KR102375540B1 - METHOD FOR PREPARING MESOPOROUS SiC-BASED CERAMIC MONOLITHS DERIVED FROM MOLDABLE IN-SITU MICROPHASE SEPARATED ORGANIC-INORGANIC BLOCK POLYMERS - Google Patents

Abstract

The present invention relates to a method for manufacturing a mesoporous ceramic structure, and more particularly, to a mesoporous ceramic structure having a three-dimensionally continuous pore structure by organic-inorganic hybrid polymerization-induced microphase separation (H-PIMS) method. It relates to a simple and direct manufacturing method without any process required.

Description

Real-time microphase separation Method for manufacturing a mesoporous SiC-based ceramic structure molded from organic-inorganic block copolymer

The present invention relates to a method for manufacturing a mesoporous ceramic structure, and more particularly, to a mesoporous ceramic having a three-dimensionally continuous pore structure by a microphase separation (H-PIMS) method induced by organic-inorganic hybrid polymerization. It relates to a method of manufacturing a structure simply and directly without any post-processing.

The process of converting a polymer into a non-oxide ceramic by heat treatment can be dramatically applied to manufacturing a ceramic material having a complex structure that cannot be realized in a traditional powder-based ceramic process. If a polymer is used as a precursor, sophisticated nanostructures can be formed at low temperatures and then converted into ceramics with excellent thermal properties through heat treatment. Typically, non-oxide ceramics such as SiC, Si ₃ N ₄ , SiOC and SiCN are It can be obtained through pyrolysis of a ceramic precursor made of a polymer. This is the basis for realizing stable ceramic fiber and coating technology at very high temperature.

Mesoporous SiC ceramics with pores with a size of 2-50 nm are stable and have a large surface area even at a high temperature of 1000 degrees Celsius, so they can be usefully used in various applications such as heterogeneous catalyst carriers, material separation, and high-temperature sensors. . After synthesizing a block copolymer by combining an inorganic polymer including a Si-C bond in the main chain and an organic polymer including hydrocarbons, such as siloxane, silazane, and carbosilane, a block copolymer is synthesized by heat treatment. A technique for synthesizing mesoporous SiC with a uniform pore size has been developed by simultaneously removing organic polymers and converting inorganic polymers to SiC. Since the microphase separation structure of the organic-inorganic block copolymer precursor is transferred to the mesoporous SiC ceramic, there is an advantage that the pore size, pore structure, and thermal decomposition yield can be controlled by controlling the molecular weight and composition. In particular, the research result of implementing a three-dimensional continuous pore structure ideal for mass transfer by converting a precursor of a gyroid, a type of double-continuous structure, into a ceramic has received much attention. However, it is difficult to precisely synthesize the organic-inorganic block copolymer, it is very difficult to obtain a structure that appears under very limited conditions such as a gyroid, and a process that takes a lot of time and energy such as solvent/thermal annealing is difficult. As a matter of fact, there are obvious limitations in practical application.

Meanwhile, the global ceramic market is expected to reach $780 million in 2025, and it is expected to continue the growth trend at an average annual rate of 6.4%. The market size of the domestic ceramic industry is expected to reach 117 trillion won in 2025, growing at a CAGR of 5.9%. In particular, in the case of an inorganic polymer based on polysilazane, it has excellent properties such as protection, durability, and chemical resistance, so its application range is infinite in electronic materials, medical care, automobiles, and aerospace industries, and the range of related technologies is very wide. . In the present invention, a simple and direct synthesis method for manufacturing a three-dimensional mesoporous ceramic single structure without post-processing is presented as a novel organic-inorganic hybrid polymerization-induced microphase separation method. Because liquid organic-inorganic polymer is used, it is possible to overcome the problems of the conventional molding process using ceramic powder, thanks to excellent moldability. In addition, the mesoporous ceramic proposed in the present invention can be usefully used in defense and aerospace industries as a lightweight material in addition to applications such as a heterogeneous catalyst carrier utilizing a large surface area, material separation, and high-temperature sensors, and also Since it can be applied to the development of functional mesoporous ceramic materials with functions such as material, catalyst, and separation, it is expected to secure excellent marketability.

Korean Patent Publication No. 10-2007-0086531

The present invention relates to a method for producing a mesoporous ceramic structure having a three-dimensionally continuous pore structure by organic-inorganic hybrid polymerization-induced microphase separation (H-PIMS) method in a direct method that does not require any post-processing, and the method To provide a mesoporous ceramic structure to be manufactured.

The present invention, the organic polymer represented by the following formula (1), an inorganic polymer represented by the following formula (2), preparing a mixed solution comprising a comonomer and a thermal radical initiator (step a); performing a copolymerization reaction on the mixed solution (step b); And it provides a method of manufacturing a mesoporous ceramic structure comprising the step (step c) of the subsequent heat treatment.

[Formula 1]

In Formula 1, n is an integer according to molecular weight. More specifically, n is 225 ≤ n ≤ 452.

[Formula 2]

In Formula 2, R is H or CH=CH ₂ , and m is 3 ≤ m ≤4.

The copolymerization reaction may be a block copolymerization reaction.

In the method, an organic-inorganic block copolymer having a bicontinuous structure formed by the copolymerization reaction may be formed. More specifically, microphase separation may be induced while the organic-inorganic block copolymer is synthesized by a copolymerization reaction to form an organic-inorganic block copolymer having a double continuous structure.

