Method for producing a porous ceramic body

Abstract

The invention relates to a method for producing a porous, preferably mesoporous, ceramic body; a porous, preferably mesoporous, ceramic body obtainable by such a method; and a radiation-curable composition for producing a porous, preferably mesoporous, ceramic body.

Description

[0001] Process for producing a porous ceramic body

[0002] Subject of the invention

[0003] The invention relates to a process for producing a porous, preferably mesoporous, ceramic body; a porous, preferably mesoporous, ceramic body obtainable by such a process; and a radiation-curable composition for producing a porous, preferably mesoporous, ceramic body.

[0004] Background of the invention

[0005] Ceramic materials with controlled porosity are promising materials for a wide range of functional and structural applications, such as filters, thermal insulation, or preforms for the production of composite materials. Hardness, chemical resistance, corrosion and wear resistance, and low density are important for the potential applications of porous ceramic materials. This group also includes mesoporous silica, which exhibits a high specific surface area, low density, and high thermal and chemical stability. Therefore, applications in the fields of sensor technology, catalysis, chromatography, and filtration are conceivable and intended. Examples of mesoporous materials include the porous silica materials MCM-41 (Mobil Composition of Matter No. 41) and SBA-15 (Santa Barbara Amorphous 15).To date, the shaping of mesoporous silica has been limited by traditional manufacturing methods, requiring improved processes to enable new applications of mesoporous materials. Additive manufacturing has gained significant interest in recent years as it offers a fast, precise, and customized solution for geometrically challenging objects and shapes. It is particularly suitable for the production of geometrically complex composite materials and objects consisting of multiple materials with different functionalities. In addition to this simple process for producing customized, complex, and multifunctional objects, the use of additive manufacturing can accelerate and reduce the costs associated with product development and reduce material waste.However, the additive manufacturing of silica with a defined and controllable pore structure and in particular with mesopores or in-situ functionalized mesopores has not yet been demonstrated or has only been inadequately demonstrated.

[0006] Initial approaches to additive manufacturing of transparent silica glass without nanoscale pores were obtained using a dispersion with a high silica nanoparticle density (40 nm diameter). A matrix obtained by radical photopolymerization of hydroxyethyl methacrylate (HEMA) was used. The organic polymer network was then thermally removed at 1300 °C (Rapp et al. Nature 2017, 544, 337-339).

[0007] The hybrid printing solutions developed in the meantime, consisting of inorganic metal alkoxide precursors and photopolymerizable monomer (Moore et al., Nature Materials 2020, 19, 212-217), produce a nanoporous structure with cavities between 150-320 nm, which are subsequently sintered at higher temperatures to form transparent glass.

[0008] The hybrid printing solution composition undergoes different mechanisms during light-induced curing, namely free radical polymerization of the monomers and polycondensation of the metal alkoxide precursors. After pyrolysis and thus the removal of the organic chemical components, the hybrid structures form a poorly controllable nanoporous structure. Furthermore, no direct functionalization of the nanoporous structure is demonstrated.

[0009] TASK

[0010] Against this background, the object of the present invention was therefore to provide a process with which a porous, ceramic body, preferably with mesopores or in-situ functionalized mesopores, can be produced in a simple manner and in a short time, which has a comparable or even better quality and / or a more controlled mesopore structure.

[0011] DESCRIPTION OF THE INVENTION

[0012] This object is achieved according to the invention by a method for producing a porous, ceramic body, comprising the following steps: a) providing a radiation-curable composition comprising i. a metal alkoxide precursor, ii. a preferably polymeric template, iii. a first photoinitiator selected from the group consisting of photoacid generators and / or photobase generators, b) activating the photoinitiator and at least partially curing the radiation-curable composition, which is carried out by means of radiation-induced, additive manufacturing technology, in order to form the porous, ceramic body.

[0013] In the first step of the process according to the invention, the radiation-curable composition is first prepared. This comprises at least components i.-iii., but can also comprise other components. The first component, the (organofunctional) metal alkoxide precursor, is polymerizable and / or crosslinkable and serves as the starting material for the formation of the inorganic network of the porous, ceramic body. Typically, these are silanes and silicates such as tetramethylorthosilicate (TMOS), trimethoxymethylsilane (MTMS), tetraethylorthosilicate (TEOS), or tetraisopropylorthosilicate (TPOS). Poly(dimethoxysiloxane) (PDMOS) is particularly preferred according to the invention due to its viscosity, which limits the diffusion of the generated acids / bases in the solution.Structurally similar oligomeric silica precursors such as poly(diethoxysiloxanes) or partially precondensed silicates (as mentioned above) can also be used instead of PDMOS. Precondensation can be performed using water, acid, and / or base, or a mixture thereof.

