Benzocyclobutene functionalized organic-inorganic hybrid microsphere as well as preparation method and application thereof

Abstract

The invention discloses benzocyclobutene functionalized organic-inorganic hybrid microspheres as well as a preparation method and application thereof, and relates to the technical field of modified materials. The hybrid microsphere disclosed by the invention is a siloxane hybrid microsphere prepared by hydrolytic condensation of a silane precursor; the interior of the hybrid microsphere has a ladder-cage type polysilsesquioxane structure, and when the microsphere is added into BCB resin, the dielectric constant of the BCB resin can be remarkably reduced through mutual cooperation between a nanoscale cavity in the cage type structure and the low polarizability effect of the ladder type structure; moreover, the surface of the microsphere contains a large number of benzocyclobutene functional groups, the crosslinking density of a composite material and the dispersity and compatibility of the hybrid microsphere in BCB resin can be remarkably improved, so that the adverse effect of a modified material on the performance of the BCB resin is remarkably improved, and the method is suitable for large-scale application in dielectric reduction modification of the BCB resin.

Description

Technical Field

[0001] This invention relates to the field of modified materials technology, mainly to the field of polymer modified materials technology, and specifically to a benzocyclobutene-functionalized organic-inorganic hybrid microsphere, its preparation method and application. Background Technology

[0002] Benzocyclobutene (BCB) resins, especially divinylsiloxane-bisbenzocyclobutene resin (DVSBCB), have become core substrates in high-frequency communications, microelectronic packaging, and copper-clad laminates due to their low dielectric constant (approximately 2.65), good thermal stability, and low water absorption after curing. However, with the continuous development of 5G and next-generation communication technologies, the requirements for the dielectric properties of materials are further increasing. Therefore, it is urgent to reduce the dielectric constant of BCB resins to below 2.40, while maintaining the excellent thermal stability, dimensional stability, and transparency of BCB resins, and avoiding problems such as reduced compatibility and performance degradation caused by the addition of fillers.

[0003] Traditional methods for dielectric reduction modification of BCB resins mainly involve introducing fluorine atoms or bulky groups into the resin molecular structure. While these methods can lower the dielectric constant, they are complex to synthesize, costly, and may reduce the material's thermal stability. Another common method is to add inorganic fillers to the resin, such as polyhedral oligomeric silsesquioxanes (POSS) and silica. However, these traditional inorganic fillers lack chemical bonding sites with the resin matrix, resulting in poor compatibility and easy aggregation within the resin. This leads to problems such as decreased transparency, increased dielectric loss, and a significantly higher coefficient of thermal expansion in the composite material. Furthermore, existing technologies also utilize benzocyclobutene-functionalized nanofillers and hybrid fillers to achieve dielectric reduction modification of BCB resins. However, the preparation of existing benzocyclobutene-functionalized nanofillers often requires expensive raw materials and suffers from low yield, low purity, and instability. The preparation of hybrid fillers requires high-temperature reactions or the use of surfactants to control morphology, resulting in complex processes and the potential for residual impurities to affect material properties. Meanwhile, existing methods for modifying BCB resin to reduce dielectric constant have limited efficiency at low addition levels. Typically, a higher filler addition (greater than 10 wt%) is required to reduce the dielectric constant to below 2.40, which is accompanied by a deterioration in mechanical properties.

[0004] Chinese patent CN108516986A discloses a benzocyclobutene-functionalized tetra(dimethylsiloxy)silane and its preparation method. This patent introduces benzocyclobutene functional groups into siloxane compounds via hydrosilylation for the preparation of organosilicon resins. However, the benzocyclobutene-functionalized tetra(dimethylsiloxy)silane prepared by this patent is a monomeric compound, exhibiting insufficient dispersion and compatibility in resins, and suffers from problems such as easy agglomeration and poor dielectric reduction effect.

[0005] Chinese patent CN107987278A discloses a benzocyclobutene-functionalized organosilicon resin and its preparation method. This patent employs the Piers-Rubinsztajn (PR) polycondensation reaction, utilizing compounds containing silane bonds (which are mandatory) and organosilicon compounds containing silane groups to prepare organosilicon polymers (with linear or hyperbranched structures) containing benzocyclobutene functional groups. This method requires complex raw material ratios, and the product structure is difficult to control precisely, resulting in poor dielectric reduction and deterioration of the modified resin's mechanical properties.

[0006] Therefore, there is an urgent need for a modified material that is compatible with benzocyclobutene resin, can significantly reduce dielectric properties, and has a simple preparation process to achieve efficient modification of BCB resin, so as to improve the problems of complex process, poor dispersibility and compatibility, and low dielectric reduction efficiency of existing modification processes. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of complex preparation process, poor dispersibility and compatibility, and low dielectric reduction efficiency of existing BCB resin-modified materials. This invention proposes a benzocyclobutene-functionalized organic-inorganic hybrid microsphere, its preparation method, and its application.

[0008] To achieve the above objectives, the present invention provides a benzocyclobutene-functionalized organic-inorganic hybrid microsphere, wherein the hybrid microsphere is prepared by hydrolysis and condensation of a silane precursor and has both cage-like and ladder-like polysilsesquioxane structures; the surface of the hybrid microsphere contains benzocyclobutene functional groups. The silane precursor has the structure shown in Formula I: , Ⅰ; Wherein, R1 is one of the C1 to C6 alkylene groups or is not present; R2 to R4 are each one of the C1 to C6 alkyl groups.

