METHOD FOR PRODUCING MICROPARTICLES

Description

[0001] The application relates to a process for producing microparticles.

[0002] Polysiloxanes are used in many fields. These materials are subject to increasingly stringent demands, necessitating improvements to commercially available systems. One potential application for polysiloxanes is the encapsulation of optoelectronic components. The operating conditions of light-emitting diodes (LEDs), for example, require high photophysical and thermal stability, high transparency, a high refractive index, and good processability of the cured and uncured encapsulation materials to ensure high efficiency and a long lifetime of the component.

[0003] For example, polysiloxane-based encapsulation materials are used, which are based on two-component elastomer systems and are thermally curable using a platinum catalyst. However, for ecological and economic reasons, the use of non-recyclable precious metals such as platinum should be avoided. Previously known epoxy-based polysiloxanes, which can be cured without platinum, are heat- or light-sensitive, resulting in, for example, discoloration due to the presence of the epoxy groups. Furthermore, the materials often require high flexibility, which has not been achieved to date.

[0004] US 2001 / 025080 A1 relates to a process for producing water-based coating compositions capable of forming highly scratch- and abrasion-resistant matte coatings in which crosslinked silicone particles are well dispersed. The process involves adding an aqueous suspension of crosslinked silicone particles with an average diameter of 0.1-200 µm to a water-based coating composition. The process is characterized in that the suspension is an aqueous crosslinked silicone particle suspension provided by effecting crosslinking of a condensation reaction-crosslinkable silicone composition comprising (A) an organopolysiloxane containing at least two silanol groups in each molecule, (B) a crosslinking agent, and (C) a condensation reaction catalyst. Crosslinking is effected in the emulsified composition in an aqueous solution of an anionic surfactant.

[0005] The object of at least one embodiment of the invention is to provide a production process for a polysiloxane material with improved properties.

[0006] These objects are achieved by the method according to claim 1. Advantageous embodiments and further developments of the invention are the subject of dependent claims and the description.

[0007] According to the invention, a method for producing microparticles is provided, which comprises the steps: A) Preparation of a solution of a surfactant in a polar solvent B) Addition of a fusible precursor of a polysiloxane-glass hybrid to produce a mixture of fusible precursor and solution of the surfactant C) Heating the mixture above the melting temperature of the fusible precursor to produce an emulsion, preferably microemulsion, of droplets of the fusible precursor, wherein the size of the droplets is adjusted by stirring and / or ultrasound D) Addition of a catalyst to initiate a crosslinking reaction on the surface of the droplets to produce microparticles, wherein the fusible precursor of the polysiloxane-glass hybrid is selected from the group consisting of one of the compositions (A), (B) and a mixture thereof: (A) a polymeric material prepared by condensation reactions of a trialkoxysilane monomer unit and / or a dialkoxysilane monomer unit, wherein the trialkoxysilane monomer unit (3) has the structure (I) and the dialkoxysilane monomer unit (4) has the structure (II) wherein the radicals R1 and R2 in the trialkoxysilane monomer unit of structure (I) are independently selected from the group consisting of C1-C24 alkyl, C3-C24 cycloalkyl, C2-C24 alkynes, C7-C24 cycloalkynes, C2-C24 alkenyl, C1-C24 alkoxy, C3-C24 cycloalkoxy, C6-C14 aryl and C6-C14 aryloxy, and wherein the radicals R1, R2 and R3 in the dialkoxysilane monomer unit of structure (II) are independently selected from the group consisting of C1-C24 alkyl, C3-C24 cycloalkyl, C2-C24 alkyne, C7-C24 cycloalkyne, C2-C24 alkenyl, C1-C24 alkoxy, C3-C24-cycloalkoxy, C6-C14-aryl, C6-C14-aryloxy, wherein preferably R 1 for the respective trialkoxysilane or dialkoxysilane monomer unit is independently selected from methyl or ethyl, and wherein preferably R 2 , R 3 for the respective trialkoxysilane or dialkoxysilane monomer unit are independently selected from methyl or phenyl;(B) a material comprising a three-dimensional network of partially cross-linked monomer units and an alkoxy-terminated oligo- or polysiloxane, wherein the monomer units comprise at least one trialkoxysilane and at least one dialkoxysilane, wherein the material preferably has the general structural formula; where R 1< , R 2< , R 3< and R 4< are independently selected from aryl, alkyl, alkenyl, allyl, substituted aryl, substituted alkenyl, substituted alkyl and vinyl, preferably from phenyl and methyl, where u+v+w is the number of Si atoms used and u, v and w are independently selected from the range 1 to 20,000, where the groups indexed with u, v and w are randomly distributed in the general structural formula.

[0008] Microparticles are understood to mean particles with a preferably spherical shape and a diameter of 0.1 to 100 µm, preferably 2 to 30 µm, more preferably 2 to 20 µm, even more preferably 2 to 10 µm, in particular 3 to 8 µm, as measured by light or electron microscopy. The same applies to the shape and size of droplets in the microemulsion according to the invention.

[0009] This process has the technical advantage that numerous properties of the microparticles can be adjusted using the process. For example, the polarity of the microparticles or their surface functionalization can be controlled, making a large number of compatible matrices available in which the microparticles can be embedded. These microparticles can be used in a wide variety of polymer matrices to specifically adjust their refractive index or to utilize the fluorescence properties of the dyes that can be integrated into the particles even in matrix materials in which these dyes are otherwise insoluble. In addition, the particulate form offers extensive possibilities for use in technical applications. For example, films of the particles can be produced on a wide variety of substrates, or emulsion paints or polysiloxane-based printing inks can be produced by dispersing the particles.In addition to their use as encapsulation for fluorescent dyes, their use as a matrix material for other organic substances is also conceivable, such as encapsulated carrier materials for fragrances, dyes, pharmaceuticals, or similar. Due to the polysiloxane-like structure of the materials, the biological, pharmaceutical, and cosmetic sectors are particularly suitable for application.

[0010] The meltable precursor of the polysiloxane-glass hybrid is preferably a high- to low-viscosity liquid or a glassy solid at 20°C and 100 kPa. The meltable precursor flows at 100 kPa at temperature T1 and consolidates irreversibly and permanently at temperature T2, where T2>T1 and T1, T2 = 70-200°C. The consolidation time t1 depends on the selected T2 and is preferably 0.5 to 95 hours. The melting or flowing of the meltable precursors of the polysiloxane-glass hybrid is not melting in the thermodynamic sense, but is due to the incomplete crosslinking of the meltable precursor. Consolidation at temperature T2 is attributable to a higher degree of crosslinking. Partial consolidation can also be induced by treatment with bases or acids. The properties of the unconsolidated and consolidated material can be controlled by the ratio of the monomers used.

