Biosourced Janus molecules for functional additives

The estimated global production of biomass is about 1011 ton/year and only 3% is cultivated, harvested, and used, for food and non food applications. The agricultural dry biomass waste is about 20 Gton. Hence, it really makes sense to start from biosources and in particular from the 2nd generation ones, which do not have impact on the food chain, to prepare new and more sustainable materials. The research here reported moved from biousourced C3 and C6 building blocks: glycerol and aldaric acids. By applying the basic principles of green chemistry, they were transformed in functional chemicals, suitable for the preparation of a large variety of materials. Fil rouge of these chemicals is the ability to combine the typical features and reactivity of the biosourced molecule with those arising from the chemical modifications. In this respect, they are Janus molecules. An example of a Janus molecule is 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP), obtained from 2-amino-1,3-propandiol (serinol), a glycerol derivative. SP was found to be a universal functionalization agent for sp2 carbon allotropes and inorganic oxy-hydroxides. Hybrid systems were also prepared, based on both carbon and inorganic materials. The innovative chemical structure of such a Janus molecule allowed to perform functionalization reactions which are easier and more sustainable than the traditional ones. Nanosized sp2 carbon allotropes were successfully functionalized and the adducts found pervasive applications, from nanocatalysis for low temperature organic chemistry reactions to bionanocomposites, to functional additives for piezoresistive and antibacterial coatings, to reinforcing fillers for rubber composites for tires. The chemistry developed with these biosourced Janus molecules is becoming a technology, as different applications are at the pre-industrial scale

A green approach to the edge functionalization of graphene layers with a bio-based 2-pyrone

Increasing awareness and concerns about climate change have spotlighted the need for a sustainable development. Green chemistry, defined as “the design of chemical products and processes to reduce or eliminate the use and generation of hazardous substances”, pursues the aim to transform hydrolyzed biomass, mainly composed by carbohydrates, into suitable building blocks. In this context, 2-pyrones build up a class of C-6 unsaturated lactone from lignocellulosic feedstock and intriguing building blocks for the preparation of key intermediates in synthetic organic, medicinal and polymeric chemistry. In this work, a green and efficient pathway for the preparation of a 2-pyrone starting from mucic acid is presented. Furthermore, a 2-pyrone derivative, ethyl 3-hydroxy-2-oxo-2H-pyran-6-carboxylate (Pyr-COOEt ), was used for selectively decorating the edge of a nano-sized graphite with high surface area (HSAG), without altering the graphitic bulk structure. The preparation of adducts between HSAG and Pyr-COOEt was performed through a sustainable method, with the help of either thermal or mechanical energy, reaching high functionalization yield (up to 90%). Few layers of graphene were easily obtained by means of a mild sonication of a water dispersion of the HSAG/Pyr-COOEt adducts

Controlled Functionalization of Graphene Layers

Controlled functionalization of graphene layers is one of the most important research objectives in the material chemistry. A well established procedure is the oxidation with strong acids and oxidizing agents often in harsh and dangerous reaction conditions giving products of unknown precise structure. In this chapter, the controlled functionalization of graphene layers with a derivative of serinol is presented, avoiding toxic reagents and dangerous reaction conditions. The derivative is the bio‐based serinol pyrrole, obtained through the neat reaction of serinol with 2,5‐hexanedione; the graphitic substrate was high surface area graphite (HSAG) with high‐shape anisotropy. The functionalization reaction, characterized by a 85% atomic efficiency (water is the only by‐product), evolved with high yields leading to functionalized graphene layers through the controlled introduction of oxygen and nitrogen‐containing functional groups. Sustainable processes were adopted, such as ball milling and heating. The mechanism pathway, the characterization of HSAG and reaction products through a wide range of analytical methods, some successful applications of the adducts are discussed in this chapter. The functionalization left the bulk crystalline structure of the layers substantially unaltered. Stable dispersions in water and eco‐friendly solvents were prepared

Edge functionalization of graphene layers with a 2-pyrone

Conversion of hydrolyzed biomass, mainly composed by carbohydrates, into suitable building blocks is one of the major purposes of Green Chemistry, defined as ‘‘the design of chemical products and processes to reduce or eliminate the use and generation of hazardous substances”. 2-pyrones are a class of unsaturated heterocyclic C-6 sugar derivatives, prevalent in many natural products and, due to their versatile chemical reactivity, intriguing building blocks in organic and polymer chemistry. In this work, a green and efficient procedure for the preparation of 2-pyrone is presented, starting from galactaric acid, also known as mucic acid, easily obtained from galactose or galacturonic acid. A 2-pyrone derivative, 5-hydroxy-6-oxo-6H-pyran-2-carboxylic acid ethyl ester (Pyr-COOEt) was used for the functionalization of nano-sized graphite with high surface area (HSAG). Adducts of Pyr-COOEt with HSAG were prepared by means of a simple and sustainable method, with the help of either thermal or mechanical energy. Functionalization yield was in all cases larger than 90%. After the functionalization reaction, the bulk structure of HSAG remained substantially unaltered, thanks to the edge functionalization. Few layers graphene were easily obtained by means of a mild sonication of a water dispersion of the HSAG/Pyr-COOEt adducts

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

Controlled functionalization of sp2 carbon allotropes for the reinforcement of diene elastomers

To achieve important mechanical properties, natural and synthetic rubbers need reinforcing fillers. sp2 carbon allotropes are indeed relevant reinforcing fillers for rubber compounds. Carbon black has been used for over a century and nanofillers such as graphene, graphene related materials and carbon nanotubes are dramatically increasing their importance. Ultimate distribution and dispersion of the carbon fillers in the rubber compounds has to be obtained. To achieve this goal, carbon allotropes should be used as such or should they be functionalized? In this work, controlled functionalization of sp2 carbon allotropes was performed. In particular, the aim was to introduce, on carbon allotropes, oxygenated functional groups, without altering the graphitic structure of the substrate. Methods developed are presented. They were based on reaction of carbon materials with hydrogen peroxide, potassium hydroxide and a derivative of 2-amino-1,3- propandiol, better known as serinol. All the reactions were inspired to the basic principle of sustainable chemistry, with the aim to avoid the use of solvents and catalysts. Research performed with the serinol derivative is in particular discussed. The Paal-Knorr reaction of serinol with 2,5-hexanedione was performed, obtaining 2- (2,5-dimethyl-1H-pyrrol-1-yl)-1,3-propanediol, named as serinolpyrrole (SP). The aromatic ring in SP was exploited to form stable adducts with the carbon allotropes. Hypothesis on the mechanism for the adduct formation is presented. Rubber compounds, based either only on carbon black or on carbon black and silica as the filler systems, were prepared and sulphur-based crosslinking behavior and dynamic-mechanical properties were investigated