Electro-optical material capable of initiating crosslinking by visible light as well as preparation method and application of electro-optical material

Abstract

The invention discloses an electro-optical material capable of initiating crosslinking by visible light and a preparation method and application thereof, a novel phenyl diazo ester structural unit is introduced in design of the material, and the structure can be efficiently decomposed under irradiation of visible light with the wavelength larger than 400 nm to generate an active carbene intermediate; compared with a traditional crosslinking system which depends on purple light external initiation, the material has lower requirements on light energy, a crosslinking reaction can be carried out under a mild condition, the problem of electro-optical chromophore degradation possibly caused by ultraviolet light is remarkably reduced, the light stability of the material is further improved, the service life of the material is further prolonged, meanwhile, no extra high-energy by-product is introduced into a carbene insertion mechanism, and the cost is low. The reaction process is clean, the adaptability is high, and the method is suitable for electro-optical active molecular systems of various structures.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic electro-optical materials, and in particular relates to an electro-optical material capable of being cross-linked by visible light, a preparation method thereof and an application thereof. Background Art

[0002] As a new generation of photoelectric conversion media, organic electro-optical functional materials have important application value in the fields of high-speed information transmission, photonic computing and integrated optoelectronic devices. Compared with traditional inorganic nonlinear optical materials, this type of polymer material not only exhibits a significantly enhanced Pockels effect (r 33 The device's unique low dielectric constant (relative dielectric constant below 8) facilitates signal modulation over a wider bandwidth. It can also be fabricated using simple fabrication techniques such as solution processing, making it compatible with heterogeneous integration of silicon-based optoelectronics, meta-optics, and plasmonics.

[0003] In recent years, the research and development of silicon-based organic hybrid (SOH) and plasmonic organic hybrid (POH) electro-optical modulators has made significant progress, achieving breakthroughs in key performance indicators, including ultra-wide modulation bandwidth (exceeding 500 GHz), excellent voltage-length product characteristics (V π L is less than 50 V·μm) and extremely low energy consumption (less than 100 aJ / bit), showing good industrialization prospects.

[0004] However, this type of functional material still faces two core challenges in the process of practical application: insufficient thermal stability and difficulty in balancing performance. To improve thermal stability, researchers have developed a variety of material curing schemes, among which thermal cross-linking technology based on click chemistry is widely used. By constructing a cross-linked network structure, molecular motion is inhibited and T is improved. g However, such systems often have the following shortcomings:

[0005] The crosslinking temperature does not match the polarization temperature: For example, the olefin-anthracene ring addition reaction often needs to be completed at above 150°C, while the polarization process is usually carried out at a lower temperature (<100°C). High-temperature crosslinking will lead to increased conductivity, decreased polarization field strength, and even molecular degradation, which will significantly affect r 33 value.

[0006] The cross-linking process affects the orientation efficiency: the gradual formation of the cross-linked network inhibits the orientation freedom of the chromophore, resulting in incomplete orientation and decreased polarization efficiency.

[0007] Chromophore structures with high thermal cross-linking activity are easily degraded: for example, CLD-type chromophores with conjugated polyene structures are prone to side reactions with other unsaturated structures at high temperatures, destroying the electro-optically active structure.

[0008] In contrast, photoinitiated cross-linking technology has become an important means of material stabilization because it can independently perform the cross-linking process after polarization is complete, avoiding disturbances in molecular orientation. Existing UV-light cross-linking systems introduce photosensitive groups (such as aromatic azides and benzophenones) that can be excited by UV light at relatively low temperatures to generate reactive species (such as nitrenes, free radicals, or carbenes), enabling rapid cross-linking reactions. This technology not only maintains the polarization electric field strength and molecular integrity, but also exhibits excellent spatial selectivity and compatibility with micro- and nanofabrication, demonstrating significant advantages in the field of organic electro-optical materials.

