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Projeto de investigação
Ionic Liquid Crystals as Multi-stimuli versatile chromogenic materials
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Impact of nanoconfinement on the physical state and conductivity mechanisms of a 2-picolinium ionic liquid crystal
Publication . Santos, Andreia F. M.; Teresa Viciosa, M.; Matos, Inês; Sotomayor, João C.; Figueirinhas, João L.; Godinho, Maria H.; Branco, Luís C.; Dias, C. J.; Dionísio, Madalena; DQ - Departamento de Química; LAQV@REQUIMTE; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Elsevier
Hybrid solid-like materials prepared from the incorporation of liquid-like ionic conductors into nanoporous matrices could represent an advantage for a variety of electronic applications. Aiming to obtain such materials, three composites of the polymorphic ionic liquid crystal (ILC) 1-hexadecyl-2-methylpyridinium bromide ([C16-2-Pic][Br]), loaded in the mesoporous inorganic silica SBA-15 (∼6.8 nm in pore diameter), were prepared at guest–host weight fractions of ∼ 40, 60 and 80% (w/w) and investigated by different techniques: ATR-FTIR, BET, TGA, XRD and DSC. Complete amorphisation was achieved for the 40 and 60% composites, while the 80% preparation was stabilised in the low-T morph of native C16, being in the liquid state at room temperature. Furthermore, through Dielectric Relaxation Spectroscopy, the ionic conductivity of the three hybrid materials was characterised, allowing to deconvolute this property in a pure ohmic contribution (conductivity I) and the overlapping of ac − dc transition with interfacial polarisation resulting from the coexistence of the ionic liquid and the quasi-insulating inorganic matrix (conductivity II). From –20 to 20 °C, the conductivity and the corresponding charge migration are faster in all composites relative to the neat ILC, as deduced from the inferior radii of Nyquist arcs. The 60% preparation stood out from the other materials, exhibiting direct conductivity unaffected by electrode polarisation over a larger T-range, leading to the assumption of a nearly continuous silica-mediated charge migration pathway, which is never reached for the 40% composite, while, in the 80% preparation, some C16 deposits on the outer surface of the pores. Incorporation into the silica matrix proved to be a good strategy for the production of cost-efficient materials with long-term stabilisation of the ionic liquid in a single phase over a large range of temperatures, enabling the prediction of flow and conductive properties.
Ferrocene-Based Porous Organic Polymer (FPOP)
Publication . Petrovski, Zeljko; Moreira, Mateus P.; Santos, Andreia F. M.; Freitas, Sunny K. S.; Jordão, Noémi; Maia, Renata A.; Nunes, Ana V. M.; Branco, Luis C.; Cruz, Hugo; Esteves, Pierre M.; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI - Multidisciplinary Digital Publishing Institute
Ferrocene-based porous organic polymers (FPOPs) were prepared fromphenol-formaldehyde polymer (Bakelite) and phenol as starting materials; and two possible mechanisms for polymerization were discussed. Solid-state 13C CP-MAS NMR, FTIR, powder XRD, elemental analysis and ICP (Fe, Na, B) were performed to characterize the prepared materials. The two synthetic approaches produced polymers with different pore sizes: the FPOP synthesized through Bakelite presented a higher surface area (52 m2 g1) when compared to the one obtained by the bottom-up polymerization from phenol (only 5 m2 g1). Thermogravimetric analysis confirmed the thermal stability of the material, which decomposed at 350 C. Furthermore, cyclic voltammetry (CV) of the new FPOP on modified electrodes, in ACN and 0.1 M TBAP as an electrolyte, showed fully reversible electron transfer, which is similar to that observed for the ferrocene probe dissolved in the same electrolyte. As a proof-of-concept for an electrochromic device, this novel material was also tested, with a color change detected between yellow/brownish coloration (reduced form) and green/blue coloration (oxidized form). The new hybrid FPOP seems very promising for material science, energy storage and electrochromic applications, as well as for plastic degradation.
Development of ionic liquid crystals based on pyridinium and picolinium cations
Publication . Santos, Andreia F. M.; DQ - Departamento de Química; LAQV@REQUIMTE; Taylor & Francis
The search for novel materials and technologies with improved performance increased in the last decades. In particular, ionic liquid crystals (ILCs), a modern class of advanced materials that benefits from the synergistic properties of ionic liquids and liquid crystals, are playing an important role in different areas of knowledge, attracting the interest of the academia and industry, driven by their peculiar tailoring ability. Herein, it comprises a brief synopsis of several pyridinium and picolinium ILCs previously prepared to understand how their mesomorphism and conductivity profiles are affected by small structural changes in terms of the methyl group position and alkyl chain length, providing important insights into future design of functional materials by a simple anionic exchange. Moreover, microwave-assisted reactions were emphasised as a simple and greener synthetic method to prepare ionic liquid crystals through alkylation, which can also be applied to other organic salts.
Bioactivity of Ionic Liquids Based on Valproate in SH-SY5Y Human Neuroblastoma Cell Line
Publication . Dias, Ana Rita; Ferraz, Ricardo; Costa-Rodrigues, João; Santos, Andreia F. M.; Jacinto, Manuel L.; Prudêncio, Cristina; Noronha, João Paulo; Branco, Luis C.; Petrovski, Zeljko; DQ - Departamento de Química; LAQV@REQUIMTE; MDPI - Multidisciplinary Digital Publishing Institute
The search for alternative and effective therapies to fight cancer is one of the main goals of the pharmaceutical industry. Recently, ionic liquids (ILs) have emerged as potential therapeutic agents with antitumor properties. The goal of this study was to synthesize and evaluate the bioactivity of different ILs coupled with the active pharmaceutical ingredient (API) valproate (VPA) as an antitumor agent. The toxicity of the prepared ionic liquids was evaluated by the MTT cell metabolic assay in human neuroblastoma SH-SY5Y and human primary Gingival Fibroblast (GF) cell lines, in which they showed inhibitory effects during the study period. In addition, low cytotoxicity against GF cell lines was observed, suggesting that these compounds are not toxic to human cell lines. [C2OHDMiM][VPA] demonstrated an outstanding antitumor activity against SH-SY5Y and lower activity against the non-neoplastic GF line. The herein assessed compounds played an important role in the modulation of the signaling pathways involved in the cellular behavior. This work also highlights the potential of these ILs-API as possible antitumor agents
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
OE
Número da atribuição
SFRH/BD/132551/2017