[0009] This invention discloses a benzocyclobutene-functionalized organic-inorganic hybrid microsphere. The microsphere possesses cage-like and ladder-like polysilsesquioxane structures, enabling a significant reduction in the dielectric constant of BCB resin (high dielectric efficiency) through the synergistic effect of the nanoscale cavities (filled with air, with a dielectric constant far lower than that of silsesquioxane) in the cage-like structure and the low polarizability of the ladder-like structure. Furthermore, the microsphere's structural features and the benzocyclobutene functional groups on its surface significantly improve the dispersibility and compatibility of the hybrid microspheres in BCB resin, thereby significantly mitigating the adverse effects of the modified material on the properties of BCB resin. This makes it suitable for large-scale application in the dielectric reduction modification of BCB resin.

[0010] Preferably, the hybrid microspheres have a particle size of 0.2~3μm; if the particle size is too small, the sphericity of the microspheres is poor and they are prone to agglomeration; if the particle size is too large, it will affect the stable dispersion in the resin and will have a negative effect on reducing the dielectric properties of the composite material. At the same time, the particle size of the hybrid microspheres directly affects their modification effect on the dielectric properties and thermal stability of BCB resin. Especially at low addition levels, the particle size of the hybrid microspheres is in the submicron range, which has a better modification effect on the dielectric properties and thermal stability of BCB resin. More preferably, the particle size of the hybrid microspheres is 1±0.1μm.

[0011] In the silane precursor, if there are too many carbon atoms in R1-R4, the steric hindrance will increase, which will affect the hydrolysis reaction rate and slow down the reaction rate, so that microspheres cannot be formed and only viscous liquid can be formed; preferably, in the silane precursor, R1 is methylene or ethylene or is absent, and R2-R4 are one of methyl and ethyl.

[0012] Preferably, the hybrid microspheres are prepared by co-hydrolysis and condensation of a silane precursor and a silane coupling agent. By adding a silane coupling agent to participate in the hydrolysis and condensation reaction, the content of BCB groups on the surface of the hybrid microspheres can be adjusted. At the same time, other functional groups (such as amino, phenyl, vinyl, epoxy, etc.) can be introduced to increase the functionality of the hybrid microspheres and meet different functional requirements.

[0013] The higher the proportion of silane coupling agent, the lower the proportion of BCB groups on the surface of the hybrid microspheres, which is not conducive to the bonding between the hybrid microspheres and BCB resin and reduces compatibility. Preferably, the molar ratio of the silane precursor to the silane coupling agent is 1:0~0.3; more preferably, the molar ratio of the silane precursor to the silane coupling agent is 1:0~0.1.

[0014] Preferably, the silane coupling agent is methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, divinyldimethoxysilane, divinyldiethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, triphenylmethoxysilane, trivinylmethoxysilane, trivinylethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, triethylmethoxysilane, triethylethoxysilane, propyltrimethoxysilane. At least one of the following: alkyl, propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, tert-butyltrimethoxysilane, tert-butyltriethoxysilane, aminotrimethoxysilane, aminotriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidyletheroxypropyltrimethoxysilane, 3-glycidyletheroxypropyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, preferably at least one of the following: methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, tert-butyltrimethoxysilane, tert-butyltriethoxysilane, tetramethoxysilane, tetraethoxysilane.

[0015] To achieve the above objectives, the present invention further provides a method for preparing benzocyclobutene-functionalized organic-inorganic hybrid microspheres, comprising: (1) 4-halogenated benzocyclobutene, vinyltrialkoxysilane, acid-binding agent, palladium catalyst and organophosphorus ligand are added to an organic solvent and Heck coupling reaction is carried out under an inert atmosphere and at 80-120℃ to obtain silane precursor. (2) After the silane precursor, silane coupling agent, basic compound and solvent are stirred and mixed evenly, hydrolysis and condensation reaction is carried out at 0-100℃ to obtain benzocyclobutene functionalized organic-inorganic hybrid microspheres.

[0016] This invention discloses a method for preparing benzocyclobutene-functionalized organic-inorganic hybrid microspheres. First, 4-halobenzocyclobutene and vinyl-containing trialkoxysilanes are used as raw materials. A silane precursor is generated via a Heck coupling reaction. Then, hybrid microspheres with cage-like and ladder-like polysilsesquioxane structures and rich in benzocyclobutene functional groups are obtained via a sol-gel method. This method is not only safe and simple (no organic solvents are required; the reaction can proceed under conventional alkaline compound conditions), and does not require surfactants (through hydrolysis-condensation reactions with itself or other types of alkoxysilanes) or high temperatures (the reaction can proceed at room temperature), facilitating industrial production, but also allows for precise control of the hybrid microsphere structure (the ratio of cage-like to ladder-like structures, and particle size) by adjusting the raw material ratio and preparation process parameters. This allows for the preparation of hybrid microspheres with different properties to meet different market demands, making them more suitable for large-scale application.

[0017] In step (1), preferably, the molar ratio of the substances containing 4-halobenzocyclobutene, vinyltrialkoxysilane, palladium catalyst, organophosphorus ligand and basic compound is 1.0:1.0~2.0:0.001~0.05:0.01~0.5:1.0~3.0.

[0018] Preferably, the amount of organic solvent used is 2 to 100 times the mass of 4-halobenzocyclobutene; more preferably, the amount used is 5 to 40 times.

[0019] Preferably, the 4-halogenated benzocyclobutene is 4-bromobenzocyclobutene and / or 4-iodobenzocyclobutene.

[0020] Preferably, the palladium-based catalyst is at least one of palladium acetate (Pd(OAc)2), palladium chloride, 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride (Pd(dppf)Cl2), and tetra(triphenylphosphine)palladium (Pd(PPh3)4).