The comonomer may include an aromatic ring that can be converted to carbon by heat treatment. More specifically, the comonomer may be a compound represented by the following formula (3). In addition, the comonomer may be used to fix the disordered double-continuous structure by microphase separation.

[Formula 3]

In Chemical Formula 3, the comonomer may be divinylbenzene. The comonomer is used to fix the disordered double-continuous structure by microphase separation, and may contain an aromatic ring that can be converted to carbon by heat treatment.

The thermal radical initiator may be azobisisobutyronitrile.

In the above method, a polymer compound represented by the following formula (4) can be prepared by the copolymerization reaction in step b.

[Formula 4]

In Formula 4, R is H or CH=CH ₂ , n is 225 ≤ n ≤ 452, m is 3 ≤ m ≤ 4, and X is 0.75 ≤ X ≤ 0.85.

More specifically in the above method, the amount of PEO-CTA may be adjusted to 30% of the total weight of the mixture, and may follow the same molar ratio of [PEO-CTA]: [AIBN] = 1: 0.3-0.6.

The organic polymer represented by Formula 1, the inorganic polymer represented by Formula 2, the comonomer, and the thermal radical initiator may be mixed in a weight ratio of 0.3: 0.65: 0.05: 0.0015-0.0030. When mixed within the above range, it is possible to synthesize an organic-inorganic block-copolymerized ceramic precursor that is subjected to real-time microphase separation at the same time as polymer polymerization.

The copolymerization reaction in step b may be performed at 70-90° C. for 12-24 hours.

The heat treatment in step c may be performed at a rate of 1 ℃ min ^-1 at 550 ~ 1000 ℃.

In the above method, by the heat treatment of step c, the organic-inorganic block copolymer prepared by the copolymerization reaction may decompose the organic block and convert the inorganic block into a ceramic through heat treatment. More specifically, by the heat treatment of step c, the PEO-bP (mVSZ-co-DVB) organic-inorganic block copolymer prepared by the copolymerization reaction may decompose the PEO organic block through heat treatment, and P(mVSZ-co- DVB) blocks can be converted to ceramic. Finally, mesoporous silicon carbide nitride can be obtained.

In addition, the method may control the pore size of the ceramic structure by controlling the molar mass of the organic polymer represented by Chemical Formula 1 above.

The molar mass of the compound represented by Formula 1 may be 10 to 20 kgmol ^-1 .

In addition, the present invention can provide a mesoporous ceramic structure manufactured by the above method, characterized in that it has mesopores having a diameter of 3 to 11 nm.

The specific surface area of the structure may be 107 ~ 410 m ² /g.

The present invention provides a simple and direct method for preparing a single mesoporous ceramic structure by organic-inorganic hybrid polymerization induced microphase separation (H-PIMS) method. The method can be converted into an organic-inorganic block copolymer in which a double continuous structure is formed through microphase separation induced by organic-inorganic hybrid polymerization by simple heating of the hybrid polymerization solution. The phase-separated organic-inorganic hybrid polymerization precursor is subjected to thermal PEO decomposition, and a mesoporous silicon carbide nitride (SiCxNy) material supported by a three-dimensionally continuous ceramic skeleton can be obtained through ceramic conversion of inorganic polymers. In this case, the pore size can be controlled by controlling the molar mass of the organic phase PEO sacrificial block induced into the pores.

In addition, the present invention is a technology for manufacturing a three-dimensional continuous mesoporous ceramic, suitable for mass synthesis, excellent formability, and can be applied to various ceramic manufacturing by different ceramic precursors, so it is widely used in functional mesoporous ceramic materials and energy applications. can be used In addition, the ceramic structure according to the present invention is a stable mesoporous ceramic at a high temperature of about 1000 ° C., and can be applied to a heterogeneous catalyst carrier, material separation, sensor, etc., and as a lightweight ceramic material, it is also applicable to the national defense and aerospace industries.