[0011] The fusible precursor of the polysiloxane-glass hybrid is an organically modified silica gel. According to the invention, the fusible precursor of the polysiloxane-glass hybrid is selected from the group consisting of a material (A), (B), and a mixture thereof: (A) a polymeric material prepared by condensation reactions of a trialkoxysilane monomer unit and / or a dialkoxysilane monomer unit, wherein the trialkoxysilane monomer unit (3) has the structure (I) and the dialkoxysilane monomer unit (4) has the structure (II) wherein the radicals R1 and R2 in the trialkoxysilane monomer unit of structure (I) are independently selected from the group consisting of C1-C24 alkyl, C3-C24 cycloalkyl, C2-C24 alkynes, C7-C24 cycloalkynes, C2-C24 alkenyl, C1-C24 alkoxy, C3-C24 cycloalkoxy, C6-C14 aryl and C6-C14 aryloxy, and wherein the radicals R1, R2 and R3 in the dialkoxysilane monomer unit of structure (II) are independently selected from the group consisting of C1-C24 alkyl, C3-C24 cycloalkyl, C2-C24 alkyne, C7-C24 cycloalkyne, C2-C24 alkenyl, C1-C24 alkoxy, C3-C24-cycloalkoxy, C6-C14-aryl, C6-C14-aryloxy, wherein preferably R 1 for the respective trialkoxysilane or dialkoxysilane monomer unit is independently selected from methyl or ethyl, and wherein preferably R 2 , R 3 for the respective trialkoxysilane or dialkoxysilane monomer unit are independently selected from methyl or phenyl.A production process for this is described in the document EP 3613809 A1. Material (A) also includes polysilsesquioxanes, in particular polyphenylsilsesquioxanes, which can be obtained using exclusively trialkoxysilane monomers; (B) a material comprising a three-dimensional network of partially cross-linked monomer units and an alkoxy-terminated oligo- or polysiloxane, wherein the monomer units comprise at least one trialkoxysilane and at least one dialkoxysilane, wherein the material preferably has the general structural formula . where R 1< , R 2< , R 3< and R 4< are independently selected from aryl, alkyl, alkenyl, allyl, substituted aryl, substituted alkenyl, substituted alkyl and vinyl, preferably from phenyl and methyl, where u+v+w is the number of Si atoms used and u, v and w are independently selected from the range 1 to 20,000, the groups indexed with u, v and w being randomly distributed in the general structural formula. A preparation process for this is described in the document EP 3613793 A1.

[0012] Preferably, in step A), the polar solvent is a polar-protic solvent, preferably selected from the group consisting of C1-C3 alcohols, preferably methanol, water and a mixture thereof, in particular water.

[0013] Preferably, in step A), the surfactant is a non-ionic surfactant, preferably an alkylphenol ethoxylate, or an ionic surfactant, in particular sodium lauryl sulfate (SLS or SDS) or cetyltrimethylammonium bromide (CTAB).

[0014] Preferably, in step C), the catalyst is not a metal catalyst, preferably not a noble metal catalyst, in particular not a platinum catalyst, and is preferably an alkali, more preferably an inorganic base, particularly preferably a metal hydroxide, for example sodium or potassium hydroxide, or an organic base, for example an organic amine compound.

[0015] According to the invention, in step C), the diameter of the droplets is adjusted by stirring and / or ultrasound, preferably by stirring, using a dispersing device. By varying the stirring speed, the numerical size and size distribution of the droplets, measured as diameter using a light or electron microscopy image, and consequently also of the microparticles produced from the droplets, can be adjusted. The droplets, which are preferably spherical in shape, are preferably adjusted to a diameter of 0.1 to 100 µm, preferably 2 to 30 µm, more preferably 2 to 20 µm, even more preferably 2 to 10 µm, in particular 3 to 8 µm, as measured by light or electron microscopy. By increasing the stirring speed, smaller particle sizes with a narrower size distribution can be obtained.Preferably, the emulsion is stirred at a stirring speed of 300 to 15,000 min -1< , more preferably 500 to 12,000 min -1< , in particular 8,000 to 12,000 min -1< for preferably 1 min to 5 h, more preferably 1 min to 2 h, in particular 2 to 15 min.

[0016] Preferably, the method further comprises step E) isolating the microparticles, preferably by centrifuging, and optionally drying under elevated temperature and optionally reduced pressure to remove the solvent, wherein the drying conditions are selected such that surfactant molecules bound to the microparticles remain bound.

[0017] Preferably, after step E) isolating the microparticles, further heating is carried out, optionally under reduced pressure, wherein the conditions are selected such that surfactant molecules bound to the microparticles are removed and the microparticles are optionally consolidated.

[0018] Preferably, a material selected from the group consisting of conversion material for wavelength conversion, preferably selected from the group consisting of organic fluorescent dye, preferably based on perylenediimide, inorganic phosphor and mixtures thereof, odorant, color, drug and a mixture thereof, is embedded in the fusible precursor of the polysiloxane-glass hybrid.

[0019] A reference example concerns microparticles comprising: Surface-crosslinked material made from a meltable precursor of a polysiloxane-glass hybrid; and surfactant molecules bound to the surface of the surface-crosslinked particles. The microparticles can be obtained by the process according to the first aspect of the invention. After isolation, they are heated only to the extent, optionally under reduced pressure, that surfactant molecules remain bound to the surface of the microparticles. The microparticles are not consolidated, are completely soluble in organic solvents such as toluene, chloroform, acetone, and diethyl ether, and flow at T1.

[0020] Preferably, the fusible precursor of the polysiloxane-glass hybrid is selected from the group consisting of one of the materials (A), (B) defined above and a mixture thereof.

[0021] Preferably, a material selected from the group consisting of conversion material for wavelength conversion, preferably selected from the group consisting of organic fluorescent dye, preferably based on perylenediimide, inorganic phosphor and mixtures thereof, odorant, color, drug and a mixture thereof, is embedded in the fusible precursor of the polysiloxane-glass hybrid.

[0022] Another reference example relates to microparticles comprising consolidated material made of a polysiloxane-glass hybrid, preferably based on the fusible precursor of the polysiloxane-glass hybrid, which is selected from the group consisting of one of the above-defined materials (A), (B), and a mixture thereof. The materials consolidated at T2 are transparent, thermally resilient (>250 °C), hydrophobic, and adjustable in their hardness or elasticity by selecting the materials and, if appropriate, by controlling the degree of crosslinking. Furthermore, the microparticles according to the third aspect of the invention are insoluble in organic solvents, such as toluene, chloroform, acetone, and diethyl ether.