[0014] Furthermore, hybrid organofunctional polymerizable and / or crosslinkable silica precursors can also be used as starting materials. Hybrid polymerizable and / or crosslinkable silica precursors are compounds that can undergo both a sol-gel process through Si alkoxide groups and a polymerization process, particularly a photopolymerization process, due to a second functional group, such as an acrylic group. Examples include 3-acryloxypropyltrimethoxysilane (APTMS), vinyltrimethoxysilane, vinyltriethoxysilane, and 2-(chloromethyl)allyltrimethoxysilane. With such hybrid precursors, rapid shape formation is achieved through photoinduced radical polymerization, and the comparatively slow hydrolysis and condensation occur in the presence of photoacid / photobase generators upon exposure or during the printing process, whereby subsequent hydrolysis and condensation reactions are possible.Other metal alkoxide precursors such as tetraisopropyl orthotitanate, zirconium(IV) propoxide, aluminum triisoprone, etc. can also be used.

[0015] The radiation-curable composition is preferably provided by a thin film deposition, for example on a carrier, which can then be irradiated in the subsequent step bi).

[0016] According to the invention, the radiation-curable composition provided in step a) is at least partially, preferably completely, cured in step bi) by a radiation-induced additive manufacturing technique, thereby forming the porous, ceramic body with a template contained in the pores. Such a body is also referred to as a hybrid porous, ceramic body. Additive manufacturing processes (also 3D printing) are processes in which material is built up from smaller units, such as layers, to produce three-dimensional objects. According to the invention, the layer-by-layer construction takes place using radiation, which activates the first photoinitiator, i.e. the photoacid and / or photobase generator, so that the polymerization and / or crosslinking of the metal alkoxide precursor compound and thus the curing can take place at least partially, preferably completely, during the printing process.

[0017] The electromagnetic radiation used for this purpose, without the use of a photosensitizer, is preferably in the wavelength range from 200 to 1000 nm, more preferably in the range from 200 to 800 nm, even more preferably in the range from 200 to 400 nm.

[0018] When using a photosensitizer, the electromagnetic radiation used for this purpose is preferably in the wavelength range from 200 to 1000 nm, more preferably in the range from 300 to 800 nm, even more preferably in the range from 300 to 600 nm and most preferably in the range from 350 to 450 nm.

[0019] The radiation intensity for the first photoinitiator to activate the photoacid and / or photobase generator to initiate the sol-gel reaction is preferably in the range of 0.1 mW / cm 2 up to 4000 mW / cm 2 , preferably in the range of 5 mW / cm 2 up to 1000 mW / cm 2 , most preferably in the range of 5 mW / cm 2 up to 100 mW / cm 2. If a polymerizable and / or crosslinkable polymer precursor compound is used, which is polymerized with the aid of a second photoinitiator, the radiation intensity is preferably in the range of 0.1 mW / cm 2 up to 1000 mW / cm 2 , preferably in the range of 0.1 mW / cm 2 up to 100 mW / cm 2 , most preferably in the range of 0.1 mW / cm 2 up to 50 mW / cm 2. An LED is preferably used to generate the radiation, preferably an LED with a spectral range selected from UVA, UVB, UVC and / or white light (white light = spectral range 400 to 800 nm), particularly preferably a UVA LED (range: 320-400 nm), a blue LED (spectral range 400 to 500 nm) or a green LED (spectral range 490 to 570 nm). An LED is particularly advantageous due to its narrow spectral range, particularly high energy efficiency and low heat generation. Optionally, a laser can also be used to generate the radiation.

[0020] After curing the composition, the hybrid porous ceramic body with template-filled mesopores is obtained. According to the lUPAC definition (Rouquerol, J. et al.: Recommendations for the characterization of porous solids. In: PureAppl. Chem., 66th year, 1994, pp. 1739-1758), a mesoporous solid is a porous material with a pore diameter between 2 nm and 50 nm. Curing occurs via the well-known steps of the light-induced sol-gel process, namely hydrolysis, condensation of the metal alkoxide precursor via gel formation, and self-assembly of the template.

[0021] The template, as a component of the radiation-curable composition, serves as a template for structuring the (hybrid) porous, ceramic body to be synthesized and can form a 3D arrangement—preferably through a change in the environment, for example, upon exposure to radiation—thereby providing a structure-directing effect. The inorganic network builds up around the template structure during curing. This results in porous, ceramic bodies with "filled" pores. The template molecules that comprise the template can be removed in subsequent steps, resulting in a porous body with unfilled pores. Optionally, a functional template, i.e., a template with or made of a functional polymer, can remain in the pores, enabling direct functionalization (also called in-situ functionalization) of the printed porous body.The shape and size of the resulting pores can be specifically controlled by using different templates. The template strategy used can be selected from soft or hard templating. Soft templating is based on the use of colloidal structures, such as emulsions, whose droplets create the structure. Alternatively, amphiphilic compounds capable of forming micelles can be used and serve as the structure-defining element. In hard templating processes, such as colloidal crystal templating, colloidal particles, preferably polymeric particles, are used.

