Sequential curing of thiol-acetoacetate-acrylate thermosets by latent Michael addition reactions

Thiol-acetoacetate-acrylate ternary dual-curing thermosets were prepared by a sequential process consisting of thiol-Michael addition to acrylates at room temperature followed by Michael addition of acetoacetates to acrylates at moderately elevated temperature. The curing sequence can be controlled with the help of the different acidities of the protons on thiol and acetoacetate groups, the favorable pKa of the base used as catalyst and the self-limiting character of Michael additions. The latency of the curing steps can be regulated by selection of the right catalysts, temperature and curing conditions. The properties of the intermediate and final materials can be tuned by changing the structure of the monomers and the contribution of both Michael addition reactions.Postprint (author's final draft

Acetoacetate based thermosets prepared by dual-Michael addition reactions

A novel set of dual-curable multiacetoacetate-multiacrylate-divinyl sulfone ternary materials with versatile and manipulable properties are presented. In contrast to common dual-curing systems, the first stage polymer herein consists of a densely crosslinked, high Tg network as a result of base-catalyzed multiacetoacetate-divinyl sulfone Michael addition. A more flexible secondary network forms after base-catalyzed Michael addition of remaining multiacetoacetate to multiacrylate. Curing is truly sequential as the rates of the two Michael additions are significantly different. Curing kinetics were analyzed using differential scanning calorimetry (DSC) and Fourier-transform infrared (FTIR). The materials at each curing stage were characterized using dynamic mechanical analysis (DMA) and SEM. Although some phase separation was observed in certain formulations, the incompatibilities were minimized when the molar percentage of the acetoacetate-divinyl sulfone polymer network was above 75%. Furthermore, the environmental scanning electron microscopy (ESEM) images of these materials show that the more flexible acetoacetate-acrylate phase is dispersed in the form of polymeric spheres within the rigid acetoacetate-divinyl sulfone matrix. This unique dual microstructure can potentially render these materials highly resilient in applications requiring densely crosslinked polymer architectures with enhanced toughnesPostprint (published version

Chemical control of the viscoelastic properties of vinylogous urethane vitrimers

International audienc

Synthesis of new Biginelli polycondensates: renewable materials with tunable high glass transition temperatures

The Biginelli reaction was applied as a simple one‐pot multicomponent polycondensation approach to efficiently synthesize a set of 15 new and fully renewable poly(3,4‐dihydropyrimidin‐2(1H)‐one)s. One of six bis‐acetoacetates or three bis‐acetoacetamides, terephthalic aldehyde and (methyl‐)urea were used as renewable starting materials in various combinations, hence significantly expanding the known set of monomers as well as polymer structures. The bis‐acetoacetates and bis‐acetoacetamides with different spacer lengths were synthesized in yields of up to 99% in a one‐step process. Thermal analysis of the obtained set of polymers revealed high glass transition temperatures (T$_{g}$) ranging from 160 to 308 °C. The T$_{g}$ was tunable in small steps of 10 °C by simple variation of bis‐acetoacetate or bis‐acetoacetamide monomers as well as the choice of (methyl‐)urea. The poly(3,4‐dihydropyrimidin‐2(1H)‐one)s showed good thermal stability with T_{d5%} values well above the respective high T$_{g}$ values

Benzothiazole durch C-C-Spaltung von alpha-[(2-Nitrophenyl)thio]ketonen

Einwirkung von Ammoniak bzw. Natronlauge auf die -[(2-Nitrophenyl)thio]ketone 4, 11a-c und 16 führt unter CC-Spaltung zu den Benzothiazol-N-oxid-Derivaten 8, 12ac und 17; aus dem 3-[(2-Nitrophenyl)thio]-4-piperidon-Derivat 22 entsteht der 2-Benzothiazolcarbaldehyd 23