[0023] Preferably, a material selected from the group consisting of conversion material for wavelength conversion, preferably selected from the group consisting of organic fluorescent dye, preferably based on perylenediimide, inorganic phosphor and mixtures thereof, odorant, color, drug and a mixture thereof, is embedded in the polysiloxane-glass hybrid.

[0024] A further reference example relates to the use of the microparticles defined in the second and / or third aspect of the invention as a film on various substrates, as a dispersion in emulsion paints or printing inks, as an encapsulation for fluorescent dyes or encapsulated carrier materials for odorants, paints or pharmaceuticals.

[0025] A further reference example relates to a component having at least one component comprising microparticles according to the second or third aspect of the invention.

[0026] Preferably, the component is an optoelectronic component and contains an encapsulation comprising the microparticles and / or a conversion layer comprising the microparticles. Fig. 1 shows schematically the synthesis of the precursor of a polysiloxane hybrid glass as material (A) in the variant of a fluorescent solid polyphenylsilsesquioxane hybrid glass. Fig. 2 shows schematically the production of microparticles from the according to the scheme of Fig. 1 manufactured material. Fig. 3 shows a modified procedure according to Fig. 2 , in which a dispersing device is used to control the particle size and distribution. Fig. 4 shows the effect of different dispersing devices and processes on the particle size and distribution in the process according to Fig. 3 . Fig. 5 shows the schematic side view of an optoelectronic component according to an embodiment.

[0027] Fig. 1 schematically shows the synthesis of the precursor of a polysiloxane hybrid glass as material (A) in the variant of a fluorescent solid polyphenylsilsesquioxane hybrid glass. This was melted at >80 °C without a platinum catalyst and solidified at >150 °C by conducting an acid-catalyzed condensation reaction of phenyltrimethoxysilane and subsequent addition of Lumogen®< F Red305 prior to gelation.

[0028] Fig. 2 shows schematically the production of microparticles from the according to the scheme of Fig. 1prepared material. The resulting material was transferred to a boiling solution of Triton™< X-405, forming a hot emulsion of the liquid precursor in water. The addition of sodium hydroxide to this emulsion triggered condensation and solidification of the microparticles. Further crosslinking to a fully condensed PhSiO 1.5 structure and the removal of the Triton™< X-405 molecules from the surface of the microparticles was achieved by subsequent heat treatment of the particles. The chemical shifts of the polyphenylsilsesquioxane hybrid glass (MW) 29< Si and 13< C, caused by the consistency of the T2 and T3 units, indicate partially crosslinked structures. It was subsequently solidified at 200 °C, resulting in incomplete condensation of the structure (degree of condensation: 85%).

[0029] The FTIR spectra of the gases released by consolidation during the TGA measurement show only vibrations of the condensation products methanol and water. The consolidated hybrid glass (MG Cons.) shows no further mass loss due to consolidation. Its T95 value was determined at 488 °C. The material is still partially cross-linked, as demonstrated by 29< Si and 13< C spectroscopy.

[0030] The freshly prepared and untreated microparticles (MGP) also exhibit partially cross-linked polyphenylsilsesquioxane structures, indicated by chemical shifts of the T2 and T3 units at 29<Si and 13<C (TLC: 84%). The particles are no longer meltable or flowable, demonstrating a structural change and further cross-linking by the microparticle synthesis process. NMR data of the subsequently heat-treated microparticles (MGP-T, 200 °C, 4 h) demonstrate complete condensation into a PhSiO 1.5 network due to the exclusive presence of T3 units. This structural change primarily explains the solubility behavior of these materials in organic solvents such as acetone. The less cross-linked materials consisting of T2 and T3 units are soluble, while the fully cross-linked and heat-treated MGP-T microparticles are not, and their morphology is retained.

[0031] The microparticles (MGP-T) exhibit red fluorescence with an emission maximum at 647 nm (15456 cm -1 ). The quantum yield of 0.82 is slightly reduced compared to that of MG, which is caused by scattering and reabsorption processes induced by the change in solid-phase morphology from the transparent hybrid glass to the microparticle powder. Despite the fully cross-linked structure of the matrix, the dye can be leached from the microparticles by treatment with organic solvents such as acetone. The particles can be homogeneously coated into curable polysiloxane resins, for example, the curable polysiloxane resin disclosed in EP 3613793 A1 or polyphenylmethylsiloxane resin [Dow Corning OE6630; Dow(1)], and show a slight decrease in absorption at 450 nm after 25 hours by irradiation with 450 nm wavelength at ~0.85 mW / m 2 < and thus a high photostability.

[0032] The mean particle size distribution was optimized through five experiments with different stirring speeds or energy input. The narrowest distribution and the smallest particles, measuring 3.09±0.71 µm, were obtained using the Ultra-Turrax™ dispersing device.

[0033] Figure 5 shows a schematic side view of an optoelectronic component according to an embodiment. The component, for example, an LED, comprises a substrate 10 on which a semiconductor layer sequence 20 is arranged. The semiconductor layer sequence 20 is configured to emit primary radiation, for example, short-wave light with a wavelength maximum of approximately 450 nm.

[0034] A conversion layer 30 made of hardened polysiloxane resin (e.g., polyphenylmethylsiloxane resin [Dow Corning OE6630; Dow(1)]) with inventive consolidated microparticles (MGP-T) embedded therein, comprising Lumogen®< F Red305 embedded in the microparticles, is arranged in the beam path of the primary radiation. This conversion layer completely encloses the semiconductor layer sequence 20, i.e., in a material-locking and form-fitting manner, and is thus introduced as a potting compound in a recess of the housing 40. The conversion layer 30 thus serves, on the one hand, to encapsulate the semiconductor layer sequence 20 and, on the other hand, to convert the primary radiation into secondary radiation. The conversion layer contains the consolidated microparticles embedded in a matrix formed from a composition.

[0035] Alternatively, the conversion layer 30 can be arranged at a distance from the semiconductor layer sequence 20 (not shown here). In this case, an encapsulation formed from cured polysiloxane resin (e.g., polyphenylmethylsiloxane resin [Dow Corning OE6630; Dow(1)]) with consolidated microparticles (MGP-T) embedded therein, comprising Lumogen®< F Red305 embedded in the microparticles, can be arranged between the semiconductor layer sequence 20 and the conversion layer 30. Example 1: General procedure for the preparation of the fusible precursor of a polysiloxane-glass hybrid as material (A) - Option 1

