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Berride F, Troche-Pesqueira E, Feio G, Cabrita EJ, Sierra T, Navarro-Vázquez A, Cid MM. Chiral amplification of disodium cromoglycate chromonics induced by a codeine derivative. Soft Matter 2017; 13:6810-6815. [PMID: 28819662 DOI: 10.1039/c7sm01227f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Chromonic liquid crystals (CLC) are lyotropic phases formed by discotic mesogens in water. Simple chiral dopants such as amino acids have been reported to turn chromonic liquid crystals into their cholesteric counterparts. Here we report a chirality amplification effect in the nematic phase of a 9 wt% disodium cromoglycate (DSCG) lyotropic liquid crystal (LLC) upon doping with a water-soluble codeine derivative. The transition on cooling the isotropic to the nematic phase showed the presence of homochiral spindle-shaped droplets (tactoids). NMR DOSY experiments on a triple gradient probe revealed a small degree of diffusion anisotropy for the alkaloid embedded in the liquid crystal structure. These results in combination with XRD, CD and POM experiments agree with a supramolecular aggregation model based on simple columnar stacks.
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Affiliation(s)
- F Berride
- Departamento de Quıímica Orgánica, Edificio de Ciencias Experimentais, Campus Lagoas-Marcosende, Vigo, 36310, Spain.
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2
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Marcelino P, Marinho HS, Campos MC, Neves AR, Real C, Fontes FS, Carvalho A, Feio G, Martins MBF, Corvo ML. Therapeutic activity of superoxide dismutase-containing enzymosomes on rat liver ischaemia-reperfusion injury followed by magnetic resonance microscopy. Eur J Pharm Sci 2017; 109:464-471. [PMID: 28887231 DOI: 10.1016/j.ejps.2017.09.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 09/01/2017] [Accepted: 09/04/2017] [Indexed: 10/18/2022]
Abstract
Liver ischaemia-reperfusion injury (IRI) may occur during hepatic surgery and is unavoidable in liver transplantation. Superoxide dismutase enzymosomes (SOD-enzymosomes), liposomes where SOD is at the liposomal surface expressing enzymatic activity in intact form without the need of liposomal disruption, were developed with the aim of having a better insight into its antioxidant therapeutic outcome in IRI. We also aimed at validating magnetic resonance microscopy (MRM) at 7T as a tool to follow IRI. SOD-enzymosomes were characterized and tested in a rat ischaemia-reperfusion model and the therapeutic outcome was compared with conventional long circulating SOD liposomes and free SOD using biochemical liver injury biomarkers, histology and MRM. MRM results correlated with those obtained using classical biochemical biomarkers of liver injury and liver histology. Moreover, MRM images suggested that the therapeutic efficacy of both SOD liposomal formulations used was related to prevention of peripheral biliary ductular damage and disrupted vascular architecture. Therefore, MRM at 7T is a useful technique to follow IRI. SOD-enzymosomes were more effective than conventional liposomes in reducing liver ischaemia-reperfusion injury and this may be due to a short therapeutic window.
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Affiliation(s)
- Paulo Marcelino
- CEDOC, Nova Medical School, Campo dos Mártires da Pátria, 130, 1169-056 Lisboa, Portugal.
| | - H Susana Marinho
- Centro de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal and Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
| | - Maria Celeste Campos
- Anatomia Patológica, Hospital Curry Cabral, Rua da Beneficência n.° 8, 1069-166 Lisboa, Portugal.
| | - Ana Rita Neves
- Centro de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal and Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
| | - Carla Real
- Centro de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal and Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
| | - Filipa S Fontes
- Centro de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal and Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal; Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia, Universidade de Lisboa, Avenida Professor Gama Pinto, 1649-003, Lisboa, Portugal and Departamento de Farmácia Galénica e Tecnologia Farmacêutica, Faculdade de Farmácia, Universidade de Lisboa, Avenida Professor Gama Pinto, 1649-003 Lisboa, Portugal.
| | - Alexandra Carvalho
- CENIMAT-I3N-DCM, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Campus da Caparica, 2829-515 Caparica, Portugal; IEQUALTECS, Lda, R. Dr. Francisco Sá Carneiro, 36, 2500-065 S. Gregório CLD, Portugal.
| | - Gabriel Feio
- CENIMAT-I3N-DCM, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Campus da Caparica, 2829-515 Caparica, Portugal.