[0021] Preferably, the acid-binding agent is at least one selected from triethylamine, diisopropylethylamine, N,N-dimethylaniline, pyridine, potassium carbonate, sodium carbonate, potassium phosphate, and sodium acetate; more preferably, the acid-binding agent is at least one selected from triethylamine and potassium carbonate.

[0022] Preferably, the organophosphorus ligand is triphenylphosphine (PPh3) or tri-tert-butylphosphine tetrafluoroborate (P(t-Bu)3). At least one of HBF4 and 1,1'-bis(diphenylphosphino)ferrocene.

[0023] Preferably, the alkaline compound is at least one selected from potassium carbonate, sodium carbonate, cesium carbonate (Cs₂CO₃), triethylamine, and diisopropylethylamine.

[0024] Preferably, the vinyltrialkoxysilane has a structure as shown in Formula II: , II; Wherein, R1 is one of the C1 to C6 alkylene groups or is not present; R2 to R4 are each one of the C1 to C6 alkyl groups.

[0025] Preferably, the organic solvent is at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and acetonitrile (MeCN), with DMF and acetonitrile being preferred.

[0026] Preferably, the inert atmosphere is at least one of nitrogen, helium, neon, and argon.

[0027] Preferably, the reaction is terminated when the conversion rate of 4-halobenzocyclobutene is ≥95%; during the reaction, thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), or nuclear magnetic resonance spectroscopy can be used. 1 The conversion rate of 4-halogenated benzocyclobutene was monitored by 1H NMR.

[0028] In step (2), preferably, the solvent is at least one of methanol, ethanol, isopropanol, and water.

[0029] Preferably, the solvent is 5 to 100 times the mass of the silane precursor; more preferably, it is 10 to 80 times.

[0030] Preferably, the hydrolysis-condensation reaction temperature is 20~50℃, more preferably 20~40℃.

[0031] Preferably, the hydrolysis-condensation reaction time is 5 min to 24 h, more preferably 30 min to 3 h.

[0032] Preferably, the alkaline compound is at least one selected from potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, cesium carbonate, ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, triethylamine, di-n-butylamine, isopropylamine, and diisopropylethylamine.

[0033] Preferably, the amount of the alkaline compound is 0.1 to 0.5 times the mass of the silane precursor.

[0034] To further achieve the above objectives, this invention also provides an application of benzocyclobutene-functionalized organic-inorganic hybrid microspheres in the preparation of low-dielectric-constant benzocyclobutene resin composites. The hybrid microspheres of this invention, used for low-order electromodification of benzocyclobutene resins, not only significantly and efficiently reduce the dielectric constant of BCB resins, but also exhibit excellent dispersibility and compatibility within BCB resins without degrading their performance, making them more suitable for large-scale use in the low-dielectric modification of benzocyclobutene resins.

[0035] Preferably, the amount of the hybrid microspheres added to the benzocyclobutene resin composite material is 2-10 wt%; more preferably, it is 2-5 wt%.

[0036] Preferably, the benzocyclobutene resin is a divinylsilane benzocyclobutene resin and / or a 4-benzocyclobutene vinyl polysiloxane resin.

[0037] Preferably, the low dielectric constant benzocyclobutene resin composite material can be used as a prepreg for printed circuit boards, a copper-clad laminate insulation layer, a semiconductor packaging material, a high-frequency transmission line insulation layer, or an antenna substrate material.

[0038] Beneficial effects of the present invention

[0039] 1. The benzocyclobutene-functionalized organic-inorganic hybrid microspheres of this invention have cage-like and ladder-like polysilsesquioxane composite structures inside. Through the synergistic effect between the nanoscale cavities in the cage-like structure (containing air or low-dielectric-constant organic groups, much lower than the dielectric constant of siloxane) and the low polarizability effect of the ladder-like structure, a significant reduction effect on the dielectric constant of BCB resin can be achieved (high dielectric reduction efficiency, a dielectric constant of less than 2.20 can be achieved with an addition of 2wt%).

[0040] 2. The microspherical structure of the benzocyclobutene-functionalized organic-inorganic hybrid microspheres of the present invention and the benzocyclobutene functional groups on the surface can significantly improve the dispersibility and compatibility of the hybrid microspheres in BCB resin, and significantly mitigate the adverse effects of the modified material on the performance of BCB resin.

[0041] 3. The preparation method of the benzocyclobutene-functionalized organic-inorganic hybrid microspheres of the present invention is safe and simple, and can be achieved without surfactants and high-temperature reactions, which is convenient for industrial production.

[0042] 4. The method for preparing benzocyclobutene-functionalized organic-inorganic hybrid microspheres of the present invention can achieve precise control of the structure of hybrid microspheres (the ratio of cage-like structure to ladder-like structure and particle size) by adjusting the raw material ratio and preparation process parameters, thereby enabling the preparation of hybrid microspheres with different properties according to different market demands.

[0043] 5. The hybrid microspheres of this invention are used for low-order electromodification of benzocyclobutene resins. They can significantly and efficiently reduce the dielectric constant of BCB resins without degrading the performance of BCB resins, making them more suitable for large-scale use in low-dielectric modification of benzocyclobutene resins. Attached Figure Description

[0044] Figure 1 The ¹H NMR spectrum of the silane precursor prepared in step (1) of Example 1 of this invention is shown.

[0045] Figure 2 This is a SEM image of the hybrid microspheres prepared in Example 1 of the present invention.

[0046] Figure 3 The image shows the FT-IR spectrum of the hybrid microspheres prepared in Example 1 of this invention.