[0036] The material is prepared via a multi-step process. One, one, or more trialkoxysilane monomers (TAS) are stirred with an alcohol (C12-Cl alcohol, C2-C12 diol, C3-C24 cycloalcohol, C5-C24 aryl alcohol), water, and hydrochloric acid in a molar ratio of 1:4:3:0.01 in a sealed container (10-40 °C, 0.5-10 h). One, one, or more dialkoxysilane or trialkoxysilane monomers (DAS / TAS) are stirred with an alcohol (C12-Cl alcohol, C2-C12 diol, C3-C24 cycloalcohol, C5-C24 aryl alcohol) in a molar ratio of 1:4 and added dropwise to the first mixture, which is further stirred (10-40 °C, 0.5-10 h). Ammonium hydroxide solution is added to the mixture and stirring is continued (10-40 °C, 0.5-10 h). The sealed container is opened and stirring is continued until the mixture gels (10-40 °C, 0.5-200 h). The mixture is heated to remove alcohol residues (40-200 °C, 0.5-200 h).Precipitated ammonium chloride is removed by washing with acetone and filtration under reduced pressure (0.5–50 ml). A defined amount of an organic fluorescent dye is added to the mixture and mechanically incorporated. The mixture is heated to remove residual solvent (40–110°C, 0.5–200 h). The mixture is heated to remove residual water (110–200°C, 0.5–200 h). Example 2: General procedure for the preparation of the fusible precursor of a polysiloxane-glass hybrid as material (A) - Option 2

[0037] The material is prepared via a multi-step process. None, one, or several trialkoxysilane monomers (TAS) are stirred with an alcohol (C1-C12 alcohol, C2-C12 diol, C3-C24 cycloalcohols, C5-C24 aryl alcohols) in hydrochloric acid (pH -2.5; n(TAS) / n(H2O)) = 1 / 1.5) in a sealed container (10-40 °C, 0.5-10 h). One or more dialkoxysilane or trialkoxysilane monomers (DAS / TAS) are stirred in a molar ratio of 1:4 with an alcohol (C12-C12 alcohol, C2-C12 diol, C3-C24 cycloalcohol, C5-C24 aryl alcohol) and added dropwise to the first mixture, which is further stirred (10-40 °C, 0.5-10 h). The sealed vessel is opened and stirring is continued until the mixture gels (10-40 °C, 0.5-200 h). A defined amount of an organic fluorescent dye is added to the mixture and mechanically incorporated. The mixture is heated to remove residual solvent (40-110 °C, 0.5-200 h).The mixture is heated to remove water residues (110-200 °C, 0.5 - 200 h). Example 3: General procedure for the preparation of the fusible precursor of a polysiloxane-glass hybrid as material (B)

[0038] One or more trialkoxysilane monomers (TAS) are stirred with one or more dialkoxysilane monomers (DAS) in the desired molar ratio with hydrochloric acid (pH 2.5) in a molar ratio of 1:1.5 [Σn(AS):n(HCl)] in a sealed vessel (45°C, 3 h). A defined amount of an alkoxysilane-terminated polyalkylsiloxane is added to the mixture. Stirring is continued in a sealed vessel (45°C, 18 h). The mixture is then transferred to a beaker and stirred until a gel forms in which stable bubbles form (25°C). The reaction vessel is then transferred to an oven and heated to remove water and hydrochloric acid (110°C, 1 h). The resulting gel can now be processed and consolidated at elevated temperatures (>160°C). Example 4: General procedure for the preparation of microparticles

[0039] A surfactant, for example, polyoxyethylene(40)isooctylphenyl ether (Triton™ X-405, 70 wt% in water [approx. 0.356 mmol / g]) is added to water (14 ml, 0.77 mol) and stirred (500 min -1 < , 100 °C). A defined amount of the meltable polymer precursor is added (e.g., 100 mg). The resulting emulsion is further stirred (0.4 - 2 h, 100 °C). Sodium hydroxide solution is added to the reaction mixture (1 ml, 3 mol / L). After further stirring (500 min -1 < , 0.4 h, 100 °C), the emulsion is cooled (ice water). The resulting microparticles are isolated by centrifugation, washed (water, 4 times), and dried under reduced pressure (80 °C, 500 Pa). Subsequent heat treatment at temperatures above 200 °C removes the excess surfactant from the particle surface. The material is then post-cured. Example 4: Production of microparticles from composition (A) in the variant of a polyphenylsilsesquioxane-like hybrid glass

[0040] The hybrid glass microparticles were synthesized in a two-step process. First, a polyphenylsilsesquioxane-like precursor hybrid glass (MG) was prepared. During synthesis, a specific perylenediimide dye was added for incorporation into the material. The dye used in this work was Lumogen®< F Red 305, which is physically integrated into the hybrid glass. Example 4.1: Synthesis of precursor hybrid glass (MG)

[0041] Phenyltrimethoxysilane (25 g, 126.07 mmol, [PhSi(OMe)3]) and hydrochloric acid (pH=2.5, 3.41 g, 189.12 mmol) were stirred in a sealed vial at 45 °C for 6 h. Absolute methanol (1.80 g, 56.18 mmol) was added dropwise with continued stirring at 40 °C for 2 h. The solution was transferred to a 100 mL beaker, and a specific amount of one of the perylenediimide dyes was added (18 mg, n(LG305) = 16.68 µmol). The mixture was stirred until gelation was complete (25 °C, 18 h). The beaker was transferred to a chamber dryer and evaporated of water, hydrochloric acid, and methanol in two steps to interrupt the reactions. Therefore, the material was heated at 70 °C for 24 hours and then at 110 °C for another 24 hours. The red materials were cooled to room temperature to obtain solid hybrid glasses (15.24 g, 1200 ppm / 1.09 µmol g -1 < ¬ LG305). The hybrid glasses soften reversibly at temperatures > 80 °C.At temperatures > 150 °C, the materials solidify irreversibly. The unsolidified materials were designated MG (LG305). The solidified materials were designated MG Cons (LG305). Example 4.2: Synthesis of hybrid glass microparticles (MGP)

[0042] Polyoxyethylene(40) isooctylphenyl ether solution (90 mg, Triton™ X-405, 70 wt% in water [~0.356 mmol / g]) was added to water (14 mL, 0.77 mol) and stirred at 100 °C at 500 rpm. The 100 mg of the hybrid glass precursor was added to the hot solution. The emulsion formed by melting the precursor was further stirred at 100 °C for 0.4–2 h. Sodium hydroxide solution (1 mL, 3 mol L -1 < ) was added to the emulsion. After further stirring at 500 rpm for 0.4 h at 100 °C, the emulsion was cooled in an ice-water bath. The resulting hybrid glass microparticles were isolated, washed with water by centrifugation four times, and dried in a drying cabinet under reduced pressure at 80 °C and 5 mbar. The resulting products are referred to as MGP (LG305). Subsequent heat treatment of the particles was also performed for comparison with the untreated particles. The heat-treated particles were referred to as MGP-T (LG305). Example 5: Synthesis of composition (B)

