9 results on '"Lazzara G."'
Search Results
2. Selectivity of cyclodextrins as a parameter to tune the formation of pseudorotaxanes and micelles supramolecular assemblies. A systematic SANS study
- Author
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Lazzara, G., primary, Prevost, S., additional, and Gradzielski, M., additional
- Published
- 2011
- Full Text
- View/download PDF
3. On the effect of the nature of counterions on the self-assembly of polyoxyethylene alkyl ether carboxylic acids
- Author
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Giuseppe Lazzara, Chiara Crivello, Leonardo Chiappisi, Crivello C., Lazzara G., and Chiappisi L.
- Subjects
inorganic chemicals ,chemistry.chemical_classification ,Ethylene oxide ,Charge density ,02 engineering and technology ,General Chemistry ,Neutron scattering ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Pulmonary surfactant ,chemistry ,Sodium hydroxide ,Counterion condensation ,Surfactant ,Polymer chemistry ,Counterion ,0210 nano-technology ,Alkyl ,Settore CHIM/02 - Chimica Fisica - Abstract
In this contribution, we investigate the effect of the type of counterion on the properties of dilute solutions of polyoxyethylene alkyl ether carboxylic acids. Two different surfactants, presenting an oleic acid alkyl chain and on-average five and nine ethylene oxide units, and terminated by a weakly anionic carboxymethyl group were studied. The surfactants were gradually ionized with sodium hydroxide, arginine, and choline hydroxide. The solutions properties were probed by light scattering, electrophoretic mobility, density and sound velocity measurements, as well as by small-angle neutron scattering. To our initial surprise, no specific effect arising from the nature of the counterion could be determined. We ascribe this phenomenon to the fact that the presence of the ethylene oxide units markedly dilutes the surfactant head group charge density, reducing counterion condensation and subsequent counterion specific effects. This journal is
- Published
- 2020
4. Dicationic organic salts: gelators for ionic liquids
- Author
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Giuseppe Lazzara, Renato Noto, Francesca D'Anna, Carla Rizzo, Paola Vitale, D'Anna, F, Rizzo, C, Vitale, P, Lazzara, G, and Noto R
- Subjects
ionogel, ionic liquid, organic salts ,Inorganic chemistry ,Settore CHIM/06 - Chimica Organica ,General Chemistry ,Condensed Matter Physics ,Resonance (chemistry) ,Light scattering ,Ion ,Dielectric spectroscopy ,chemistry.chemical_compound ,chemistry ,Bromide ,Ionic liquid ,Thermal stability ,Naphthalene - Abstract
Diimidazolium and dipyrrolidinium organic salts were tested for their ability to gel both organic solvents and ionic liquids. Organic salts containing 1-(1-imidazolylmethyl)-3,5-di-(3'-octylimidazolylmethyl)-benzene and 1-(N-pyrrolidylmethyl)-3,5-di-(N,N-octylpyrrolidylmethyl)-benzene cations were used. In addition to the simple bromide anion, also dianions having a naphthalene core such as 1,5- and 2,6-naphthalenedisulfonate and 2,6-naphthalenedicarboxylate were taken into account. Gelation tests demonstrated that organic salts used were able to harden ionic liquids. The materials obtained were investigated for their thermal stability and also for electric conductivity properties using micro-DSC and dielectric spectroscopy. Furthermore, the opacity of some gel phases was monitored using UV-vis measurements. To obtain information about the gelation mechanism, gel phase formation was studied as a function of time by means of resonance light scattering investigation. Finally, the ability of materials to respond to external stimuli such as magnetic stirring or ultrasound irradiation was also analyzed. Data collected show that different relationships exist among the gelator and the ionic liquid structure, determining the properties of materials and their possible applications.
- Published
- 2014
5. Temperature-responsive inclusion complex of cationic PNIPAAM diblock copolymer and γ-cyclodextrin
- Author
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Kaizheng Zhu, Bo Nyström, Karin Schillén, Gerd Olofsson, Viveka Alfredsson, Giuseppe Lazzara, Lazzara, G, Olofsson, G, Alfredsson, V, Zhu, K, Nystrom, B, and Schillen, K
- Subjects
chemistry.chemical_classification ,Aqueous solution ,Cyclodextrin ,Chemistry ,supramolecule, cyclodextrin, PNIPAAM, rotaxanes ,Cationic polymerization ,General Chemistry ,Condensed Matter Physics ,Lower critical solution temperature ,Fluorescence spectroscopy ,Dynamic light scattering ,Polymer chemistry ,Copolymer ,Molecule ,Settore CHIM/02 - Chimica Fisica - Abstract
Aqueous mixtures of γ-cyclodextrin (γ-CD) and the thermosensitive cationic diblock copolymer poly(N-isopropylacrylamide)-b-poly(3-acrylamidopropyl)trimethylammonium chloride (PNIPAAM24-b-PAMPTAM(+)9) or the PNIPAAM homopolymer PNIPAAM47 have been investigated using various experimental methods. Solid γ-CD–polymer inclusion complexes (pseudopolyrotaxanes) form at ambient temperatures in fairly concentrated CD solutions. The NMR measurements showed that the stoichiometry of the inclusion complexes is close to two NIPAAM units per CD molecule. The cationic block of the copolymer is not incorporated into the CD cavity. Synchrotron radiation X-ray diffraction spectra of the solid inclusion complexes indicate a compact columnar structure of CD molecules threaded onto the PNIPAAM chains. In water, square-shaped cyclodextrin aggregates were found to co-exist with single cyclodextrin molecules. In mixed solutions of γ-CD and PNIPAAM24-b-PAMPTAM(+)9 these aggregates disintegrate with time as inclusion complexes are formed and the kinetics was studied using time-resolved static and dynamic light scattering and cryo-TEM. Steady-state fluorescence spectroscopy measurements reveal that the CD molecules dethread from the PNIPAAM chains upon increasing the temperature to 40 °C, which is above the lower critical solution temperature of PNIPAAM.