[0047] Figure 4 This is a static water contact angle diagram of the hybrid microspheres prepared in Example 1 of the present invention.

[0048] Figure 5 The image shows the XRD curve of the hybrid microspheres in Example 1 of this invention.

[0049] Figure 6 The TGA curve is shown for the composite material prepared by adding 2 wt% of hybrid microspheres in Example 1 of this invention. Detailed Implementation

[0050] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0051] The technical terms in the following examples are defined as follows: Heck coupling reaction refers to the carbon-carbon coupling reaction between aryl halides and olefins under the action of palladium catalyst and organophosphorus ligand; sol-gel method refers to the process by which compounds containing hydrolyzable groups (such as alkoxysilanes) form gels through hydrolysis and condensation reactions in a solvent; cage-like siloxane structure refers to the three-dimensional cage-like framework structure formed by siloxane units; ladder-like siloxane structure refers to the two-dimensional ladder-like framework structure formed by siloxane units.

[0052] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available products.

[0053] Example 1

[0054] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere is prepared by the following method: (1) Preparation of silane precursor by Heck coupling reaction: In a 250 mL two-necked flask, 4-bromobenzocyclobutene (10 mmol), vinyltrimethoxysilane (15 mmol), triethylamine (16 mmol), Pd(OAc)2 (0.03 mmol), tri-o-tolylphosphine (0.12 mmol), and acetonitrile (70 mL) were added sequentially. The mixture was heated to 80 °C and refluxed for 18 h under nitrogen protection, and the reaction was terminated. The reaction solution was cooled to room temperature, filtered to remove the precipitated salt, and the filtrate was washed three times with n-hexane. After concentration under reduced pressure, the solution was distilled under reduced pressure, and the fraction was collected to obtain a pale yellow liquid silane precursor (proton nuclear magnetic resonance (¹H NMR) spectrum as shown in Figure 1). Figure 1 (as shown) (2) Preparation of hybrid microspheres: Silane precursor (0.5 g, 2 mmol), methyltrimethoxysilane (0.014 g, 0.1 mmol), TMAOH (0.1 g), and ethanol / water mixed solvent (40 mL, ethanol:water (volume ratio) = 1:1, which is 40 times the mass of the silane precursor) were added to a beaker and stirred at 30 °C for 2 h to form a white suspension. The suspension was centrifuged at 8000 rpm for 10 min, and the precipitate was ultrasonically dispersed and washed 4 times with ethanol. It was then vacuum dried at 60 °C for 8 h to obtain white powdered hybrid microspheres (SEM image as shown). Figure 2 As shown, the FT-IR spectrum is as follows Figure 3 As shown; static water contact angle test as follows Figure 4 As shown; XRD pattern as shown Figure 5 (As shown).

[0055] DLS testing showed that the hybrid microspheres had a particle size of 1.1 μm and a PDI of 0.03. SEM observation revealed uniform particle size and no agglomeration. The 1.1 μm microspheres belong to the submicron scale, exhibiting good dispersibility in resin and minimal sedimentation. The particle size of the hybrid microspheres in this invention is related to the hydrolysis-condensation rate, precursor concentration, and stirring rate.

[0056] ¹H NMR spectra show that the peaks at chemical shifts δ 7.2–7.4 ppm of the silane precursor belong to hydrogen atoms on the benzene ring of benzocyclobutene, the peaks at δ 6.0–6.5 ppm belong to hydrogen atoms on the vinyl group, the peak at δ 3.5 ppm belongs to hydrogen atoms on the methoxy group, and the peak at δ 3.0 ppm belongs to hydrogen atoms on the four-membered ring of benzocyclobutene. The integral ratios of the characteristic peaks are consistent with the theoretical structure of (4-vinylbenzocyclobutenyl)trimethoxysilane, proving that the precursor structure is correct. The trimethoxy group in the precursor is a hydrolyzable group, which can undergo hydrolysis under alkaline conditions to generate silanol groups (Si-OH). The silanol groups further condense to form silicon-oxygen-silicon bonds (Si-O-Si), thereby constructing the framework structure of the hybrid microspheres.

[0057] SEM images show that the hybrid microspheres are well-formed spheres with smooth surfaces and no obvious aggregation. The spherical morphology is due to the sol-gel reaction occurring in solution, where surface tension during growth causes the microspheres to tend towards the lowest energy spherical shape. The absence of aggregation indicates that the microsphere surface is rich in benzocyclobutene functional groups. Benzocyclobutene is a hydrophobic aromatic group that provides steric hindrance and electrostatic repulsion, preventing contact aggregation between microspheres.

[0058] The FT-IR spectrum shows: 2900 cm⁻¹ - The absorption peak at ¹ is attributed to the CH stretching vibrations of the methylene (benzocyclobutene four-membered ring) and the methyl (co-hydrolyzed methyltrimethoxysilane); 1600 cm⁻¹ - ¹ and 1580cm - The absorption peak near ¹ is attributed to the stretching vibration of the benzene ring skeleton; 1470 cm⁻¹ - The absorption peak at ¹ is attributed to the characteristic vibration of the four-membered ring of benzocyclobutene; 1000-1200 cm⁻¹ - The strong absorption peak at ¹ is attributed to the stretching vibration of the Si-O-Si bond, and the multiple splitting of this vibration peak indicates that there are multiple bonding environments for siloxane bonds. The Si-O-Si bond vibration absorption peak in the cage-like siloxane structure is located at 1130 cm⁻¹. - ¹Near; the Si-O-Si bond vibration absorption peak in the ladder-shaped siloxane structure is located at 1050 cm⁻¹. - ¹Nearby. Figure 3 1050 cm - ¹ and 1130 cm - The presence of absorption peaks at all locations indicates that the hybrid microspheres possess cage-like and ladder-like polysilsesquioxane composite structures.

[0059] Static water contact angle test results show that in the hybrid microspheres, benzocyclobutene is a hydrophobic aromatic group. The microsphere surface is rich in benzocyclobutene functional groups, which makes the microsphere surface highly hydrophobic, with a static water contact angle of 154° (≥145°), which is much higher than that of silica microspheres without BCB functional groups (contact angle of about 30°). The highly hydrophobic surface is beneficial to the compatibility of microspheres with benzocyclobutene resins, because benzocyclobutene resins are themselves hydrophobic polymers. Microspheres with similar surface hydrophobicity have good dispersibility in the resin and are not prone to agglomeration.

[0060] The XRD pattern shows: 2θ = 5.85 A strong and sharp characteristic peak appears at this point, corresponding to the most significant long-range interlayer spacing (approximately 1.51 nm), which can be attributed to the ordered interchain stacking of ladder-type / cage-type polysilsesquioxanes; 20 The nearby broad peak corresponds to the short-range ordered distance within the Si–O–Si chain. This small-angle strong peak demonstrates that the hybrid microspheres possess a highly ordered long-range structure, reflecting that under alkaline hydrolysis conditions, Si–OH fully condenses to form a stable ladder-type / cage-type polysilsesquioxane framework.

[0061] Example 2

[0062] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere is prepared by the following method: (1) Preparation of silane precursor: In a 250 mL three-necked flask, 4-iodobenzocyclobutene (10 mmol), vinyltriethoxysilane (11 mmol), potassium carbonate (15 mmol), Pd(OAc)2 (0.01 mmol), tritert-butylphosphine tetrafluoroborate (0.05 mmol) and acetonitrile (50 mL) were added in sequence. The mixture was heated to 90 °C under an argon atmosphere and reacted for 8 h. The reaction was then terminated. After cooling, the solid impurities were removed by filtration. The filtrate was washed twice with deionized water, dried with anhydrous sodium sulfate for 40 min, filtered, and then distilled under reduced pressure to obtain a pale yellow liquid silane precursor. (2) Preparation of hybrid microspheres: Silane precursor (0.58 g, 2 mmol), vinyltrimethoxysilane (0.030 g, 0.2 mmol), tetramethylammonium hydroxide (0.2 g), and isopropanol (30 mL, 30 times the mass of silane precursor) were added to a beaker and stirred at 25 °C for 1.5 h. After centrifugation at 9000 rpm for 5 min, the precipitate was washed three times with isopropanol and dried under vacuum at 80 °C for 8 h to obtain white hybrid microspheres.

[0063] DLS testing showed that the hybrid microspheres had a particle size of 1.8 μm and a PDI of 0.05; SEM observation showed that the spheres were regular in shape and the particle size distribution was concentrated.

[0064] Example 3

[0065] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere is prepared by the following method: (1) Preparation of silane precursor: In a 250 mL three-necked flask, 4-bromobenzocyclobutene (10 mmol), vinyltriethoxysilane (10.5 mmol), diisopropylethylamine (12 mmol), Pd(dppf)Cl2 (0.03 mmol), 1,1'-bis(diphenylphosphine)ferrocene (0.06 mmol) and DMAc (30 mL) were added sequentially. The mixture was heated to 110 °C under a nitrogen atmosphere and reacted for 5 h. The reaction was then terminated. After cooling, the mixture was filtered, the filtrate was washed twice with water, dried over anhydrous magnesium sulfate for 30 min, and then distilled under reduced pressure to obtain the silane precursor. (2) Preparation of hybrid microspheres: Silane precursor (0.58 g, 2 mmol), phenyltrimethoxysilane (0.060 g, 0.3 mmol), ammonia (0.5 mL, 25%), and ethanol (50 mL, 50 times the mass of silane precursor) were added to a beaker and stirred at 35 °C for 1 h. After centrifugation at 8500 rpm for 10 min, the precipitate was washed three times with ethanol and dried under vacuum at 70 °C for 10 h to obtain white hybrid microspheres.

[0066] DLS testing showed that the hybrid microspheres had a particle size of 1.5 μm and a PDI of 0.05; SEM observation showed that they were uniformly dispersed with no obvious particle size difference.

[0067] Example 4

[0068] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere is prepared by the following method: (1) Preparation of silane precursor: In a 250 mL three-necked flask, 4-bromobenzocyclobutene (10 mmol), vinyltriethoxysilane (13 mmol), triethylamine (18 mmol), Pd(PPh3)4 (0.04 mmol), triphenylphosphine (0.15 mmol) and acetonitrile (35 mL) were added sequentially. The mixture was heated to 85 °C under a nitrogen atmosphere and reacted for 7 h. The reaction was then terminated. The reaction solution was cooled to room temperature, filtered to remove the precipitated salt, and the filtrate was washed three times with n-hexane. After being concentrated under reduced pressure, the solution was distilled under reduced pressure, and the fraction was collected to obtain a pale yellow liquid silane precursor. (2) Preparation of hybrid microspheres: Silane precursor (0.58 g, 2 mmol), tetramethoxysilane (0.061 g, 0.4 mmol), cesium carbonate (0.4 g), and ethanol / water mixed solvent (60 mL, ethanol:water (volume ratio) = 2:1, which is 60 times the mass of silane precursor) were added to a beaker, stirred at 28 °C for 2.5 h, centrifuged at 9000 rpm for 10 min, and the precipitate was washed and dried under vacuum at 65 °C for 11 h to obtain white hybrid microspheres.