[0009] However, the traditional UV-induced cross-linking system still has the following shortcomings:

[0010] 1. The required ultraviolet light (<365 nm) has high energy, which can easily cause photooxidation and degradation of the chromophore structure, affecting the long-term stability of the material;

[0011] 2. The light intensity requirement is high, and the equipment is prone to aging and difficult to evenly illuminate a large area;

[0012] 3. Some sensitized systems have narrow absorption bandwidth and low activity, which limits the reaction efficiency and cross-linking depth. Summary of the Invention

[0013] To address the aforementioned shortcomings of the prior art, the present invention provides an electro-optical material capable of visible light-induced cross-linking, as well as its preparation method and application. This material incorporates a novel phenyldiazoester structural unit, which efficiently decomposes upon irradiation with visible light of wavelengths greater than 400 nm to generate an active carbene intermediate. This carbene undergoes insertion reactions with the saturated C-H bonds commonly found in the material's backbone or side chains, rapidly constructing a dense and stable three-dimensional cross-linked network, effectively "locking" the molecular orientation and improving the material's orientation retention and thermal stability. Compared to traditional cross-linking systems that rely on ultraviolet light for external initiation, this material exhibits lower light energy requirements and can undergo cross-linking reactions under mild conditions, significantly reducing the potential for ultraviolet-induced degradation of electro-optical chromophores, thereby improving the material's photostability and service life. Furthermore, this carbene insertion mechanism does not introduce additional high-energy byproducts, resulting in a clean reaction process and strong adaptability, making it suitable for electro-optically active molecular systems of various structures.

[0014] To achieve the above-mentioned purpose, the technical solution adopted by the present invention to solve the technical problem is:

[0015] An electro-optical material that can be cross-linked by visible light has the following structural formula:

[0016] Mode

[0017] Wherein, R1: C1-C20 alkyl, or one of the following groups:

[0018]

[0019] R2: C1-C20 straight or branched alkyl, or one of the following groups:

[0020] .

[0021] The method for preparing the electro-optical material capable of cross-linking induced by visible light comprises the following steps:

[0022] (1) 4-(Dihydroxymethyl)aniline was dissolved in anhydrous dichloromethane, triphenylsilyl chloride and a catalyst were added, and the reaction was stirred at room temperature until the raw material was completely converted. The reaction solution was evaporated to remove the solvent, extracted with ethyl acetate, dried over anhydrous magnesium sulfate, and purified by column chromatography to obtain compound 2;

[0023] (2) Compound 2 was dissolved in anhydrous tetrahydrofuran, sodium hydride was added and stirred in an ice bath to alkalize, and then a thienyl phosphate reagent was added dropwise. The reaction was allowed to proceed at room temperature for several hours. After the reaction was completed, water was added to quench the reaction, and the mixture was extracted, dried, and purified by column chromatography to obtain compound 3;

[0024] (3) Compound 3 was activated by reacting with n-butyl lithium in anhydrous DMF, and the temperature was controlled to -78 °C. DMF was then slowly added dropwise to carry out hydroformylation reaction. After the reaction, water was added, extraction was performed, and column chromatography was performed to purify the product to obtain compound 4 containing an aldehyde structure.

[0025] (4) LiAlH4 was slowly added to the THF solution of compound 4 at -78 °C and stirred for reaction. The reaction solution was treated with wet silica gel and purified after extraction to obtain the reduced product hydroxy compound 5;

[0026] (5) Add bromoethanol and potassium carbonate to a DMF solution of compound 5, react at 60°C overnight, pour into water for extraction, wash with concentrated brine, dry, and purify by column chromatography to obtain the etherified product compound 6;

[0027] (6) n-Butyl lithium was added to a THF solution of compound 6, and DMF was added after the reaction at -78 °C for a certain period of time. The mixture was stirred at room temperature overnight. The reaction solution was washed with water and then dried by rotary evaporation. The resulting solid was dissolved in anhydrous THF, and tetrabutylammonium fluoride was added to remove the TBDPS protecting group. The mixture was reacted at room temperature to obtain compound 7.

[0028] (7) Compound 7 was mixed with 4-azido-2,3,5,6-tetrafluorobenzoic acid, EDCI and DMAP in anhydrous dichloromethane and stirred at room temperature overnight. After the reaction, the mixture was washed with water, extracted, dried and purified by column chromatography to obtain compound 8.

[0029] (8) Compound 8 was mixed with an equimolar electron acceptor in anhydrous ethanol and heated to 75°C for reaction. After the reaction was completed, the solvent was dried and purified by column chromatography to obtain the product.

[0030] Furthermore, the catalyst in step (1) is pyridine or a basic organic amine.

[0031] Furthermore, the electron acceptor structure in step (8) is as follows:

[0032] Formula II .

[0033] The application of the above electro-optical material capable of cross-linking induced by visible light in the preparation of electro-optical films.

[0034] Furthermore, the specific operation is as follows: after the electro-optical material is formed into a film, it is polarized by an electric field to obtain electro-optical properties, and then irradiated with visible light of 400-500nm and intensity of 1-10 mW / cm² for 30-120s for cross-linking and curing to obtain an electro-optical film.

[0035] The beneficial effects produced by the present invention are:

[0036] 1. The present invention introduces a cross-linking structural unit initiated by visible light, namely a nitrophenyl diazo ester group, through design. This structure can decompose under low-temperature conditions and under the excitation of visible light with a wavelength greater than 400 nm to produce an active carbene intermediate, which then undergoes an insertion reaction with the main chain alkyl C–H bond, thereby achieving cross-linking and curing between material molecules.

[0037] 2. Compared with the traditional UV crosslinking method, the visible light crosslinking technology of the present invention has the following advantages:

[0038] (1) By introducing a visible light-responsive diazoester structure into the electro-optical molecule, polarization orientation is achieved and then cross-linking is carried out under visible light to construct a three-dimensional stable network, effectively locking the molecular orientation, improving the long-term thermal stability of the material, avoiding the degradation of chromophores caused by high-energy ultraviolet light, significantly improving the stability of the material and maintaining the excellent electro-optical properties of the material, making it suitable for high-temperature operating environments in high-density optoelectronic integrated systems;

[0039] (2) Active carbenes can be efficiently generated and rapidly cross-linked under low-intensity visible light conditions, simplifying equipment requirements, shortening illumination time, and facilitating large-area processing;

[0040] (3) It has excellent light penetration and spatial uniformity, suitable for deep cross-linking in complex device structures;

[0041] (4) The photocrosslinking process is physically decoupled from the electric field polarization process, which facilitates the realization of high orientation efficiency and high r 33 Collaborative optimization of values;

[0042] (5) It is highly compatible with photolithography processes and has excellent adaptability to micro-nano processing and process amplification potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is the differential thermal analysis (DSC) curve of the electro-optical material;

[0044] Figure 2 This is a statistical diagram of the changes in the ultraviolet spectrum of the electro-optical material after irradiation and cross-linking at 420 nm for different times;

[0045] Figure 3 is the polarization efficiency diagram of the electro-optical material film;

[0046] Figure 4 This is a statistical diagram of the temporal stability of the electro-optic coefficient at different temperatures. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, rather than all embodiments.

[0048] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0049] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0050] The features and performance of the present invention are further described in detail below with reference to the embodiments and drawings.

[0051] Example 1

[0052] An electro-optical material that can be cross-linked by visible light has the following structural formula:

[0053]

[0054] The synthesis process of the electro-optical material capable of cross-linking by visible light is as follows:

[0055]

[0056] The specific synthesis method is:

[0057] Step S1: Preparation of Intermediate 2

[0058] Dissolve 1 equivalent of 4-(dihydroxymethyl)aniline (Compound 1) in anhydrous dichloromethane, add 1.2 equivalents of triphenylsilyl chloride (TBDPS-Cl) and catalyst pyridine, and stir at room temperature until the raw material is completely converted. The reaction solution is evaporated to remove the solvent, extracted with ethyl acetate three times, dried over anhydrous magnesium sulfate, and purified by column chromatography to obtain the TBDPS-protected intermediate (Compound 2), which can be used directly in subsequent reactions.

