A method of diacetylene topological chemical reaction

Abstract

The application discloses a method for diacetylene topological chemical reaction, which comprises the following steps: spin-coating a diacetylene solution on a substrate to form a coating film; and irradiating the coating film with an infrared light source to generate polydiacetylene through reaction. Compared with the side reactions and degradation caused by high-energy rays which make materials enter an electronic excited state, and the material fragmentation caused by the violent spatial change of molecules under high polymerization, the mid-infrared light vibration excitation in the method can be used as a means for initiating the vibration of molecules in an electronic ground state, and can be more widely close to a potential energy surface under mild conditions, so that various adverse effects generated in the electronic excited state can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of infrared vibration excitation chemical reaction. More particularly, it relates to a method for topological chemical reaction of diacetylene. BACKGROUND

[0002] Diacetylenes (DAs) are a class of compounds containing 1,3-butadiyne structure, such as Figure 1 The process of topological chemical polymerization of DAs to form polydiacetylene (PDA) is shown in the figure. PDA is a model system of one-dimensional conjugated π electrons, which has wide application value in nonlinear optics (NLO). People have carried out a lot of research on its electronic and optical properties. In third-order NLO materials, its ultrafast response makes it one of the first organic materials to reach the full optical switch index, and long-chain alkyl, carboxylic acid or aromatic ring can be introduced through side chain, which can change the crystal lattice packing while keeping the conjugated skeleton, improve the third-order nonlinear susceptibility and dispersion relationship. In second-order NLO, it also provides new candidates for electro-optic modulators and terahertz wave generators. In addition, DAs can be prepared into single crystals, LB films, thin films, nanofibers, etc., to meet different integration scenarios such as photonic chips and flexible waveguides. These properties make it have device-level applications in all-optical switches / modulators, optical limiting and laser protection devices, and electro-optic modulators, and its processing temperature is also compatible with CMOS back-end, and it has continuous application value in photonic chips, optical communication, etc. In production preparation, except for a few exceptions, most DAs can be polymerized by topological chemical reaction at a temperature lower than their melting point through γ quantum, X-ray, ultraviolet / visible light or heating (Journal of Polymer Science: Polymer Physics Edition, 1978, 16(5): 859-881.). However, the initiation conditions of high-energy rays usually cause degradation of PDA materials, and after high polymerization, the material will also crack due to the drastic spatial change of molecules, which will hinder the application of PDA in devices to some extent; in addition, the polymerization induced by heating means will face the problems of high-temperature phase change and melting of DAs, and the slow polymerization rate of materials in low-temperature environment will also lead to low preparation efficiency, which greatly restricts its application value. SUMMARY

[0003] Based on the above problems, the purpose of the present application is to provide a method for topological chemical reaction of diacetylene.

[0004] Compared with the side reactions and degradation caused by high-energy rays making the material into an electronic excited state, and the material fragmentation caused by the violent spatial change of the molecules under high polymerization, the mid-infrared light vibration excitation in the method of the present application can be used as a means to induce the vibration of the molecules in the electronic ground state, and can avoid the various adverse effects caused by the electronic excited state under the above-mentioned conditions. The infrared vibration excitation has been proved to be used for inducing general gaseous chemical reactions and some low-energy barrier condensed state chemical reactions. In the condensed state system, the solid-state polymerization of diacetylene as a common topological chemical model system effectively avoids the disorder often existing in the homogeneous solution reaction, and the chain amplification characteristics are also conducive to realizing the vibration excitation reaction with a high energy barrier in the condensed phase.

[0005] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows:

[0006] A method for diacetylene topological chemical reaction, comprising the following steps:

[0007] The diacetylene solution is spin-coated on the substrate to form a coating film.

[0008] The coating film is irradiated by using an infrared light source, and a polydiacetylene is generated by reaction.

[0009] Further, the diacetylene is selected from 2,4-heptadecyne acid.

[0010] Further, the concentration of the diacetylene solution is 10-50 mg / ml.

[0011] Further, the diacetylene solution is obtained by dissolving diacetylene in super-dry n-hexane.

