Master curves for the sulphur assisted crosslinking reaction of natural rubber in the presence of nano- and nano-structured sp2 carbon allotropes

In this paper, master curves are reported for the crosslinking of a diene rubber with a sulphur based system in the presence of either nano- or nano-structured carbon allotropes, such as carbon nanotubes (CNT), a nanosized graphite with high surface area (HSAG) and carbon black (CB). Poly(1,4-cis-isoprene) from Hevea Brasiliensis was the diene rubber and crosslinking was performed in temperatures ranging from 151 to 180°C, with carbon allotropes below and above their percolation threshold. Such carbon allotropes were characterized by different aspect ratio, surface area and pH. However, in the crosslinking reaction, they revealed common behaviour. In fact, the specific interfacial area could be used to correlate crosslinking parameters, such as induction time (ts1) and activation energy (Ea) calculated by applying the autocatalytic model. Monotonous decrease of ts1 and increase of Ea were observed, with points lying on master curves, regardless of the nature of the carbon allotropes. Remarkable differences were however observed in the structure of the crosslinking network: when the carbon allotrope was above the percolation threshold much larger crosslinking density was obtained in the presence of CNT whereas composites based on HSAG became soluble in hydrocarbon solvent, after the reaction with a thiol. Proposed explanation of these results is based on the reactivity of carbon allotropes with sulphur and sulphur based compounds, demonstrated through the reaction of 1-dodecanethiol and sulphur with CNT and HSAG and with a model substrate such as anthracene

Sustainable Synthesis of N-Alkyl-Pyrrolecarboxylic and Pyrrolepyrazinones Derivatives from Biosourced 3-Hydroxy-2-pyrones and Amines

Pyrroles are important compounds present in biological systems, used for drug synthesis and in material chemistry. A typical strategy for the pyrrolic ring formation is centered on the Paal−Knorr reaction, where 1,4-dicarbonyl compounds react with amines giving N-substituted pyrrole derivatives. Often, the main problem of this approach is the availability of the appropriate carbonyl compounds. Here, we report a sustainable synthesis of N-substituted pyrrole carboxylic acid derivatives by the reaction of primary amines and 3-hydroxy-2-pyrones. These last compounds can easily be prepared using renewable sources and show the property to be masked 1,4-dicarbonyl compounds that are able to react efficiently with amines to form substituted pyrrolic rings. The reactions can be performed under sustainable conditions without solvents at 50−75 °C or in basic water−methanol solutions at room temperature, obtaining symmetric and asymmetric pyrroles from good to high yields. Moreover, dihydropyrrolepyrazinone derivatives can easily be prepared in high yields by the reaction of 3-hydroxy-2-pyrones and ethylenediamine

Synthesis of pyrrole derivatives of serinol for functionalization of carbon allotropes

N-Pyrrole-based heterocycles are present in many natural products,[1] medicinal agents,[2] and functional materials,[3,4] therefore substantial attention has been paid to develop efficient methods for pyrroles synthesis. Moreover, they are precursors for the synthesis of poly N-alkyl pyrroles which have wide ranging applications in electronics and sensors due to their tunable optoelectronic properties. We present here one operationally simple, practical and economical Paal-Knorr pyrrole condensation of serinol (2-amino-propan-1,3-diol, 1) with beta-dicarbonyl compounds 2 (and related acetal/ketals or enolesters), under neat conditions in the absence of any catalysts, which allows the synthesis of N-serinopyrrole derivatives (3) in good to excellent yield. Depending on substituents, compounds 3 show quite interesting amphiphilic polar/unpolar and variable -interaction properties. The mechanistic conclusion reached in the study, allowed to identify a direct method for the preparation of the precursor serinol-pyrrole from sugar derivatives. Typical examples of this reaction is the dehydrative condensation of galactaric acid (4) with serinol (1) (i.e. its serinol salt or other derivatives). Methods for the derivatization of carbon allotropes (CNT, Graphenes and Carbon Black) by the prepared pyrroles were investigated and the good dispersion properties of the resulting material proved

Serinol: a biosourced building block for better mechanical reinforcement and sustainable vulcanization of rubber compounds

Serinol and serinol derivatives were used to promote the mechanical reinforcement and the sulphur based crosslinking of rubber compounds. Reaction of serinol was performed with aldehydes and ketones, such as cinnamaldehyde, acetone, 2,5-hexanedione and camphor, obtaining the regiospecific synthesis of either imines or oxazolidines. Paal-Knorr reaction was as well carried out between serinol and 2,5-hexanedione, obtaining a serinol derivative containing a pyrrole ring, 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3-propanediol, named as serinolpyrrole. All the reactions were performed in the absence of solvents and catalysts and were characterized by high and also quantitative yields. Thanks to the reactions’ specificity, pure substances were obtained, with controlled atoms hybridization. The aromatic pyrrole ring was exploited to form adducts of serinolpyrrole with carbon allotropes. Adducts of SP with carbon black promoted the reduction of filler networking in silica based compounds. Serinol and immine as well oxazolidine derivatives were efficient secondary accelerators in silica based compounds and are thus suitable substances for the replacement of DPG. Tuning of vulcanization kinetics was performed

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements