Understanding the Structure and Dynamics of Nanocellulose-Based Composites with Neutral and ionic Poly(methacrylate) Derivatives using Inelastic Neutron Scattering and DFT Calculations

Exploring asymmetry induced entropy in tetraalkylammonium-urea DES systems: what can be learned from inelastic neutron scattering?

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.

From PEF to PBF: What difference does the longer alkyl chain make a computational spectroscopy study of poly(butylene 2,5-furandicarboxylate)

This work explores the conformational preferences and the structure-property correlations of poly(butylene 2,5-furandicarboxylate) (PBF), a longer chain analogue of the most well-known biobased polyester from the furan family, poly(ethylene 2,5-furandicarboxylate) (PEF). A thorough computational spectroscopic study-including infrared, Raman and inelastic neutron scattering spectroscopy, combined with discrete and periodic density functional theory calculations-allowed the identification of dominant structural motifs in the amorphous and crystalline regions. Discrete calculations and vibrational spectroscopy of semi-crystalline and amorphous samples strongly support the predominance of gauche, trans, gauche conformations of the butylene glycol fragment in both the crystalline and amorphous domains. In what concerns the furandicarboxylate fragment, amorphous domains are dominated by syn,syn conformations, while in the crystalline domains the anti,anti forms prevail. A possible crystalline structure-built from these conformational preferences and including a network of C-H···O hydrogen bond contacts-was optimized using periodic density functional theory. This proposed crystal structure avoids the unrealistic structural features of the previously proposed X-ray structure, provides an excellent description of the inelastic neutron scattering spectrum of the semi-crystalline form, and allows the correlation between microscopic structure and macroscopic properties of the polymer.

Pineapple Agro-Industrial Biomass to Produce Biomedical Applications in a Circular Economy Context in Costa Rica

Pineapple is a highly demanded fruit in international markets due to its unique appearance and flavor, high fiber content, vitamins, folic acid, and minerals. It makes pineapple production and processing a significant source of income for producing countries, such as Costa Rica. This review collects bibliographic information dating back to the beginnings of pineapple production in Costa Rica to the state of the market today. It details the impacts of its production chain and proposes a biorefinery as a solution to environmental problems. Besides the potentiality of new sustainable markets to contribute to the post-COVID-19 economy in Costa Rica is highlighted. The general characteristics of pineapple by-products -cellulose, hemicellulose, lignin, and other high-value products like bromelain y saponin- are described, as well as the primary processes for their ex-traction via biorefinery and main applications in the medical field. Finally, a brief description of the main works in the literature involving modeling and simulation studies of pineapple by-products properties is included.

Structural Dynamics of Chloromethanes through Computational Spectroscopy: Combining INS and DFT

In this work, the structural dynamics of the chloromethanes CCl₄, CHCl₃ and CH₂Cl₂ were evaluated through a computational spectroscopy approach by comparing experimental inelastic neutron scattering (INS) spectra with the corresponding simulated spectra obtained from periodic DFT calculations. The overall excellent agreement between experimental and calculated spectra allows a confident assignment of the vibrational features, including not only the molecular fundamental modes but also lattice and combination modes. In particular, an impressive overtone sequence for CHCl₃ is fully described by the simulated INS spectrum. In the CCl₄ spectrum, the splitting of the ν3 mode at ca. 765–790 cm⁻¹ is discussed on the basis of the Fermi resonance vs. crystal splitting controversy.

Natural Polymers-Based Materials: A Contribution to a Greener Future

Natural polymers have emerged as promising candidates for the sustainable development of materials in areas ranging from food packaging and biomedicine to energy storage and electronics. In tandem, there is a growing interest in the design of advanced materials devised from naturally abundant and renewable feedstocks, in alignment with the principles of Green Chemistry and the 2030 Agenda for Sustainable Development. This review aims to highlight some examples of the research efforts conducted at the Research Team BioPol4fun, Innovation in BioPolymer-based Functional Materials and Bioactive Compounds, from the Portuguese Associate Laboratory CICECO–Aveiro Institute of Materials at the University of Aveiro, regarding the exploitation of natural polymers (and derivatives thereof) for the development of distinct sustainable biobased materials. In particular, focus will be given to the use of polysaccharides (cellulose, chitosan, pullulan, hyaluronic acid, fucoidan, alginate, and agar) and proteins (lysozyme and gelatin) for the assembly of composites, coatings, films, membranes, patches, nanosystems, and microneedles using environmentally friendly strategies, and to address their main domains of application.

New Insights on the Vibrational Dynamics of 2-Methoxy-, 4-Methoxy- and 4-Ethoxy-Benzaldehyde from INS Spectra and Periodic DFT Calculations

The dynamics of 2-methoxybenzaldehyde, 4-methoxybenzaldehyde, and 4-ethoxybenzaldehyde in the solid state are assessed through INS spectroscopy combined with periodic DFT calculations. In the absence of experimental data for 4-ethoxybenzaldehyde, a tentative crystal structure, based on its similarity with 4-methoxybenzaldehyde, is considered and evaluated. The excellent agreement between calculated and experimental spectra allows a confident assignment of the vibrational modes. Several spectral features in the INS spectra are unambiguously assigned and torsional potential barriers for the methyl groups are derived from experimental frequencies. The intramolecular nature of the potential energy barrier for methyl rotation about O–CH₃ bonds compares with the one reported for torsion about saturated C–CH₃ bonds. On the other hand, the intermolecular contribution to the potential energy barrier may represent 1/3 of the barrier height in these systems.

Dynamics & Spectroscopy with Neutrons-Recent Developments & Emerging Opportunities

This work provides an up-to-date overview of recent developments in neutron spectroscopic techniques and associated computational tools to interrogate the structural properties and dynamical behavior of complex and disordered materials, with a focus on those of a soft and polymeric nature. These have and continue to pave the way for new scientific opportunities simply thought unthinkable not so long ago, and have particularly benefited from advances in high-resolution, broadband techniques spanning energy transfers from the meV to the eV. Topical areas include the identification and robust assignment of low-energy modes underpinning functionality in soft solids and supramolecular frameworks, or the quantification in the laboratory of hitherto unexplored nuclear quantum effects dictating thermodynamic properties. In addition to novel classes of materials, we also discuss recent discoveries around water and its phase diagram, which continue to surprise us. All throughout, emphasis is placed on linking these ongoing and exciting experimental and computational developments to specific scientific questions in the context of the discovery of new materials for sustainable technologies.