[0022] The structure of the template is preferably influenced by light (“light-induced self-assembly”), for example by irradiation of a template, particularly preferably by irradiation during printing step bi) of the process according to the invention. The process according to the invention enables the production of various geometrically sophisticated, tailor-made shapes from (meso)porous, ceramic material within a very short time. By using the template in light-induced sol-gel chemistry combined with the printing process, in addition to macroscopic shape formation, a possible in-situ functionalization of the printed porous, ceramic body is achieved during exposure. Thus, with a suitable choice of template, no further treatment of the porous hybrid material is necessary. In addition, co-condensation approaches can also be used to functionalize the porous, ceramic body during printing.Since radical polymerization processes are not absolutely necessary for the formation of a stabilizing matrix for the porous material, a three-dimensional, complex component consisting of differently functionalized porous ceramic regions can be created by varying the solution composition. Furthermore, the invention enables the introduction of functionalities during or after the production of the porous ceramic body.

[0023] The template contained in the pores, especially the mesopores, can be removed after the formation of the hybrid porous ceramic body, for example, by washing the body with a solvent, optionally containing an acid or base, thereby extracting the template. Alternatively, removal can also be achieved by thermal treatment, especially thermal decomposition of the template, for example, by a temperature treatment at 100-1000°C, preferably at 200-800°C, particularly preferably at 250-600°C.

[0024] The template preferably comprises or consists of a template compound that has a structure-directing function and is preferably selected from the group consisting of amphiphilic block copolymers or block co-oligomers, micelle-forming compounds, low-molecular-weight amphiphilic compounds, functional, particularly stimuli-responsive block copolymers, macrocycles, and / or dendrimers. Stimuli-responsive functional block copolymers that react to stimuli and subsequently undergo a change ("stimuli-responsive") are particularly preferred, since the retention of the functional templates in the pores after the printing process enables the direct production of hybrid, porous bodies with switchable properties. The functionality of the template can continue to be utilized after production.Depending on their functionality, applications of in-situ functionalized (meso)porous ceramic materials in areas such as filtration and sensor technology are conceivable, for example, to detect corresponding analytes (sensor applications) or to bind them to active ingredients. One example is the block copolymer PEO-δ-PNBA (polyethylene oxide-δ-poly(2-nitrobenzyl acrylate), which enables time-dependent control of free acrylic acid groups in the filled pores. Further examples of functional templates are PS-δ-PAA (polystyrene-δ-polyacrylic acid), PEO-δ-PAA (polyethylene oxide-δ-polyacrylic acid), PS-δ-P2VP (polystyrene-δ-poly(2-vinylpyridine)), and PFS-δ-P2VP (polyferrocenylsilane-δ-poly(2-vinylpyridine), the latter possessing a silane end group for covalent bonding to the pore wall.

[0025] Particularly preferably, the template compounds are selected from the group consisting of polyacids, polyimines, polyamines, ions, in particular polybasic ions, polyethylene oxides, polypropylene oxides, polyvinylpyrrolidones, poly(meth)acrylates, polyvinylopyridines and mixtures and / or copolymers of the aforementioned.

[0026] Additionally or alternatively, functionalization can occur after the production of the porous ceramic body, for example, by grafting functionalized silane compounds such as 3-aminopropyltriethoxysilane (APTES) or 3-(mercaptopropyl)trimethoxysilane (MPTS). These amino or thiol groups can then be used to bind dyes or other molecules to the porous ceramic body, for example, using click chemistry. Using different shapes of the porous ceramic body, these can be shape-selectively functionalized, allowing them to be used for complex sensor and screening tasks.

[0027] In addition to the three components i.-iii., ie organofunctional polymerizable and / or crosslinkable metal oxide precursors, preferably polymeric template, and photoinitiator, the composition may also comprise further components, such as solvents, fillers or one or more photosensitizers.

[0028] Such a photosensitizer is preferably selected from the group consisting of polycyclic aromatics with 2-5 rings, thioxanthones, 2-chlorothioxanthones, 2-isopropylthioxanthones, aromatic compounds with at least one ketone chromophore, and / or combinations thereof. 2-isopropylthioxanthones are particularly preferred.

[0029] As specific examples of polycyclic aromatic photosensitizers suitable for the invention, anthracene, 9-vinylanthracene, 9,10-dimethylanthracene, 9,10-dichloroanthracene, 9,10-dibromoanthracene, 9,10-diethylanthracene, 9,10-diethoxyanthracene, 2-ethyl-9,10-dimethylanthracene, naphthacene, pentacene, benzo[a]anthracene, 7,12-dimethylbenz[a]anthracene and azulene may be mentioned. As specific examples of aromatic ketones suitable as photosensitizer for the present invention, there may be mentioned 2-chlorothioxanthone, 2-isopropylthioxanthone, thioxanthone, anthraquinone, benzophenone, 1-chloroanthraquinone and bianthrone.

[0030] Another preferred additional component is water, which particularly influences the hydrolysis step of the curing process and the transport of the released acid. The water content of the curable composition is particularly preferably in the range of 0.1 to 20 wt.%, more preferably in the range of 0.5 to 10 wt.%, and most preferably in the range of 0.5-5 wt.%, based on the total weight of metal alkoxide, template, first photoinitiator, and the optional components photosensitizer and solvent. Within this range, a porous, ceramic body with particularly sharp edges is achieved.

