Documents disponibles écrits par cet auteur

Temperature responsive gels based on pluronic F127 and poly(vinyl alcohol) / Maria Bercea in Industrial & engineering chemistry research, Vol. 50 N° 7 (Avril 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 7 (Avril 2011) . - pp. 4199-4206 Titre : Temperature responsive gels based on pluronic F127 and poly(vinyl alcohol) Type de document : texte imprimé Auteurs : Maria Bercea, Auteur ; Raluca Nicoleta Darie, Auteur ; Loredana Elena Nita, Auteur Année de publication : 2011 Article en page(s) : pp. 4199-4206 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Pluronic  Vinyl  alcohol Résumé : Aqueous mixtures of Pluronic F127 and poly(vinyl alcohol) (20% polymer concentration in the system) were prepared and investigated by rheology and laser particle size distribution, in order to obtain temperature responsive gels for biomedical applications. The influence of the gelation conditions and system composition on the viscoelastic parameters and particle size distribution (which are very sensitive to the sol―gel transition process) was followed. The investigations realized at physiological temperature (37 °C) showed the thixotropic profile of the gels, the yield stress induced by the Pluronic presence, and the high elasticity evidenced in the creep-recovery tests. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1024408 [article] Temperature responsive gels based on pluronic F127 and poly(vinyl alcohol) [texte imprimé] / Maria Bercea, Auteur ; Raluca Nicoleta Darie, Auteur ; Loredana Elena Nita, Auteur . - 2011 . - pp. 4199-4206. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 7 (Avril 2011) . - pp. 4199-4206 Mots-clés : Pluronic  Vinyl  alcohol Résumé : Aqueous mixtures of Pluronic F127 and poly(vinyl alcohol) (20% polymer concentration in the system) were prepared and investigated by rheology and laser particle size distribution, in order to obtain temperature responsive gels for biomedical applications. The influence of the gelation conditions and system composition on the viscoelastic parameters and particle size distribution (which are very sensitive to the sol―gel transition process) was followed. The investigations realized at physiological temperature (37 °C) showed the thixotropic profile of the gels, the yield stress induced by the Pluronic presence, and the high elasticity evidenced in the creep-recovery tests. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1024408

The Behavior of chitosan in solvents with different ionic strengths / Simona Morariu in Industrial & engineering chemistry research, Vol. 51 N° 39 (Octobre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 39 (Octobre 2012) . - pp. 12959–12966 Titre : The Behavior of chitosan in solvents with different ionic strengths Type de document : texte imprimé Auteurs : Simona Morariu, Auteur ; Cristina-Eliza Brunchi, Auteur ; Maria Bercea, Auteur Année de publication : 2012 Article en page(s) : pp. 12959–12966 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Solvents  Ionic  strengths Résumé : The thermodynamic behavior of chitosan in acidic aqueous solutions with ionic strengths between 0.04 × 10–2 and 24.30 × 10–2 M was investigated at 25 °C. The intrinsic viscosity and other thermodynamic parameters of chitosan with the molecular weight and the degree of acetylation of 7.14 × 105 g mol–1 and 26%, respectively, were determined and discussed by using both classical equations (Huggins and Fedors) and a new model (Wolf). At low ionic strengths of the solvent, the highest values of the intrinsic viscosity were obtained due to the expansion of the chitosan chains. Two critical concentrations, c* (which separates the dilute-semidilute regimes) and c+ (at which the dimensions of the polymer coils are considered to have shrunk to their unperturbed dimensions), were estimated, and the effect of the solvent ionic strength on their values was discussed. By increasing of the solvent ionic strength from 0.04 × 10–2 to 24.30 × 10–2 M, the persistence length decreased from 17.14 to 4.60 nm, suggesting an increase of the chitosan flexibility due to the decrease of repulsive potential between the polymer chains. The radius of gyration and the persistence length in the unperturbed state were determined as being 52.50 and 3.90 nm, respectively. The viscometric data were corroborated with those obtained by the zeta potential, conductivity, and turbidity measurements for the ionic strength of the solvent between 0.04 × 10–2 and 42.25 × 10–2 M. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie301309g [article] The Behavior of chitosan in solvents with different ionic strengths [texte imprimé] / Simona Morariu, Auteur ; Cristina-Eliza Brunchi, Auteur ; Maria Bercea, Auteur . - 2012 . - pp. 12959–12966. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 39 (Octobre 2012) . - pp. 12959–12966 Mots-clés : Solvents  Ionic  strengths Résumé : The thermodynamic behavior of chitosan in acidic aqueous solutions with ionic strengths between 0.04 × 10–2 and 24.30 × 10–2 M was investigated at 25 °C. The intrinsic viscosity and other thermodynamic parameters of chitosan with the molecular weight and the degree of acetylation of 7.14 × 105 g mol–1 and 26%, respectively, were determined and discussed by using both classical equations (Huggins and Fedors) and a new model (Wolf). At low ionic strengths of the solvent, the highest values of the intrinsic viscosity were obtained due to the expansion of the chitosan chains. Two critical concentrations, c* (which separates the dilute-semidilute regimes) and c+ (at which the dimensions of the polymer coils are considered to have shrunk to their unperturbed dimensions), were estimated, and the effect of the solvent ionic strength on their values was discussed. By increasing of the solvent ionic strength from 0.04 × 10–2 to 24.30 × 10–2 M, the persistence length decreased from 17.14 to 4.60 nm, suggesting an increase of the chitosan flexibility due to the decrease of repulsive potential between the polymer chains. The radius of gyration and the persistence length in the unperturbed state were determined as being 52.50 and 3.90 nm, respectively. The viscometric data were corroborated with those obtained by the zeta potential, conductivity, and turbidity measurements for the ionic strength of the solvent between 0.04 × 10–2 and 42.25 × 10–2 M. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie301309g