| | - M Bárbara F Martins
- Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia, Universidade de Lisboa, Avenida Professor Gama Pinto, 1649-003, Lisboa, Portugal and Departamento de Farmácia Galénica e Tecnologia Farmacêutica, Faculdade de Farmácia, Universidade de Lisboa, Avenida Professor Gama Pinto, 1649-003 Lisboa, Portugal.
| | - M Luísa Corvo
- Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia, Universidade de Lisboa, Avenida Professor Gama Pinto, 1649-003, Lisboa, Portugal and Departamento de Farmácia Galénica e Tecnologia Farmacêutica, Faculdade de Farmácia, Universidade de Lisboa, Avenida Professor Gama Pinto, 1649-003 Lisboa, Portugal.
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Fundo JF, Galvis-Sanchez A, Madureira AR, Carvalho A, Feio G, Silva CL, Quintas MA. NMR water transverse relaxation time approach to understand storage stability of fresh-cut ‘Rocha’ pear. Lebensm Wiss Technol 2016. [DOI: 10.1016/j.lwt.2016.07.050] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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4
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Fundo JF, Carvalho A, Feio G, Silva CL, Quintas MA. Relationship between molecular mobility, microstructure and functional properties in chitosan/glycerol films. INNOV FOOD SCI EMERG 2015. [DOI: 10.1016/j.ifset.2015.01.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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5
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Carvalho A, Martins MBF, Corvo ML, Feio G. Enhanced contrast efficiency in MRI by PEGylated magnetoliposomes loaded with PEGylated SPION: effect of SPION coating and micro-environment. Mater Sci Eng C Mater Biol Appl 2014; 43:521-6. [PMID: 25175245 DOI: 10.1016/j.msec.2014.07.055] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 05/14/2014] [Accepted: 07/15/2014] [Indexed: 01/04/2023]
Abstract
Magnetic core coatings modify the efficiency of nanoparticles used as contrast agents for MRI. In studies of these phenomena, care should be given to take into account possible effects of the specific micro-environment where coated nanoparticles are embedded. In the present work, the longitudinal and transverse relaxivities of superparamagnetic iron oxide nanoparticles stabilized with short-chain polyethylene glycol molecules (PEGylated SPIONs) were measured in a 7T magnetic field. PEGylated SPIONs with two different diameters (5 and 10nm) were studied. Two different PEGylated magnetoliposomes having liposome bilayer membranes composed of egg-phosphatidylcholine, cholesterol and 1,2-distearoyl-sn-glycerol-3-phosphoethanolamine-N-[methoxy PEG-2000] were also studied for their relaxivities, after being loaded with the PEGylated SPION of 5 or 10nm. This type of liposomes is known to have long residence time in bloodstream that leads to an attractive option for therapeutic applications. The influence of the magnetic core coating on the efficiency of the nanosystem as a negative contrast agent for MRI was then compared to the cumulative effect of the coating plus the specific micro-environment components. As a result, it was found that the PEGylated magnetoliposomes present a 4-fold higher efficiency as negative contrast agents for MRI than the PEGylated SPION.
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Affiliation(s)
- A Carvalho
- CENIMAT-I3N-DCM, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Campus da Caparica, 2829-515 Caparica, Portugal.
| | - M B F Martins
- iMed.UL, Faculdade de Farmácia da Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - M L Corvo
- iMed.UL, Faculdade de Farmácia da Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - G Feio
- CENIMAT-I3N-DCM, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Campus da Caparica, 2829-515 Caparica, Portugal
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Fundo JF, Fernandes R, Almeida PM, Carvalho A, Feio G, Silva CL, Quintas MA. Molecular mobility, composition and structure analysis in glycerol plasticised chitosan films. Food Chem 2014; 144:2-8. [DOI: 10.1016/j.foodchem.2013.05.127] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Revised: 04/30/2013] [Accepted: 05/28/2013] [Indexed: 11/30/2022]
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Nogueira LS, Ribeiro S, Granadeiro CM, Pereira E, Feio G, Cunha-Silva L, Balula SS. Novel polyoxometalate silica nano-sized spheres: efficient catalysts for olefin oxidation and the deep desulfurization process. Dalton Trans 2014; 43:9518-28. [DOI: 10.1039/c3dt53444h] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel method to prepare silica nano-sized particles incorporating polyoxometalates was developed leading to a new efficient heterogeneous oxidative catalyst.