1 schematically shows a route for synthesizing a mesoporous SiC-based ceramic structure from a moldable block polymer PEO-bP (mVSZ-co-DVB) precursor. (A) Liquid polymerization mixture of PEO-CTA, mVSZ, DVB and AIBN. (B) PEO-bP (mVSZ-co-DVB) structures molded into various shapes through RAFT copolymerization. The crosslinked precursor has a double continuous structure composed of PEO and P (mVSZ-co-DVB) microdomains via H-PIMS process leading to real-time microphase separation during polymerization. (C) SiCN ceramic structure obtained by thermal decomposition of the precursor at 1000 °C in N ₂ atmosphere. A three-dimensional continuous mesoporous structure is formed by PEO degradation. Thermal stability was demonstrated by heating with a torch flame. Samples prepared from PEO-CTA with M _n = 10, 20 kg mol ^-1 were visualized.
Figure 2 is (A) VSZ and (B) ¹ H-NMR spectrum of mVSZ modified with 2-IEM. The inset represents the resonance corresponding to the alkene proton (e) and methylene proton (c, d) of 2-IEM. The peaks at δ = 7.18-7.30 and δ = 2.3 are from toluene used as a solvent for the resin modification process.
3 is an FT-IR analysis result of VSZ and 2-IEM-modified mVSZ.
4 is for PEO-CTA samples with different molar masses. Red: 11 kg mol ^-1. Blue: 22 kg mol ^-1 . (A) SEC trace (THF, RI detector, 1 mL min ⁻¹ ). (B) ¹ H-NMR spectrum (CDCl ₃ , 300 MHz, 20°C). It also shows the molecular structure of PEO-CTA.
5 shows the pyrolytic conversion of block copolymer precursors to mesoporous ceramics. (A) Scheme schematically showing structural changes with increasing temperature. (B) FTIR spectra after heat treatment at various temperatures. (C) TGA data of PEO-CTA, mVSZ and PEO-bP (mVSZ-co-DVB) under N ₂ at a heating rate of 10 °C min ^-1 . The thermal stability of the pyrolyzed products at various temperatures was analyzed by TGA in N ₂ and air atmosphere. (DE) In-situ SAXS data of PEO-bP (mVSZ-co-DVB) with increasing temperature from 25 to 400 °C (D) and from 450 to 750 °C (E). Data were obtained at a heating rate of 1° C. min ⁻¹ in an N ₂ atmosphere. All samples were prepared from PEO-CTA with M _n = 10 kg mol ⁻¹ .
6 is an FT-IR analysis result for PEO-CTA ( M _n =10 kg mol ^-1 ), DVB and mVSZ.
7 shows the thermal decomposition behavior of PEO-bP (mVSZ-co-DVB) prepared from PEO-CTA of M _n = 20 kg mol ^-1 . The final ceramic yield of the precursor was 49%, which was measured by TGA in N ₂ atmosphere.
8 is an FT-IR analysis result of PEO-bP (mVSZ-co-DVB) at various pyrolysis temperatures. All samples were pyrolyzed at a heating rate of 1° C. min ⁻¹ in an N ₂ atmosphere. Samples were prepared from PEO-CTA of M _n = 20 kg mol ⁻¹ .
Figure 9 shows cross-linked (A) homo-PEO/mVSZ/DVB samples (polymerized to homo-PEO ( M _n = 10 kg mol ^-1 ) at [mVSZ]:[DVB] = 4:1) and (B) SAXS analysis results of mVSZ/DVB samples (polymerized to [mVSZ]:[DVB] = 4:1 without PEO-CTA).
10 is a photographic image of a crosslinked solid of (A) homo-PEO/mVSZ/DVB, (B) mVSZ/DVB and (C) PEO-bP (mVSZ-co-DVB). (A) homo-PEO at [mVSZ]:[DVB] = 4:1 ( M _n = 10 kg mol ^{-1 )} , (B) without PEO-CTA, [mVSZ]:[DVB] = 4:1 (C ) [mVSZ]:[DVB] = 4:1 The sample was prepared by polymerization of PEO-CTA ( M _n = 10 kg mol ⁻¹ ). The opaque white solid samples of (A) and (B) showed that no microphase separation was formed. On the other hand, (C) demonstrates the formation of a nanostructure in the yellow transparent structure.
11 is a SAXS analysis result of a crosslinked structure of PEO-bP (mVSZ-co-DVB) and PEO-bP (mVSZ) without DVB at various pyrolysis temperatures. All samples were prepared from PEO-CTA of M _n = 10 kg mol ⁻¹ and pyrolyzed at 450° C. in N ₂ atmosphere at a heating rate of 1° C. min ⁻¹ .
12 is a SAXS analysis result of a cross-linked structure of PEO-bP (mVSZ-co-DVB) from PEO-CTA with M _n = 20 kg mol ^-1 at various pyrolysis temperatures. Black: precursor, q *=0.22 nm ^-1 , d =28.5 nm, red: pyrolysis at 550 °C, q *=0.24 nm ^-1 , d =25.8 nm, dashed line: pyrolysis at 650 ^o C, q * =0.26nm ^-1 , d =23.7nm, blue: pyrolysis at 750 °C, q *=0.27nm ^-1 , d =22.8nm, orange: thermal decomposition at 1000 °C, q *=0.29nm ^-1 , d =21.1nm . All samples were heat-treated in an N ₂ atmosphere at a heating rate of 1 °C min ^-1 .
13 is a TEM image of a mesoporous ceramic. (A) Synthesis from PEO-CTA of M _n n = 10 kg mol ^-1 , heat treated at 750°C. (BE) Synthesized from PEO-CTA of M _n n = 20 kg mol ⁻¹ , heat treated at 750° C. (C) and 1000° C. (CE). (E) shows elemental mapping by TEM-EDX.
14 shows the pore properties of the mesoporous ceramic according to the PEO molar mass and the thermal decomposition temperature. (A) Nitrogen adsorption isotherms. (B) BJH pore size distribution.

Hereinafter, the present invention will be described in detail.

The present invention easily manufactures a mesoporous ceramic material having a three-dimensionally continuous pore structure through an organic-inorganic hybrid polymerization-induced microphase separation (H-PIMS) method, It relates to a method that can be molded. Unlike the conventional method of synthesizing organic-inorganic block copolymers first and inducing microphase separation, liquid The polymerization mixture can be directly converted into an organic-inorganic block copolymer having a double continuous structure through microphase separation. Since polymerization occurs simply by heating the mixture, an organic-inorganic block copolymer molded into a desired shape can be easily obtained by placing the polymerization mixture in a suitable container and polymerization. If the organic polymer is decomposed by heat treatment and the inorganic polymer is converted into ceramic, a mesoporous ceramic material supported by a three-dimensionally continuous ceramic skeleton can be obtained.

According to the present invention, a three-dimensional continuous mesoporous ceramic structure can be directly synthesized from a polymerization mixture, and a three-dimensional continuous mesoporous structure can be directly manufactured only by heat treatment without any additional process, and the molar mass and pyrolysis temperature of organic polymers can be changed. This has the advantage of being able to control the pore size.