Freely mouldable cellulose

Tese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 201

Bimetallic Oriented (Au/Cu2O) vs. Monometallic 1.1.1 Au (0) or 2.0.0 Cu2O Graphene-Supported Nanoplatelets as Very Efficient Catalysts for Michael and Henry Additions

"This is the peer reviewed version of the following article: Simion, Andrada, Natalia Candu, Simona M. Coman, Ana Primo, Ivan Esteve-Adell, Véronique Michelet, Vasile I. Parvulescu, and Hermenegildo Garcia. 2018. Bimetallic Oriented (Au /Cu2 O) vs. Monometallic 1.1.1 Au (0) or 2.0.0 Cu2 O Graphene-Supported Nanoplatelets as Very Efficient Catalysts for Michael and Henry Additions. European Journal of Organic Chemistry 2018 (44). Wiley: 6185 90. doi:10.1002/ejoc.201801443, which has been published in final form at https://doi.org/10.1002/ejoc.201801443. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] Michael and Henry addition reactions have been investigated using mono (Au and Cu2O) and bimetallic nanoplatelets (Au/Cu2O) grafted onto few-layers graphene (fl-G) films as heterogeneous catalysts by comparison with homogeneous NaOH and K2CO3 ones. In the presence of the heterogeneous catalysts, these reactions occurred in the absence of any extrinsic (NaOH and K2CO3) base with turnover numbers (TONs) at least four orders of magnitude higher. While the homogeneous catalysts provided TONs close to the unity for Au/Cu2O/fl-G this was of the order of 10(7). These reactions also occurred with a very good selectivity to the targeted products. These performances are in line with the basicity of these catalysts demonstrated from CO2 chemisorption measurements. The effect of the nanosize and the interaction of the nanoparticles with the graphene are also important to achieve this high activity.This work was supported by the Ministere de l' Education, de la Recherche et des Affaires Etrangeres (Brancusi Program) of France (PN-III-CEI-BIM-PM, nr. 80BM/2017), UEFISCDI (PN-III-P4-ID-PCE-2016-0146, nr. 121/2017) and COST Action CA15106 (CHAOS)Simion, A.; Candu, N.; Coman, SM.; Primo Arnau, AM.; Esteve-Adell, I.; Michelet, V.; Parvulescu, VI.... (2018). Bimetallic Oriented (Au/Cu2O) vs. Monometallic 1.1.1 Au (0) or 2.0.0 Cu2O Graphene-Supported Nanoplatelets as Very Efficient Catalysts for Michael and Henry Additions. European Journal of Organic Chemistry. 2018(44):6185-6190. https://doi.org/10.1002/ejoc.201801443S61856190201844Michael, A. (1887). Ueber die Addition von Natriumacetessig- und Natriummalonsäureäthern zu den Aethern ungesättigter Säuren. Journal für Praktische Chemie, 35(1), 349-356. doi:10.1002/prac.18870350136Michael, A. (1894). 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5,6-Dihydro-2H-pyran-3(4H)-on als Baustein zur Synthese pyrananellierter Heterocyclen

Während 5,6-Dihydro-2H-pyran-3(4H)-on (3) sich mit ortho-substituierten Phenylcarbonylverbindungen nur in Einzelfällen regioselektiv zu pyrananellierten Heterocyclen umsetzt - z. B. zum Pyrano[2,3-b]chinolin 7c -, gelingt das besser mit dem aus 3 hergestellten Enamin 15d, dem Silylenolether 18 und dem daraus gewonnenen Lithiumenolat 14. Diese Pyranderivate mit 2,3-oder 3,4-Doppelbindungen eignen sich zur gezielten Darstellung von 2- oder 4-substituierten 3-Pyranonen - z.B. 2, 21a, 21b, 23a-c, 26a-c, 31a-c, 32, sowie 35a-c - und von Pyrano[3,2-b]- oder -[3,4-b]chinolinen, -chinolonen, -chromonen und -thiochromonen 6a, 30a-c und 38a-d