[0043] In a headspace vial, 5.00 g of PhSi(OMe) 3 , 1.05 g of MeSi(OMe) 3 , and 2.46 g of Me 2 Si(OMe) 2 were mixed with 1.45 mL of HCl solution (pH 2.5) and sealed hermetically. The reaction mixture was then stirred for 3 h at 45 °C and 500 min -1 <. Subsequently, 0.30 g of polydimethyldimethoxysilane PDMS (PDMSi 11 (OMe) 2 ) was added, and stirring continued at this temperature. The vial was then opened, and the reaction mixture was dried for 1 h at 110 °C in a drying oven. Example 6: Preparation of microparticles from composition (B)

[0044] 125 mg of composition (B) was added to 17.5 mL of 6.9 gL Triton X solution and emulsified at a stirring speed of 500 min for at least 30 min. Subsequently, 50 µL of 3 M NaOH solution was added and stirred at 100 °C for a further 24 h at 500 min. The reaction solution was then cooled to room temperature and centrifuged at least three times at 8000 min and washed with deionized water. The particles were then dried in a vacuum drying oven at 80 °C for at least 24 h. Results and discussion Polysilsesquioxane precursor

[0045] Fluorescent hybrid glass microparticles were synthesized by forming a surface-active emulsion from a dye-containing polyphenylsilsesquioxane precursor. The precursor was prepared by an acid-catalyzed polycondensation reaction of phenyltrimethoxysilane to form partially cross-linked structures (Scheme 1).

[0046] During a gelation step, the organic fluorescent dyes can be added to the synthesis process or the material. The resulting samples are solid, transparent, and rigid, and soften reversibly at temperatures > 80 °C.

[0047] The precursor was characterized by FTIR and NMR spectroscopy. The FTIR spectra show the expected vibrational bands of an MG polyphenylsilsesquioxane network, indicated by broad (Si-O) vibrational bands at 1052, 1016, and 806 cm -1 and phenyl side groups at 3050, 3072, 2953, and 2910 [(CH)AR]; 1130 [Si-C)AR; 726 cm -1 [(CH)]; and 694 cm -1 [(Si-C)]. Additionally, the vibrational bands at 3380 (OH), 2840 [(CH[O-CH 3 ])], and 846 [(Si-O-CH 3 )] are caused by the pendant and terminal methoxy groups of the polymers, as well as by unreacted monomers, methanol, or water. The 1< H and 13< C NMR spectra show the chemical shifts of the phenyl protons [8.07 - 6.84 (m, phenyl)] and the alkoxy protons [3.96 - 2.97 (m, MeOR [R= H, CH 3 ])], as well as the corresponding carbon chemical shifts at -134.26 to -127.93 ppm [phenyl] and -50.78 ppm [MeOR [R= H, CH 3 ].Signals from the integrated dye are undetectable due to the low dye concentration. Two-dimensional 1< H- 29< Si HMBC NMR spectroscopy was used to characterize the crosslinking of the silicon atoms in the precursor. In addition to the chemical shifts of the trifunctional T2 units of phenyltrimethoxysilane monomers, T3 units are also detectable (Table 1). The additional chemical shift at -22 ppm can be attributed to small traces of silicone grease. Table 1. 29< Si and 1< H chemical shift of the polyphenylsilsesquioxane precursor detected by two-dimensional 1< H- 29< Si HMBC NMR spectroscopy. 29< Si [Ph Si (OR) 3-x ] 1< H [ Ph Yes(OMe) 3x ] 1< H [PhSi(O Me ) 3-x ] Functional group -75...-80 8.07...6.84 - T 3< -64...-74 8.07...6.84 3.96...2.97 T 2<

[0048] The prepared polysilsesquioxane precursor consists of a partially cross-linked structure of T2 and T3 units. The material softens and melts even at elevated temperatures, which is due to the flexibility of the polymer chains, which consist of a high proportion of linearly connected T2-phenyltrimethoxysilane units. During the reaction process, a fully cross-linked polysilsesquioxane with the composition PhSiO 1.5 is formed, but some alkoxy groups are not yet hydrolyzed, which can be inferred from the T2 units by 2D NMR. This partial cross-linking of phenyltrialkoxysilanes has previously been reported for silsesquioxane-based particles obtained by sol-gel reactions. The bulky phenyl substituents are thought to prevent the formation of dense T3 networks for steric reasons.The cross-peak of the chemical shift of the T2 units and the methoxy protons in the 29<Si NMR also confirms the presence of unreacted methoxy groups on the silicon atoms. The number of remaining methoxy groups was calculated from the change in the intensity of the 1<H methoxy chemical shift before and after synthesis. 10% of the original amount of methoxy groups is still present in the polymer. The number of T2 units cannot be calculated from the NMR data because hydrolyzed and unhydrolyzed units cannot be separated in the 1<H spectrum, and due to the 1<H-29<Si HMBC experiment, a quantitative evaluation of the 29<Si NMR peak areas is not meaningful. Precursor consolidation

[0049] The precursor is soluble in organic solvents and can be thermally strengthened by additional heat treatment at temperatures >200°C. The strengthening is caused by the condensation of any methoxy and hydroxy groups remaining in the partially cross-linked precursor. After strengthening, the material is no longer meltable but still soluble in organic solvents. Thermal analysis of the precursor reveals differences in the material's behavior before and after thermal strengthening. Heat treatment of the precursor leads to irreversible strengthening of the material, caused by further condensation of T2 units. The TG measurement of MG shows a mass loss of 3% starting at 216°C, caused by this condensation reaction.The FTIR spectra of the gases released at these temperatures show exclusively vibrations of the condensation product methanol and water at 3082 [(OH)], 2980, 1467 [(CH [O-CH 3 ])], and 1033 cm -1 < [(CO)]. After this event, the signal intensity of the methanol vibrations decreases, and the material is irreversibly solidified.

[0050] No additional mass loss was observed due to further condensation reactions or due to the formation of by-products such as cyclosiloxanes, which has been described in the literature for comparable condensation reactions of materials containing tri- and dialkoxysilane monomers. After this solidification step, the degradation of MG Cons. begins at 488 °C, defined by the T95 value, at which 95% of the initial mass remains. The ATR-FTIR spectra of the solidified material show no relevant changes compared to the unsolidified material; only the water vibrations at 3380 cm -1 < [(OH)] have disappeared. In the 29< Si NMR spectrum of the solidified sample, T3 and T2 units at -80 and -72 ppm, respectively, as well as carbon from remaining methoxy groups in the and 13< C CP-MAS NMR at -50.38 ppm are still detectable. This suggests that the material is irreversibly strengthened by the heat treatment, but is not completely cross-linked afterwards.A semiquantitative analysis of the chemical shift peak areas in 29< Si CP-MAS NMR by fitting a Lorentzian function leads to a total percentage of T3 units of 55% and a degree of condensation (DC) of 85%. This formation of partially cross-linked structures from T2 and T3 units through thermal strengthening has already been discussed in the literature for polysiloxane-based hybrid glasses containing dialkoxysilane. Hybrid glass microparticles

[0051] For the subsequent formation of microparticles, the unsolidified polysilsesquioxane precursor was added to a boiling solution of a nonionic surfactant in water (Triton™< X-405). The material softens, and a hot emulsion forms.