The pore size can be controlled in the range of 3-11 nm by changing the molar mass and pyrolysis temperature of PEO. In particular, it was confirmed that the thermal stability was very high as it maintained a diameter of 9.1 nm and a specific surface area of 107 m ² /g even at 1000 °C.

The ceramic framework provides high thermal stability to mesoporous materials, which are important for high-temperature operations such as separation and catalysis. The present invention provides a method for manufacturing 3D continuous mesoporous ceramic monoliths in three dimensions through an organic-inorganic hybrid polymerization-induced microphase separation (H-PIMS) method. can Controlled radical polymerization of modified silazane monomers can produce crosslinked block polymers and simultaneously induce sacrificial and microphase separation into ceramic precursor microdomains. The pyrolysis of the precursor produces silicon carbonitride (SiCxNy) with a mesopore structure derived from a microphase-separated morphology that maintains the structure shape and enables pore size control by controlling the molar mass of the sacrificial polymer block. The formable and scalable synthesis of mesoporous ceramic materials is useful for advanced materials and energy applications.

In the present invention, a synthetic route starting with a homogeneous polymerization mixture containing an organic polymer monomer as a sacrificial block, an inorganic polymer monomer and a vinyl crosslinking agent as a carbon source is presented.

The mixture is polymerized to spontaneously produce a microphase-separated block polymer having a disordered bicontinuous morphology as a precursor of a SiC-based ceramic structure having a 3D continuous mesoporous structure.

The organic-inorganic hybrid polymerization induced microphase separation (H-PIMS) method according to the present invention can produce a double-continuous nano-structured block copolymer in real time during polymerization without using an external template and an additional annealing process. . The molded polymeric structures can be easily fabricated and converted to mesoporous silicon carbide (SiC _x N _y ) to exhibit high thermal stability. The pore size can be controlled in the range of 3-11 nm with various molar masses of PEO and pyrolysis temperature. This approach could turn powder-based ceramic technology into a liquid-based one by avoiding the difficulties associated with high-temperature sintering processes, and could provide new possibilities for mesoporous ceramics in multi-purpose applications including micro-reactor microfluidic separation. there is.

The synthetic route to the mesoporous SiCN ceramic is schematically shown in FIG. 1 . As an embodiment of the present invention, the H-PIMS process uses poly(ethylene oxide) (PEO) as an organic polymer and a well-known ceramic precursor (vinyl silazane, VSZ)-based polymer is used as an inorganic polymer to prepare a block copolymer. Prepare a PEO polymer containing a chain transfer agent (CTA) at the end, and react 2-isocyanatoethyl methacrylate with vinylsilazane (VSZ) in the presence of it Radical polymerization of mVSZ substituted with a methacrylate group results in a PEO-b-PmVSZ copolymer according to a reversible addition-fragmentation chain transfer (RAFT) polymerization mechanism. At this time, divinylbenzen (DVB) containing an aromatic ring that can be converted to carbon is added as a comonomer to fix the disordered double-continuous structure as a microphase separation structure induced by polymerization, and PEO-bP (mVSZ-co -CVB) is synthesized. Microphase separation occurs spontaneously as the phase separation strength increases as polymerization proceeds, and at the same time, cross-linking fixes the disordered bicontinuous morphology.

RAFT polymerization of vinylsilazane (VSZ) was difficult to control due to the low reaction activity of the vinyl group, but a methacrylate moiety was introduced at the chain end to form a block polymer by a trithiocarbonate group. Synthesis is possible (Fig. 4). In addition, as methacrylate is introduced into vinylsilazane, it can act as an important factor in maintaining the mechanical stability and dimensional stability of the ceramic skeleton structure.

In general, the polymerization mixture contains 30% by weight of PEO-CTA with a number average molar mass M _n = 10 or 20 kg mol ⁻¹ in a mixture of mVSZ and DVB ([mVSZ] : [DVB] molar ratio = 4 : 1) . The inclusion of DVB in the polymerization mixture induces microphase separation by increasing the separation strength between P(mVSZ-co-DVB) and PEO, and is also important for stabilizing the ceramic skeleton by conversion to carbon upon pyrolysis. RAFT copolymerization was performed with azobisisobutyronitrile (AIBN) as a thermal radical initiator at 80 °C for 24 h to obtain a quantitative yield (93.2%) of the crosslinked block polymer PEO-bP (mVSZ-co-DVB). generated ( FIG. 1A ). It was then heated to 140 °C in an N ₂ atmosphere to further strengthen the precursor by consumption of remaining double bonds. When the yellow polymerization precursor was heat treated at 550 ~ 1000 °C in an N ₂ atmosphere, the P(mVSZ-co-DVB) block was gradually converted into a ceramic solid framework, while PEO was decomposed to produce mesoporous pores (Figs. 1B and 1C). ). The shrinkage following heat treatment was measured to be ~19 and ~32% at 550 and 1000 °C, respectively. No deformation or crack formation was observed during the heat treatment, as it causes isotropic shrinkage due to the nature of the double-continuous structure. The ceramic structure heat treated at 1000 °C retains its shape when exposed to a torch flame, which shows excellent thermal stability.