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Affiliation(s)
- Lucie S. Nogueira
- REQUIMTE & Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade do Porto
- 4169-007 Porto, Portugal
| | - Susana Ribeiro
- REQUIMTE & Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade do Porto
- 4169-007 Porto, Portugal
| | - Carlos M. Granadeiro
- REQUIMTE & Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade do Porto
- 4169-007 Porto, Portugal
| | - Eulália Pereira
- REQUIMTE & Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade do Porto
- 4169-007 Porto, Portugal
| | - Gabriel Feio
- CENIMAT/I3N
- Departamento de Ciência dos Materiais
- Faculdade de Ciências e Tecnologia
- Universidade Nova de Lisboa
- 2829-516 Monte da Caparica, Portugal
| | - Luís Cunha-Silva
- REQUIMTE & Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade do Porto
- 4169-007 Porto, Portugal
| | - Salete S. Balula
- REQUIMTE & Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade do Porto
- 4169-007 Porto, Portugal
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Oliveira FS, Pereiro AB, Araújo JMM, Bernardes CES, Canongia Lopes JN, Todorovic S, Feio G, Almeida PL, Rebelo LPN, Marrucho IM. High ionicity ionic liquids (HIILs): comparing the effect of ethylsulfonate and ethylsulfate anions. Phys Chem Chem Phys 2013; 15:18138-47. [PMID: 24061089 DOI: 10.1039/c3cp52642a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The subject of ionicity has been extensively discussed in the last decade, due to the importance of understanding the thermodynamic and thermophysical behaviour of ionic liquids. In our previous work, we established that ionic liquids' ionicity could be improved by the dissolution of simple inorganic salts in their milieu. In this work, a comparison between the thermophysical properties of two binary systems of ionic liquid + inorganic salt is presented. The effect of the ammonium thiocyanate salt on the ionicity of two similar ionic liquids, 1-ethyl-3-methylimidazolium ethylsulfonate and ethylsulfate, is investigated in terms of the related thermophysical properties, such as density, viscosity and ionic conductivity in the temperature range 298.15-323.15 K. In addition, spectroscopic (NMR and Raman) and molecular dynamic studies were conducted in order to better understand the interactions that occur at a molecular level. The obtained results reveal that although the two anions of the ionic liquid exhibit similar chemical structures, the presence of one additional oxygen in the ethylsulfate anion has a major impact on the thermophysical properties of the studied systems.
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Affiliation(s)
- Filipe S Oliveira
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apartado 127, 2780-157 Oeiras, Portugal.
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9
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Daniel CI, Vaca Chávez F, Feio G, Portugal CAM, Crespo JG, Sebastião PJ. 1H NMR Relaxometry, Viscometry, and PFG NMR Studies of Magnetic and Nonmagnetic Ionic Liquids. J Phys Chem B 2013; 117:11877-84. [DOI: 10.1021/jp4078536] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Carla I. Daniel
- REQUIMTE/CQFB,
Departamento de Quı́mica, Faculdade de Cien̂cias
e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
| | - Fabián Vaca Chávez
- Condensed
Matter Physics Centre, University of Lisbon, Av. Prof. Gama Pinto 2, 1649-003 Lisbon, Portugal
| | - Gabriel Feio
- CENIMAT
- Centro de Investigação em Materiais, Faculdade de
Cien̂cias e Tecnologia, Universidade Nova de Lisboa, Campus da Caparica, 2829-516 Caparica, Portugal
| | - Carla A. M. Portugal
- REQUIMTE/CQFB,
Departamento de Quı́mica, Faculdade de Cien̂cias
e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
| | - João G. Crespo
- REQUIMTE/CQFB,
Departamento de Quı́mica, Faculdade de Cien̂cias
e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
| | - Pedro J. Sebastião
- Condensed
Matter Physics Centre, University of Lisbon, Av. Prof. Gama Pinto 2, 1649-003 Lisbon, Portugal
- Departamento
de Física, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco
Pais, 1049-001 Lisbon, Portugal
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Neves CS, Granadeiro CM, Cunha-Silva L, Ananias D, Gago S, Feio G, Carvalho PA, Eaton P, Balula SS, Pereira E. Europium Polyoxometalates Encapsulated in Silica Nanoparticles - Characterization and Photoluminescence Studies. Eur J Inorg Chem 2013. [DOI: 10.1002/ejic.201201482] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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11
