinum complex, an ether compound or a tin compound.

7. The use according to claim 1, wherein in step (3), the mass ratio of the macromolecular fluorescent compound to the silicone elastomer substrate is 1.

8. The use according to claim 1, wherein in the step (3), the good organic solvent is one or a mixture of any two or more of tetrahydrofuran, dichloromethane or chloroform.