FTIR, thermogravimetric analysis (TGA), and in-situ small angle X-ray scattering (SAXS) were analyzed according to the temperature rise for the formation process of the mesoporous ceramic through PEO removal according to the temperature rise, and the results are shown in FIG. 5A . A large change in the FTIR spectrum was confirmed in the temperature range of 450 to 550 °C (Fig. 5B). The two vibrational bands at 2300 cm ^-1 and 3400 cm ^-1 corresponding to NH and Si-H disappear completely by the amination reaction from ~Si-NH-Si to Si-N(Si)-Si. lost. Due to the thermal decomposition of PEO and other organic components, the peak intensities of 2900 cm ^-1 for CH stretch, 1100 cm ^-1 for CO stretch, and 1300 cm ^-1 for Si-CH ₃ were significantly reduced (FIG. 6). In the end, only one broad overlapping peak from 1200 cm ^-1 to 800 cm ^-1 appeared after pyrolysis at 1000 ° C, which was assigned to the overlapping Si-N and Si-C stretching vibrations so that the polymer precursor was completely transformed into an inorganic state. indicates that it has been converted.

The chemical transformation observed by FTIR is consistent with weight loss in the TGA data. The PEO-bP(mVSZ-co-DVB) precursor showed a mass loss of 45 wt% at 550 °C mainly due to the pyrolysis of PEO with a 30 wt% fraction with removal of some organic components from P(mVSZ-co-DVB). showed The monomeric PEO-CTA was almost completely decomposed at 400 °C. The ceramic yield was 51% at 1000 °C (Fig. 5C). The reason that the ceramic yield of PEO-bP (mVSZ-co-DVB) and the pristine mVSZ yield are similar (72 %) in spite of high-temperature heat treatment Because of its important contribution to making the structure bearable. Finally, the sample annealed at 1000 °C did not show any observable weight change when exposed to nitrogen or air below 1000 °C, unlike the sample annealed at 750 °C. Obviously, heat treatment at 1000 °C completely converted the inorganic polymer into a thermally stable ceramic phase. PEO-bP (mVSZ-co-DVB) prepared from PEO-CTA with M _n = 20 kg mol ⁻¹ also showed similar thermal behavior in pyrolysis and was successfully converted to ceramics in the same way ( FIGS. 7 and 8 ). .

In addition, structural changes during heat treatment were analyzed in real time through in-situ SAXS analysis. PEO-bP (mVSZ-co-DVB) synthesized at 140 ° C showed a broad scattering peak at the scattering vector q* = 0.41 nm ^-1 (domain spacing d = 2π/ q * = 15.3 nm), This was consistent with the disordered bicontinuity structure composed of PEO and P (mVSZ-co-DVB) microdomains generated by the PIMS process. The absence of higher-order scattering peaks indicates a low alignment of the ordered structures in the precursor. It is noteworthy that samples obtained by free radical polymerization of mixtures containing PEO without CTA moiety/mVSZ/DVB or mVSZ/DVB showed no scattering peaks in the SAXS data (Figures 9 and 10). Therefore, it can be said that RAFT polymerization in the presence of macro-CTA is essential to grow organic-inorganic block polymers with real-time microphase separation.

The scattering intensity continued to increase up to 400 °C with a shift from q* to a lower q because the degree of phase separation increased due to consumption of residual double bonds in the P(mVSZ-co-DVB) domain. At 450 ~ 600 °C, a sharp change in the scattering pattern was observed, and the slope decreased with a large decrease in peak intensity in the higher q region. The degradation of PEO and the accompanying transamination at P(mVSZ-co-DVB) appear to somewhat miscible the microphase separated structures and form ambiguous interfaces. However, when the polymeric structures were heat treated above 650° C., the scattering intensity increased again with a significant shift from q* to higher q 0.55 nm ⁻¹ . Based on the FT-IR and TGA data, it is interpreted that the complete removal of the PEO organic sacrificial block from the precursor creates mesoporous pores, resulting in a high electron density difference with the air-filled ceramic framework block. At the same time, the pyrolytic conversion of the P (mVSZ-co-DVB) domain to the ceramic phase induced isotropic shrinkage at the nanoscale due to densification. Catastrophic changes in both microdomains resulted in a significant decrease in d-spacing as reflected by the q* shift. PEO-bP (mVSZ) synthesized without DVB showed a scattering peak consistent with the disordered double-fold continuity structure, but the peak disappeared at 450 °C (Fig. 11). This suggests that the presence of DVB in the P(mVSZ-co-DVB) domain is beneficial for preserving the dimensional stability of the mesoporous structure.

Linear contraction by ceramic structure dimension measurement, TGA and SAXS analysis Processing Temperature ( ^o C) Monolith
length (cm) TGA weight
percentage (%) SAXS d-spacing (nm) PEO-CTA-10K ^a PEO-CTA-20K ^b 140 1.20 100 15.3 28.5 550 0.98 57.0 12.5 25.8 650 - 54.8 11.4 23.7 750 - 52.8 11.1 22.8 100 0.82 51.0 - 21.1

d-spacing was estimated from in-situ SAXS analysis by increasing the temperature from 25 °C to 750 °C at a heating rate of 1 °C min ^-1 in ^a N ₂ atmosphere. A sample was prepared from PEO-CTA of M _n = 10 kg mol ⁻¹ .

^b d-spacing was estimated from SAXS analysis. A sample was prepared from PEO-CTA of M _n = 20 kg mol ⁻¹ with a treatment temperature in N ₂ atmosphere.