[0031] Preferably, the radiation-curable composition comprises, as a further component in addition to the organofunctional polymerizable and / or crosslinkable metal alkoxide precursor, a polymerizable and / or crosslinkable polymer precursor compound, in which case the process comprises the additional step of polymerizing this additional polymer precursor compound.

[0032] According to the invention, “polymer precursor compounds” are understood to mean those compounds from which polymers can be obtained by polymerization and / or polymer crosslinking reactions.

[0033] In this context, “polymer” is understood to mean a chemical substance which contains more than 50 wt%, preferably more than 70 wt%, more preferably more than 80 wt%, even more preferably more than 90 wt% and most preferably more than 95 wt% macromolecules.

[0034] "Macromolecules" are molecules composed of one or more identical or similar structural units, the constitutional repeating units (IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"), A.D. McNaught, A. Wilkinson, Blackwell Scientific Publications, Oxford (1997), S.J. Chalk. ISBN 0-9678550-9-8). Such macromolecules have more than 10 repeating units, preferably more than 15 repeating units. The molecular weight is preferably at least 3,000 g / mol, preferably at least 5,000 g / mol, more preferably at least 7,000 g / mol, and most preferably at least 10,000 g / mol. Polymers are usually prepared by the reaction of monomers or oligomers containing one or more of the constitutional repeating units in a polymerization reaction.An oligomer is a molecule formed from several monomers and therefore composed of a large number of structurally identical or similar structural units. In the context of the invention, oligomers are defined as molecules produced from a reaction of 2-10, preferably 2-8, and preferably 3-7 monomers.

[0035] Both monomers and oligomers are "polymer precursor compounds" within the meaning of the present invention. However, the term "polymer precursor compounds" also includes so-called prepolymers, i.e., chemical substances that contain more than 50 wt. %, preferably more than 70 wt. %, more preferably more than 80 wt. %, even more preferably more than 90 wt. %, and most preferably more than 95 wt. % macromolecules capable of undergoing further polymerization through reactive groups, whereby these contribute two or more, preferably 10 or more, monomer units to at least one chain of the final macromolecule (IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"), A.D. McNaught and A. Wilkinson, Blackwell Scientific Publications, Oxford (1997), S.J. Chalk. ISBN 0-9678550-9-8). Examples of these are resins, such as acrylate resins or epoxy resins.

[0036] Preferably, the polymerizable and / or crosslinkable polymer precursor compound is a radically polymerizable or crosslinkable monomer, preferably selected from the group consisting of ethylenically unsaturated monomers, in particular (meth)acrylates, acrylonitrile, styrene, vinyl acetate, vinylpyrrolidone; epoxy resins and siloxanes.

[0037] The formation of a preferably cross-linked polymer from this additional polymer precursor compound preferably occurs simultaneously with the formation of the porous, ceramic body.

[0038] Particularly preferred are polymerizable or crosslinkable monomers, oligomers, or resins due to the rapid formation of corresponding polymers. In this case, the radiation-curable composition preferably further comprises an initiator and / or catalyst, which can preferably be activated by photoinduced light. A photoinduced-activatable catalyst can catalyze a reaction upon exposure to an appropriate wavelength and accelerate its rate. These include, for example, crosslinking reactions and / or polymerization reactions. Particular preference is given to free-radical photoinitiators, particularly preferably those selected from the group consisting of α-hydroxy, α-alkoxy, or α-amino aryl ketones, azides, diazonium compounds, and acylphosphine oxides.Optionally, a radical scavenger, such as hydroquinone, can be used during radical polymerization to capture excess radicals outside the exposed area.

[0039] Particularly preferably, the polymerizable and / or crosslinkable polymer precursor compound is a monomer, an oligomer or a resin, such as (meth)acrylates.

[0040] According to the invention, "resins" are understood to mean precursors of thermosetting plastics, i.e., polymers (cf. IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"), AD McNaught and A. Wilkinson, Blackwell Scientific Publications, Oxford (1997)), which can be used in particular as components of coatings, varnishes, and paints. These are particularly preferably resins, in particular resins obtained by radical polymerization, in particular polyurethane (PU), polyester, polyamide, urea, melamine, formaldehyde, PVC, (meth)acrylic, or epoxy resins.

[0041] Particularly preferred are polymerizable monomers and / or oligomers, such as (meth)acrylates, 1,6-hexanediol diacrylate, (1-methyl-1,2-ethanediyl)bis[oxy(methyl-2,1-ethanediyl)]diacrylate.

[0042] The invention also relates to a porous ceramic body, preferably a mesoporous ceramic body, obtainable by the process according to the invention.

[0043] Preferably, the porous ceramic body obtained by the process according to the invention has a specific surface area in the range of 50 to 250 m 2 / g, preferably in the range of 100-200 m 2 / g, and most preferably in the range of 120 to 180 m 2 / G.

