Preparation method and application of cyclosiloxane-boroxane copolymer

Abstract

The invention belongs to the technical field of supramolecular materials, and relates to a preparation method of a cyclosiloxane-boroxane copolymer. The method comprises the following steps: adding a cyclosiloxane compound and a boric acid compound containing an unsaturated bond into chloroform under the protection of inert gas, adding a Karst catalyst, and reacting to obtain a cyclosiloxane compound containing a boron-oxygen bond; the cyclosiloxane compound containing the boron-oxygen bond is stirred in a methanol and dichloromethane solvent at normal temperature, a boric acid group modified cyclosiloxane compound is prepared through proton exchange reaction deprotection, and the cyclosiloxane-boroxane copolymer is prepared through heating dehydration. The synthesis method is simple, the synthesis condition is mild, the prepared boron-oxygen-silicon microtube is simple in process, uniform in structure and stable in thermodynamic property, and a new thought is provided for research of the boron-oxygen-silicon microtube serving as a microreactor, an artificial capillary, a biomedical stent and other medical advanced devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of supramolecular materials, and relates to a preparation method and application of a cyclosiloxane-cycloboroxane copolymer. Background Art

[0002] Cyclosiloxane compounds have characteristics such as flexible and high-strength Si-O bonds and high reactivity under specific conditions in organic reactions, and are often used to prepare polymethylhydrogensiloxanes with various specific hydrogen contents and required chain units, as well as functional group-modified polysiloxanes. Cycloboroxanes are usually formed by dehydration of three boric acid molecules and have a very high bond dissociation energy. Due to its unique tripod ring structure, it plays an important role in different fields such as dendritic polymers, hyperbranched polymers, catalysis, and small molecule recognition receptors. With the increasing demand for high-value functional materials in society, especially those with dynamic properties, the research on integrating multiple functions into a single material has received more and more attention.

[0003] In recent years, the research on hollow fibers has received more and more attention. This material has the characteristics of diverse preparation methods, rich types, and wide applications. The preparation methods mainly include coextrusion / coaxial electrospinning method, template method, 3D printing method, electrospinning method, self-curling method, and gas foaming method, etc.; the applications mainly focus on fields such as gas separation, cell culture, microfluidic channels, and artificial tubular tissues. For example, Zhang et al. developed a new type of vascular module based on a PDMS hollow tube, which closely simulates the morphology and characteristics of human blood vessels to integrate multiple organ chips. Currently, artificial blood vessels (diameter > 6 mm) have been successfully applied in the treatment of large arteries, but the research and application of small-sized microvascular substitutes are still a challenge. Summary of the Invention

[0004] The present invention proposes a preparation method and application of a novel cyclosiloxane-cycloboroxane copolymer for the problems existing in the research and application of traditional small-sized microvascular substitutes.

[0005] In order to achieve the above purpose, the present invention is realized by adopting the following technical solution: A preparation method of a cyclosiloxane-cycloboroxane copolymer. Under the protection of an inert gas, a cyclosiloxane compound and a boric acid compound containing an unsaturated bond are added to chloroform, and a Karstedt catalyst is added, and a cyclosiloxane compound containing a boron-oxygen bond is obtained by reaction; the cyclosiloxane compound containing a boron-oxygen bond is stirred at room temperature in a methanol and dichloromethane solvent, and deprotection is carried out through a proton exchange reaction to obtain a cyclosiloxane compound modified with a boric acid group, and heating dehydration is carried out to obtain a cyclosiloxane-cycloboroxane copolymer.

[0006] The above preparation method of the cyclosiloxane-cycloboroxane copolymer comprises the following steps: (1)Under the protection of inert gas, tetramethylcyclotetrasiloxane and 4-vinylphenylboronic acid pinacol ester were added to chloroform, and a Kester catalyst was added. The mixture was reacted at 60 °C for at least 12 h to obtain a boroxine-bond-containing cyclic siloxane compound c.

[0007] The reaction equation is as follows: .