When the sample was further heated to 750 °C, the d-spacing was ca. It decreased slightly to 11.1 nm corresponding to 28% shrinkage (Table 1). Due to the limitation of the temperature range of the in-situ SAXS experiment, the sample annealed at 1000 °C was analyzed by a conventional SAXS experiment. No peaks appeared suggesting that pore collapse occurred because the framework could not withstand the high Laplace pressure from the large free surface energy (Figure 12). On the other hand, the PEO-bP (mVSZ-co-DVB) precursor synthesized with a larger molar mass PEO-CTA (M _n = 20 kg mol ⁻¹ ) produced larger mesopores and was retained even after heat treatment at 1000 °C. The change of q* with temperature is generally similar to the precursor of M _n = 10 kg mol ^-1 , but the q* position is much smaller, indicating the formation of larger mesopores. The d-spacing and thermally decomposed values of the synthesized sample at 750 and 1000 °C were 28.5, 22.8, and 21.1 nm, respectively (FIG. 13). The d-spacing shrinkage of the measured values according to various structural changes (21.1 / 28.5 nm = 74 > 26 %) is similar to that of macroscopic contraction (68 > 32 %). This suggests that this approach of controlling the pore size by adjusting the PEO molar mass can produce stable mesoporous ceramics at >1000 °C.

14 is a TEM image of a mesoporous ceramic prepared from two PEO-CTAs with different molar masses. In general, disordered wormhole-like pores were observed to be consistent with the three-dimensionally interconnected mesopores generated by the PIMS process.

The organic-inorganic block copolymer synthesized from PEO-CTA having M _n = 10 kg mol ⁻¹ was thermally decomposed at 750° C., and mesopores of ca.3 nm were generated ( FIG. 14A ). After pyrolysis of the organic-inorganic block copolymer synthesized from PEO-CTA having M _n = 20 kg mol ⁻¹ at 750 and 1000° C., a larger ca. 9 nm mesopores were created. (FIGS. 14B and 14C). HR-TEM images showed that the DVB-derived graphitic carbon phase of the P(mVSZ-co-DVB) domain with a spacing of 3.25 s, similar to the intrinsic (002) spacing of graphite (3.35 ㅕ). ) was shown ( FIG. 14D ). Energy dispersive X-ray spectroscopy (EDX) mapping of the mesoporous ceramic obtained at 1000 °C shows a SiC _1.32 O _0.68 N _0.33 ceramic phase, which is carbon compared to SiC _0.57 O _0.41 N _0.51 ceramic obtained from a pure VSZ precursor. is more abundant

The pore properties of the mesoporous ceramics were analyzed by nitrogen adsorption isotherm measurements performed at 77 K as shown in FIG. 15 and Table 2. The sample demonstrated the presence of mesopores created by PEO removal and exhibited a type IV adsorption isotherm with hysteresis at high relative pressures (P/P ₀ ). The significant adsorption at low P/P ₀ suggests that micropores coexist in the mesoporous framework.

The pore size templated by 10 kg mol ^-1 PEO-CTA was estimated to be ca.3 nm by BJH (Barrett-Joyner-Halenda) analysis, which was in good agreement with the TEM image (detailed pore properties are shown in Table 2). summarized). The specific surface area based on BET (Brunauer-Emmett-Teller) analysis was 410 m ² g ⁻¹ ( FIG. 4 , black). Increasing the PEO molar mass to 20 kg mol ⁻¹ increased the pore size to 9 nm, consistent with TEM and SAXS analysis. This supports the controllability of the mesopore size by the block copolymer self-assembly principle (Fig. 15B). Compared to the sample obtained by pyrolysis at 750° C., heating to 1000° C. does not change the mesopore size but significantly reduces microporosity by densification of the scaffold. This is evidenced by a decrease in absorption at low P/P ₀ , resulting in smaller BET surface areas (343 to 107 m ² g ⁻¹ ). In the case of PEO-CTA with M _n = 20 kg mol ^-1 , mesopores corresponding to 3.8 nm in the pore size distribution may appear artificially due to the tensile strength effect.

Surface area and pore size distribution (measured by nitrogen adsorption isotherms) of the two interpolymers pyrolyzed at 650-1000 °C, prepared from PEO-CTA of M _n = 10, 20 kg mol ^-1 . Sample Processing
Temperature ( ^o C) S _{BET (} m ₂ g _-1)a D _BJH (nm) ^b micropores mesopores total PEO-CTA-10K ^c
( M _n = 10 kg mol ^-1 ) 650 222 150 372 4.2 750 194 216 410 3.2 1000 - 3 3 - PEO-CTA-20K ^d
( M _n = 20 kg mol ^-1 ) 650 147 105 253 11.6 750 119 223 343 9.4 1000 3 104 107 9.1

^a The surface area is determined by multipoint BET analysis at points between 0.05 < P/P ₀ < 0.35. The micropore surface area is determined by the t-plot method from points between 0.2 < P/P ₀ < 0.45. The outer surface area is determined by the t-plot method.

^b The pore diameter is determined by BJH analysis.

^c A sample was prepared from PEO-CTA of M _n = 10 kg mol ^-1 at the corresponding treatment temperature in N ₂ atmosphere.

A sample was prepared from PEO-CTA of M _n = 20 kg mol ⁻¹ at the corresponding treatment temperature in ^d N ₂ atmosphere.