[0059] Step S2: Preparation of Intermediate 3

[0060] Compound 2 was dissolved in anhydrous tetrahydrofuran (THF), and 1.5 equivalents of sodium hydride (NaH) was added under ice bath conditions with stirring to alkalize. Subsequently, 1.2 equivalents of thienyl phosphate reagent was added dropwise. The reaction was allowed to react at room temperature for several hours. The reaction progress was monitored in real time by thin layer chromatography (TLC) to determine whether the reaction had reached the endpoint. After the reaction was completed, water was added to quench the reaction. The target intermediate compound 3 was obtained by extraction, drying, and column chromatography purification. The yield was 63.2%. Mass spectrometry (ESI) showed that the molecular peak M⁺ was 865.41 (C 54 H 67 NO3SSi2);

[0061] Step S3: Aldehyde formation to obtain compound 4

[0062] In anhydrous DMF, compound 3 was activated by reacting with 2.2 equivalents of n-butyl lithium. The temperature was controlled to -78 °C, and DMF was then slowly added dropwise for hydroformylation. After the reaction, water was added, extraction was performed, and column chromatography was performed to obtain compound 4 containing an aldehyde structure with a yield of 45.6% and MS (ESI) M⁺ = 888.40 (C 56 H 68 N2O2SSi2);

[0063] Step S4: Reduction of aldehyde group to hydroxyl group 5

[0064] At -78 °C, 2.0 equivalents of LiAlH4 were slowly added to a THF solution of compound 4 and stirred for 2 hours. The reaction solution was treated with wet silica gel, extracted, and purified to obtain the reduced product hydroxy compound 5 with a yield of 76.2% and MS (ESI) M⁺ = 891.43 (C 56 H 69 NO3SSi2);

[0065] Step S5: Etherification to generate compound 6

[0066] 1.5 equivalents of bromoethanol and 2.0 equivalents of potassium carbonate were added to a DMF solution of compound 5 and reacted at 60°C overnight. After the reaction, the mixture was poured into water for extraction, washed with concentrated brine, dried, and purified by column chromatography to obtain the etherified product compound 6 with a yield of 85.4% and MS (ESI) M⁺ = 935.63 (C 58 H 73 NO5SSi2);

[0067] Step S6: Removal of the TBDPS protecting group to obtain compound 7

[0068] 1.2 equivalents of n-butyl lithium were added to a THF solution of compound 6. After reacting at -78 °C for 1 hour, 2.0 equivalents of DMF were added and stirred at room temperature overnight. The reaction solution was washed with water and then dried by spin drying. The resulting solid was dissolved in anhydrous THF and 1.5 equivalents of tetrabutylammonium fluoride (TBAF) was added to remove the TBDPS protecting group. The reaction was continued at room temperature for 30 minutes to obtain compound 7 without further purification; the yield was 95.2%, and the MS (ESI) M⁺ = 415.20 (C 24 H 33 NO3S);

[0069] Step S7: Introduce a photocrosslinking group to obtain compound 8

[0070] In anhydrous dichloromethane, compound 7 was mixed with 2.4 equivalents of 4-azido-2,3,5,6-tetrafluorobenzoic acid, 3.0 equivalents of EDCI, and a catalytic amount of DMAP. The mixture was stirred at room temperature overnight. After the reaction, the mixture was washed with water, extracted, dried, and purified by column chromatography to obtain compound 8 with a yield of 81.4%. MS (ESI) M⁺ = 849.12 (C 38 H 31 F8N7O5S).