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Carvalho A, Gonçalves MC, Martins MBF, Meixedo D, Feio G. Relaxivities of magnetoliposomes: the effect of cholesterol. Magn Reson Imaging 2013; 31:610-2. [PMID: 23333578 DOI: 10.1016/j.mri.2012.10.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 10/17/2012] [Accepted: 10/30/2012] [Indexed: 10/27/2022]
Abstract
We present relaxivities measurements for both the longitudinal and transverse relaxations of two types of liposomes loaded with ultra small superparamagnetic iron oxide nanoparticles. The magnetoliposome systems presented are soybean phosphatidylcholine liposomes, with and without cholesterol, in the phospholipid bilayer with different molar ratios lipid:cholesterol. In fact, cholesterol is needed to obtain stable liposomes for intravenous administration. The longitudinal and transverse relaxivities were measured with a NMR spectrometer in a 7T magnetic field. For the studied concentrations, the liposomes show a negligible effect on the longitudinal relaxation time T1 of the medium, but they are very efficient on decreasing the transverse relaxation time T2, the behaviour one expects for a negative CA. We observed a lower transverse relaxivity for the magnetoliposome nanosystem with cholesterol, which strongly decreases with the cholesterol content in the liposome bilayer.
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Affiliation(s)
- Alexandra Carvalho
- CENIMAT-I3N/DCM/FCT/UNL, Campus da Caparica, 2829-516 Caparica, Portugal.
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12
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Salústio P, Feio G, Figueirinhas J, Cabral-Marques H, Costa P, Pinto J. Release profile of ibuprofen in β-cyclodextrin complexes from two different solid dosage forms. POWDER TECHNOL 2012. [DOI: 10.1016/j.powtec.2012.01.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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13
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Figueirinhas JL, Feio G, Cruz C, Lehmann M, Köhn C, Dong RY. Nuclear magnetic resonance spectroscopic investigations of phase biaxiality in the nematic glass of a shape-persistent V-shaped mesogen. J Chem Phys 2010; 133:174509. [DOI: 10.1063/1.3496491] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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14
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Lehmann M, Köhn C, Figueirinhas J, Feio G, Cruz C, Dong R. Biaxial Nematic Mesophases from Shape-Persistent Mesogens with a Fluorenone Bending Unit. Chemistry 2010; 16:8275-9. [DOI: 10.1002/chem.201001214] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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Kundu S, Feio G, Pinto LFV, Almeida PL, Figueirinhas JL, Godinho MH. Deuterium NMR Study of Orientational Order in Cellulosic Network Microfibers. Macromolecules 2010. [DOI: 10.1021/ma100882w] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S. Kundu
- CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - G. Feio
- CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
- CFMC−UL, Av. Prof. Gama Pinto 2, 1649-003 Lisboa, Portugal
| | - L. F. V. Pinto
- CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - P. L. Almeida
- CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
- ACF−DEEA, ISEL/IPL, R. Conselheiro Emídio Navarro, 1, 1950-062 Lisboa, Portugal
| | - J. L. Figueirinhas
- CFMC−UL, Av. Prof. Gama Pinto 2, 1649-003 Lisboa, Portugal
- Departamento de Física, IST-TU-Lisbon, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
| | - M. H. Godinho
- CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
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Feio G, Figueirinhas JL, Tajbakhsh AR, Terentjev EM. Deuterium NMR study of mobility and fluctuations in nematic and isotropic elastomers. J Chem Phys 2009; 131:074903. [DOI: 10.1063/1.3211107] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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17
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Salústio P, Feio G, Figueirinhas J, Pinto J, Cabral Marques H. The influence of the preparation methods on the inclusion of model drugs in a β-cyclodextrin cavity. Eur J Pharm Biopharm 2009; 71:377-86. [DOI: 10.1016/j.ejpb.2008.09.027] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 08/06/2008] [Accepted: 09/30/2008] [Indexed: 11/26/2022]
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Cruz C, Figueirinhas JL, Filip D, Feio G, Ribeiro AC, Frère Y, Meyer T, Mehl GH. Biaxial nematic order and phase behavior studies in an organosiloxane tetrapode using complementary deuterium NMR experiments. Phys Rev E Stat Nonlin Soft Matter Phys 2008; 78:051702. [PMID: 19113138 DOI: 10.1103/physreve.78.051702] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Revised: 07/10/2008] [Indexed: 05/27/2023]