In summary, the present inventors have developed an organic-inorganic hybrid polymerization induced microphase separation (H-PIMS) method as an easy synthetic route to fabricate three-dimensionally interconnected mesoporous SiC-based ceramic structures. Real-time microphase separation during polymerization directly prepared cross-linked and block polymerization precursor structures with double-continuous nanostructured PEO and P(mVSZ-co-DVB) domains that can be shaped into various shapes. The thermal decomposition of the precursor transformed PEO and P(mVSZ-co-DVB) into disordered mesoporous pores and SiC _x O _y N _z ceramic framework, and maintained the form with thermal stability at high temperatures up to 1000 °C. By controlling the weight and pyrolysis temperature of PEO, the mesopore size was adjustable from 3 to 11 nm, and the surface area was changed to 107 to 410 cm ² g ⁻¹ . The simple synthesis and excellent processability of this approach are expected to increase the application of mesoporous SiC-based ceramics in various applications requiring high temperature and chemical stability.

Hereinafter, the present invention will be described in more detail through examples. Objects, features, and advantages of the present invention will be easily understood through the following examples. The present invention is not limited to the embodiments described herein, and may be embodied in other forms. The embodiments introduced herein are provided so that the spirit of the present invention can be sufficiently conveyed to those of ordinary skill in the art to which the present invention pertains. Therefore, the present invention should not be limited by the following examples.

material

Unless otherwise noted, poly(ethylene oxide), PEO, Mn= 10 and 20 kg mol ^-1 ), 2-isocyanatoethyl methacrylate (IEM) and Divinylbenzene (DVB) (80 %, tech.) was purchased from Sigma-Aldrich (St. Louis, MO). DVB was purified by passing through a basic alumina column prior to polymerization. Azobisisobutyronitrile (AIBN, 98%) and methanol (≥99.8%) were purchased from Junsei (Tokyo, Japan). AIBN was purified by recrystallization in methanol and vinylsilazane (vinylsilazane, VL20, PVSZ, KION Corp., Mw-300) was used as received. S-1-Dodecyl-S′-(R,R′-dimethyl-R′-acetic acid)trithiocarbonate (S-1-Dodecyl-S′-(R,R′-dimethyl- R''-acetic acid) trithiocarbonate) (CTA) (DDMAT) was prepared

method

¹ H (NMR) spectroscopy was performed using a Bruker Avance 400 MHz spectrometer (Billerica, Mass.) using the residual NMR solvent signal as an internal reference. Size exclusion chromatography (SEC) was performed at 35 °C on an Agilent 1260 Infinity system (Santa Clara, CA) equipped with a refractive index detector and three PLgel 10 μm Mixed-B columns in series with a molar mass range of 500 - 10,000,000 g mol ⁻¹ . was carried out with chloroform. The molar mass of the polymer was calculated against a linear polystyrene standard (EasiCal) purchased from Agilent Technologies. Fourier transform infrared spectra were recorded in the range of 650–4000 cm ⁻¹ using a JASCO FT/IR-4600 equipped with a universal ZnSe ATR accessory. Synchrotron Small-angle X-ray scattering (SAXS) experiments were performed at the 9A beamline of Pohang Accelerator Laboratory (PAL). A monochromatized X-ray radiation source of 19.96 keV (0.0621 nm) with a sample-detector distance of 6.47 m was used. The scattering intensity was monitored with a Mar 165 mm diameter CCD detector with 2048 × 2048 pixels. The two-dimensional scattering pattern was azimuthally integrated to give a one-dimensional profile presented as the scattering vector (q) versus the scattering intensity, and the magnitude of the scattering vector is given by q = (4π/λ) sinθ. The heat-treated ceramic structure was crushed into small crushed pieces for analysis. To observe the porous morphology using a transmission electron microscope (TEM, JEOL JEM-1011, Japan), a pyrolytic monolith sample was placed on a 200-mech carbon-coated copper grid (FCF-200-Cu, Electron Microscopy Sciences, UK). made it The thermal properties of cross-linked and pyrolysis samples of PEO-bP (mVSZ-co-DVB) were analyzed by thermogravimetric analysis (TGA, SDT Q600, TA instrument) under nitrogen and air, at a rate of 10° C. min ⁻¹ . N ₂ adsorption/desorption was performed in Autosorb-Iq & Quadrasorb SI (Quantachrome). After degassing the sample in vacuum at 250 °C for 6 hours, the N ₂ adsorption/desorption isotherm at 77 K was measured.

Synthesis of PEO-CTA

Combining poly(ethylene oxide) macro-chain transfer agents with Mn = 10 kg mol ^-1 and 20 kg mol ^-1 with DDMAT using acid chloride esterification was synthesized. Characterization data of ¹ H NMR spectra and SEC traces of PEO-CTAs are shown in FIG. 4 , respectively.

Synthesis of methacrylate functionalized preceramic polymer (mVSZ)

The polymerization reaction rate was improved by replacing vinylsilazane (VSZ) with 2-isocyanatoethyl methacrylate (IEM), and a previously reported method (refer to: TA Pham, D .-P. Kim, T.-W. Lim, S.-H. Park, D.-Y. Yang, K.-S. Lee, Adv. Funct. Mater. 2006, 16 , 1235-1241) were followed. . In a typical grafting reaction, VSZ was mixed with IEM in anhydrous toluene in a molar ratio of 1:0.75, and reacted in an oil bath at 45° C. for 12 hours under an argon atmosphere. The solvent was removed by rotary evaporator for 2 h. ¹ H NMR spectrum and FT-IR confirmation results are shown in FIGS. 2 and 3, respectively.

