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Evaluation of the conductor-like screening model for real solvents for the prediction of the water activity coefficient at infinite dilution in ionic liquids
Publication . Kurnia, Kiki A.; Pinho, SimĆ£o; Coutinho, JoĆ£o A.P.
Ionic liquids (ILs) have attracted great attention, from both industry and academia, as alternative fluids for very different types of applications. The large number of cations and anions allow a wide range of physical and chemical characteristics to be designed. However, the exhaustive measurement of all these systems is impractical, thus requiring the use of a predictive model for their study. In this work, the predictive capability of the conductor-like screening model for real solvents (COSMO-RS), a model based on unimolecular quantum chemistry calculations, was evaluated for the prediction water activity coefficient at infinite dilution, gamma(infinity)(w), in several classes of ILs. A critical evaluation of the experimental and predicted data using COSMO-RS was carried out. The global average relative deviation was found to be 27.2%, indicating that the model presents a satisfactory prediction ability to estimate gamma(infinity)(w) in a broad range of ILs. The results also showed that the basicity of the ILs anions plays an important role in their interaction with water, and it considerably determines the enthalpic behavior of the binary mixtures composed by Its and water. Concerning the cation effect, it is possible to state that generally gamma(infinity)(w) increases with the cation size, but it is shown that the cation-anion interaction strength is also important and is strongly correlated to the anion ability to interact with water. The results here reported are relevant in the understanding of ILs-water interactions and the impact of the various structural features of its on the gamma(infinity)(w) as these allow the development of guidelines for the choice of the most suitable lLs with enhanced interaction with water.
SĆntese e caracterizaĆ§Ć£o de polĆmeros condutores com aplicaƧƵes em cĆ©lulas solares
Publication . Ribeiro, Clementina da ConceiĆ§Ć£o Soares; Dias, Rolando
Neste trabalho foi realizada a sĆntese de PEDOT (Poli (3,4-etilenodioxitiofeno)) atravĆ©s
de trĆŖs tipos de polimerizaĆ§Ć£o a partir do monĆ³mero EDOT (3,4-etilenodioxitiofeno):
PolimerizaĆ§Ć£o oxidativa de EDOT, polimerizaĆ§Ć£o oxidativa de EDOT:PSS (Poli (4- Ć”cido
estirenossulfĆ³nico)) e eletropolimerizaĆ§Ć£o de EDOT. TambĆ©m foi feita interpenetraĆ§Ć£o
de PEDOT num hidrogel de Ć”cido acrĆlico atravĆ©s de diversos mĆ©todos, nomeadamente a
sĆntese de PEDOT:PSS com interpenetraĆ§Ć£o simultĆ¢nea em hidrogel de Ć”cido acrĆlico
inicialmente seco, sĆntese de PEDOT:PSS em simultĆ¢neo com a polimerizaĆ§Ć£o de
hidrogel de Ć”cido acrĆlico, interpenetraĆ§Ć£o de PEDOT:PSS seco em hidrogel de Ć”cido
acrĆlico seco e interpenetraĆ§Ć£o de PEDOT:PSS em hidrogel de Ć”cido acrĆlico. O mĆ©todo
que se verificou funcionar de forma mais adequada foi o de sĆntese de PEDOT:PSS com
interpenetraĆ§Ć£o simultĆ¢nea em hidrogel de Ć”cido acrĆlico inicialmente seco. A
interpenetraĆ§Ć£o de PEDOT:PSS em hidrogel de Ć”cido acrĆlico mostrou ser tambĆ©m
parcialmente viĆ”vel. Estes testes tiveram como objetivo avaliar a sĆntese de materiais
hĆbridos, nomeadamente hidrogĆ©is estimulĆ”veis pela corrente elĆ©trica.
Procedeu-se tambĆ©m Ć caraterizaĆ§Ć£o dos materiais obtidos atravĆ©s de, espetroscopia UV
(Ultravioleta), anĆ”lise microscĆ³pica, testes de condutividade do material, e voltametria
cĆclica (CV).
Na fase final do trabalho foram estudadas duas aplicaƧƵes prƔticas dos materiais
sintetizados. Procedeu-se Ć construĆ§Ć£o de DSCās (cĆ©lulas solares sensibilizadas por
corante) com aplicaĆ§Ć£o de PEDOT no contra elĆ©trodo e comprovou-se tambĆ©m o efeito
electrocrĆ³mico do polĆmero atravĆ©s de voltametria cĆclica. No Ćŗltimo caso foi realizada a
eletropolimerizaĆ§Ć£o de EDOT num vidro FTO (Ćxido de Estanho Dopado com FlĆŗor).