[0008] (2)Under the protection of inert gas, methylboronic acid and trifluoroacetic acid were added to the boroxine-bond-containing cyclic siloxane compound c prepared in the above step, and then dichloromethane was added. The mixture was stirred at room temperature until white solid precipitated, then methanol was added to dissolve the white solid, and the mixture was continuously stirred at room temperature for at least 12 h to obtain a boronic acid group-modified cyclic siloxane compound d.

[0009] The reaction equation is as follows: .

[0010] (3)The boronic acid group-modified cyclic siloxane compound d was heated to about 150 °C, and bubbles and steam emerged. The hydroxyl groups on boric acid dehydrated to form a ring by three molecules of water. When there were no more bubbles and steam emerging, it was proved that the formation of boroxine bond was completed, and a cyclic siloxane-cyclic boroxine copolymer was obtained.

[0011] The reaction equation is as follows: .

[0012] Preferably, in step (1), the molar ratio of tetramethylcyclotetrasiloxane to 4-vinylphenylboronic acid pinacol ester is 1:6.

[0013] The above cyclic siloxane-cyclic boroxine copolymer can be used to prepare borosilicate microtubes. The specific operation steps are as follows: The cyclic siloxane-cyclic boroxine copolymer was added to a mixed solution with a volume ratio of methanol to dichloromethane of 1:1. After being fully mixed and homogenized, it was poured onto a hot plate, and the hot plate was set to heat at a constant temperature of 145-155 °C. While heating, it was slowly drawn outwards, and borosilicate microtubes could be prepared.

[0014] After testing, the surface of the microtubes prepared by the above method is very smooth and uniform, no obvious rough or defective areas are found, and at the same time, no phase separation, unevenness, etc. are observed. Further characterization of the cross-section of the microtubes found that the prepared microtubes are hollow structures, and the cross-section is a uniform circular shape.

[0015] The boron-oxygen-silicon microtubes prepared by the present invention can be filled to serve as a micro-reactor and used as a reaction carrier in some micro-scale scenarios such as biosensors. A photochromic agent is loaded into the microtubes, and both ends are instantaneously heated, and the two sides of the ports are sealed. Then, when the microtubes are irradiated with a 365 nm ultraviolet lamp, it is found that the microtubes without the fluorescent agent filled show blue fluorescence, and the microtubes filled with the fluorescent agent emit green fluorescence, and the distribution of the fluorescent agent in the microtubes can be observed.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. The present invention provides a cyclosiloxane-cyclic boroxane copolymer with a simple synthesis method and mild synthesis conditions. The addition of the silicon-oxygen bond can increase the hydrophobicity of the material surface and protect the water sensitivity of the boron-oxygen bond itself.

[0017] 2. The boron-oxygen-silicon microtubes prepared by the present invention have a simple process, uniform structure and stable thermodynamic performance, providing new ideas for the research of advanced medical devices such as micro-reactors, artificial capillaries and biomedical scaffolds. Description of the Drawings

[0018] Figure 1 SEM characterization diagram of the boron-oxygen-silicon microtubes prepared in Example 2.

[0019] Figure 2 Image of the boron-oxygen-silicon microtubes prepared in Example 2 under an optical microscope.

[0020] Figure 3 SEM characterization diagram of the internal hollow structure of the boron-oxygen-silicon microtubes prepared in Example 2.

[0021] Figure 4 Application diagram of the boron-oxygen-silicon microtubes prepared in Example 2. Detailed Description of the Invention

[0022] In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0023] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed in the following specification.

[0024] Example 1 This example provides a synthesis route of cyclosiloxane-cyclic boroxane copolymer, and the specific steps are as follows.

