- Synthesis, characterization, and photocuring of siloxane-oxirane monomers
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The aim of this study was to synthesize, characterize, and evaluate alternative monomers for use in dentistry. Three siloxane-oxirane low-shrinkage monomers were synthesized, and the products' conversion was followed by Fourier transform-infrared spectroscopy. The products obtained were characterized by 1H and 13C NMR and evaluated for viscosity and a refractive index. The polymerization was evaluated by formulating two experimental photoinitiation systems, which varied for the presence of 1,2 ethanediol. A ternary system with camphorquinone (CQ), ethyl 4-dimethylaminobenzoate (EDAB), and diphenyliodonium hexafluorphosphate (DPI) was used as control. The degree of conversion was assessed by differential scanning calorimetry (DSC). The NMR confirmed the synthesis success with 75, 87, and 55% yields for the monomers synthesized. The viscosity and the refractive index of the monomers showed favorable rheological and physical behaviors for application in dentistry. Moreover, the presence of 1,2-ethanediol increased the degree of conversion of the siloxane-oxirane monomers. This study showed a simple and effective way to synthesize siloxane-oxirane monomers with a high potential for application in dental materials.
- Leal, Fernanda B.,Pereira, Claudio M.,Ogliari, Fabrício A.
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- Involvement of supramolecular complexes in the capture and release of protonic acids during the cationic ring-opening polymerization of epoxides
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The kinetics of the cationic ring-opening polymerizations of epoxide monomers were controlled through the use of supramolecular proton complexes. α,ω-Diglycidyl oligoethylene oxides bearing multiple ethyleneoxy spacer groups form metastable supramolecular proton complexes with strong Bronsted acids generated either by the photolysis of onium salts or by their redox reactions with reducing agents. Trapping of the Bronsted acids by in situ complex formation results in a delay of the onset of cationic ring-opening. However, once polymerization begins, the epoxide groups of the monomer are very rapidly consumed resulting in characteristically highly exothermic autoaccelerated polymerization reactions. Crown ethers can also form supramolecular complexes with hydronium ions derived from the reaction of protonic acids with water and these complexes can be used to modify the kinetic behavior of the cationic ring-opening thermal and photopolymerizations of a variety of epoxide monomers. The ring size of a crown ether has a strong influence on the stability of the supramolecular complex formed, and this was shown to have a major impact on the kinetics of the cationic ring-opening polymerizations.
- Ryu,Spencer,Crivello
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- Microwave synthesis method of 1,3-bis[2-(3, 4-epoxycyclohexyl)ethyl]tetramethyldisiloxane
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The invention discloses a microwave synthesis method of 1,3-bis[2-(3,4-epoxycyclohexyl)ethyl]tetramethyldisiloxane. The synthesis method comprises the following steps: (1) under the protection of inert gas, sequentially adding tetramethyldisiloxane, an organic solvent and 4-vinyl-1,2-epoxy cyclohexene into a reaction flask, stirring the reaction liquid, then adding a supported Pt/Y molecular sievecatalyst, finally adding absolute ethyl alcohol, and continuously stirring the reaction liquid to obtain a suspension; and (2) transferring the suspension into a microwave synthesis reactor for reaction, after the reaction is finished, reducing the pressure of the reaction liquid to remove the solvent and low-boiling-point substances, and then carrying out centrifugal separation to obtain the 1,3-bis [2-(3,4-epoxycyclohexyl)ethyl]tetramethyldisiloxane. The method has the advantages of mild reaction conditions, short reaction time, high raw material active hydrogen conversion rate, excellent activity and stability of the catalyst, recyclability, cost reduction, high yield of the prepared target product, and good industrialization prospect.
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Paragraph 0022-0058
(2020/07/02)
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- Synthesis method of 1, 3-bis [2-(3, 4-epoxy cyclohexyl) ethyl]tetramethyldisiloxane
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The invention discloses a synthesis method of 1, 3-bis [2-(3, 4-epoxy cyclohexyl)ethyl]tetramethyldisiloxane. The preparation method comprises the following steps: (1) roasting a Y molecular sieve; (2) dissolving the Y molecular sieve, adjusting the pH value, filtering, drying and grinding; (3) diluting a chloroplatinic acid/isopropanol solution, adding the material obtained in the step (2), and adjusting the pH value; (4) refluxing, depositing, filtering and washing until Cl does not exist; and (5) roasting the material obtained in the step (4) to obtain the Y molecular sieve supported platinum catalyst. The target product is synthesized by the following steps: (1) under the protection of inert gas, adding required materials into a reaction bottle; and (2) after the reaction, removingthe solvent, and separating the catalyst to obtain the 1,3-bis [2-(3, 4-epoxy cyclohexyl) ethyl] tetramethyldisiloxane. The method has the advantages of mild reaction conditions, high active hydrogenconversion rate of the raw materials, excellent activity and stability of the self-made catalyst, repeated use, cost reduction, high product yield and good industrial prospect.
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Paragraph 0030-0045
(2020/07/02)
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- Stable, cationically polymerizable/crosslinkable dental compositions having high filler contents
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Stable, highly filled cationic dental compositions useful for the production of dental prostheses and dental restoration materials contain: (1) at least one compound which is reactive cationically when activated, advantageously at least one UV-and cationically reactive oxirane-functionalized silicone; (2) at least one dental filler, advantageously SiO2; (3) at least one organic polymer or copolymer dispersant having an amine index less than or equal to 100 mg of potassium hydroxide per gram of dispersant, advantageously a polyurethane/acrylate copolymer or alkylammonium salt thereof; (4) at least one cationic photoinitiator, advantageously iodonium borate; and (5) optionally, at least one photosensitizer.
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Page/Page column 11
(2008/06/13)
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- Method for preparing oxirane-containing organosilicon compositions
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A method for preparing an organosilicon composition from an olefin and a silicon hydride with a hydrosilation catalyst PtL2X2, in an amount less than 1 ppm based on the weight of the product composition, is disclosed. The method is particularly useful in lowering the cost, coloration, and stability of the product, particularly when an oxirane-containing olefin is used in the hydrosilation. In this method no inhibitor is needed to prevent the undesired polymerization of oxiranes in the reaction, and no purification of the product is required after removal of volatile components, including solvent.
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