FACILE FUNCTIONALIZATION OF sp2 CARBON ALLOTROPES WITH A BIOBASED JANUS MOLECULE

A simple, versatile, sustainable, not expensive method for the functionalization of sp2 carbon allotropes, both nanosized and nano-structured, without altering their bulk crystalline organization, is presented. Carbon materials available at the commercial scale were used: furnace carbon black (CB), nano-sized graphite with high surface area, and multiwalled carbon nanotubes. A bio-sourced molecule, 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole), was used for the functionalization. Serinol pyrrole (SP) was obtained from serinol through a reaction with atomic efficiency of about 82%, performed in the absence of solvents or catalysts. Synthesis of serinol pyrrole was performed as well on carbon allotropes as the solid support. Adducts of serinol pyrrole with a carbon allotrope were prepared with the help of either thermal or mechanical energy. Functionalization yield was in all cases larger than 90%. With such adducts, stable dispersions in water and inNRlatex were prepared.Afew layers of graphene were isolated from the water dispersions, and NR-based composites precipitated from the latex revealed very even distribution of fine graphitic particles. Composites were prepared, based on NR, IR, andBRas the rubbers andCBand silica as the fillers, with different amounts of CB–SPadduct, and were cross-linked with a sulfur-based system without observing appreciable effect of functionalization on vulcanization kinetics. The CB–SP adduct led to appreciable reduction of the Payne effect

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

Reduction of filler networking in silica based elastomeric nanocomposites with exfoliated organo-montmorillonite

Montmorillonite with dimethyl di(hydrogenatedtalloyl) ammonium as the compensating cation was added to a silica based elastomeric composite and the hybrid filler system led to reduction of filler networking phenomenon, better stability of elastic modulus with temperature, enhancement of stresses at all elongations, improvement of ultimate properties. This composite was based on a blend of natural rubber, poly(1,4-cis-isoprene) and poly(styrene-co-butadiene) from anionic polymerization and contained 70 parts per hundred rubber (phr) of silica. The organically modified clay (OC) was below the threshold required to establish an hybrid OC-silica filler network. Such threshold (about 7 phr) was estimated by preparing silica based nanocomposites containing various amounts of OC and determining shear storage and loss moduli as a function of strain amplitude. This work demonstrates that exfoliated OC favour lower dissipation of energy of silica based elastomeric composites under dynamic mechanical stresses and paves the way for further large scale applications

Biosourced Aromatic Derivatives in the Upcycling of Recycled PET: Mellophanic Dianhydride as a Chain Extender

The synthesis of mellophanic dianhydride (MEDA) from biosourced 1,2,3,4-benzene tetracarboxylic derivatives and its use as a chain extender for mechanically recycled PET (R-PET) as an alternative to traditional oil-based pyromellitic dianhydride (PMDA) is reported. The rheological tests performed on the R-PET extruded with MEDA have shown similar results to those obtained with PMDA, and dynamic mechanical thermal analysis (DMTA) showed that, in the 90–110 °C range (i.e., the temperature range commonly used for blow molding of bottles), Young’s modulus of R-PET containing MEDA is about 20% higher in comparison to that of pristine R-PET. The advantage of MEDA is that it can be prepared using building blocks obtained from agricultural waste via a sustainable protocol, whereas PMDA is a product of oil-based chemistr

Master curves for the mechanical reinforcement of diene elastomers with sp2 carbon allotropes