The temperature influence upon the complexation process between poly(aspartic acid) and poly(ethylene glycol) / Loredana E. Nita in Industrial & engineering chemistry research, Vol. 50 N° 9 (Mai 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 9 (Mai 2011) . - pp. 5369-5375 Titre : The temperature influence upon the complexation process between poly(aspartic acid) and poly(ethylene glycol) Type de document : texte imprimé Auteurs : Loredana E. Nita, Auteur ; Aurica P. Chiriac, Auteur ; Maria Bercea, Auteur Année de publication : 2011 Article en page(s) : pp. 5369-5375 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Complexation Résumé : The temperature influence upon the formation of an interpolymer complex (IPC) based on poly(aspartic acid) (PAS) and poly(ethylene glycol) (PEG), was investigated. The water PAS/PEG mixture was studied in the temperature range between 22 and 37 °C. The registered data were correlated with the blend composition and the molecular weight of PEG. The intervened interchain physical interactions, especially the hydrogen-bonds, were evidenced by FT-IR spectroscopy. The miscibility and polymer-polymer interactions were experimentally estimated from the dynamic viscosity. The determination of the zeta potential and electrical conductivity of the interpolymer complexes during their formation are in good agreement with the rheological and spectral data. The variation of the composition, respectively, the PAS/PEG ratio, and the different molecular weights of PEG were used in order to establish the optimum conditions for the IPC achievement. The information was correlated on the mentioned interval of temperature. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24128659 [article] The temperature influence upon the complexation process between poly(aspartic acid) and poly(ethylene glycol) [texte imprimé] / Loredana E. Nita, Auteur ; Aurica P. Chiriac, Auteur ; Maria Bercea, Auteur . - 2011 . - pp. 5369-5375. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 9 (Mai 2011) . - pp. 5369-5375 Mots-clés : Complexation Résumé : The temperature influence upon the formation of an interpolymer complex (IPC) based on poly(aspartic acid) (PAS) and poly(ethylene glycol) (PEG), was investigated. The water PAS/PEG mixture was studied in the temperature range between 22 and 37 °C. The registered data were correlated with the blend composition and the molecular weight of PEG. The intervened interchain physical interactions, especially the hydrogen-bonds, were evidenced by FT-IR spectroscopy. The miscibility and polymer-polymer interactions were experimentally estimated from the dynamic viscosity. The determination of the zeta potential and electrical conductivity of the interpolymer complexes during their formation are in good agreement with the rheological and spectral data. The variation of the composition, respectively, the PAS/PEG ratio, and the different molecular weights of PEG were used in order to establish the optimum conditions for the IPC achievement. The information was correlated on the mentioned interval of temperature. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24128659

Vapor pressures of polymer solutions and the modeling of their composition dependence / Maria Bercea in Industrial & engineering chemistry research, Vol. 48 N° 9 (Mai 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 9 (Mai 2009) . - pp. 4603–4606 Titre : Vapor pressures of polymer solutions and the modeling of their composition dependence Type de document : texte imprimé Auteurs : Maria Bercea, Auteur ; John Eckelt, Auteur ; Bernhard A. Wolf, Auteur Année de publication : 2009 Article en page(s) : pp. 4603–4606 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Vapor  pressures  Poly(vinyl  methyl  ether)  Polystyrene  Tetrahydrofuran Résumé : Equilibrium vapor pressures, p, are reported for the systems tetrahydrofuran + poly(vinyl methyl ether) and tetrahydrofuran + polystyrene at 20, 40, and 60 °C. These data plus information from the literature serve to demonstrate that the composition dependence of p can be modeled quantitatively for polymer solutions in thermodynamically very different solvents by means of three, physically meaningful parameters. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801965h [article] Vapor pressures of polymer solutions and the modeling of their composition dependence [texte imprimé] / Maria Bercea, Auteur ; John Eckelt, Auteur ; Bernhard A. Wolf, Auteur . - 2009 . - pp. 4603–4606. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 9 (Mai 2009) . - pp. 4603–4606 Mots-clés : Vapor  pressures  Poly(vinyl  methyl  ether)  Polystyrene  Tetrahydrofuran Résumé : Equilibrium vapor pressures, p, are reported for the systems tetrahydrofuran + poly(vinyl methyl ether) and tetrahydrofuran + polystyrene at 20, 40, and 60 °C. These data plus information from the literature serve to demonstrate that the composition dependence of p can be modeled quantitatively for polymer solutions in thermodynamically very different solvents by means of three, physically meaningful parameters. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801965h