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Ionic Liquid Crystals as Versatile Functional Materials
Publication . Santos, Andreia Filipa Magalhães Seixas Lopes dos; Branco, Luís; Andrade, Maria Madalena; Godinho, Maria Helena
Ionic liquid crystals (ILCs) have emerged as a promising approach to develop versatile soft
materials, exhibiting liquid crystalline behaviour. As they combine characteristics of both liquid
crystals and ionic liquids, it is possible to tune their physicochemical and self-assembly prop-
erties by the wise pairing of cation and anion, allowing the design of new functional and re-
sponsive materials. It is known that the rigidity of the cation linked to the flexibility of the alkyl
moiety are main requirements for the formation of ionic liquid crystals. In this thesis, a new
series of ILCs based on pyridinium and picolinium cations was synthesised through sustainable
methods and further characterised by thermal (TGA and DSC), microscopic (POM) and spec-
troscopic (NMR, ATR-FTIR, XRD and DRS) techniques. Moreover, the influence of the methyl
group position (
ortho-,
meta- and
para-) and the alkyl chain length (C6, C12 and C16) on their
mesomorphism and conductive behaviour is provided, revealing smectic phases for all mate-
rials with the exception of C6-substituted ionic liquid. Furthermore, it is presented multiple ways
of exploring the selected organic salts:
i) fundamental studies regarding modifications at mo-
lecular level;
ii) lyotropic aqueous mesophases and shear-induced foams;
iii) enhancement of
the performance by incorporating in porous silica matrices;
iv) stimuli-responsive formulations
using ionic liquid crystals as additives for fuel dyes.
These synthesised organic salts acted as model compounds to evaluate the correlation
between chemical structure, phase transitions and conductivity behaviour, guiding also the
future design of sustainable electronic and smart materials.
Ionic Liquid Crystals as Chromogenic Materials
Publication . Santos, Andreia F.M.; Figueirinhas, João L.; Dionísio, Madalena; Godinho, Maria H.; Branco, Luis C.; LAQV@REQUIMTE; Faculdade de Ciências e Tecnologia (FCT); DQ - Departamento de Química; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Molecular Diversity Preservation International (MDPI)
Ionic liquid crystals (ILCs), a class of soft matter materials whose properties can be tuned by the wise pairing of the cation and anion, have recently emerged as promising candidates for different applications, combining the characteristics of ionic liquids and liquid crystals. Among those potential uses, this review aims to cover chromogenic ILCs. In this context, examples of photo-, electro- and thermochromism based on ILCs are provided. Furthermore, thermotropic and lyotropic ionic liquid crystals are also summarised, including the most common chemical and phase structures, as well as the advantages of confining these materials. This manuscript also comprises the following main experimental techniques used to characterise ILCs: Differential Scanning Calorimetry (DSC), Polarised Optical Microscopy (POM) and X-Ray Powder Diffraction (XRD). Chromogenic ILCs can be interesting smart materials for energy and health purposes.
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Fundação para a Ciência e a Tecnologia
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SFRH/BD/132551/2017