[0052] The hydrophobic properties of the integrated perylene-based dye allow it to remain dissolved in the precursor phase without leaching into the solution. Upon addition of sodium hydroxide to the solution, the surface molecules of the materials begin to crosslink with the silicon atoms through base-catalyzed hydrolysis and condensation reactions of hydroxy groups (Scheme 2). Hydrolysis reaction: X = Me, Y = H Condensation reaction: X = Me or H, Y = PhSi(OR) 3

[0053] As a result, the droplets begin to chemically consolidate while retaining their spherical morphology. After cooling the solution to room temperature, the microparticles can be isolated by centrifugation. After the particles were isolated and dried at 80°C under reduced pressure, the color of the material changed from red to pink due to light scattering effects. The resulting microparticles are insoluble in water or ethanol and are still coated with the surfactant used in the synthesis. The surfactant makes the sphere hydrophilic. Further heat treatment at 200°C leads to the removal of the surfactant and a more hydrophobic spherical surface. At the same time, the microsphere structure is further cross-linked, making the material insoluble in organic solvents.

[0054] The mean sphere size was varied by changing the stirring method and stirring speed to synthesize spheres of different sizes. The properties of the hybrid glass precursor (MG) and the hybrid glass microparticles (MGP) were investigated using 1D and 2D nuclear magnetic resonance spectroscopy (1H, 29Si and 1H-29Si HMBC 2D NMR, MAS NMR), infrared spectroscopy (ATR-FTIR), and thermogravimetric methods (TG, TG-FTIR).

[0055] The size and morphology of the microparticles were examined by light microscopy, and the optical properties of the integrated dye were investigated by fluorescence spectroscopy and quantum yield determination.

[0056] A subsequent heat treatment at 200 °C for 4 h was also performed to compare properties such as structure, solubility, and surface coating with undamaged microparticles. The untreated microparticles are designated MGP, and the additionally heat-treated ones are designated MGP-T. To further characterize the material structure, 29< Si and 13< C CP-MAS NMR, as well as FTIR spectroscopy and thermal analysis methods were performed. The ATR-FTIR spectra of MG and MGP-T show no significant differences compared to the precursor or the consolidated precursor of the microparticles. Furthermore, no vibrational bands caused by a surface coating of MG with Triton™< X-405 could be detected. The morphology of the MGP-T particles is also unaffected by the heat treatment.

[0057] In the 13< C MAS NMR spectra of MGP, the surfactant could be detected by the chemical shifts generated by the Triton™< X-405 structure. The chemical shifts at 133, 129, and 127 ppm (CH [phenoxy / phenyl]) are generated by the aromatic protons of the phenyl and phenoxy groups of the polyphenylsilsesquioxane structure and the surfactant. Further shifts of the surfactant are detected at 70 (O-CH 2 ), 37 (C-CH 2 ), and 31 ppm (C-CH 3 ). The additional chemical shift at 49 ppm is caused by the unreacted methoxy groups of the T2 units of the polysilsesquioxane. The presence of this shift also suggests that chemical consolidation also leads to partially cross-linked structures. After heat treatment, the signal intensity of the surfactant and the chemical shifts of the methoxy groups decreased or even disappeared.

[0058] This finding is confirmed by the 29< Si CP-MAS NMR data. In the NMR spectrum of the chemically consolidated MGP microparticles, T2 and T3 units can be detected at -71 and -79 ppm, respectively. The calculated percentage of T3 units is 53%, and the TLC value is 84%, which is slightly lower than that calculated for the thermally consolidated precursor. For other thermally untreated polyphenylsilsesquioxane-based particles, the TLC ranges between 40 and 90%. The reason for the partially cross-linked structure was discussed above.

[0059] In the spectrum of the thermally consolidated MGP-T particles, only the chemical shift T3 at -79 ppm can be reliably assigned, indicating a fully cross-linked PhSiO 1.5 structure. This shows that the thermal consolidation process of the microparticles differs from that of the precursor, in which T2 units are still present. It also demonstrates a direct influence of the pretreatment of the spheres with sodium hydroxide on further structure formation. The subsequent thermal treatment leads to a degree of cross-linking of 100%. This allows two different processes to be investigated.

[0060] After the base initiates the chemical consolidation of the liquid precursor droplets, their structure is partially cross-linked, and their surface is coated with a layer of the surfactant Triton™ X-45. This results in a hydrophilic surface that is highly dispersible in water. After heat treatment, the surfactant is removed from the surface, and the T2 methoxy and hydroxy groups condense to form a fully cross-linked polyphenylsilsesquioxane structure with only T3 units. The particles can no longer be homogeneously suspended in water, indicating that the surface is now hydrophilic.

[0061] The solubility of the untreated MGP materials is equal to that of the precursor material. The untreated MGP microparticles with a partially cross-linked structure are soluble in organic solvents, while the additionally heat-treated and fully cross-linked MGP-T particles are insoluble, and their spherical morphology is retained. This diversity in solubility is also caused by the different degrees of cross-linking of the microparticles, as discussed above. The MGP-T microparticles consist of a fully cross-linked PhSiO 1.5 structure, while the MGP microparticles are partially cross-linked. The integrated dye is leached from both material structures, as shown in acetone for MGP and MGP-T. In applications where the particles are used in solvent-free media or in polar solvents such as water or ethanol, the dye is not leached from the particle structure.Due to the leaching behavior, SEM images of the freshly prepared and heat-treated particles were taken to examine the morphology of the surface structure in detail. The particle structure is smooth, and there is no change in morphology due to the heat treatment. There are some holes in some of the particles, but no porous structure is visible in these images. One reason for the dye leaching could be areas where the structure is less dense. The T3 network still has some space for the dye to diffuse through the particle structure. To further characterize the surface, a higher-resolution TEM image is required. Thermal analysis of microparticles

[0062] The 13< C MAS NMR data revealed the presence of a Triton™< X-405 layer on the surface of the microparticles following chemical consolidation and isolation, which is removed by the thermally initiated post-condensation process of these spheres at 200 °C for 4 h. This process was verified by thermal analysis of the unmanipulated MGP microparticles. A mass loss of 5% was observed, starting at 213 °C. This mass loss could be attributed to the removal of Triton™< X-405 by FTIR spectroscopy. The vibrational bands detected at 2863 [(OH)], 2358 [(CH)], and 1745, 1164, and 669 cm -1 [(CO)] could be assigned to Triton™< X-405. This was verified by an isothermal TG-FTIR measurement of the MGP microparticles and the Triton™< X-405 solution used at 220 °C. The IR spectra of the gas released by the particles and the Triton™< X-405 solution are identical.

