Valeria Harabagiu | Petru Poni Institute of Macromolecular Chemistry Iasi Romania (original) (raw)
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Papers by Valeria Harabagiu
Conventional synthetic methods can produce only carbon materials with a random porosity. Recently... more Conventional synthetic methods can produce only carbon materials with a random porosity. Recently, templated method has been applied for the mesoporous carbon synthesis using amorphous silica resulting in its successful replication. This method allows controlling the pore size, pore morphology and ordering of the carbon mesostructure.This research examines the pyrolizing temperature effect on the mesoporous carbon textural properties. The textural properties have been determined from the adsorption of nitrogen at 77 K and the conventional BET equation has been used for the quantification of the surface area and porosity of the carbon materials. The results showed that the pyrolizing temperature influences the carbon properties, decreasing its surface area and pore diameter with the temperature increase. As a consequence, the porosity of the mesoporous carbon material is reduced. Interesting is to conclude that the pyrolizing temperature does not affect directly the carbon texture, b...
Nanomaterials, 2020
Porous titania was successfully synthesized by an ultrasound-assisted sol-gel route. The synthesi... more Porous titania was successfully synthesized by an ultrasound-assisted sol-gel route. The synthesis process was empirically modeled and optimized using the response surface methodology (RSM). Input variables adopted for optimization dealt with the weight ratio of precursors (r) and the sonication time (t), representing the used factors in the synthesis procedure. With regard to application, the synthesized TiO2 samples were tested for the photodegradation of two water-soluble organic pollutants under UV–Vis irradiation. Optimal conditions for the efficient pollutants’ photodegradation were found to involve a precursors ratio of 3 and a sonication time of 60 min. Thus, the M5 sample prepared under the founded optimal conditions yielded the maximal removal efficiencies of 98.4% and 46.3% for the photodegradation of CR dye and 2,4-D herbicide, respectively. In addition, the photodegradation kinetics revealed the pseudo first-order rate constants, showing the photodegradation of CR (k1 =...
Environmental Engineering and Management Journal, 2015
The present research reports the synthesis of poly-N-isopropylacrylamide / mesoporous carbon comp... more The present research reports the synthesis of poly-N-isopropylacrylamide / mesoporous carbon composites, prepared by radical polymerization of N-isopropylacrylamide inside mesoporous carbon pores functionalized with carboxylic groups. The deposition of poly-N-isopropylacrylamide on mesoporous carbon was confirmed by FT-IR spectroscopy, TEM, N 2-sorption measurements. The mesoporous carbon material was found to adsorb vitamin B2 from aqueous solution at room temperature. The obtained composite, poly-N-isopropylacrylamide / mesoporous carbon, exhibited a higher adsorption capacity for vitamin B2 as compared to un-functionalized mesoporous carbon sample, due to hydrogen bonding between carbonyl groups of poly-Nisopropylacrylamide immobilized on the mesoporous carbon surface and amino groups of vitamin B2 molecules.
e-Polymers, 2012
This communication describes the synthesis of polymethylphenylsilane by the microwave-assisted co... more This communication describes the synthesis of polymethylphenylsilane by the microwave-assisted coupling of methylphenyldichlorosilane using metallic sodium in solvent free conditions. The instant heating melts the sodium particles within the liquid methylphenyldichlorosilane and the polymerization reaction is achieved in minutes with total consumption of the monomer. The process is carried out in a high performance microwave reactor using the closed vessel operating facility which ensures control of the reaction parameters and highly reproducible results.
Biomacromolecules, 2010
Some effects of water at levels up to 25% (dry solids basis db) on regenerated cellulose films wi... more Some effects of water at levels up to 25% (dry solids basis db) on regenerated cellulose films with a thickness of 100 mum were investigated by dynamic vapor sorption (DVS), X-ray diffraction, tensile testing, and proton-nuclear magnetic resonance (NMR). The sorption isotherm fitted by the D'Arcy and Watt model and the increase in NMR T(2) with water content suggest that a mobile water fraction appears at water contents above 10%db. Water absorption increased the crystallinity of cellulose films from 31% (dry) to 38% (25%db) and altered the dimensions of crystallites. Mechanical measurements on planar and notched samples at all the water contents used here showed ductile fracture behavior. Although the properties of water in these cellulose films are comparable to previously reported data on starch, cellulose films at low water content are much less brittle than starch. The reasons for this difference are explored.