- Published
- 2012
6. Thermoresponsive behavior of cyclodextrin inclusion complexes with weakly anionic alkyl ethoxy carboxylates.
- Author
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Dos Santos Silva Araújo L, Lazzara G, and Chiappisi L
- Abstract
This study investigates the temperature responsive behavior of inclusion complexes formed by weakly anionic alkyl ethoxy carboxylates and α (αCD) and β-cyclodextrins (βCD). Small-angle neutron scattering (SANS) was performed to probe the structural behaviour at the 1-100 nanometer scale of the hierarchical assemblies at different temperatures. The phase transitions and thermodynamics were systematically monitored as a function of the degree of ionization of the surfactant by differential scanning calorimetry (DSC). Herein, we investigate the effect of the surfactant degree of ionization on the thermoresponsive properties of the inclusion complex supramolecular assemblies. Inclusion complexes formed with the ionized surfactant spontaneously assemble into multilayered structures, which soften with increasing temperature. We also found that the presence of charges is not only required to impart order to the supramolecular assemblies, but also induced in-plane crystallization of the inclusion complexes. Finally, the use of a weakly anionic surfactant allows us to probe the interplay between the charge density and temperature on the assembly of surfactant-cyclodextrin inclusion complexes. This study helps to improve the design of multi-responsive supramolecular systems based on cyclodextrins.
- Published
- 2023
- Full Text
- View/download PDF
7. Hierarchical assembly of pH-responsive surfactant-cyclodextrin complexes.
- Author
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Dos Santos Silva Araújo L, Watson L, Traore DAK, Lazzara G, and Chiappisi L
- Abstract
In this work, the inclusion complexes of alkyl ethoxy carboxylates with α-cyclodextrin (αCD) and β-cyclodextrin (βCD) were investigated. The thermodynamics of the complexation process was probed by isothermal titration calorimetry (ITC) and volumetry as a function of the degree of ionization of the surfactant. The complexation process was shown to be an enthalpically driven pH-independent process. For both types of cyclodextrins, the complexes were found to spontaneously self-assemble into highly-ordered supramolecular aggregates probed by small-angle neutron scattering and electron and optical microscopy. Herein, we report the formation of thin platelets for nonionized surfactant systems and equally spaced multilayered hollow cylinders for ionized systems in a hierarchical self-assembly process. In addition, the analysis allowed unveiling the effect of the number of ethylene oxides in the surfactants and the CD cavity size on the morphology of the aggregates. Finally, this study also highlights the importance of examining the tuning parameters' influence on the short and long-range interactions involved in the control of the assembly process.
- Published
- 2022
- Full Text
- View/download PDF
8. On the effect of the nature of counterions on the self-assembly of polyoxyethylene alkyl ether carboxylic acids.
- Author
-
Crivello C, Lazzara G, and Chiappisi L
- Abstract
In this contribution, we investigate the effect of the type of counterion on the properties of dilute solutions of polyoxyethylene alkyl ether carboxylic acids. Two different surfactants, presenting an oleic acid alkyl chain and on-average five and nine ethylene oxide units, and terminated by a weakly anionic carboxymethyl group were studied. The surfactants were gradually ionized with sodium hydroxide, arginine, and choline hydroxide. The solutions properties were probed by light scattering, electrophoretic mobility, density and sound velocity measurements, as well as by small-angle neutron scattering. To our initial surprise, no specific effect arising from the nature of the counterion could be determined. We ascribe this phenomenon to the fact that the presence of the ethylene oxide units markedly dilutes the surfactant head group charge density, reducing counterion condensation and subsequent counterion specific effects.
- Published
- 2020
- Full Text
- View/download PDF
9. Dicationic organic salts: gelators for ionic liquids.
- Author
-
D'Anna F, Rizzo C, Vitale P, Lazzara G, and Noto R
- Abstract
Diimidazolium and dipyrrolidinium organic salts were tested for their ability to gel both organic solvents and ionic liquids. Organic salts containing 1-(1-imidazolylmethyl)-3,5-di-(3'-octylimidazolylmethyl)-benzene and 1-(N-pyrrolidylmethyl)-3,5-di-(N,N-octylpyrrolidylmethyl)-benzene cations were used. In addition to the simple bromide anion, also dianions having a naphthalene core such as 1,5- and 2,6-naphthalenedisulfonate and 2,6-naphthalenedicarboxylate were taken into account. Gelation tests demonstrated that organic salts used were able to harden ionic liquids. The materials obtained were investigated for their thermal stability and also for electric conductivity properties using micro-DSC and dielectric spectroscopy. Furthermore, the opacity of some gel phases was monitored using UV-vis measurements. To obtain information about the gelation mechanism, gel phase formation was studied as a function of time by means of resonance light scattering investigation. Finally, the ability of materials to respond to external stimuli such as magnetic stirring or ultrasound irradiation was also analyzed. Data collected show that different relationships exist among the gelator and the ionic liquid structure, determining the properties of materials and their possible applications.
- Published
- 2014
- Full Text
- View/download PDF
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