Neste trabalho sĆ£o tambĆ©m apresentadas as curvas I-V das DSCās elaboradas e sĆ£o
analisados os valores obtidos nos testes que lhes foram efetuados. Pretendeu-se desta
forma comparar o desempenho das DSCās produzidas com soluƧƵes jĆ” padronizadas.
Electrochemical activity of sulfur networks synthesized through RAFT polymerization
Publication . Almeida, Carlos M.F.; Costa, Hugo Davide; Kadhirvel, Porkodi; Queiroz, Ana; Dias, Rolando; Costa, MƔrio Rui
Novel results concerning the inverse vulcanization of sulfur using reversible additionāfragmentation chain transfer (RAFT)
polymerization are here reported. It is shown that RAFT polymerization can be used to carry out this cross-linking process, with the
additional possibility to extend the reaction time from a few minutes as with classical free radical polymerization (FRP) to several
hours. Higher control on viscosity and processability of the synthesized networks, as well as, the implementation of semibatch feed
policies during cross-linking are important advantages of the RAFT process here explored comparatively to the FRP inverse vulcanization.
Using cyclic voltammetry, it was assessed the electrochemical activity of the synthesized sulfur-rich polymer networks. It is
shown that the fundamental electrochemical activity of the elemental sulfur was preserved in the produced materials. Testing of electrochemical
cells assembled with lithium in the anode and different sulfur based materials in the cathode, including the synthesized
RAFT networks, is also shown. The results here presented highlight the new opportunities introduced by reversible-deactivation radical
polymerization mechanisms on the control of the synthesis process and in the design of such advanced materials and show also
that many potential derivatizing possibilities can be achieved.
Impact of the cation symmetry on the mutual solubilities between water and imidazolium-based ionic liquids
Publication . Martins, MĆ³nia A.R.; Neves, Catarina M.S.S.; Kurnia, Kiki A.; LuĆs, Andreia; Santos, LuĆs M.N.B.F.; Freire, Mara G.; Pinho, SimĆ£o; Coutinho, JoĆ£o A.P.
Aiming at the evaluation of the impact of the ionic liquids (ILs) cation symmetry on their phase behaviour, in this work, novel mutual solubilities with water of the symmetric series of [C(n)C(n)im][NTf2] (with n=1-5) were determined and compared with their isomeric forms of the asymmetric [C(n)C(1)im][NTf2] group. While the solubility of isomeric ILs in water was found to be similar, the solubility of water in ILs follows the same trend up to a maximum cation alkyl side chain length. For n >= 4 in [C(n)C(n)im][NTf2] the solubility of water in the asymmetric ILs is slightly higher than that observed in the symmetric counterparts. The thermodynamic properties of solution and solvation derived from the experimental solubility data of ILs in water at infinite dilution, namely the Gibbs energy, enthalpy and entropy were used to evaluate the cation symmetry effect on the ILs solvation. It is shown that the solubility of ILs in water is entropically driven and highly influenced by the cation size. Accordingly, it was found that the ILs solubility in water of both symmetric and asymmetric series depends on their molecular volume. Based on these findings, a linear correlation between the logarithm of the solubility of ILs in water and their molar volume is here proposed for the [NTf2]-based ILs at a fixed temperature.
Study of the encapsulation efficiency and release profiles of alginate microspheres containing Ī±-tocopherol
Publication . Vieira, Dalila; Amaral, Joana S.; Barreiro, M.F.
Vitamin E, a lipophilic natural antioxidant comprising different vitamers (Ī±, Ī², Ī³ and Ī“-tocopherols and tocotrianols), is frequently used in food supplements and added in different products, such as foodstuffs and cosmetics, to prevent lipid oxidation processes. Due to solubility and stability issues, Ī±-tocopherol is generally administrated as succinate or acetate derivatives, which have lower bioavailability. In this work, alginate microspheres containing Ī±-tocopherol were produced and evaluated for encapsulation efficiency and release profiles at different pH conditions during 24h. In vitro release tests showed that alginate microspheres maintain its integrity under simulated gastric conditions. By the contrary, under simulated intestinal conditions, an almost complete release is achieved during 24h, with a major portion (70%) being released after 2h.
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Funding agency
FundaĆ§Ć£o para a CiĆŖncia e a Tecnologia
Funding programme
COMPETE
Funding Award Number
PEst-C/EQB/LA0020/2013