Fundamental studies on natural deep eutectic solvents: physico-chemical, thermal and rheological properties

When combined at particular molar fractions, sugars, aminoacids or organic acids a present a high melting point depression, becoming liquids at room temperature. These are called Natural Deep Eutectic Solvents – NADES and are envisaged to play a major role on the chemical engineering processes of the future. Nonetheless, there is a significant lack of knowledge of its fundamental and basic properties, which is hindering their industrial applications. For this reason it is important to extend the knowledge on these systems, boosting their application development [1]. In this work, we have developed and characterized NADES based on choline chloride, organic acids, amino acids and sugars. Their density, thermal behavior, conductivity and polarity were assessed for different compositions. The conductivity was measured from 0 to 40 °C and the temperature effect was well described by the Vogel-Fulcher-Tammann equation. The morphological characterization of the crystallizable materials was done by polarized optical microscopy that provided also evidence of homogeneity/phase separation. Additionally, the rheological and thermodynamic properties of the NADES and the effect of water content were also studied. The results show these systems have Newtonian behavior and present significant viscosity decrease with temperature and water content, due to increase on the molecular mobility. The anhydrous systems present viscosities that range from higher than 1000Pa.s at 20°C to less than 1Pa.s at 70°C. DSC characterization confirms that for water content as high as 1:1:1 molar ratio, the mixture retains its single phase behavior. The results obtained demonstrate that the NADES properties can be finely tunned by careful selection of its constituents. NADES present the necessary properties for use as extraction solvents. They can be prepared from inexpensive raw materials and tailored for the selective extraction of target molecules. The data produced in this work is hereafter importance for the selection of the most promising candidates avoiding a time consuming and expensive trial and error phase providing also data for the development of models able to predict their properties and the mechanisms that allow the formation of the deep eutectic mixtures.Rita Craveiro and Alexandre Paiva are grateful for financial support from Fundação para a Ciência e a Tecnologia (FCT) through the grants PTDC/EQUEPR/12191/2010/ENIGMA and SFRH/BPD/44946/2008. The research leading to these results has received funding from through the projects ENIGMA - PTDC/EQU-EPR/121491/2010, PTDC/QUI-QUI/119210/2010, PTDC/EQUEQU/122106/2010, PEst-C/EQB/LA0006/2013 from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° REGPOT-CT2012-316331-POLARIS and from Project “Novel smart and biomimetic materials for innovative regenerative medicine approaches (Ref.: RL1 - ABMR - NORTE-01-0124-FEDER-000016)” co-financed by North Portugal Regional Operational Programme (ON.2 – O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF)

Design of controlled release systems for THEDES - therapeutic deep eutectic solvents, using supercritical fluid technology

Deep eutectic solvents (DES) can be formed by bioactive compounds or pharmaceutical ingredients. A therapeutic DES (THEDES) based on ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), and menthol was synthesized and its thermal behavior was analyzed by differential scanning calorimetry (DSC). A controlled drug delivery system was developed by impregnating a starch:poly-ϵ-caprolactone polymeric blend (SPCL 30:70) with the menthol:ibuprofen THEDES in different ratios (10 and 20 wt%), after supercritical fluid sintering at 20 MPa and 50 °C. The morphological characterization of SPCL matrices impregnated with THEDES was performed by scanning electron microscopy (SEM) and micro-computed tomography (micro-CT). Drug release studies were carried out in a phosphate buffered saline. The results obtained provide important clues for the development of carriers for the sustainable delivery of bioactive compounds.Projects ENIGMA - PTDC/EQU-EPR/121491/2010, PTDC/QUI-QUI/119210/2010, PTDC/EQU-EQU/122106/2010, PEst-C/EQB/LA0006/2013 from the European Union’s Seventh Framework Programme (FP7/2007-2013) under grant agreement n° REGPOT - CT2012-316331-POLARIS and from Project “Novel smart and biomimetic materials for innovative regenerative medicine approaches (Ref.: RL1 - ABMR - NORTE-01-0124-FEDER-000016)” co-financed by North Portugal Regional Operational Programme (ON.2–O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF)

Occurrence of non-toxic bioemulsifiers during polyhydroxyalkanoate production by Pseudomonas strains valorizing crude glycerol by-product

While screening for polyhydroxyalkanoate (PHA) producing strains, using glycerol rich byproduct as carbon source, it was observed that extracellular polymers were also secreted into the culture broth. The scope of this study was to characterize both intracellular and extracellular polymers, produced by Pseudomonas putida NRRL B 14875 and Pseudomonas chlororaphis DSM 50083, mostly focusing on those novel extracellular polymers. It was found that they fall into the class of bioemulsifiers (BE), as they showed excellent emulsion stability against different hydrocarbons/oils at various pH conditions, temperature and salinity concentrations. Cytotoxicity tests revealed that BE produced by P. chlororaphis inhibited the growth of highly pigmented human melanoma cells (MNT-1) by 50% at concentrations between 150-200 μg/mL, while no effect was observed on normal skin primary keratinocytes and melanocytes. This is the first study reporting mcl-PHA production by P. putida NRRL B-14785 and bioemulsifier production from both P. putida and P. chlororaphis strains

Aplicacao de tecnicas dielectricas a estudos de dinamica e estrutura molecular Misturas solidas polimero / corante, polimero / polimero e solucoes soluto polar / solventes liquidos apolares