Abstract
The biaxial nematic phase was recently observed in different thermotropic liquid crystals, namely bent-core compounds, side-chain polymers, bent-core dimers, and organosiloxane tetrapodes. In this work, a series of experiments with a nematic organosiloxane tetrapode where nuclear magnetic resonance (NMR) spectra are collected while the sample is continuously rotating around an axis perpendicular to the magnetic field, are discussed in conjunction with the analysis of a deuterium NMR experiment on the same system reported earlier. The sample used is a mixture of a deuterated probe with the tetrapode. The mixture exhibits a nematic range between -40 degrees C and 37 degrees C. The results of the two independent, but complementary deuterium NMR experiments confirm the existence of a biaxial nematic phase for temperatures below 0 degrees C with high values of the asymmetry parameter at low temperatures. The presence of slow movements of the tetrapode mesogenic units in the low-temperature regime could also be detected through the analysis of the NMR spectra. Simulations indicate that these movements are mainly slow molecular reorientations of the mesogenic units associated with the presence of collective modes in the nematic phases of this compound. In the case of tetrapodes, recent investigations attribute the origin of biaxiality to the hindering of reorientations of the laterally attached mesogenic units which constitute the tetrapode. This study relates the molecular movements with the nematic biaxial ordering of the system.
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Affiliation(s)
- C Cruz
- CFMC-UL, Av. Prof. Gama Pinto 2, 1649-003 Lisboa, Portugal
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19
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Figueirinhas JL, Cruz C, Filip D, Feio G, Ribeiro AC, Frère Y, Meyer T, Mehl GH. Deuterium NMR investigation of the biaxial nematic phase in an organosiloxane tetrapode. Phys Rev Lett 2005; 94:107802. [PMID: 15783524 DOI: 10.1103/physrevlett.94.107802] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2004] [Indexed: 05/24/2023]
Abstract
Deuterium NMR is used to examine the molecular order exhibited by an organosiloxane tetrapode giving the first experimental evidence, using a bulk sample, for the existence of a biaxial nematic phase in this type of compounds. The temperature dependence of the averaged quadrupolar coupling constant and asymmetry parameter was determined in the compound's nematic phase. Two distinct regimes could be identified, one with a vanishing asymmetry parameter corresponding to a uniaxial nematic phase and another with a significant temperature dependent asymmetry parameter, corresponding to a biaxial nematic phase. The high values obtained for the asymmetry parameter at the lower end of the nematic range are well above experimental error and constitute a definite proof of the biaxial nature of the nematic phase exhibited by the studied compound for those temperatures.
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Affiliation(s)
- J L Figueirinhas
- CFMC-UL, Avenida Professor Gama Pinto 2, 1649-003 Lisboa, Portugal
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20
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Trescos E, Rachdi F, de Menorval LC, Fajula F, Nunes T, Feio G. ESR and NMR studies of sodium and rubidium loaded in NaY zeolite cavities. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100148a001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Feio G, Burrows HD, Geraldes CFGC, Pinheiro TJT. Multinuclear nuclear magnetic resonance, studies of lead(II) soaps. Part 3.—Studies on the liquid phase with reference to the behaviour of the corresponding acids. ACTA ACUST UNITED AC 1993. [DOI: 10.1039/ft9938903117] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Feio G, Buntinx G, Cohen-Addad JP. NMR Approach to the kinetics of polymer crystallization. II. Polydimethylsiloxane solutions. ACTA ACUST UNITED AC 1989. [DOI: 10.1002/polb.1989.090270101] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Cohen-Addad JP, Feio G. Effects of polymer chain disentanglement on NMR properties. II. 13C magnetic relaxation in polystyrene. ACTA ACUST UNITED AC 1984. [DOI: 10.1002/pol.1984.180220603] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Feio G, Cohen-Addad J. Dynamical polymer coil overlap observed by NMR on polystyrene chains. Polym Bull (Berl) 1981. [DOI: 10.1007/bf00254714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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