[0025] Under nitrogen protection, 1 g of tetramethylcyclotetrasiloxane (CAS No.: 2370-88-9) and 3.8 g of 4-vinylphenylboronic acid pinacol ester were successively added to a three-necked flask using a 10 mL syringe. The temperature was raised to 60 °C, and after waiting for the temperature to be constant, 0.03 g of the catalyst platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane (CAS No.: 68478-92-2) was slowly injected into the three-necked flask using a syringe. Then, 60 mL of chloroform was added to the three-necked flask as a solvent, and the mixture was refluxed and reacted overnight for at least 12 h. During the reaction, it could be observed that bubbles continuously emerged in the solution, which was the hydrogen released by hydrosilylation. At the end of the reaction time, thin-layer chromatography (TLC) analysis was used to detect whether the reaction was complete. After the reaction was completed, the chloroform solvent was removed by a rotary evaporator (40 °C, 80 rpm, 2 h) to obtain a crude product. The crude product was purified by silica gel column chromatography, and the eluent was petroleum ether:dichloromethane = 1:1, v / v. Through column chromatography separation, a cyclic siloxane compound c was obtained, which was a transparent oily liquid. Finally, after calculation, the yield of the target product was 80.2%. The structure of the synthesized compound c was characterized: an appropriate amount of c was weighed into a nuclear magnetic resonance tube, dissolved in deuterated chloroform, and tested using a nuclear magnetic resonance spectrometer at 25 °C. After detection, there were no impurity peaks in the spectrum, indicating that the product reached a high purity. The nuclear magnetic data are as follows: 1 H NMR(400 MHz, CDCl3): δ7.63-7.50(d, 8H), 7.12(s, 8H), 2.43-2.40(m, 8H), 1.20(s, 48H), 0.91-0.88(m,8H), 0.12-0.08(m, 12H).

[0026] Weigh 0.2 g of the synthesized cyclic siloxane compound c and add 0.371 g of methylboronic acid into the reaction flask. Then, add 0.55 mL of trifluoroacetic acid into the reaction flask using a syringe, and add 11 mL of dichloromethane. After stirring at 200 rpm at room temperature for 2 h, it is found that white solid precipitates in the system. This is due to the progress of the proton exchange reaction, and the generated target product is insoluble in the dichloromethane solvent. At this time, add 2 mL of methanol, and it is found that the white solid dissolves rapidly and the system returns to a homogeneous state. Continue to stir at 200 rpm at room temperature for 12 h, and then analyze by thin layer chromatography (TLC) to detect whether the reaction is complete. After the reaction is complete, add 20 mL of deionized water to the reaction flask. At this time, filter and wash the precipitated white solid, wash it three times with water and dichloromethane respectively, about 3 mL each time, to remove the unreacted methylboronic acid and compound c in the system. Then, perform vacuum drying operation on the white solid for 3 h, and at this time, cyclic siloxane compound d is obtained. Characterize the structure of the synthesized compound d: Weigh an appropriate amount of d into a nuclear magnetic tube, dissolve it with deuterated methanol, and test it using a nuclear magnetic resonance instrument at 25 °C. After detection, there are no impurity peaks in the spectrum, indicating that the product reaches a high purity. The nuclear magnetic data are as follows: 1 H NMR(400 MHz, CD3OD): δ7.63-7.50(d, 8H), 7.12(s,8H), 4.58(s, 6H), 2.65(s, 8H), 1.20(s, 6H), 0.91-0.88(m, 8H), 0.12-0.08(m,12H).

[0027] Put the synthesized pure product d into a 50 mL small beaker, place it in an oil bath to heat it evenly, use a temperature probe to monitor the temperature, and ensure that the temperature is heated to about 150 °C until it reaches the molten state. It can be observed that bubbles continuously emerge in the molten liquid during this process. This is a dehydration process, and the hydroxyl groups on boric acid lose three molecules of water to form a ring to construct a cyclic boroxine structure. After no bubbles and steam emerge, it proves that the formation of the boron-oxygen bond into a ring is completed, and a cyclic siloxane-cyclic boroxine copolymer is obtained.

[0028] Example 2 In this example, the cyclic siloxane-cyclic boroxine copolymer prepared in Example 1 is used to synthesize boron-oxygen-silicon microtubes.

[0029] The synthesized cyclosiloxane-cyclic boroxane copolymer was dissolved in a 10 mL small beaker with a 5 mL mixed solution of methanol and dichloromethane (volume ratio 1:1) to make the solution viscous. After thoroughly stirring and mixing evenly with a glass rod, it was poured onto a hot plate, and the hot plate was set at a constant temperature of 150 °C. During the heating process of the hot plate, while stirring with a glass rod until it reached a state where it could be drawn into filaments, then the viscous liquid was picked up from the small beaker and stuck to the hot plate, and while heating, it was slowly drawn outwards. During the heating process, methanol and dichloromethane gradually evaporated and escaped from the system, evaporating simultaneously from the outside and inside, resulting in rapid solidification of the outer part of the fiber, and thus a hollow-structured microtube could be prepared.