[0071] Step S8: Grafting electron acceptors to obtain the target photocrosslinked chromophore PC-FTC1

[0072] Compound 8 was mixed with an equimolar electron acceptor in anhydrous ethanol and heated to 75 °C for 1 hour. After the reaction, the solvent was dried and purified by column chromatography to obtain the target photocrosslinking chromophore PC-FTC1 with a yield of 54% and MS (ESI) M⁺ = 1310.27 (C 58 H 42 F 12 N 12 O9S).

[0073] Test example

[0074] The electro-optical material prepared in the present invention has excellent solubility and can be dissolved in common solvents such as cyclopentanone and 1,1,2-trichloroethane (TCE), and has good process adaptability. It is suitable for simple film-forming processes such as spin coating and doctor blade coating, and can form uniform, defect-free functional films on glass, indium tin oxide (ITO) conductive glass, silicon substrates, metal electrode surfaces, and dielectric material substrates such as hafnium oxide (HfO2) and titanium oxide (TiO2). The specific preparation process is as follows:

[0075] 1. Solution preparation and film forming process

[0076] First, 100 mg of electro-optical material was dissolved in 1.15 g of TCE solvent and stirred continuously under closed conditions for 12 hours. The solution was then purified by passing it through a 0.2 μm pore size filter membrane. After the filtrate was allowed to stand for half an hour, a clear and transparent solution with a concentration of 8 wt% was obtained. Thin films were prepared using a spin coating technique. 100 μL of the solution was evenly coated on the surface of a 1 cm square substrate using a micropipette. The coating was continued at a speed of 400 rpm for 60 seconds. After the film was formed, it was first baked on a 70°C hot plate for 5 minutes to remove residual solvent, and then vacuum dried for 12 hours to finally obtain a uniform film with a thickness of approximately 1 μm.

[0077] 2. Polarization orientation and light curing

[0078] To impart electro-optical properties to the film, the dried film needs to be subjected to electric field polarization. This experiment employed surface-contact polarization, applying an 80 V / μm external electric field. Following polarization, photocuring and crosslinking were performed at room temperature using a 420 nm LED light source. Visible light intensity was controlled at 5 mW / cm², and the irradiation time was 10 minutes to ensure complete crosslinking. The entire photocuring process was completed in an inert atmosphere to prevent oxygen from interfering with the crosslinking reaction. After crosslinking, the material's heat deformation temperature was significantly increased, while exhibiting excellent solvent resistance and mechanical strength. Unexposed areas can be selectively removed with solvents such as chloroform, enabling patterning.

[0079] Figure 1is the DSC curve of the electro-optical material. After visible light cross-linking, the T g Over 150°C.

[0080] Figure 2 This is a statistical graph showing changes in the absorption spectrum of the electro-optical material after cross-linking for different times. The photocrosslinking groups can be rapidly decomposed under 420nm visible light irradiation. The absorption peak of the photocrosslinked structure around 350nm decreases rapidly and then disappears, indicating that the crosslinking is complete.

[0081] 3. Photoelectric properties characterization

[0082] The electro-optic coefficient of the cross-linked film was measured using the Teng-Man reflection measurement technique. By analyzing the variation trend of the electro-optic coefficient with the polarization field strength and calculating the slope of the curve, the polarization efficiency of the material can be obtained. This index reflects the response characteristics of the material to the electric field at different doping concentrations. Related test data and polarization efficiency evaluation are as follows: Figure 3 As shown in the figure, the experimentally measured maximum electro-optic coefficient reaches 228 pm / V.

[0083] 4. Heat resistance evaluation

[0084] In order to investigate the high temperature stability of the material, the following accelerated aging experiments were designed: 1) continuous storage in a nitrogen environment at 85°C for 1000 hours; 2) constant temperature maintenance at 100°C in a nitrogen atmosphere for 1000 hours; 3) aging at a high temperature of 120°C for 1000 hours. Figure 4 Test results show that the material retains more than 99% of its electro-optical performance after aging at 85°C; it still maintains more than 90% of its initial performance after treatment at 100°C; and even under harsh conditions of 120°C, it can maintain more than 80% of its electro-optical activity, fully demonstrating its excellent thermal stability.