Synthesis of PEO-b-P (mVSZ-co-DVB)

Bulk copolymerization of VSZ and DVB in the presence of PEO-CTA yielded a monolithic crosslinked PEO-bP (mVSZ-co-DVB) precursor. The cross-linked PEO-bP (mVSZ-co-DVB) precursor was prepared according to the following protocol with the same molar ratio of [mVSZ] : [DVB] = 4 : 1, [PEO-CTA] : [AIBN] = 1 : 0.3 became The amount of PEO-CTA was adjusted to 30% of the total mixture weight. A solution of PEO(10K)-CTA (0.6 g, 58.3 μmol) and AIBN (0.0029 g, 17.5 μmol) in a mixture of mVSZ (1.3 g, 3.10 mmol) and DVB (0.1 g, 0.77 mmol) was prepared and placed in an ampoule. . After three cycles of freeze-pump-thaw, the mixture was reacted in an oil bath at 80 °C. After reaction for 24 hours, the polymerization mixture was cooled to RT. The resulting yellow transparent solid was placed in a 140° C. tube furnace in order to evaporate the solvent and anneal in a N ₂ atmosphere.

Pyrolytic conversion to mesoporous SiCN

The prepared PEO-bP (mVSZ-co-DVB) structure was slowly heated at 300 °C for thermal crosslinking of the ceramic precursor at a rate of 1 °C min ^-1 for 3 hours. For thermal decomposition of the ceramic precursor structure at various target temperatures (550 ~ 1000 °C), the temperature was gradually increased at a rate of 1 °C min ^-1 , and then cooled to room temperature at a rate of 1 °C min ^-1 . Thermally decomposed samples were analyzed by TEM, SAXS, and N ₂ adsorption/desorption. The cross-linked PEO-bP (mVSZ-co-DVB) precursor and the corresponding mesoporous SiC were characterized by SAXS and N ₂ adsorption/desorption and the results are summarized in Table 2.

Claims (16)

Preparing a mixed solution including an organic polymer represented by the following formula (1), an inorganic polymer represented by the following formula (2), a comonomer represented by the following formula (3), and a thermal radical initiator (step a); performing a copolymerization reaction on the mixed solution (step b); And a method of manufacturing a mesoporous ceramic structure comprising the step (step c) of the subsequent heat treatment:

[Formula 1]

[Formula 2]

[Formula 3]

In Chemical Formula 1, n is 225 ≤ n ≤ 452 according to molecular weight, R in Chemical Formula 2 is H or CH=CH ₂ , and m is 3 ≤ m ≤4.
The method according to claim 1,
A method for producing a mesoporous ceramic structure, characterized in that the organic-inorganic block copolymer having a bicontinuous structure formed by the copolymerization reaction is prepared.
The method according to claim 1,
The method is a method for producing a mesoporous ceramic structure, characterized in that by inducing microphase separation during synthesis of the organic-inorganic block copolymer by the copolymerization reaction to form a double-continuous structure.
The method according to claim 1,
The comonomer is a method of manufacturing a mesoporous ceramic structure, characterized in that it comprises an aromatic ring that can be converted to carbon by heat treatment.
delete The method according to claim 1,
The comonomer is a method of manufacturing a mesoporous ceramic structure, characterized in that used to fix the disordered double-continuous structure by microphase separation.
The method according to claim 1,
The method of manufacturing a mesoporous ceramic structure, characterized in that the thermal radical initiator is azobisisobutyronitrile.
The method according to claim 1,
The method is a method for producing a mesoporous ceramic structure, characterized in that for preparing a polymer compound represented by the following formula (4) by the copolymerization reaction in step b.
[Formula 4]

In Formula 4, R is H or CH=CH ₂ , n is 225 ≤ n ≤ 452, m is 3 ≤ m ≤ 4, and X is 0.75 ≤ X ≤ 0.85.
The method according to claim 1,
The organic polymer represented by Formula 1, the inorganic polymer represented by Formula 2, the comonomer, and the thermal radical initiator are mixed in a weight ratio of 0.3: 0.65: 0.05: 0.0015-0.0030. Method for producing a mesoporous ceramic structure.
The method according to claim 1,
The copolymerization reaction in step b is a real-time microphase separation-induced organic-inorganic block copolymer preparation method, characterized in that it is carried out at 70-90° C. for 12-24 hours.
The method according to claim 1,
The heat treatment in step c is a method of manufacturing a mesoporous ceramic structure, characterized in that 1 ℃ min ^-1 is performed at 550 ~ 1000 ℃
The method according to claim 1,
In the above method, by the heat treatment of step c, the organic-inorganic block copolymer prepared by the copolymerization reaction is decomposed through heat treatment and the inorganic block is converted into a ceramic.
The method according to claim 1,
The method is a method of manufacturing a mesoporous ceramic structure, characterized in that the pore size of the ceramic structure is controlled by controlling the molar mass of the organic polymer represented by Formula 1 above.
The method according to claim 1,
The method for producing a mesoporous ceramic structure, characterized in that the molar mass of the organic polymer represented by Formula 1 is 10.278 ~ 20.266 kgmol ^-1 .
A mesoporous ceramic structure manufactured by the method of claim 1 and having mesopores having a diameter of 3 to 11 nm.
16. The method of claim 15,
The specific surface area of the ceramic structure is 107 ~ 410 m ² /g, characterized in that the mesoporous ceramic structure.

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