[0069] DLS testing showed that the hybrid microspheres had a particle size of 2.0 μm and a PDI of 0.12; SEM observation showed excellent particle size uniformity.

[0070] Example 5

[0071] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere is prepared by the following method: (1) Preparation of silane precursor: In a 250 mL three-necked flask, 4-iodobenzocyclobutene (10 mmol), vinyltrimethoxysilane (14 mmol), potassium carbonate (15 mmol), Pd(OAc)2 (0.02 mmol), tritert-butylphosphine tetrafluoroborate (0.08 mmol) and DMF (46 mL, 20 times the mass of 4-iodobenzocyclobutene) were added sequentially. The mixture was heated to 95 °C under an argon atmosphere and reacted for 6 h, and the reaction was terminated. The reaction solution was cooled to room temperature, filtered to remove the precipitated salt, and the filtrate was washed three times with n-hexane. After being concentrated under reduced pressure, the solution was distilled under reduced pressure, and the fraction was collected to obtain a pale yellow liquid silane precursor. (2) Preparation of hybrid microspheres: Silane precursor (0.5 g, 2 mmol), propyltrimethoxysilane (0.082 g, 0.5 mmol), sodium hydroxide (0.1 g), and water / methanol mixed solvent (35 mL, water:methanol (volume ratio) = 1:1, which is 35 times the mass of silane precursor) were added to a beaker, stirred at 32 °C for 1.8 h, centrifuged at 8000 rpm for 12 min, washed the precipitate, and dried under vacuum at 75 °C for 9 h to obtain white hybrid microspheres.

[0072] DLS testing showed that the hybrid microspheres had a particle size of 2.1 μm and a PDI of 0.14. SEM observation showed no agglomeration and good particle size uniformity.

[0073] Example 6

[0074] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere is prepared by the following method: (1) Preparation of silane precursor: In a 250 mL three-necked flask, 4-bromobenzocyclobutene (10 mmol), vinyltriethoxysilane (11 mmol), triethylamine (14 mmol), Pd(dppf)Cl2 (0.025 mmol), 1,1'-bis(diphenylphosphino)ferrocene (0.05 mmol) and DMSO (37 mL, 20 times the mass of 4-bromobenzocyclobutene) were added sequentially. The mixture was heated to 105 °C and reacted for 5.5 h under a nitrogen atmosphere, and the reaction was terminated. The reaction solution was cooled to room temperature, filtered to remove the precipitated salt, and the filtrate was washed three times with n-hexane. After being concentrated under reduced pressure, the solution was distilled under reduced pressure, and the fraction was collected to obtain a pale yellow liquid silane precursor.

[0075] (2) Preparation of hybrid microspheres: Silane precursor (0.58 g, 2 mmol), vinyltriethoxysilane (0.114 g, 0.6 mmol), triethylamine (0.3 g), and isopropanol / water mixed solvent (45 mL, isopropanol:water (volume ratio) = 3:1, which is 45 times the mass of silane precursor) were added to a beaker, stirred at 22 °C for 2 h, centrifuged at 8500 rpm for 10 min, and the precipitate was washed and dried under vacuum at 60 °C for 12 h to obtain white hybrid microspheres.

[0076] DLS testing showed that the hybrid microspheres had a particle size of 1.7 μm and a PDI of 0.08; SEM observation showed that the spheres were regular in shape and uniform in size.

[0077] Examples 7-10

[0078] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere was prepared using the same raw materials and preparation process as in Example 1, with the difference being that the amount and ratio of raw materials were adjusted, as well as the process parameters (specifically: in Example 7, the concentration of the silane precursor in step (2) was reduced to 0.5 wt% (0.2 g of silane precursor, 40 mL of solvent), the amount of tetramethylammonium hydroxide was reduced to 0.02 g, the reaction temperature was reduced to 20°C, and the reaction time was extended to 3 h; in Example 8, the concentration of the silane precursor in step (2) was increased to 1.5 wt% (0.6 g of silane precursor, 40 mL of solvent), the amount of tetramethylammonium hydroxide was reduced to 0.05 g, the reaction temperature was reduced to 25°C, and the reaction time was 2 h; in Example 9, the concentration of the silane precursor in step (2) was increased to 3.5 wt% (1.4 g of silane precursor, 40 mL of solvent), and the amount of tetramethylammonium hydroxide was increased to 0.15 wt%). g, the reaction temperature was increased to 35℃, and the reaction time was shortened to 1.5 h; in Example 10, the concentration of silane precursor in step (2) was increased to 5.0 wt% (2.0 g of silane precursor, 40 mL of solvent), the amount of tetramethylammonium hydroxide was increased to 0.2 g, the reaction temperature was increased to 40℃, and the reaction time was shortened to 1 h), so that the particle size and polydispersity index (PDI) of the resulting hybrid microspheres are shown in Table 1.

[0079] Table 1. Particle size and PDI value of hybrid microspheres in Examples 7-10

[0080] The mechanism for controlling the particle size of hybrid microspheres is as follows: increasing the concentration of the silane precursor increases the monomer concentration in the hydrolysis-condensation reaction, shortens the nucleation period, promotes growth, and ultimately increases the particle size; increasing the amount of basic compound accelerates the hydrolysis-condensation rate, thus accelerating the microsphere growth rate and increasing the final particle size; increasing the reaction temperature accelerates the hydrolysis-condensation rate, thus accelerating the microsphere growth rate and increasing the final particle size; and extending the reaction time prolongs the microsphere growth time, further increasing the final particle size. Through the synergistic regulation of these parameters, the particle size of hybrid microspheres can be precisely controlled within the range of 0.2-3 μm.