[0012] Further, the coating film comprises amorphous regions and microcrystalline domains, and the diameter of the microcrystalline grains in the microcrystalline domains is 0.1-10 μm.

[0013] Further, the XRD result of the thin film contains (010), (200) and (030) crystal face diffraction peaks. The intensity of the crystal face diffraction peak is high.

[0014] Further, the substrate is an infrared transmission substrate. If the substrate is a non-infrared transmission substrate such as a glass sheet, unnecessary thermal effects may be caused.

[0015] Further, the substrate is selected from calcium fluoride, zinc selenide or a silicon wafer.

[0016] Further, the thickness of the coating film is less than 1 μm.

[0017] Further, the thickness of the coating film is 200-500 nm.

[0018] Further, the thickness of the coating film is 200-400 nm.

[0019] Further, the spin coating condition is: room temperature about 25-27℃, rotation speed is 3000-3500 rpm, time is 30-60 s.

[0020] Further, the spin coating condition is: room temperature about 25-27℃, rotation speed is 3000 rpm, time is 60 s.

[0021] Further, the infrared light source is one or several of the infrared light sources with wavelength of 1-25 μm. By controlling the wavelength of the infrared light source, the situation that the polymer film or crystal obtained by polymerization under the electronic excited state is easy to crack or decompose can be improved.

[0022] Further, the infrared light source is several of the infrared light sources with wavelength of 3-10 μm.

[0023] Further, the infrared light source is a mixed light source of at least one of the infrared light sources with wavelength of 3-5 μm and at least one of the infrared light sources with wavelength of 5-10 μm. In this condition, the effect of improving the situation that the polymer film or crystal obtained by polymerization under the electronic excited state is easy to crack or decompose is better.

[0024] Further, the infrared light source is a mixed light source of two or more of the infrared light sources with wavelength of 3-5 μm and at least one of the infrared light sources with wavelength of 5.5-10 μm. In this condition, the effect of improving the situation that the polymer film or crystal obtained by polymerization under the electronic excited state is easy to crack or decompose is optimal.

[0025] Further, the power density of the infrared light source irradiation is 10-7000 mW / cm 2 .

[0026] Further, the incident angle of the infrared light source irradiation to the coating film is 40-45°.

[0027] Further, the incident angle of the infrared light source irradiation to the coating film is 45°.

[0028] Further, the infrared light source can control the temperature below the melting point and phase transition point of the sample DAs. In this condition, the adverse effects of non-topological chemical reaction (such as reaction rate reduction, sample property change) can be well improved.

[0029] The beneficial effects of the present application are as follows:

[0030] The diacetylene topological chemical reaction method provided in the technical scheme avoids various adverse effects caused by high-energy rays in the electronic excited state, and overcomes defects such as melting at high temperature and slow reaction rate at low temperature in the thermal reaction. BRIEF DESCRIPTION OF DRAWINGS

[0031] The specific embodiments of the present application are described in further detail below with reference to the accompanying drawings.

[0032] Figure 1 A schematic diagram of the polymerization of diacetylene topological chemistry is shown.

[0033] Figure 2 A scanning electron microscope of the microcrystalline domain of the microcrystalline grain morphology and optical microscope of the thin film obtained by spin coating is shown.

[0034] Figure 3 A schematic diagram of the reaction light path and its in-situ temperature control detection device is shown.

[0035] Figure 4 A schematic diagram of the sample preparation scheme and mechanism is shown.

[0036] Figure 5 The FTIR spectra and UV-Vis spectra of 2,4-heptadecanediyne acid after UV and IR reaction conditions at 30℃ are shown, wherein A is the XRD information of the sample before, during and after the early stage of UV irradiation reaction, A shows the FTIR spectra of the early, middle and late stages of UV irradiation reaction; B is the FTIR spectra of the pre-irradiation, end of reaction and supersaturation after reaction; C is the kinetic curve obtained by in-situ characterization device determination spectrum evolution, the slope indicates the reaction rate; D shows the UV-Vis spectra of the sample before, during and after the early stage of UV irradiation reaction, and the sample before and after the completion of IR irradiation at 30℃.