European Polymer Journal, 1990
Polycondensation of 4,4'-azobis-4-cyanovaleryl chloride and :t,co-bis(3-hydroxypropyl)polydimethy... more Polycondensation of 4,4'-azobis-4-cyanovaleryl chloride and :t,co-bis(3-hydroxypropyl)polydimethylsiloxane was carried out to yield poly(azo-containing siloxane ester)s. These were used to induce the radical polymerization of various vinyl monomers through the thermal decomposition of the azo groups, resulting in the formation of poly(siloxane-b-vinyl) copolymers.
![Research paper thumbnail of Synthesis and characterization of a poly[2,7-(9,9-dioctylfluorene- alt-2,7-fluorene/β-CD)] main chain polyrotaxane](https://attachments.academia-assets.com/48019557/thumbnails/1.jpg)
](European Polymer Journal, 2009
Poly[2,7-(9,9-dioctylfluorene-alt-2,7-fluorene/b-CD)] main chain polyrotaxane was synthesized thr... more Poly[2,7-(9,9-dioctylfluorene-alt-2,7-fluorene/b-CD)] main chain polyrotaxane was synthesized through organometallic Suzuki coupling by reacting b-cyclodextrin/2,7-dibromofluorene inclusion complex with 9,9-dioctylfluorene-2,7-bis(trimethyleneborate). The IR, NMR and elemental analysis data support the presence of b-cyclodextrin in the copolymer structure. No glass transition or melting phenomena were detected in DSC curves of the polyrotaxane on the heating run in the 50-250°range. As compared with the reference copolymer obtained in the absence of b-cyclodextrin, the rotaxane copolymer is more hygroscopic and soluble in polar/non-polar solvent mixtures. The expected modification of the optical properties of the fluorene copolymer with rotaxane architecture in the main chain was proved by fluorescence and UV-vis spectroscopy and consists in a blue-shifted emission.
Cyclodextrins are widely used nowadays in many fields, including therapeutic systems, due to thei... more Cyclodextrins are widely used nowadays in many fields, including therapeutic systems, due to their ability to form inclusion complexes with a wide variety of compounds. In this study we present a series of molecular dynamics (MD) simulations on β-cyclodextrin/propiconazole inclusion complexes in order to gain insights on the inclusion process. The data obtained from constraint-free molecular dynamics simulations revealed spontaneous complexation processes resulting in several geometries with small differences in the free energy of binding, which are predicted to co-exist in aqueous solution. Semiempirical quantum mechanical computations (PM3) were also performed in gas phase on the MD obtained complexes and the results could be at least qualitatively correlated with the MD findings. However, the lack of explicit solvent representation in PM3 calculations can constitute a major drawback in evaluating the relative energies of complexation of different inclusion modes.
Conventional synthetic methods can produce only carbon materials with a random porosity. Recently... more Conventional synthetic methods can produce only carbon materials with a random porosity. Recently, templated method has been applied for the mesoporous carbon synthesis using amorphous silica resulting in its successful replication. This method allows controlling the pore size, pore morphology and ordering of the carbon mesostructure.This research examines the pyrolizing temperature effect on the mesoporous carbon textural properties. The textural properties have been determined from the adsorption of nitrogen at 77 K and the conventional BET equation has been used for the quantification of the surface area and porosity of the carbon materials. The results showed that the pyrolizing temperature influences the carbon properties, decreasing its surface area and pore diameter with the temperature increase. As a consequence, the porosity of the mesoporous carbon material is reduced. Interesting is to conclude that the pyrolizing temperature does not affect directly the carbon texture, b...
Nanomaterials, 2020
Porous titania was successfully synthesized by an ultrasound-assisted sol-gel route. The synthesi... more Porous titania was successfully synthesized by an ultrasound-assisted sol-gel route. The synthesis process was empirically modeled and optimized using the response surface methodology (RSM). Input variables adopted for optimization dealt with the weight ratio of precursors (r) and the sonication time (t), representing the used factors in the synthesis procedure. With regard to application, the synthesized TiO2 samples were tested for the photodegradation of two water-soluble organic pollutants under UV–Vis irradiation. Optimal conditions for the efficient pollutants’ photodegradation were found to involve a precursors ratio of 3 and a sonication time of 60 min. Thus, the M5 sample prepared under the founded optimal conditions yielded the maximal removal efficiencies of 98.4% and 46.3% for the photodegradation of CR dye and 2,4-D herbicide, respectively. In addition, the photodegradation kinetics revealed the pseudo first-order rate constants, showing the photodegradation of CR (k1 =...