[0030] The hollow-structured microtubes prepared in this example were characterized, and the results are as Figures 1-4 shown. Among them Figure 1 is the SEM characterization image of the borosilicate microtubes prepared in this example. Figure 2 is the image of the borosilicate microtubes prepared in this example under an optical microscope. From Figure 1 and Figure 2 , it can be seen that the surface of the microtubes prepared in this example is very smooth and uniform, no obvious rough or defective areas are found, and at the same time, no phase separation, unevenness, etc. are observed. Figure 3 is the SEM characterization image of the internal hollow structure of the borosilicate microtubes prepared in this example. From Figure 3 , it can be seen that the microtubes prepared in this example have a hollow structure, and the cross-section is a uniform circular shape.

[0031] A fluorescent dye solution was filled into the microtubes, and both ends were instantaneously heated with a hot air gun to seal the two sides of the ports. As Figure 4 shown, when the microtubes were irradiated with a 365 nm ultraviolet lamp, the microtubes without the filled fluorescent agent showed blue fluorescence, and the microtubes filled with the fluorescent agent emitted green fluorescence, and the distribution of the fluorescent agent in the microtubes could be observed. Thus, it was verified that this kind of microtube could be filled and used as a kind of microreactor, applied as a reaction carrier in some microscale scenarios such as biosensors. Currently, artificial blood vessels (diameter > 6 mm) have been successfully applied in the treatment of large arteries, but the research on small-sized microvascular substitutes is still a challenge. The research of this example provides new ideas for the research of medical advanced devices such as its use as a microreactor, artificial capillaries, and biomedical scaffolds.

[0032] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a cyclic siloxane-cyclic boroxane copolymer, characterized in that, Under the protection of inert gas, a cyclic siloxane compound and a boric acid compound containing an unsaturated bond are added to chloroform, and a Kaster catalyst is added, and a cyclic siloxane compound containing a boron-oxygen bond is obtained through reaction; the cyclic siloxane compound containing a boron-oxygen bond is stirred at room temperature in a methanol and dichloromethane solvent, and deprotected through a proton exchange reaction to obtain a cyclic siloxane compound modified with a boric acid group, and heating and dehydration are carried out to obtain a cyclic siloxane-cyclic boroxine copolymer.

2. The preparation method of the cyclosiloxane-cycloboroxane copolymer according to claim 1, wherein, The steps are as follows: (1) Under the protection of inert gas, tetramethylcyclotetrasiloxane and 4-vinylphenylboronic acid pinacol ester are added to chloroform, and a Kaster catalyst is added, and the mixture is reacted for at least 12 h to obtain a cyclic siloxane compound c containing a boron-oxygen bond; (2) Under the protection of inert gas, methylboronic acid and trifluoroacetic acid are added to the cyclic siloxane compound c containing a boron-oxygen bond, and then dichloromethane is added. When white solid precipitates upon stirring at room temperature, methanol is added to dissolve the white solid, and stirring is continued at room temperature for at least 12 h to obtain a cyclic siloxane compound d modified with a boric acid group; (3) The cyclic siloxane compound d modified with a boric acid group is heated until bubbles and steam emerge, and then kept warm until the bubbles and steam disappear to obtain a cyclic siloxane-cyclic boroxine copolymer.

3. The preparation method of the cyclosiloxane-cycloboroxane copolymer according to claim 2, characterized in that, In step (1), the molar ratio of tetramethylcyclotetrasiloxane to 4-vinylphenylboronic acid pinacol ester is 1:

6.

4. A method for preparing boron-oxygen-silicon microtubes, characterized in that The cyclic siloxane-cyclic boroxine copolymer prepared in claim 2 or 3 is added to a mixed solution of methanol and dichloromethane. After mixing evenly, it is poured onto a hot plate and heated at 145-155 °C, and then slowly drawn into a boron-oxygen-silicon microtube.

5. Use of the boron-oxygen-silicon microtube according to claim 4 in a microreactor, an artificial capillary, and a biomedical stent.

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