A facile and sustainable functionalization of graphene layers was performed with pyrrole compounds (PyC) prepared through the Paal-Knorr reaction of a primary amine with 2,5-hexanedione. A good number of primary amines were used: hexanamine, dodecanamine, octadecanamine, 2-aminoacetic acid, 2-amino-1,3-propanediol, 3-(triethoxysilyl)propan-1-amine. The reactions were characterized by good yield, up to 96 %, and indeed satisfactory atom efficiency, up to 80 %. The functionalization of graphene layers was obtained by mixing PyC with a high surface area graphite and heating at a temperature range from 130 °C to 150 °C for 3 h. The yield of functionalization reaction was larger than 60 % and also up to about 90 % for the pyrrole compounds from dodecanamine and 2-amino-1,3-propanediol, respectively. The cycloaddition reaction between the graphene layers and the pyrrole compound, oxidized in two position, is proposed as working hypothesis to account for such efficient functionalization. Raman spectroscopy revealed that the structure of the graphitic substrate remained substantially unaltered, after the reaction. Stable dispersions of HSAG adducts with different PyC were prepared in solvents with different solubility parameters and HRTEM analysis showed the presence of aggregates of only few layers of graphene. Qualitative results of dispersion tests were used to calculate the Hansen sphere for the HSAG adduct with the pyrrole compound based on dodecanamine so to provide a first estimate of its Hansen solubility parameters. This work paves the way for the facile and sustainable modification of the solubility parameters of graphene layers and for the predictive assessment of their compatibility with different environments.
A technique for poly-3-hydroxybutyrate (P(3HB)) extraction with safer, non-chlorinated solvents, was developed, aiming to attain high recovery yields and purities. A wide range of solvents was selected from the GlaxoSmithKline guide as sustainable industrial solvents and the solubility of P(3HB) on those solvents calculated using predictive equations from literature. Anisole, * Corresponding author: Tel.: +351 21 8419137; Fax: +351 21 8419062. e-mail address: teresa.cesario@tecnico.ulisboa.pt + Current address: Politecnico di Milano, Dipartimento di Chimica Materiali e Ingegneria Chimica "Giulio Natta". Via Mancinelli, 7 -20131 Milano MI 2 cyclohexanone and phenetole were used as extraction solvents and the relevant process variables (extraction temperature, extraction time and mass of cells/solvent volume ratio) were optimized.Polymer recovery yields of 97% and 93% were obtained with anisole and cyclohexanone, respectively, at 120-130°C using a cell/solvent ratio of 1.5% (w/v). Maximum polymer purities using these experimental conditions were 98% for both solvents. Recovery yields and polymer purity attained with chloroform (reference solvent) were 97 and 98%, respectively. Higher cell/solvent ratios of 6.0 % (w/v) showed slightly lower recovery yields and purities The average molecular weight and the thermal properties of the polymers extracted with the alternative solvents were comparable to those of the polymers obtained by chloroform extraction, showing that the applied conditions did not significantly alter the properties of the extracted P(3HB).
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