One of the purposes of this work was to analyse the influence of a polar organic solute of low molecular weight in the molecular dynamics of a polymeric matrix. The experimental technique applied to this study was the dielectric relaxation spectroscopy. Its basic concepts are presented in chapter 1 and a description in chapter 2. In this chapter we also described the methods of determination of the parameters associated to this technique. In chapter 3 we present the studies of the #alpha# relaxation of poly (vinyl acetate) / p-nitroaniline mixtures. It is shown that the p-nitroaniline, pna, acts like a normal plasticizer and its amino group interacts with the acetate groups of PVAc via hydrogen bond interactions. In chapter 4 we study the effect of the same solute in the following dielectric relaxation processes: the B relaxation of the poly (ethyl methacrylate), PEMA, and the #alpha#B relaxation of the poly (n butyl methacrylate), PEMA, and the #alpha#B relaxation of the poly(n butyl methacrylate), Pn BMA. We also present the study of the dielectric relaxation of the pure polymers. In PMMA and PEMA the solute acts in a similar manner to a temperature increase. Consequently, the relaxation deviates to an #alpha# B region accompanied by a enhancement of the #alpha# relaxation and an inhibition of the B process. In Pn BMA / pna mixtures the #alpha# characteristics of the relaxation process of the matrix are enhanced. We conclude from the analysis of the different dielectric relaxations spectra, that the solute interacts with the PMMA via hydrogen bonding; this effect is less pronounced in PEMA and it is absent in Pn BMA. The practical application of the dielectric spectroscopy is completed in chapter 5 with a preliminary study of miscibility of poly (vinyl acetate) poly (ethyl methacrylate) blends. We conclude that the 50 e 75% (weight percent in PVAc) blends are incompatible and that the 25% blend between 50 and 100 deg C is compatible..Available from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1249-074 Lisboa, Portugal / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga

Aplicacao de tecnicas dielecticas a estudos de dinamica e estrutura molecular misturas solidas polimero/corante, polimero/polimero e solucoes soluto polar/solventes liquidos apolares

The experimental technique applied to the present study was the dielectric relaxation spectroscopy. Its basic concepts are presented in chapter 1 and a description in chapter 2. In chapter 3 we present the studies of the #alpha# relaxation of poly(vinyl acetate), PVAac, and of the dielectic relaxation of poly(vinyl acetate)/p-nitroaniline mixtures. It is shown that the p-nitroaline, pNA, acts like a normal plasticizer and its amino group interacts with the acetate groups of PVac via hydrogen bond interactions. In chapter 4 we study the effect of the same solute in the following dielectric relaxation processes: the poly(methyl methacrylate), PMMA, the the #beta# and #alpha# #beta# relaxations of the poly(ethyl methacrylate), PEMA, and the #alpha# #beta# relaxation of the poly(n-butyl methacrylate), PnBMA. We also present the study of the dielectric relaxation of the pure polymers. In PNMMA and PEMA the solute acts in a similar manner to a temperature increase. Consequently, the relaxation deviates to an #alpha# #beta# region accompained by a enhancement of the #alpha# relaxation and an inhibition of the #beta# process. In PnBMA/pNA mixturesd the #alpha# characteristics of the relaxation process of the matrix are enhanced. We conclude from the analysis of the different dielectric relaxations spectra, that the solute interacts with the PMMA via hydrogen bonding; this effect is less pronounced in PEMA and it is absent in PnBMA. In chapter 5 we present a preliminary suty of miscibility of poly(vinyl acetate)/poly(ethyl methacrylate) blends. We conclude that the 50 e 75% (Weight percent in PVac)blends are incompatible and that the 25% blend between 50 and 100 degrees C is compatible. Another purpose of this work was to apply the dielectric techniques to structural studies. In chapter 6 we accomplish this studying the conformational equilibrium of the trans-1,2-dibromocyclohexane in n-alkanes solvents: n-C_5, nC_6,n-C_8, nC_10 and n_C_1_2. Long n-dibromocyclohexane in n-alkanes solvents are characterized by a short range molecular order which stabilize the extended conformations. The aim of this work was therefore to check if the anisotropy of the molecular shape of the long n-alkanes could stabilize the diequatorial conformer of the trans-1,2-dibromocyclohexane (wich have a more elongate shape), knowing that the conformers have different dipole moments. The dipole moments mesured in each solvent have been compared with the dipole moment of the trans-1,2-dibromocyclohexane in cyclohexane, a globular solvent, and we observed that the dipole moment in the n-alkane solvents is higher than in the xcyclic solvent. There is also a slight of the dipole moment with the number of carbon atoms. This facts be interpreted as a stabilization effect of the fdiequatorial conformer with the increase of the degree of order of the solventAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga

Kinetics of free-radical polymerization probed by dielectric relaxation spectroscopy under high conductivity conditions

Polymerization kinetics of tri-ethylene glycol dimethacrylate (TrEGDMA)/2,2-azobis-isobutyronitrile (AIBN) mixtures (0.1% w.t.) at different temperatures was investigated by using dielectric relaxation spectroscopy. The dielectric spectra at the polymerization temperatures studied are dominated by high conductivity leading us to employ the electric modulus representation in order to extract information about the evolution of the system during isothermal reaction. An intense peak appears in the imaginary component of the complex dielectric modulus which is related to conductivity. The variation of the strength of this peak and of its relaxation time with the polymerization time allows us to determine the polymerization degree evolution and the moment in which vitrification is attained, which can be compared with results obtained by temperature modulated DSC in a previous work (Viciosa MT, Hoyo JQ Dionisio M, Gomez Ribelles JL Journal of Thermal Analysis and Calorimetry 2007; 90:407-414).Fundacao para a Ciencia e Tecnologia by financial support, SFRH/BPD/3961/2007.Viciosa, MT.; Dionisio, M.; Gómez Ribelles, JL. (2011). Kinetics of free-radical polymerization probed by dielectric relaxation spectroscopy under high conductivity conditions. Polymer. 52(9):1944-1953. doi:10.1016/j.polymer.2011.03.006S1944195352