[0044] Preferably, the porous ceramic body obtained by the process according to the invention has a specific surface area in the range of 50 to 800 m when using a radiation-curable composition without additional polymerizable and / or crosslinkable polymer precursor compound 2 / g, preferably in the range of 100-500 m 2 / g, and most preferably in the range of 100 to 300 m 2 / G.

[0045] When using a radiation-curable composition with an additional polymerizable and / or crosslinkable polymer precursor compound, the (hybrid) porous, ceramic body obtained by the process according to the invention has a specific surface area in the range of 100 to 1000 m 2 / g, preferably in the range of 200 to 700 m 2 / g and most preferably in the range of 300 to 500 m 2 / G.

[0046] Preferably, the (hybrid) porous ceramic body obtained by the process according to the invention has an average pore diameter in the range of 2 nm to 50 nm, preferably in the range of 2 nm to 30 nm and most preferably in the range of 2 nm to 20 nm. The pore size distribution is in the range of 0 to 10 nm, preferably in the range of 0.3 to 5 nm and most preferably in the range of 0.3 to 2.5 nm around the most frequently occurring pore size.

[0047] In addition, the (hybrid) porous ceramic body obtained by the process according to the invention can have micropores with a pore size of < 2 nm. When using a polymerizable and / or crosslinkable polymer precursor compound, the porous ceramic body can, after removal of the organic polymer network, have so-called macropores or larger cavities in the micrometer range, e.g., in the range of 0.05 to 100 pm pore size.

[0048] Preferably, the (hybrid) porous ceramic body obtained by the process according to the invention has mesopores, wherein the volume of the mesopores compared to the volume of the porous ceramic body corresponds to the range between 20 to 80 vol%, preferably in the range between 20 to 70 vol%, and most preferably in the range between 20 to 60 vol%.

[0049] In one embodiment of the invention, the pores are partially or completely filled, in particular with the template. In another embodiment, the pores are completely free.

[0050] The invention also relates to a radiation-curable composition as used in the process according to the invention, which is defined as above and in claims 1-7.

[0051] The invention also relates to the use of a template, which is preferably arranged in a 3D structure in a light-induced manner, in a 3D printing process of a ceramic body.

[0052] The invention also relates to the use of a solution composition, preferably containing a functional template, which is used in light-induced sol-gel chemistry in a 3D printing process for producing a hybrid porous, ceramic body, preferably with mesopores.

[0053] The invention further relates to the use of the radiation-curable composition according to the invention for producing a preferably hybrid, porous, ceramic body, in particular by an additive manufacturing technique.

[0054] EXAMPLES

[0055] The invention will now be explained in more detail using specific embodiments. Example 1 demonstrates the use of a solution composition of a radiation-curable composition with metal alkoxide precursors, template, first photoinitiator, photosensitizer, and solvent. In Example 2, a polymerizable and / or crosslinkable polymer precursor compound and a radical photoinitiator are additionally added to the solution.

[0056] Table 1 : Chemicals 'The synthesis of the block copolymer was carried out as described in the literature: Macromol. Chem. Phys.

[0057] 2019, 220, 1900238 | Pharmaceutical Research 2004, 160 | J.Polym. Be. Part A: Polym. Chem. 2014, 52, 2192. Analysis methods

[0058] Fluorescence measurements

[0059] A Vilber Fusion FX7 Edge (Eberhardzell, Germany) was used for fluorescence detection with different filters for the selected dye Alexa 647 (illumination c640, emission f695).

[0060] ATR infrared spectroscopy (ATR-IR)

[0061] ATR-IR spectra of the printed mesoporous silica molds were measured without substrates using the ATR mode (attenuated total reflection) of a Spectrum One Fourier transform infrared spectrometer (FT-IR) from PerkinElmer (Rodgau, Germany) in the range of 4000-650 cm -1 with a resolution of 0.4 cm -1 (10 scans). The ATR-IR spectra were assigned to the asymmetric stretching vibration of Si-O-Si at 1041 cm -1 Background and baseline correction were performed automatically using Spectrum software (version 10.5.4 from Perkin Elmer).

[0062] Transmission electron microscopy (TEM)

[0063] TEM images were acquired using a JEOL JEM 2100F transmission electron microscope (Tokyo, Japan) with a maximum resolution of 2 Å at an accelerating voltage of 200 kV. Samples were prepared by dispersing them in absolute ethanol. After 10 minutes of sonication, 3.05 mm Cu grids (200 mesh) coated with a Lacey carbon film (Plano GmbH, item number S166-2) were immersed in the dispersed solution. The sample-covered TEM grid was dried under ambient conditions.

[0064] Scanning electron microscopy (SEM)

[0065] SEM images were acquired using a Zeiss EVO 10 electron microscope and SmartSEM V06.03 software (Oberkochen, Germany) with a SE detector at an accelerating voltage of 15–20 kV. The samples were coated with a 10–15 nm thick layer of Pt / Pd (from ESG Edelmetall-Service, Rheinstetten, Germany) using a Cressington 208 HR sputter coater (Cressington Scientific Instruments, distributed by TESCAN, Dortmund, Germany).

