Temperature-enhanced synthesis of DMSO-Melanin

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2014-01-06

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Elsevier B.V.

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Melanins are a class of pigmentary conjugated macromolecules found in many biological systems. Functionalization of synthetic melanin provides interesting new properties like the greater solubility of melanin synthesized in dimethyl sulfoxide, D-Melanin. In this work we have studied the influence of temperature on D-Melanin synthesis and its properties. To this end, UV-Vis, Fourier-transform infrared (FTIR) spectroscopy and Nuclear Magnetic Resonance (NMR) techniques have been employed to analyze D-Melanin synthesized within the range of 25-100 degrees C. Our results reveal that by increasing the synthesis temperature up to 100 degrees C, the synthesis time can be decreased by a factor of 7 when compared to room temperature. From FTIR and C-13 CP/MAS NMR analyses the increase in temperature causes a decrease in the number of carbonyl groups from carboxylic acid and from ionized carboxylic acid. The decarboxylation of D-Melanin monomers at higher temperatures shows that the use of higher synthesis temperatures influences the elimination of carbonyls present in the precursor molecules, thus facilitating the polymerization of D-Melanin. (C) 2013 Elsevier B.V. All rights reserved.

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Journal Of Molecular Structure. Amsterdam: Elsevier Science Bv, v. 1056, p. 135-140, 2014.

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