[0081] Examples 11-12

[0082] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere was prepared using the same raw materials and preparation process as in Example 1, except that the molar ratio of the silane precursor to the silane coupling agent in step (2) was adjusted (specifically, in Example 11, the molar ratio of the silane precursor to the silane coupling agent in step (2) was 1:0; in Example 12, the molar ratio of the silane precursor to the silane coupling agent in step (2) was 1:0.3). DLS testing showed that the hybrid microspheres in Examples 11 and 12 had a particle size of 1.11 μm and a PDI of 0.03.

[0083] Comparative Example 1

[0084] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere was prepared using the same raw materials and preparation process as in Example 1, except that the molar ratio of silane precursor to silane coupling agent in step (2) was adjusted to 1:0.5.

[0085] Comparative Example 2

[0086] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere was prepared using the same raw materials and preparation process as in Example 1, except that: in step (2), the concentration of silane precursor was reduced to 0.2 wt% (0.08 g silane precursor, 40 mL solvent), the amount of tetramethylammonium hydroxide was reduced to 0.01 g, the reaction temperature was reduced to 15 °C, and the reaction time was extended to 4 h; the particle size of the hybrid microsphere was 0.1 μm as determined by DLS testing.

[0087] Comparative Example 3

[0088] A benzocyclobutene-functionalized organic-inorganic hybrid microsphere was prepared using the same raw materials and preparation process as in Example 1, except that: in step (2), the concentration of silane precursor was increased to 10 wt% (4.0 g silane precursor, 40 mL solvent), the amount of tetramethylammonium hydroxide was increased to 0.5 g, the reaction temperature was increased to 50 °C, and the reaction time was shortened to 0.5 h; the particle size of the hybrid microsphere was 7 μm as determined by DLS testing.

[0089] Comparative Example 4

[0090] A hybrid microsphere was prepared using methyltrimethoxysilane as a single precursor and the microsphere preparation process in step (2) of Example 1. The hybrid microspheres without BCB functional groups were obtained (the particle size was 1.0 μm as measured by DLS).

[0091] Comparative Example 5

[0092] Octadecyl POSS (octavinyl polyhedral oligomeric silsesquioxane).

[0093] Comparative Example 6

[0094] The silane precursor prepared in step (1) of Example 1.

[0095] Experimental Example 1: The hybrid microspheres prepared in Examples 1 and 10 were mixed with DVSBCB resin at mass fractions of 2%, 5%, 10%, and 20%, respectively (a 0 wt% blank example was set). Toluene (solid-liquid ratio = 1:1, g / mL) was added, and the mixture was ultrasonically dispersed for 30 min, then stirred at room temperature for 4 h. The mixture was poured into a glass mold and vacuum dried at 120 °C for 4 h to remove the solvent. Subsequently, it was cured according to the following program: 180 °C / 4 h, 220 °C / 2 h, 240 °C / 2 h to prepare the composite material. The properties of the composite material were tested (dielectric constant and dielectric loss at 10 MHz (GB / T 1409-2006); thermal decomposition temperature (T)). 5% According to GB / T 27761-2011, thermogravimetric analyzer, N2 atmosphere, heating rate 10℃ / min), the test results are shown in Table 2: Table 2. Test results of composite material properties

[0096] The TGA curve of the DVSBCB resin composite material with a hybrid microsphere addition of 2% in Example 1 is shown below. Figure 6 As shown.

[0097] The hybrid microspheres prepared in Examples 7 and 8 were mixed with DVSBCB resin at mass fractions of 2%, 5%, 10%, and 20% respectively (a 0 wt% blank example was set up; Example 7 additionally added an experiment with an addition of 30 wt%). Toluene (solid-liquid ratio = 1:1, g / mL) was added, and the mixture was ultrasonically dispersed for 30 min and stirred at room temperature for 4 h. The mixture was poured into a glass mold and vacuum dried at 120℃ for 4 h to remove the solvent. Subsequently, it was cured according to the following program: 180℃ / 4 h, 220℃ / 2 h, 240℃ / 2 h to prepare the composite material. The properties of the composite material were tested (dielectric constant and dielectric loss at 10 MHz (GB / T 1409-2006); thermal decomposition temperature (T)). 5% According to GB / T 27761-2011, thermogravimetric analyzer, N2 atmosphere, heating rate 10℃ / min), the test results are shown in Table 3: Table 3. Test results of composite material properties

[0098] Analysis of the test results in Tables 2 and 3 shows that the hybrid microspheres (particle size 1 ± 0.1 μm) prepared in this invention have a significant effect on reducing the dielectric constant of BCB resin at a low addition amount (2-5%), and also have a significant effect on improving thermal stability.

[0099] Experiment Example 2

[0100] The hybrid microspheres prepared in Examples 1-12 and the modified materials in Comparative Examples 1-6 were mixed with DVSBCB resin at an addition amount of 2 wt%. Toluene (solid-liquid ratio = 1:1, g / mL) was added, and the mixture was ultrasonically dispersed for 30 min and stirred at room temperature for 4 h. The mixture was then poured into a glass mold and vacuum dried at 120 °C for 4 h to remove the solvent. Subsequently, it was cured according to the following program: 180 °C / 4 h, 220 °C / 2 h, 240 °C / 2 h to prepare the composite material. The properties of the composite material were tested (dielectric constant and dielectric loss at 10 MHz at room temperature (GB / T 1409-2006); thermal decomposition temperature (T)). 5% According to GB / T 27761-2011, thermogravimetric analyzer, N2 atmosphere, heating rate 10℃ / min), the test results are shown in Table 4: Table 4. Test results of composite material properties

[0101] Analysis of the test results in Table 4 shows that, compared with conventional inorganic fillers, the hybrid microspheres prepared in this invention have unique and excellent compatibility in BCB resin, significantly reduce the dielectric constant of the composite material, and also have a good effect on improving thermal stability; in particular, when the particle size of the hybrid microspheres is in the submicron range, its addition amount can be reduced to less than 5%.

[0102] The mechanism by which the hybrid microspheres of this invention reduce the dielectric constant is as follows: the hybrid microspheres possess cage-like and ladder-like polysilsesquioxane composite structures. In the cage-like structure, siloxane units form a three-dimensional cage-like framework, within which nanoscale cavities filled with air exist. Air has a dielectric constant of 1, far lower than that of BCB resin (2.65). Therefore, the presence of the cage-like structure reduces the overall dielectric constant of the composite material (the main factor). The ladder-like / cage-like structures, as large-volume functional groups, increase the free volume of the system, reduce the material density, and also contribute to reducing the dielectric constant. Furthermore, the chemical reaction between the microsphere surface and the resin results in a tight bond between the microspheres and the resin interface, with no interfacial phase separation. These factors contribute to the significant reduction in the dielectric constant of the composite material.

[0103] The mechanism for the reduction in the coefficient of thermal expansion (CTE) lies in the abundance of BCB groups on the surface of the hybrid microspheres. During curing, these groups crosslink with the matrix resin (DVS-BCB resin), increasing the crosslinking density of the composite material and restricting polymer chain movement, thereby reducing CTE. Simultaneously, the silicon-oxygen-silicon network formed by the hydrolysis and condensation of the hybrid microspheres possesses a certain degree of rigidity. Uniformly dispersing this rigid filler in the resin matrix can physically constrain the flexible polymer chains, limiting their thermal movement and further reducing the thermal expansion of the composite material.

[0104] The mechanism for improved thermal stability lies in the following: As mentioned earlier, the microsphere filler and the resin matrix form chemical crosslinks through the reaction of BCB groups, constructing a denser and more stable three-dimensional network structure. This highly crosslinked network effectively prevents the polymer backbone from dissociating and volatilizing at high temperatures, thereby significantly increasing the thermal decomposition temperature. Furthermore, the microspheres themselves possess high thermal stability (initial decomposition temperature > 500℃), thus further enhancing the thermal decomposition temperature of the composite material.

[0105] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A benzocyclobutene-functionalized organic-inorganic hybrid microsphere, characterized in that, The hybrid microspheres are polysilsesquioxane composite microspheres with both cage-like and ladder-like structures, obtained by hydrolysis and condensation of silane precursors; the surface of the hybrid microspheres contains benzocyclobutene functional groups. The silane precursor has the structure shown in Formula I: ， Ⅰ； Wherein, R1 is one of the C1 to C6 alkylene groups or is not present; R2 to R4 are each one of the C1 to C6 alkyl groups.

2. The benzocyclobutene-functionalized organic-inorganic hybrid microspheres according to claim 1, characterized in that, The hybrid microspheres have a particle size of 0.2~3μm; preferably, the particle size is 1±0.1μm.

3. The benzocyclobutene-functionalized organic-inorganic hybrid microspheres according to claim 1, characterized in that, The hybrid microspheres were prepared by co-hydrolysis and condensation of a silane precursor and a silane coupling agent.

4. The benzocyclobutene-functionalized organic-inorganic hybrid microspheres according to claim 3, characterized in that, The molar ratio of the silane precursor to the silane coupling agent is 1:0 to 0.3; preferably, the molar ratio of the silane precursor to the silane coupling agent is 1:0 to 0.

1.

5. A method for preparing benzocyclobutene-functionalized organic-inorganic hybrid microspheres according to any one of claims 1-4, characterized in that, Includes the following steps: (1) 4-halogenated benzocyclobutene, vinyl-containing trialkoxysilane, acid-binding agent, palladium catalyst and organophosphorus ligand are added to an organic solvent and Heck coupling reaction is carried out under an inert atmosphere and at 80-120℃ to obtain silane precursor. (2) After the silane precursor, silane coupling agent, basic compound and solvent are stirred and mixed evenly, hydrolysis and condensation reaction is carried out at 0-100℃ to obtain benzocyclobutene functionalized organic-inorganic hybrid microspheres.

6. The preparation method according to claim 5, characterized in that, In step (1), the molar ratio of the 4-halogenated benzocyclobutene, the vinyl-containing trialkoxysilane, the palladium catalyst, the organophosphorus ligand and the basic compound is 1.0:1.0~2.0:0.001~0.05:0.01~0.5:1.0~3.

0.

7. The preparation method according to claim 5, characterized in that, In step (2), the hydrolysis-condensation reaction temperature is 20~50℃, more preferably 20~40℃.

8. The preparation method according to claim 5, characterized in that, In step (2), the amount of the alkaline compound used is 0.1 to 0.5 times the mass of the silane precursor.

9. The application of the benzocyclobutene-functionalized organic-inorganic hybrid microspheres according to any one of claims 1-4 in the preparation of benzocyclobutene-based resin composite materials with low dielectric constant.

10. The application according to claim 9, characterized in that, The amount of the hybrid microspheres added to the benzocyclobutene resin composite material is 2-10 wt%; preferably 2-5 wt%.

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