Decanedioic Acid (C10H18O4)/Dodecanedioic Acid (C12H22O4) System: Polymorphism of the Components and Experimental Phase Diagram

• Published in: Helvetica chimica acta Vol. 91; no. 7; pp. 1286 - 1298
• Main Authors: Ventolà, Lourdes, Bayés, Laura, Benages, Raül, Novegil-Anleo, Francisco Javier, Cuevas-Diarte, Miquel Ángel, Calvet, Teresa, Mondieig, Denise
• Format: Journal Article
• Language: English
• Published: Zürich WILEY-VCH Verlag 01.07.2008; WILEY‐VCH Verlag
• Subjects: Decanedioic acid; Dodecanedioic acid; Phase diagrams; Phase-change materials; Polymorphism; Scanning electron microscopy (SEM)
• ISSN: 0018-019X; 1522-2675
• DOI: 10.1002/hlca.200890140

The experimental temperature/composition phase diagram of the binary system decanedioic acid (C10H18O4)/dodecanedioic acid (C12H22O4) was established by combining X‐ray powder diffraction (XRD), differential‐scanning calorimetry (DSC), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermo‐optical microscopy (TOM). Both compounds crystallize in the same ordered form, C (P21/c), which is the phase that melts in both cases. The C form melts in C12H22O4 earlier than in C10H18O4, in contrast to other unbranched‐chain compounds (alkanes, alkanols, and alkanoic acids) in which the melting temperatures increase as the C‐atom number rises. Contrary to what might be expected, total solid‐state miscibility is not observed. The C10H18O4/C12H22O4 binary system shows a complex phase diagram. At low temperatures, a new monoclinic form, Ci (P21/c), stabilizes as a result of the disorder of composition in the mixed samples; two [C+Ci] domains appear. Upon heating, four solid–solid and seven solid–liquid domains appear related by eutectic and peritectic invariants. All the crystallographic forms observed are isostructural.