[0063] The thermally consolidated MGP-T microparticles no longer exhibit mass loss caused by further condensation reactions. After this consolidation step, the materials begin to decompose at 438 °C, defined by the T95 value. This value is slightly reduced compared to MG Cons. due to the powdery state. Consequently, the Triton™< X-405 layer on the microsphere surface can be easily removed by heat treatment at 200 °C, which is verified by the 5% mass loss shown in the TG-FTIR spectra. At the same time, the particle structure is fully cross-linked, as previously described. Stirring influence on particle size distribution

[0064] During microparticle synthesis, an emulsion forms. A narrow size distribution can be achieved by simply stirring the emulsion at different stirring speeds using a standard laboratory stirrer. To optimize particle size and distribution, five additional experiments were conducted by changing the stirring speed, rate, or method (Table 2). The stirring speed with a standard rod was changed from 500 (MGP-1) to 800 min -1 (MGP-3), and the stirring time was changed from 1 h (MGP-1) to 2 h (MGP-2) at 500 min -1. 2. Table Sample name and differences in stirring speed and time used for the synthesis of hybrid glass microparticles. sample Stirring rate / min -1< Stirring time / min Average particle size / µm MGP-1 500 1 h 7.22 ± 3.11 MGP-2 500 2 h 7.50 ± 3.16 MGP-3 800 1 h 5.73 ± 2.28 MGP-US 1. 500 10 minutes 7.28 ± 6.04 2. Ultrasound only (150 W) 2 minutes MGP-UT 1. 500 10 minutes 3.09 ± 0.71 2. 10000 (dispersing device) 2 minutes

[0065] The influence of high-energy processes on particle morphology was investigated using an ultrasonic finger (150 W [MGP-US]) or an Ultra-Turrax™ dispersing device (10,000 rpm [MGP-UT]) after 10 minutes of stirring at 500 rpm. All experiments were conducted with the hot emulsion of the precursor material before the sodium hydroxide was added to initiate chemical solidification or to form a suspension.

[0066] Particle size and distribution were determined by measuring and counting particles from microscopy images. All measured particles, regardless of the method, are smaller than 20µm. Simply stirring the emulsion at 500 min-1 for 1 or 2 h (MGP-1 / 2) does not significantly change the particle size distribution. Increasing the stirring speed to 800 min-1 narrows the distribution and decreases the particle size (MGP-3). Additional ultrasonication leads to a broader distribution and larger particle sizes (MGP-US). The narrowest distribution and smallest particles were achieved using the Ultra-Turrax™ dispenser (MGP-UT). When using a standard stirring bar, increasing the stirring speed leads to a decrease in particle size and distribution. Increasing the stirring time at the same speed does not lead to a significant change in particle size. In other sol-gel-based particle preparation processes, ultrasound-mediated synthesis also leads to a reduction in particle sizes.The use of an ultrasonic finger during our synthesis leads to an increased particle size distribution. One reason for this is the lack of mechanical stirring during sonication and the high viscosity of the liquid hybrid glass emulsion droplets. The final droplet size distribution is generally similar to the distribution immediately after droplet disruption by mechanical energy and depends on the phase viscosity of the droplets. The high viscosity hinders the disruption of the droplets by the introduction of ultrasonic energy. By using the dispersing device, small particles with a narrow distribution are formed. The reason for this is the high rotation speed of the rotor, which generates extremely strong shear and thrust forces that disrupt the droplets. This requires mechanical energy to form smaller particles through fragmentation.The energy introduced into the system by ultrasonic waves does not promote the crushing of the droplets. Fluorescence and quantum efficiency

[0067] The perylene dye Lumogen® F Red 305 was incorporated into the polyphenylsilsesquioxane hybrid glass during the gelation step of its synthesis (see experimental section). Due to its excellent solubility in phenyl-containing materials, the dye dissolved immediately in the polymer. During emulsion preparation, the dye remains dissolved in the polymer phase. The isolated and heat-treated microparticles (MGP-T) exhibit red fluorescence. At an excitation wavelength of 500 nm (20,000 cm -1 ), two emission bands are detectable at 622 nm (16,077 cm -1 ) and 647 nm (15,456 cm -1 ). At an emission wavelength of 650 nm (15384 cm -1 ), three excitation bands are detectable at 578 nm (17301 cm -1 ), 530 nm (18867 cm -1 ), and 440 nm (22727 cm -1 ). Compared to the fluorescence spectra of Lumogen ®< F Red 305 in toluene, a small bathochromic shift of the emission is observed.187 The Stokes shift in toluene was determined to be 29 nm (840 cm -1< ) in the microparticles, and 44 nm (1224 cm -1< ). The absolute quantum yield of the microparticles was 0.87 (λex=570 nm) and 0.82 (λex=450 nm). In the precursor material (MG LG305) and in other curable polyphenylmethylsiloxanes, the quantum yield of Lumogen ®< F Red 305 is slightly higher at 1.00 (λex=450 nm). Particle morphology and size cause a decrease in the quantum yield in the silica, and polymer particles have been previously reported. The reason for the shifted emission and the reduced quantum yield are reabsorption processes in the sample caused by the relatively high dye concentration (1 µmol g -1< ) and spectral distortions caused by scattering and reabsorption processes induced by the change of the solid phase morphology from transparent hybrid glass to a microparticle powder.Incomparable to polyphenylmethylsiloxanes with integrated Lumogen ®< F Red 305, no change in the quantum yield is detectable even at a high concentration of 3000 ppm. Integration of particles into a polyphenylmethylsiloxane resin

[0068] For use in an organic hybrid LED application, the hybrid glass microparticles must be homogeneously encapsulated with a silicone resin. The particles and the integrated dye must then withstand the operating conditions of the LED device, particularly the high radiation at a wavelength of 450 nm. An initial assessment of long-term photostability was determined through a long-term irradiation experiment. Therefore, the heat-treated MGP-3T particles were integrated into polyphenylmethylsiloxane resin [Dow Corning OE6630; Dow(1)], which was cast in an aluminum frame and thermally cured at 150°C for 4 h. The finished sample [Dow(1)MGP-3T] exhibits a homogeneous distribution of the particles within the sample and strong fluorescence under light exposure at a wavelength of 450 nm. Furthermore, the dye did not leach from the particles due to the process.