[0085] In summary, the optoelectronic polymer material developed in this example can not only be integrated with micro-nano optoelectronic devices through a simple process, but also can be photocrosslinked and cured at room temperature, and has both excellent electro-optical properties and high-temperature stability.

Claims

1. An electro-optical material capable of cross-linking by visible light, characterized in that: Its structural formula is as follows: Mode ; Wherein, R1: C1-C20 alkyl, or one of the following groups: ; R2: C1-C20 straight or branched alkyl, or one of the following groups: 。 2. The method for preparing an electro-optical material capable of cross-linking by visible light according to claim 1, characterized in that: The following steps are involved: (1) 4-(Dihydroxymethyl)aniline was dissolved in anhydrous dichloromethane, triphenylsilyl chloride and a catalyst were added, and the reaction was stirred at room temperature until the raw material was completely converted. The reaction solution was evaporated to remove the solvent, extracted with ethyl acetate, dried over anhydrous magnesium sulfate, and purified by column chromatography to obtain compound 2; (2) Compound 2 was dissolved in anhydrous tetrahydrofuran, sodium hydride was added and stirred in an ice bath to alkalize, and then a thienyl phosphate reagent was added dropwise. The reaction was allowed to proceed at room temperature for several hours. After the reaction was completed, water was added to quench the reaction, and the mixture was extracted, dried, and purified by column chromatography to obtain compound 3; (3) Compound 3 was activated by reacting with n-butyl lithium in anhydrous DMF, and the temperature was controlled to -78 °C. DMF was then slowly added dropwise to carry out hydroformylation reaction. After the reaction, water was added, extraction was performed, and column chromatography was performed to purify the product to obtain compound 4 containing an aldehyde structure. (4) LiAlH4 was slowly added to the THF solution of compound 4 at -78 °C and stirred for reaction. The reaction solution was treated with wet silica gel and purified after extraction to obtain the reduced product hydroxy compound 5; (5) Add bromoethanol and potassium carbonate to a DMF solution of compound 5, react at 60°C overnight, pour into water for extraction, wash with concentrated brine, dry, and purify by column chromatography to obtain the etherified product compound 6; (6) n-Butyl lithium was added to a THF solution of compound 6, and DMF was added after the reaction at -78 °C for a certain period of time. The mixture was stirred at room temperature overnight. The reaction solution was washed with water and then dried by rotary evaporation. The resulting solid was dissolved in anhydrous THF, and tetrabutylammonium fluoride was added to remove the TBDPS protecting group. The mixture was reacted at room temperature to obtain compound 7. (7) Compound 7 was mixed with 4-azido-2,3,5,6-tetrafluorobenzoic acid, EDCI and DMAP in anhydrous dichloromethane and stirred at room temperature overnight. After the reaction, the mixture was washed with water, extracted, dried and purified by column chromatography to obtain compound 8. (8) Compound 8 was mixed with an equimolar electron acceptor in anhydrous ethanol and heated to 75°C for reaction. After the reaction was completed, the solvent was dried and purified by column chromatography to obtain the product.

3. The method for preparing an electro-optical material capable of cross-linking by visible light according to claim 2, wherein: The catalyst in step (1) is pyridine or a basic organic amine.

4. The method for preparing an electro-optical material capable of cross-linking by visible light according to claim 3, wherein: The electron acceptor structure in step (8) is as follows: Formula II .

5. Use of the electro-optical material capable of cross-linking induced by visible light as claimed in claim 1 in the preparation of electro-optical films.

6. The use according to claim 5, characterized in that The specific operation is as follows: after the electro-optical material is formed into a film, it is polarized by an electric field to obtain electro-optical properties, and then irradiated with visible light of 400-500nm and intensity of 5-10 mW / cm² for 5-10 minutes for cross-linking and curing to obtain an electro-optical film.

Images