[0066] Small-angle X-ray scattering (SAXS)

[0067] SAXS measurements were performed in a XEUSS 1.0 SAXS setup (XENOCs, Grenoble, France). Monochromatic X-rays (λ=0.15419 nm) were generated using a GEN IX 3D microfocus tube. The incident X-ray beam was collimated to a size of 0.5 x 0.5 mm at the sample position. 2Scattered photons were detected using a PILATUS 100 K detector at a sample-to-detector distance of D = 2500 mm (calibrated with silver behenate as standard).

[0068] Argon adsorption measurement

[0069] For argon adsorption at 87 K, complete isotherms were measured in the relative pressure range from 0 to 1 using an Autosorb iQ (Quantachrome, distributed by Anton Paar, Ostfildern-Scharnhausen, Germany). Based on the argon adsorption isotherms, the specific surface area, pore size, and pore size distribution were determined using BET (11 points between 0.05 and 0.3 P / P0) and the corresponding NLDFT core. Before each measurement, the samples were degassed for 12 hours at 80 °C under high vacuum.

[0070] Optical microscopy

[0071] Microscopic images of the printed mesoporous ceramic bodies were taken using an Olympus Bx60 microscope (Olympus, Hamburg, Germany) in transmitted-light mode. Measurements of the resulting microscopy images were performed using ImageJ.

[0072] Thermogravimetric analysis (TGA)

[0073] Thermogravimetric analysis was performed on a Mettler Toledo TGA 1. The samples were filled into 100 L aluminum crucibles. To determine the thermal stability and silica content of the printed hybrid porous silica body using the inventive method with / without additional polymerizable and / or crosslinkable polymer precursor compound, the samples were treated with the following temperature program: from 25 °C to 600 °C at 10 Kmin. 1 Heat, then hold at 600 °C for 1 h. The temperature program was carried out under a constant air flow of 30 mLmin' 1 carried out.

[0074] Implementation - Example 1

[0075] Preparation of the radiation-curable composition

[0076] To prepare the radiation-curable compositions according to the invention, the individual components 1-3 listed below were mixed and treated in an ultrasonic bath for 10 minutes. Either Pluronic® P123 or PEO42-Ö-PNBA13 was used as template 2. Components 4 and 5 were then added to the mixture. The solution was stored in the dark and stirred overnight at room temperature. Until use, the solution was stored in a freezer at -18°C, protected from light. The appropriate amount of distilled water 6 was added only upon use.

[0077] The amounts of the individual components of the composition examples are shown in the following table: Table 2: Radiation-curable compositions 1-3

[0078] Printing of (hybrid) mesoporous silica molds

[0079] Solutions 1-3 were printed using Digital Light Processing (DLP) as the exposure source, resulting in free-standing mesoporous silica molds. The printing process took place in a UV-free yellow light environment (no irradiation below 470 nm wavelength), and solutions 1-3 were kept in the dark during stirring.

[0080] After water addition (6), solutions 1-3 are stirred for 5 min at room temperature. 0.3 mL of each solution is applied to a glass substrate using a doctor blade (gap height 20 pm, width 4 cm) (Erichsen model 360-40 mm, Hemer, Germany). The glass substrate, along with the thin solution film, is then placed in the printer (Asiga MAX X27 with 385 nm LED, Sydney, Australia).

[0081] For solution 1, the exposure time is 500 s at 40 mW / cm 2After a 5-minute rest period, the exposed pattern is washed with toluene for 1 minute and carefully dried with compressed air. After 5 minutes, the printed template-filled, mesoporous silica molds can be removed from the glass substrate. For solution 2, the exposure time is 25 s at 40 mW / cm 2 and for solution 3 250 s at 40 mW / cm 2 , keeping other parameters the same.

[0082] Calcination of the printed hybrid mesoporous silica molds

[0083] The removal of the template after printing of solutions 1 and 2 is carried out by thermal treatment in an oven with the following temperature program: Heating of the sample with 1 °C min -1 to 100 °C, maintain the temperature for 1 h, further increase the temperature with 1 °C min -1to 250 °C, holding the temperature for 4 h. The removal of the template after printing of solution 3 is carried out by thermal treatment in an oven with the following temperature program: heating the sample to 60 °C in 10 min, holding the temperature for 1 h, further increasing the temperature to 130 °C in 10 min, holding the temperature for 1 h, with 1 °C min -1 Heat to 350 °C, hold the temperature for 2 h.

[0084] Post-functionalization

[0085] To functionalize the printed and calcined mesoporous silica molds, a solution of 0.043 wt.% (3-mercaptopropyl)trimethoxysilane (MPTS) or (3-aminopropyl)triethoxysilane (APTES) in anhydrous toluene is used. The functionalization step is carried out under a nitrogen atmosphere at 80 °C for one hour. The mesoporous silica molds are then filtered and carefully washed with toluene. The mesoporous silica molds are then extracted in distilled water for 15 minutes. For covalent attachment of a dye to the amine- or thiol-functionalized mesoporous silica molds, they are immersed in an Alexa Fluor 647-NHS solution (1 pg / mL in 1 M NaHCl) for one hour. The excess, unbound dye is extracted from the mesoporous silica molds for 2 hours in distilled water. After extraction, the mesoporous silica molds are left to dry overnight at room temperature.

[0086] Analyses

[0087] The obtained (hybrid) mesoporous silica forms are shown in Fig. 1.

[0088] Figure 1 shows photographs of the mesoporous silica mold obtained using solution 1 (Fig. 1a) before and (Fig. 1b) after calcining the Pluronic® P123 template (scale bar: 4 mm). These calcined mesoporous silica molds were characterized using (Fig. 1c) TEM (scale bar: 100 nm) and argon adsorption measurements, with (Fig. 1d) showing the corresponding isotherm and (Fig. 1e) the resulting pore size distribution with an average pore size of 4.8 nm. Figure 2 shows photographs of the mesoporous silica mold obtained using solution 2 (Fig. 2a) before and (Fig. 2b) after calcining the Pluronic® P123 template (scale bar: 2 mm). The characterization of this calcined mesoporous silica form is carried out by (Fig. 2c) TEM (scale bar: 100 nm) and argon adsorption measurement, where (Fig. 2d) shows the corresponding isotherm and (Fig.2c) shows the resulting pore size distribution with an average pore size of 4.8 nm. Figure 3a shows a photograph of the hybrid mesoporous silica molds obtained using solution 3 after the printing process (scale bar: 10 mm). (Fig. 3b) ATR-IR spectrum of the hybrid mesoporous silica mold (solid line) compared with the ATR-IR spectrum of this hybrid mesoporous silica mold after calcination of the template PEO42-Ö-PNBA13 (dashed line). (Fig. 3c) TEM image of the hybrid mesoporous silica mold after calcination of the template PEO42-Ö-PNBA13 (scale bar: 100 nm).

[0089] The use of solution 1 in the printing process leads to mesoporous silica forms with a pore diameter of 2.8 nm (TEM) and 4.8 nm (argon adsorption measurement) and a pore size distribution of 2.5 nm according to argon adsorption measurement (Fig. 1c-e). The use of solution 2 in the printing process leads to mesoporous silica forms with a pore diameter of 2.7 nm (TEM) and 4.8 nm (argon adsorption measurement) and a pore size distribution of 1.9 nm according to argon adsorption measurement (Fig. 2c-e). Compared to solution 1, solution 2 achieves mesoporous silica forms with a narrower pore size distribution and a shorter exposure time of 25 s instead of 500 s. By using solution 3, hybrid mesoporous silica forms with pores filled with functional templates can be produced (Fig. 3a). Both the incorporation and calcination of the functional template in the hybrid mesoporous silica mold was confirmed by ATR-IR spectroscopy (Fig. 3b).After calcination of the hybrid mesoporous silica, the TEM image shows a mesoporous structure with an average pore size of 4.5 nm.

[0090] Implementation - Example 2

[0091] Different polymer precursors and radical photoinitiators are added to the solution composition of Example 1. The additional components or chemicals are listed in Table 3 below.

[0092] Table 3: Radically polymerizable monomers in the commercially available resin.

[0093] Preparation of the radiation-curable composition

[0094] SKresin 1330 is mixed with solution 2 in Table 2 in a volume ratio of 1:1 vol / vol for solution 4. Ligcreate Premium Flex is mixed with solution 2 in Table 2 in a volume ratio of 1:2 vol / vol (Ligcreate: solution 2) for solution 5.

[0095] Printing of (hybrid) mesoporous silica molds

[0096] After Solution 2 is mixed with SKresin 1130 or Ligcreate Premium Flex in the above-mentioned volume ratios, the so-called Solution 4 or 5 is stirred for 5 min. Subsequently, 0.9 wt% distilled water (based on the proportion of Solution 2) is added and stirring is continued for 5 min. The prepared Solution 4 or 5 is then poured into the reservoir of the 3D printer (Asiga MAXX27 with 385 nm LED, Sydney, Australia), and the print job is started using the parameters listed in Table 4. After the print job is completed, the hybrid mesoporous silica mold is thoroughly rinsed with toluene and dried using compressed air. The hybrid mesoporous silica mold is then removed from the stamper.

[0097] Table 4: Summary of printing parameters of solutions 4 and 5.

[0098] (BL) = Bottom Layer), (NL) = Normal layer

[0099] Calcination of the printed hybrid mesoporous silica molds

[0100] After the hybrid, mesoporous silica molds are removed from the stamp, they are calcined after one day of aging using an oven program up to 600 °C. For this, the printed samples are heated to 480 °C in 8 h at 1 °C min -1 heated, holding the temperature for 4 h, further heating up to 600 °C in 2 h at 1 °C min, holding the temperature for 2 h, finally slow cooling.