[0069] The sample and a sample of the consolidated precursor hybrid glass were irradiated with a 450 nm light source for >35 h at ~0.85 W / cm². To investigate the photophysical stability of the incorporated dye, the absorbance of the sample was measured periodically during the irradiation process. The relative absorbance to the initial value at 450 nm was determined. The decrease in absorbance of the consolidated hybrid glass and the hybrid glass microparticles inside the cured polysiloxane resin is almost identical within the experiment. It decreases by 10% after ~990 h (~39 d). The hybrid glass and the hybrid glass particles show a significant increase in the photostability of the incorporated dyes compared to the commercially available polysiloxane samples in which LG305 was directly incorporated into the material. There, the absorbance of the dyes decreased by 10% after 25 hours in Dow Corning OE6630.

[0070] The main difference between the materials is the degree of crosslinking, which can also influence the oxygen permeability and thus the photostability of the dyes. The polysiloxane resins are crosslinked by hydrosilylation and are still elastic. The hybrid glass is highly crosslinked by polycondensation of trialkoxysilanes, making it hard and rigid and likely less permeable to oxygen. This has also been indicated by gas barrier experiments with other hybrid glass compositions. It has also been shown that changing the morphology from a hybrid glass to microparticles does not affect the photostability properties of the dye. Therefore, the dye-containing microparticles are suitable for use in organic hybrid LED applications.

[0071] As a result, the integration of a hydrophobic perylene dye into polyphenylsilsesquioxane microparticles was achieved, resulting in a highly fluorescent microsphere powder. Under common conditions, such as in optoelectronic applications or in medical sensing or imaging, where water is typically used as a solvent or polymers as the host material, the dye remains within the particle structure. As previously described, the dye can be leached from the microparticles by treatment with organic solvents, while maintaining the integrity of the microparticles. The particles can also be encapsulated in curable polysiloxanes and thus in organic hybrid LED applications.

Claims

1. Method for the preparation of microparticles comprising the steps of: A) Preparation of a solution of a surfactant in a polar solvent B) Addition of a meltable precursor of a polysiloxane-glass hybrid for the preparation of a mixture of meltable precursor and solution of the surfactant C) Heating the mixture above the melting temperature of the meltable precursor for the preparation of a microemulsion of droplets of the meltable precursor, the size of the droplets being adjusted by stirring and / or ultrasound D) Addition of a catalyst to initiate a cross-linking reaction on the surface of the droplets for the preparation of microparticles, wherein the meltable precursor of the polysiloxane-glass hybrid is selected from the group consisting of one of the compositions (A), (B) and a mixture thereof: (A) a polymeric material prepared by condensation reactions of a trialkoxysilane monomer unit and / or a dialkoxysilane monomer unit, wherein the trialkoxysilane monomer unit (3) has the structure (I) and the dialkoxysilane monomer unit (4) has the structure (II) wherein the residues R1 and R2 in the trialkoxysilane monomer unit of structure (I) are independently selected from the group consisting of Cl-C24-alkyl, C3-C24-cycloalkyl, C2-C24-alkyne, C7-C24-cycloalkyne, C2-C24-alkenyl, Cl-C24-alkoxy, C3-C24-cycloalkoxy, C6-C14-aryl and C6-C14-aryloxy, and wherein the residues R1, R2 and R3 in the dialkoxysilane monomer unit of structure (II) are independently selected from the group consisting of Cl-C24-alkyl, C3-C24-cycloalkyl, C2-C24-alkyne, C7-C24-cycloalkyne, C2-C24-alkenyl, Cl-C24-alkoxy, C3-C24-cycloalkoxy, C6-C14-aryl, C6-C14-aryloxy, wherein preferably R1 for the respective trialkoxysilane or dialkoxysilane monomer unit is independently selected from methyl or ethyl, and wherein preferably R2, R3 for the respective trialkoxysilane or dialkoxysilane monomer unit are independently selected from methyl or phenyl; (B) a material comprising a three-dimensional network of partially cross-linked monomer units and an alkoxy-terminated oligo- or polysiloxane, said monomer units comprising at least one trialkoxysilane and at least one dialkoxysilane, said material preferably having the general structural formula wherein R1, R2, R3 and R4 are independently selected from aryl, alkyl, alkenyl, allyl, substituted aryl, substituted alkenyl, substituted alkyl and vinyl, preferably from phenyl and methyl, wherein u+v+w is the number of Si atoms employed and u, v and w are independently selected from the range 1 to 20000, wherein the groups indexed by u, v and w are statistically distributed in the general structural formula.

2. Method for the preparation of microparticles according to claim 1, wherein the meltable precursor of the polysiloxane-glass hybrid is a liquid or glassy solid of high to low viscosity at 20°C and 100 kPa, the meltable precursor preferably flowing at 100 kPa at temperature T1 and irreversibly and permanently consolidating at temperature T2, wherein T2>T1 and T1, T2 = 70-200°C.

3. Method for the preparation of microparticles according to any of the preceding claims, wherein in step A) the polar solvent is a polar protic solvent, preferably water.

4. Method for the preparation of microparticles according to any of the preceding claims, wherein in step A) the surfactant is a non-ionic surfactant, preferably an alkyphenol ethoxylate, or an ionic surfactant.

5. Method for the preparation of microparticles according to any of the preceding claims, wherein in step D) the catalyst is not a metal catalyst, preferably not a noble metal catalyst, in particular not a platinum catalyst, and is preferably an alkali, more preferably a metal hydroxide, in particular sodium or potassium hydroxide.

6. Method for the preparation of microparticles according to any of the preceding claims, wherein in step C) the size of the droplets is adjusted with the aid of a dispersing device, preferably with a stirring speed of 300 to 15000 min-1, more preferably 500 to 12000 min-1, in particular 8000 to 12000 min-1 for preferably 1 min to 5 h, more preferably 1 min to 2 h, in particular 2 to 15 min.

7. Method for the preparation of microparticles according to any of the preceding claims, wherein the process further comprises step E) isolating the microparticles, preferably by centrifugation, and optionally drying under elevated temperature and optionally reduced pressure to remove the solvent, wherein the drying conditions are chosen such that surfactant molecules bound on the microparticles remain bound.

8. Method for the preparation of microparticles according to claim 7, wherein after step E) isolation of the microparticles, further heating is carried out, optionally under reduced pressure, the conditions being selected such that surfactant molecules bound on the microparticles are removed and the microparticles are optionally consolidated.

9. Method for the preparation of microparticles according to any of the preceding claims, wherein a material selected from the group consisting of conversion material for wavelength conversion, preferably selected from the group consisting of organic fluorescent dye, preferably based on perylenediimide, inorganic phosphor and a mixture thereof, odorant, color, drug and a mixture thereof is embedded in the meltable precursor of the polysiloxane-glass hybrid.