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3D Printing Amorphous Polysiloxane Terpolymers via Vat Photopolymerization
摘要： Photocuring and vat photopolymerization (VP) additive manufacturing (AM) is reported for two families of fully amorphous poly(dimethyl siloxane) (PDMS) terpolymers containing either diphenylsiloxy (DiPhS) or diethylsiloxy (DiEtS) repeating units. A thiol-functionalized PDMS crosslinker enables rapid crosslinking in air using efficient thiol–ene addition. Differential scanning calorimetry and dynamic mechanical analysis (DMA) confirm the absence of crystallinity for the DiPhS-containing systems, while DMA shows a rubbery plateau extending to greater than 200 °C for the DiEtS-containing system. VP-AM of both photopolymer systems afford well-defined 3D geometries, including high aspect ratio structures, which demonstrate feasibility of these photopolymers for the 3D printing of unique geometric objects that require elastomeric performance to temperatures as low as ?120 °C.
关键词： thiol–ene reaction,elastomers,poly(dimethyl siloxane),vat photopolymerization,siloxane terpolymers,3D printing
更新于2025-09-23 15:22:29
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Analysis of Network Structures in Thiol-Ene UV Curing System Using Reworkable Resins
摘要： An analysis of the network structures in thiol-ene UV curing resins was carried out using reworkable resins composed of di(meth)acrylate monomers having tertiary ester linkages. The effect of the functionality of the thiols, the functional ratio of the thiol and ene functions, their conversions and curing atmosphere on the chain lengths was discussed. A mixture of (meth)acrylates, thiol compounds, a photoradical initiator, and a photoacid generator was cured by irradiation at 365 nm. The cured samples were degraded by heating after irradiation at 254 nm. Size exclusion chromatography (SEC) and 1H NMR analyses of the degraded samples were carried out after the methylation. The crosslinking conditions strongly affected the network structures. The degraded samples have molecular weights between 250 and 2700. The molecular weights of the degraded resins increased with the functionality of the thiol compounds. The chain length dependence suggests that thiol compounds with a high functionality have a low reactivity due to steric hindrance. The chain lengths of the degraded networks were nearly proportional to the concentration of the (meth)acrylate monomers. The addition of reactive diluents enhanced the reactivity and increased the chain length.
关键词： thiol-ene reaction,UV curing,crosslinking,chain length,degradation,reworkability
更新于2025-09-23 15:22:29
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Biobased Aromatic-Aliphatic Polyols from Cardanol by Photochemical Thiol-ene Reaction
摘要： Biobased aromatic-aliphatic polyols were previously synthesized from a thermal thiol-ene reaction of propoxylated cardanol with 2-mercaptoethanol (ME) in the presence of azobisisobutyronitrile (AIBN) as a radical initiator. Cardanol used for this purpose was obtained as a dark-brown liquid (Gardner Color Reference ~18). The photochemical thiol-ene reaction can also be used to prepare aromatic-aliphatic polyols by employing cardanol. Via the photochemical thiol-ene reaction, 2-mercaptoethanol was added successfully to C=C double bond of cardanol, suggesting that phenolic group may not play an inhibitory role in the radical thiol-ene reaction. However, we preferred to alkoxylate the phenolic hydroxyl group of cardanol, which is much more reactive with isocyanates than phenolic hydroxyls, to generate a new aliphatic hydroxyl group. Furthermore, the functionality of polyols was also improved by two methods: 1) using 1-thio-glycerol instead of 2-mercaptoethanol and 2) using alkoxylated cardanol with glycidol (Cardanol-GLY) instead of propoxylated cardanol (Cardanol-PO). These polyols were then used in preparation of rigid polyurethane foams that can be useful in various applications such as insulation of freezers, pipes and storage tanks in food and chemical industries.
关键词： 1-thio-glycerol,2-mercaptoethanol,photochemical reactions,thiol-ene reaction,Cardanol
更新于2025-09-23 15:22:29
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Thiol-ene reaction based polymer dispersed liquid crystal composite films with low driving voltage and high contrast ratio
摘要： In this study, polymer dispersed liquid crystal composite films are obtained via a one-step fabrication technique based on photo-initiated polymerization-induced phase separation in a thiol-vinyl ether reaction. The effects of the compositions of two vinyl monomers, curing light intensity, curing light time, liquid crystal content and thiol content on the electro-optic properties of the polymer dispersed liquid crystal films were systematically investigated. It was demonstrated that a composite film with a low driving voltage (33.7 V), high contrast ratio (228.1) and short response time (<5.0 ms) was achieved. This is of great significance for the potential applications of polymer dispersed liquid crystal composite films.
关键词： contrast ratio,Thiol-ene reaction,polymer dispersed liquid crystal,driving voltage
更新于2025-09-23 15:22:29
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UV-Induced Crosslinking of Poly[2-(2’-Norbornenyl)-2-Oxazoline]s
摘要： A 2-oxazoline monomer bearing a norbornenyl functionality in the side-chain was prepared from the reaction of 5-norbornene-2-carbonitrile and 2-ethanol amine. This monomer could be successfully polymerized using a 2-oxazolinium-based macroinitiator that was in-situ generated from the methyl cation-initiated oligomerization of 2-ethyl-2-oxazoline. This polymer could be subjected to polymeranalogous reactions involving the alkene groups of the norbornenyl side-chains: A proof-of-concept was established by utilizing the polymers in photoresists that were crosslinked by thiol-ene reactions involving bisfunctional thiols. Photoinitiators for the UV-induced thiol-ene reaction were required in catalytic amounts only. After development, the resists exhibited reproduction of the geometric patterns with a resolution of 30 μm.
关键词： cationic polymerization,polymer photochemistry,microwave-assisted polymerization,poly(2-oxazoline)s,photoresist,thiol-ene reaction
更新于2025-09-23 15:21:21
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Extremely Soft, Conductive, and Transparent Ionic Gels by 3D Optical Printing
摘要： A series of 3D printable multifunctional ionic gels (IGs) are developed incorporating ionic liquid (IL) in the thiol–ene network of thiol-based end-crosslinker and acrylate monomers. The resulted gels, termed as thiol-ionic gels (T-IGs), are highly transparent and very soft with IL content of 70–85 wt%. The mechanical and conductive properties of the T-IGs are found to be largely dependent on the IL content, end-crosslinker functionalities, and chain-length of monomers. Progression of ionic conductivity is observed with an increase in IL content and conductivity as high as 5.40 mS cm?1 is attained for longer acrylate group containing T-IGs at room temperature, while further increase is observed at elevated temperature. T-IGs in all systems are found to exhibit superior thermal stability. Three-dimensional fabrication of these functional T-IGs is achieved by optical 3D printing process with microscale resolution in facile steps.
关键词： multifunctional ionic gels,3D printing,thiol–ene reaction,ionic liquids
更新于2025-09-23 15:21:01