[0101] Analyses

[0102] The obtained mesoporous silica forms are shown in the following Figures 4 and 5.

[0103] Fig. 4 shows photos of the mesoporous silica form obtained using solution 4 after the calcination step and the corresponding characterizations: (Fig. 4a) photo of the mesoporous silica form obtained after the calcination step, (Fig. 4b) SEM image, (Fig. 4c) TEM image, (Fig. 4d) isotherm of the argon adsorption measurement and (Fig. 4e) the pore size distribution calculated from it with an average pore size of 5.3 nm. Gyroidal, hybrid, mesoporous silica form obtained using solution 4 (Fig. 4f) before and (Fig. 4g) after calcination. (Fig. 5a) Photograph of the mesoporous silica obtained using solution 5 after the calcination step and the corresponding characterizations: (Fig. 5b) SEM image, (Fig. 5c) TEM image, (Fig. 5d) isotherm of the argon adsorption measurement and (Fig. 5e) the pore size distribution calculated from it with an average pore size of 5.4 nm.Cylindrical hybrid mesoporous silica obtained using solution 5 (Fig. 5f) before and (Fig. 5g) after calcination.

[0104] Using solution 4, mesoporous silica forms are obtained (Fig. 4a). After removal of the template and the organic polymer network, voids with a size of 0.8–2.6 μm are visible (Fig. 4b). The mesoporous silica form possesses mesopores with a pore size of 2.2 nm (TEM) and 5.3 nm (argon adsorption measurement) and has a pore size distribution of 2.4 nm according to argon adsorption measurement (Fig. 4c–e). Even more geometrically complex forms, such as the gyroidal mesoporous silica form (Fig. 4f–g), can be produced using this process. This geometric shape is particularly interesting in the context of fluid flow. The use of solution 5 in 3D printing leads to mesoporous silica molds (Fig. 5a), which, after removal of the template and the organic polymer network, have cavities with a size of 2-75 .mx 2-30 .m (width x height) (Fig. 5b).The mesoporous silica mold possesses mesopores with a size of 2.5 nm (TEM) and 5.4 nm (argon adsorption measurement) and a pore size distribution of 1.6 nm according to argon adsorption measurement (Fig. 5c-e). Using solution 5, for example, a hollow, mesoporous silica cylinder with staggered cavities in the cylinder wall can be printed using this process (Fig. 5f-g).

Claims

Patent claims 1. A method for producing a porous, ceramic body, comprising the following steps: a) providing a radiation-curable composition comprising i. a metal alkoxide precursor, ii. a preferably polymeric template, iii. a first photoinitiator selected from the group consisting of photoacid generators and / or photobase generators, b) activating the photoinitiator and at least partially curing the radiation-curable composition by means of radiation-induced, additive manufacturing technology to form the porous, ceramic body.

2. The method according to claim 1, wherein the porous ceramic body comprises mesopores, wherein preferably the volume of the mesopores corresponds to > 20 vol% of the volume of the porous ceramic body.

3. Method according to one of the preceding claims, wherein the preferably polymeric template comprises or consists of a functional polymer, preferably a stimuli-responsive polymer, and / or is preferably selected from the group consisting of amphiphilic block copolymers, micelle-forming compounds, low molecular weight amphiphilic compounds, stimuli-responsive block copolymers, macrocycles and / or dendrimers.

4. A method according to any one of the preceding claims, wherein the radiation-curable composition further comprises the following additional component: iv. a photosensitizer, which is preferably selected from the group consisting of polycyclic aromatics with 2-5 rings, thioxanthones, 2-chlorothioxanthones, 2-isopropylthioxanthones, aromatic compounds with at least one ketone chromophore and / or combinations thereof.

5. A method according to any one of the preceding claims, wherein the radiation-curable composition further comprises the following additional component: v. a polymerizable and / or crosslinkable polymer precursor compound, and the method comprises the following additional step: b2) forming a polymer from the polymer precursor compound.

6. The method according to claim 5, wherein the radiation-curable composition further comprises the following additional component: vi. a second photoinitiator for initiating a reaction selected from the group consisting of radical polymerization, polyaddition, polycondensation, ionic polymerization, coordinative polymerization, and / or a polymer crosslinking reaction. and the formation of the polymer in step b2) is initiated by activation of the second photoinitiator.

7. A process according to claim 5 or 6, wherein the polymer precursor compound is a polymerizable monomer.

8. A method according to any one of the preceding claims, wherein the method comprises one, several or all of the following additional steps: c) Completely curing the radiation-curable composition by thermal treatment or exposure to radiation, d) Removing the template from the pores of the ceramic body by calcining at a temperature in the range of 150-600 °C and / or washing the ceramic body with a solvent, e) removing the polymer by calcining at a temperature in the range of 150-1000 °C and / or washing the ceramic body with a solvent.

9. A porous ceramic body obtainable by a process as defined in any one of the preceding claims.

10. A radiation-curable composition for producing a porous ceramic body as defined in any one of claims 1-9.

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