Vibrational Dynamics of Crystalline 4-Phenylbenzaldehyde from INS Spectra and Periodic DFT Calculations.

Abstract

The present work emphasizes the value of periodic density functional theory (DFT) calculations in the assessment of the vibrational spectra of molecular crystals. Periodic calculations provide a nearly one-to-one match between the calculated and observed bands in the inelastic neutron scattering (INS) spectrum of crystalline 4-phenylbenzaldehyde, thus validating their assignment and correcting previous reports based on single molecule calculations. The calculations allow the unambiguous assignment of the phenyl torsional mode at ca. 118-128 cm(-1), from which a phenyl torsional barrier of ca. 4000 cm(-1) is derived, and the identification of the collective mode involving the antitranslational motion of CH…O bonded pairs, a hallmark vibrational mode of systems where C-H…O contacts are an important feature.

Mariela M. Nolasco, Catarina F. Araujo, Pedro D. Vaz, Ana M. Amado and Paulo Ribeiro-Claro.


Full Article

Poly(4-styrene sulfonic acid)/bacterial cellulose membranes: Electrochemical performance in a single-chamber microbial fuel cell.

Abstract

The present work aims at exploiting a polyelectrolyte nanocomposite based on poly(4-styrene sulfonic acid) (PSSA) and bacterial cellulose (BC) as an eco-friendly proton-exchange membrane (PEM) for application in microbial fuel cells (MFCs). The PSSA/BC-based PEM was confirmed as a true nanocomposite by inelastic neutron scattering (INS) vibrational spectroscopy. Moreover, this PEM exhibited thermal stability up to 155 °C, Young’s modulus of 11.7 ± 0.9 GPa, ion exchange capacity of 1.85 mmol g−1, and maximum protonic conductivity of 1.73 S m−1. The application of the PSSA/BC nanocomposite membrane in a single-chamber lab-scale MFC with a pure culture of Shewanella frigidimarina yielded a maximum power density of 2.42 mW m−2, open circuit voltage of 0.436 V, and internal resistance of 15.1 kΩ. These results are superior to those obtained with a commercial Nafion® membrane and, thus, confirm the potential of this bio-based PSSA/BC nanocomposite as a PEM for MFCs.

Vilela, C.; Cordeiro, D. M.; Vilas Boas, J.; Barbosa, P.; Nolasco, M. M.; Vaz, P. D.; Rudic, S.; Ribeiro-Claro, P.; Silvestre, A. J. D.; Oliveira, V. B.; Pinto, A. M. F. R.; Figueiredo, F. M. L.; Freire, C. S.R.


Full Article

Asymmetric Monomer, Amorphous Polymer? Structure-Property Relationships in 2,4-FDCA and 2,4-PEF.

Abstract

The biobased polyester poly(ethylene 2,4-furanoate) (2,4-PEF) is a potentially interesting yet insufficiently studied polymer whose resistance to crystallization fundamentally stems from the asymmetric nature of the 2,4-furandicarboxylic acid monomer. A combination of vibrational spectroscopy (infrared, Raman and inelastic neutron scattering) and ab initio calculations has been used to assess the conformational and regiochemistry preferences of 2,4-PEF. The latter polymerizes following a random distribution of monomer orientation, thereby rendering the formation of periodic interchain C-H center dot center dot center dot O contacts wholly unfeasible and ultimately favoring the formation of randomly coiled chains based on gauche-ethylene glycol segments. In the absence of C-H center dot center dot center dot O stabilization, the ordered crystalline arrangement is disfavored and polymer chains-adopting several quasi isoenergetic structures-prefer to solidify into an amorphous mess.

Nolasco, M. M.; Araujo, C. F.; Thiyagarajan, S.; Rudic, S.; Vaz, P.D.; Silvestre, A. J. D.; Ribeiro-Claro, P. J. A.; Sousa, A.F.


Full Article

Impermeáveis

Abstract

The search for waterproof materials has a long history and exemplifies the use of natural materials unknown in Europe before the first globalization; more recently, it uses artificial materials, benefiting from the development of Chemistry.

Paulo J. A. Ribeiro-Claro.


Full Article

What a difference a methyl group makes – probing choline–urea molecular interactions through urea structure modification.

Abstract

There is a lack of fundamental knowledge on deep eutectic solvents, even for the most extensively studied mixtures, such as the mixture of cholinium chloride and urea, which prevents a judicious choice of components to prepare new solvents. The objective of this work is to study and understand the fundamental interactions between cholinium chloride and urea that lead to the experimentally observed melting temperature depression. To do so, the structure of urea was strategically and progressively modified, in order to block certain interaction centres, and the solid–liquid equilibrium data of each new binary system was experimentally measured. Using this approach, it was concluded that the most important interaction between cholinium chloride and urea occurs through hydrogen bonding between the chloride anion and the amine groups. Any blockage of these groups severely hampers the melting point depression effect. Raman spectroscopy and DFT calculations were utilized to study in more detail this hydrogen bonding and its nuances.

Liliana P. Silva, Catarina F. Araújo, Dinis O. Abranches, Manuel Melle-Franco, Mónia A. R. Martins, Mariela M. Nolasco, Paulo J. A. Ribeiro-Claro and Simão P. Pinho.


Full Article

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©Copyright 2024 - Computational Spectroscopy Lab - Department of Chemistry - University of Aveiro - 3810-193 Aveiro
©Copyright 2024 - Computational Spectroscopy Lab - Department of Chemistry - University of Aveiro - 3810-193 Aveiro

©Copyright 2024 - Computational Spectroscopy Lab - Department of Chemistry - University of Aveiro - 3810-193 Aveiro