sp2 carbon allotropes are efficient reinforcing fillers for polymer melt and elastomers: carbon black (CB) has been used since early 1900’s and nanofillers such as carbon nanotubes (CNT), graphene and graphene related materials (GRM) have increased their importance over the last decades. Nanofillers can definitely establish larger interfacial area with the polymer matrix than CB and great impact on material properties is thus expected. However, it is widely acknowledged that they will not be able to completely replace CB. Hence, increasing research efforts are on hybrid systems based on CB-CNT and CB-GRM [1]. Research objective is to identify common features and behaviour of nano (CNT, GRM) and nanostructured (CB) sp2 carbon allotropes. In this work, initial modulus was determined by means of dynamic-mechanical shear measurements of composites based on either poly(1,4-cis-isoprene) or poly(styrene-co-butadiene) as the rubber and either CB or CNT or GRM or hybrid systems as the reinforcing fillers. Filler-polymer interfacial area (i.a.), calculated as the product of filler surface area, density and volume fraction, was used to establish a common correlation with the composite initial modulus. A sort of master curve was derived, able to fit all the points up to interfacial area of about 27 μm-1, corresponding to remarkable filler content. Much better efficiency was shown by carbon fillers, when composites were prepared through latex blending. To allow easy dispersion in rubber latex, sp2 carbon allotropes were functionalized with a serinol derivative: 2-(2,5-dimethyl- 1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP) [2, 3], shown in Figure 1

A Janus Molecule for Screen-Printable Conductive Carbon Ink for Composites with Superior Stretchability

Inspired by decades of research in the compatibilization of fillers into elastomeric composites for high-performance materials, a novel polyurethane-based stretchable carbon ink is created by taking advantage of a Janus molecule, 2-(2,5-dimethyl-1H-pyrrol-1-yl)propane-1,3-diol (serinol pyrrole, SP). SP is used to functionalize the carbon and comonomer in the polymer phase. The use of SPs in both the organic and inorganic phases results in an improved interaction between the two phases. When printed, the functionalized material has a factor 1.5 lower resistance-strain dependence when compared to its unfunctionalized analogue. This behavior is superior to commercially available carbon inks. To demonstrate the suitability of ink in an industrial application, an all-printed, elastomer-based force sensor is fabricated. This “pyrrole methodology” is scalable and broadly applicable, laying the foundation for the realization of printed functionalities with improved electromechanical performance.</p

Domino reaction for the controlled functionalization of sp2 carbon allotropes

Graphene and graphene related materials are a hot research topic in the material science and are becoming a reality of increasing importance in many application fields. Indeed, graphene has high charge-carrier mobilities, in-plane thermal conductivity and very high elastic modulus. It is increasingly acknowledged that application of carbon nanomaterials such as graphene has to be assisted by functionalization, which allows to tune electronic and solubility properties, phaseforming and self-assembly behaviour. In this work, functionalization of graphene layers was performed with 2-(2,5- dimethyl-1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP) [3]. SP is a serinol derivative obtained from the neat reaction of 2-amino-1,3- propandiol with 2,5-hexanedione, with atom economy of about 85%, almost quantitative yield and thus high atom efficiency, the only byproduct being water, in the absence of solvent and catalyst [1, 2, 3]. Functionalization was obtained by simply mixing nanosized high surface area graphite with SP, giving either mechanical or thermal energy. Very high functionalization yield was found, larger than 90% and even almost quantitative. Few layers graphene were isolated from stable water suspensions. Reaction of SP was applied to other sp2 carbon allotropes, such as carbon nanotubes and carbon black. Many different applications were developed: from conductive inks to carbon papers and aerogels. The reaction occurring between SP and graphene layers was investigated. Adducts of a high surface area nanosized graphite were prepared with a model molecule, 1,2,5-trimethyl-1H-pyrrole (TMP). Pristine TMP, HSAG, products formed by the reaction and HSAG-TMP adducts were studied by means of Fourier transformed infrared spectroscopy (FT-IR), 1H-NMR and thermogravimetric analysis. DFT modelling was carried out to predict IR spectra of HSAG-TMP reaction products and adducts. Reaction pathway is presented. Domino reaction appears to occur: carbocatalyzed oxidation of the pyrrole compound lead to the formation of activated double bond, able to give rise cycloaddition with the graphitic substrate. Such a facile and sustainable functionalization method allows the controlled introduction of functional groups on graphitic substrate without appreciably altering their structure

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