[0037] Figure 6 The XRD information of 2,4-heptadecanediyne acid is shown, wherein A is the XRD information of the sample after UV irradiation and IR irradiation at 30℃, and the fresh sample; B is the in-situ temperature change XRD information at 30℃, near 50℃ and near 55℃.

[0038] Figure 7 A microscope photograph of the damage cracks of the thin film after UV reaction conditions is shown.

[0039] Figure 8 A microscope photograph of the damage cracks and degradation of the thin film after high-dose UV reaction conditions is shown.

[0040] Figure 9 A microscope photograph of the thin film after IR reaction conditions is shown.

[0041] Figure 10 Results of single wavelength laser and composite wavelength infrared light excitation reaction; where the left is the absorption peak and its vibration mode corresponding to different single wavelengths, and the right is the kinetic curve of the reaction excited by each single wavelength and composite wavelength.

[0042] Figure 11 The kinetic curves of the reaction of 2,4-heptadecadiynoic acid at different temperatures and the kinetic curve of the reaction under the condition of IR excitation at 30°C are shown.

[0043] Figure 12 The polymerization kinetic curves of 2,4-heptadecadiynoic acid thin films of different thicknesses under the condition of 30°C infrared excitation are shown. DETAILED DESCRIPTION

[0044] In order to more clearly illustrate the present application, the present application will be further described below in conjunction with preferred embodiments and the accompanying drawings. Like components are denoted by the same reference numerals in the drawings. Those skilled in the art should understand that the specific description below is illustrative rather than limiting, and should not limit the protection scope of the present application.

[0045] EMBODIMENTS

[0046] 1. Materials and methods

[0047] 1.1. Preparation of diacetylene monomer:

[0048] The diacetylene sample 2,4-heptadecadiynoic acid (HD) (melting point 58.5°C) was purchased from Tci, and the powder was gray-green (partially polymerized). The sample was dissolved in ultra-dry n-hexane (97.5%, Extra dry with molecular sieves, water≤50 ppm, in resealable bottle, Innochem), 10°C, 12000 rpm, 5min centrifugation to take the supernatant, and monomer was obtained after recrystallization. The purity of the obtained sample was greater than 98% checked by high performance liquid chromatography. It was stored as a powder in a freezer (T=-20°C) to reduce spontaneous polymerization. Before the experiment, the solution was dissolved in ultra-dry n-hexane to a constant concentration of 10-50 mg / ml (for example 10 mg / ml, 15 mg / ml, 20 mg / ml, 25 mg / ml, 30 mg / ml, 35 mg / ml, 40 mg / ml, 45 mg / ml and 50 mg / ml), and used within a week.

[0049] 1.2. Preparation of thin film samples:

[0050] At room temperature, 40 μL of the above solution (25 mg / mL) was placed on a calcium fluoride (CaF2) substrate and spin-coated at 3000 rpm for 60 s to obtain a relatively uniform film. The thickness of the CaF2 sample was measured to be approximately 198 nm using white light interferometry. Table 1 shows the film thickness measurements under these spin-coating conditions for different concentrations. The thickness was determined by SEM (Sequencing). Figure 2 (as shown in A) and optical microscope ( Figure 2 As shown in Figure B, the thin film exhibits amorphous regions and microcrystalline domains, with the precipitated microcrystals ranging in size from 0.1 to 10 μm. The crystalline film formed on the substrate plane consists of domains with random orientations, and the monolayer plane is parallel to the substrate.

[0051] Table 1

[0052]

[0053] 1.3. Use and mechanism of reaction and in-situ detection and temperature control device:

[0054] A schematic diagram of the reaction optical path and its in-situ detection and temperature control device is shown below. Figure 3 As shown in Figure A, different reaction light sources are changed by optical path switching switch 1. Single-wavelength irradiation experiments were conducted using a 4.5-7 μm continuously tunable OPO laser with an incident angle of approximately 45°, a spot diameter shaped to 2.88 mm, and a power density of 70 mW / cm². 2 The composite wavelength excitation experiment was conducted using an excitation source with a wavelength range of 1-25 μm (preferably including composite infrared sources of 4.44 μm, 4.59 μm, and 5.98 μm), an incident angle of 45°, a spot diameter of 12.03 mm, and an optical power density of 10 mW / cm². 2 The wavelength of the light source is measured by reflecting off the sample reaction stage through a shaping optical path into the interferometer. After forming a coherent signal, it is detected by a detector and subjected to Fourier transform. Power density is obtained by measuring the spot size and light intensity. By changing the optical path switching switch 2, the sample is directed into the power density measurement optical path. The spot size is measured using a blade method, where a blade is fixed to the X-axis moving platform to perpendicularly cut the beam. Figure 3 As shown in Figure B, adjust the micrometer screw gauge so that the power after cutting is 90% of the total power, and record the micrometer screw gauge reading at this position as x1. Continue cutting until the power is 10% of the total power, and record the micrometer screw gauge reading at this position as x2. At this time, use formula (1) to calculate:

[0055]

[0056] wherein, Φ is the spot diameter, which is 2.88 mm. During the reaction, the CaF2 side of the sample was tightly placed in the temperature control device (INSTEC, HCS621GXY, liquid nitrogen cooling) and fixed in the detection position of the Fourier transform infrared spectrometer (Thermo Fisher, is20) by a custom-made bracket. When the kinetics was determined, each spectrum was obtained by 32 scans, the resolution was set to 4 cm -1 , and the zero padding was set to level 2. The scan lasted at least 30 min, and the reaction would approach the end point to obtain polydiacetylene.

[0057] As shown in Figure 4 , a diacetylene spin-coated film was prepared in this embodiment. By infrared light, the rotation and bending of adjacent molecules and the change of diacetylene group bond length were induced, so that the reaction centers C1 and C4 atoms were close to each other and reacted. By using a self-developed light source and an in-situ reaction detection device, a method for exciting sample reaction by infrared light of a single wavelength and its composite wavelength was realized. The in-situ detector device FT-IR can monitor the kinetics of the reaction process. By this method, a high-efficiency reaction scheme of a diacetylene sample was verified, and the reaction rate was 14 times faster than that of heating at the same temperature. After the sample reaction was completed, no cracks appeared, and FT-IR spectrum and ultraviolet-visible spectrum showed that the sample also did not appear degradation phenomenon.

[0058] As a comparison, UV light source was used for irradiation. The UV light source was a LED ultraviolet lamp (Shanghai Jiapeng Technology Co., Ltd.) with a center wavelength of 365 nm, the illumination diameter was 90 mm, and the power density was 47 mW / cm 2 .

[0059] 1.4. FT-IR characterization and measurement of kinetic data:

[0060] In the in-situ FT-IR detection temperature control device, the temperature was controlled at 30°C, and the spectral evolution of the sample under UV irradiation, IR irradiation, and no light irradiation was determined, respectively. Figure 5 In the middle A, the FT-IR spectra of the early, middle and late stages of UV irradiation reaction are shown. Figure 5 In the middle B, the FT-IR spectra of the pre-reaction, the end of the reaction and the over-saturation irradiation after the reaction are shown. Figure 5 In the middle C, the kinetic curve obtained by in-situ characterization device for determining spectral evolution is shown, and the slope indicates the reaction rate.

[0061] 1.5. UV-Vis spectrophotometer characterization:

[0062] The UV-Vis spectra of the sample before and after the reaction in the in-situ reaction device (SHIMADZU, UV-2600) were determined, and a custom-made bracket was used to transfer to ensure the repeatability of sample positioning. As Figure 5The UV-Vis spectra of the samples under 30 °C temperature control are shown in the early, middle and late stages of UV irradiation, and in the early and completed stages of IR irradiation.

[0063] 1.6. XRD characterization:

[0064] The XRD data (Bruker D8 advance) of the samples after IR irradiation and UV irradiation under 30 °C temperature control were measured, respectively. The samples showed strong (010), (200) and (030) crystal face diffraction peaks, indicating a certain periodic structure, as shown in Fig. 1.6A. Figure 6 In addition, the in-situ temperature-variable XRD (Rigaku SmartLab 9 kW) data of the fresh sample at room temperature, near 30 °C, near 50 °C and near 55 °C were measured. The results showed that at 50 °C, the (010), (200) and (030) crystal face diffraction peaks of the sample were reduced to a certain extent, and at 55 °C, the (200) and (030) diffraction peaks disappeared, indicating that the sample had phase transition at low temperature, which was not conducive to the topological chemical reaction of the material, as shown in Fig. 1.6B. Figure 6

[0065] 2. Experimental results

[0066] 2.1 Sample morphology and decomposition

[0067] Figure 7 The microscope photos of the sample after UV reaction and polymerization at different magnifications are shown. As can be seen from the figure, the surface morphology of the sample after UV reaction and polymerization presents a large number of cracks. Figure 8 The microscope photos of the thin film after 200 minutes of high-dose UV irradiation reaction at 47 mW / cm 2 show the damage cracks and degradation of the thin film. As can be seen from the figure, in order to further increase the ultraviolet irradiation dose, the color of the sample has presented the degradation color after decomposition and more cracks. Figure 9 The microscope photos of the thin film after IR reaction at different magnifications are shown. As can be seen from the figure, the surface of the sample after infrared reaction presents a complete and continuous morphology without cracks. Figure 5 The spectral information of the sample after UV and IR reaction, respectively, is shown, which can reflect the decomposition state of the material. Figure 5 Fig. 1.10A shows the FTIR spectral changes after UV reaction, and the characteristic peak of the product at 1450 cm -1 significantly decreased in the later stage of polymerization. Figure 5 Fig. 1.10B shows the FTIR spectral changes after IR reaction, and the characteristic peak of the product at 1450 cm -1 did not decrease after the supersaturation irradiation after the reaction was completed, indicating that no decomposition occurred. Figure 5 ​C represents the kinetic curve obtained from in-situ FTIR spectroscopy characterization, with the slope of the curve representing the reaction rate. The results further indicate that no decomposition occurred during the infrared reaction until the reaction endpoint, while the UV reaction showed significant decomposition in the later stages, leading to a decrease in the polymerization rate. Figure 5 In the middle D, which represents the UV-Vis spectrum, the decrease in the absorption peak of the π→π* transition in the molecule indicates that the conjugated structure is destroyed (decomposed). The results show that the absorption peak remains sharp under IR conditions, while it is significantly reduced under UV conditions. This indicates that the sample molecules can overcome the decomposition and material cracking problems faced by electronically excited state reactions induced by high-energy rays such as UV under IR reaction conditions.

[0068] 2.2. Relationship between excitation wavelength and reaction rate

[0069] Figure 10 This represents the result of the reaction under conditions of single-wavelength laser light and combined-wavelength infrared light. Specifically, Figure 10 The upper part of A shows the absorption peaks and their vibrational modes corresponding to different single wavelengths, while the lower part shows the infrared spectrum of a single wavelength of infrared light. Green: υ S (-C≡C-), corresponding to a laser wavelength of 4.59 μm; Blue: υ(COOH), corresponding to a laser wavelength of 5.98 μm; Purple: δ(CH2), corresponding to a laser wavelength of 6.81 μm. Figure 10 Figure B shows the kinetic curves of the reaction under single-wavelength and combined-wavelength infrared light conditions at 30℃. The power density of the laser used is approximately 70 mW / cm². 2 Using a 1-25μm composite light source, the power density is approximately 10mW / cm². 2 The results show the reaction rate at 30℃ as: k 1-25μm >>k υS(-C≡C-) >k υ(COOH) >k δ(CH2) >= k w / o It can be seen that composite infrared light sources have a more significant effect on improving reaction efficiency. Figure 5 Figure C shows a comparison of the kinetic curves of the reaction under different light conditions at room temperature in the photoreaction scheme. Figure 11 This section compares the reaction kinetics under different temperature conditions within a thermal reaction scheme. Among them, Figure 11 Figure A shows the kinetic curve. The green curve represents the reaction without infrared excitation; the darker the color, the higher the temperature. The red curve represents a power density of approximately 10 mW / cm³ under a controlled temperature of 30°C. 2 The reaction excited by infrared at a composite wavelength of 1-25μm. Figure 11wherein, k is the reaction rate constant, unit s-1, B is the reaction rate constant. It can be seen that the IR excitation condition plays a significant role in promoting the reaction, the reaction rate is higher than that of UV and no decomposition occurs, and the reaction rate does not decrease as it would under high-temperature conditions in the thermal reaction scheme. Compared with the reaction rate under the same temperature without light, the reaction rate is increased by 14 times.

