Please use this identifier to cite or link to this item:
https://hdl.handle.net/10216/101727
Author(s): | Costa, JCS Carlos F R A C Lima Marisa A A Rocha Ligia R Gomes Luis M N B F Santos |
Title: | Phase transition equilibrium of terthiophene isomers |
Issue Date: | 2011 |
Abstract: | The thermodynamic study of the phase transition (fusion and sublimation) of 2,2':5',2 ''-terthiophene and 3,2':5',3 ''-terthiophene is presented. The obtained data is used to evaluate the (solid + liquid) and (solid + gas) phase equilibrium, and draw the phase diagrams of the pure compounds near the triple point coordinates. For each compound the vapour pressures at different temperatures were measured by a combined Knudsen effusion method with a vacuum quartz crystal microbalance. Based on the previous results, the standard molar enthalpies, entropies and Gibbs energies of sublimation were derived at T = 298.15 K. For the two terthiophenes and for 3,3'-bithiophene, the temperature, and the molar enthalpies of fusion were measured in a power compensated differential scanning calorimetry. The relationship between structure and energetics is discussed based on the experimental results, ab initio calculations and previous literature data for 2,2'-bithiophene and 3,3'-bithiophene. The 3,2':5',3 ''-terthiophene shows a higher solid phase stability than the 2,2':5',2 ''-terthiophene isomer arising from the higher cohesive energy due to positioning of the sulphur atom in the thiophene ring. The higher phase stability of 3,3'-bithiophene relative to 2,2'-bithiophene isomer is also related to its higher absolute entropy in the solid phase associated with the ring positional degeneracy observed in the crystal structure of this isomer. A significant differentiation in the crystal phase stability between isomers was found. |
Subject: | Engenharia mecânica Mechanical engineering |
Scientific areas: | Ciências da engenharia e tecnologias::Engenharia mecânica Engineering and technology::Mechanical engineering |
URI: | https://hdl.handle.net/10216/101727 |
Document Type: | Artigo em Revista Científica Internacional |
Rights: | restrictedAccess |
Appears in Collections: | FCUP - Artigo em Revista Científica Internacional |
Files in This Item:
File | Description | Size | Format | |
---|---|---|---|---|
49120.pdf Restricted Access | 404.01 kB | Adobe PDF | Request a copy from the Author(s) |
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.