resumo
In this work, inelastic neutron scattering (INS) spectroscopy is used to investigate the impact of entropic factors on the behaviour of deep eutectic solvents (DES). Periodic density functional theory calculations (DFT) provide a reliable assignment of the vibrational modes of pure compounds. This assignment guides the analysis of INS spectra of binary mixtures - with particular attention to methyl torsional modes. Deviations from ideality in the mixtures of tetraalkylammonium salts with urea are readily determined through a simplified thermodynamic approach. This study reports and discusses the relationship between the cation's asymmetry, the INS spectra of the eutectic mixture and its deviation from ideality. Contrary to the majority of systems studied so far, the deep eutectic system comprised of [N2,2,2,1]Cl and urea appears to owe its deviation from ideality to entropic rather than enthalpic factors. Substituting a symmetric cation with an asymmetric one induces an entropy-driven pronounced melting point depression in an eutectic system which would otherwise behave ideally.
palavras-chave
TETRAETHYLAMMONIUM
categoria
Chemistry; Physics
autores
Araújo, CF; Ribeiro-Claro, P; Vaz, PD; Rudic, S; Serrano, RAF; Silva, LP; Coutinho, JAP; Nolasco, MM
nossos autores
Liliana Patrocínio da Silva
Colaborador
Mariela Martins Nolasco
Investigador Auxiliar
Pedro Miguel Duarte Vaz
Colaborador
Rafael Alexandre Farinha Serrano
Estudante de doutoramentoGrupos
G4 - Materiais Renováveis e Economia Circular
G6 - Materiais Virtuais e Inteligência Artificial
Projectos
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
agradecimentos
This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC). FCT is also acknowledged for the PhD grant to CFA (SFRH/BD/129040/2017). The STFC Rutherford Appleton Laboratory is thanked for access to neutron beam facilities (TOSCA/RB1810054, DOI: https://doi.org/10.5286/ISIS.E.RB1810054). CASTEP calculations were made possible due to the computing resources provided by STFC Scientific Computing Department's SCARF cluster.