[0070] 2.3. Relationship between film thickness and reaction rate

[0071] The relationship between film thickness and reaction rate was studied, and the results are shown in Figure 12 wherein, Figure 12 A shows the kinetic curves of thin films of different thicknesses under composite infrared light irradiation containing 4.44 microns, 4.59 microns, 5.98 microns and 6.81 microns. Figure 12 B is the curve relationship between the reaction rate and the film thickness under this condition. It can be seen that the thicker the film, the slower the reaction rate, and the relationship between the reaction rate and the film thickness conforms to formula (2):

[0072]

[0073] wherein, k is the reaction rate constant, unit s-1, B is the reaction rate constant. It can be seen that the IR excitation condition plays a significant role in promoting the reaction, the reaction rate is higher than that of UV and no decomposition occurs, and the reaction rate does not decrease as it would under high-temperature conditions in the thermal reaction scheme. Compared with the reaction rate under the same temperature without light, the reaction rate is increased by 14 times. -1 , , value is 1.1×10 -8 cm s -1 , I0 is the incident photon flux, ρ is the number of molecules per unit volume, q is the quantum yield, α is the absorption coefficient, value is 1.2×10 5 cm -1 , d is the film thickness, unit cm. The fitting function is derived from photochemical theory and is used to quantitatively relate the reaction rate to the photon flux received by the unit molecule, which explains the phenomenon that the reaction rate decreases with the increase of the film thickness, Figure 12 A shows the fitting relationship of this relationship. The fitting result can be used to predict the reaction polymerization rate of the film thickness in the range of about 200-500 nm. In practical applications, the smaller the film thickness, the higher the photon flux, and the more significant the reaction acceleration. Therefore, the reaction area can also be written on the sample by converging the reaction light, or the photon flux can be further regulated to control the reaction rate.

[0074] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description, and all the embodiments cannot be exhausted here. Any obvious changes or variations derived from the technical solutions of the present application still fall within the protection scope of the present application.

Claims

1. A method of diacetylene topological chemical reaction, characterized by, The method comprises the following steps: spinning a diacetylene solution on a substrate to form a coating film; irradiating the coating film with an infrared light source to generate polydiacetylene by reaction; The diacetylene solution is obtained by dissolving diacetylene in super-dry n-hexane, and the diacetylene is selected from 2,4-heptadecyne acid; The coating film comprises amorphous regions and microcrystalline domains, and the diameter of the microcrystalline grains in the microcrystalline domains is 0.1-10 μm; The XRD spectrum of the coating film contains (010), (200) and (030) crystal face diffraction peaks; The infrared light source is one or several of infrared light sources with a wavelength of 1-25 μm.

2. The method of claim 1, wherein, The concentration of the diacetylene solution is 10-50 mg / ml.

3. The method of claim 1, wherein, The substrate is calcium fluoride, zinc selenide or a silicon wafer.

4. The method of claim 1, wherein, The thickness of the coating film is 200-400 nm.

5. The method of claim 1, wherein, The spinning conditions are as follows: the rotation speed is 3000-3500 rpm, and the time is 30-60 s.

6. The method of claim 1, wherein, The infrared light source is several of infrared light sources with a wavelength of 3-10 μm.

7. The method of claim 6, wherein, The infrared light source is a mixed light source of at least one of infrared light sources with a wavelength of 3-5 μm and at least one of infrared light sources with a wavelength of 5-10 μm; and / or The infrared light source is a mixed light source of two or more of infrared light sources with a wavelength of 3-5 μm and at least one of infrared light sources with a wavelength of 5.5-10 μm.

8. The method of claim 1, wherein, The power density of the infrared light source is 10-7000 mW / cm 2 ; and / or The incident angle of the infrared light source irradiating the coating film is 40-45°.

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