Environmental Engineering and Management Journal, 2015
The present research reports the synthesis of poly-N-isopropylacrylamide / mesoporous carbon comp... more The present research reports the synthesis of poly-N-isopropylacrylamide / mesoporous carbon composites, prepared by radical polymerization of N-isopropylacrylamide inside mesoporous carbon pores functionalized with carboxylic groups. The deposition of poly-N-isopropylacrylamide on mesoporous carbon was confirmed by FT-IR spectroscopy, TEM, N 2-sorption measurements. The mesoporous carbon material was found to adsorb vitamin B2 from aqueous solution at room temperature. The obtained composite, poly-N-isopropylacrylamide / mesoporous carbon, exhibited a higher adsorption capacity for vitamin B2 as compared to un-functionalized mesoporous carbon sample, due to hydrogen bonding between carbonyl groups of poly-Nisopropylacrylamide immobilized on the mesoporous carbon surface and amino groups of vitamin B2 molecules.
e-Polymers, 2012
This communication describes the synthesis of polymethylphenylsilane by the microwave-assisted co... more This communication describes the synthesis of polymethylphenylsilane by the microwave-assisted coupling of methylphenyldichlorosilane using metallic sodium in solvent free conditions. The instant heating melts the sodium particles within the liquid methylphenyldichlorosilane and the polymerization reaction is achieved in minutes with total consumption of the monomer. The process is carried out in a high performance microwave reactor using the closed vessel operating facility which ensures control of the reaction parameters and highly reproducible results.
Biomacromolecules, 2010
Some effects of water at levels up to 25% (dry solids basis db) on regenerated cellulose films wi... more Some effects of water at levels up to 25% (dry solids basis db) on regenerated cellulose films with a thickness of 100 mum were investigated by dynamic vapor sorption (DVS), X-ray diffraction, tensile testing, and proton-nuclear magnetic resonance (NMR). The sorption isotherm fitted by the D'Arcy and Watt model and the increase in NMR T(2) with water content suggest that a mobile water fraction appears at water contents above 10%db. Water absorption increased the crystallinity of cellulose films from 31% (dry) to 38% (25%db) and altered the dimensions of crystallites. Mechanical measurements on planar and notched samples at all the water contents used here showed ductile fracture behavior. Although the properties of water in these cellulose films are comparable to previously reported data on starch, cellulose films at low water content are much less brittle than starch. The reasons for this difference are explored.
European Polymer Journal, 1990
Polycondensation of 4,4'-azobis-4-cyanovaleryl chloride and :t,co-bis(3-hydroxypropyl)polydimethy... more Polycondensation of 4,4'-azobis-4-cyanovaleryl chloride and :t,co-bis(3-hydroxypropyl)polydimethylsiloxane was carried out to yield poly(azo-containing siloxane ester)s. These were used to induce the radical polymerization of various vinyl monomers through the thermal decomposition of the azo groups, resulting in the formation of poly(siloxane-b-vinyl) copolymers.
European Polymer Journal, 2009
Poly[2,7-(9,9-dioctylfluorene-alt-2,7-fluorene/b-CD)] main chain polyrotaxane was synthesized thr... more Poly[2,7-(9,9-dioctylfluorene-alt-2,7-fluorene/b-CD)] main chain polyrotaxane was synthesized through organometallic Suzuki coupling by reacting b-cyclodextrin/2,7-dibromofluorene inclusion complex with 9,9-dioctylfluorene-2,7-bis(trimethyleneborate). The IR, NMR and elemental analysis data support the presence of b-cyclodextrin in the copolymer structure. No glass transition or melting phenomena were detected in DSC curves of the polyrotaxane on the heating run in the 50-250°range. As compared with the reference copolymer obtained in the absence of b-cyclodextrin, the rotaxane copolymer is more hygroscopic and soluble in polar/non-polar solvent mixtures. The expected modification of the optical properties of the fluorene copolymer with rotaxane architecture in the main chain was proved by fluorescence and UV-vis spectroscopy and consists in a blue-shifted emission.
Cyclodextrins are widely used nowadays in many fields, including therapeutic systems, due to thei... more Cyclodextrins are widely used nowadays in many fields, including therapeutic systems, due to their ability to form inclusion complexes with a wide variety of compounds. In this study we present a series of molecular dynamics (MD) simulations on β-cyclodextrin/propiconazole inclusion complexes in order to gain insights on the inclusion process. The data obtained from constraint-free molecular dynamics simulations revealed spontaneous complexation processes resulting in several geometries with small differences in the free energy of binding, which are predicted to co-exist in aqueous solution. Semiempirical quantum mechanical computations (PM3) were also performed in gas phase on the MD obtained complexes and the results could be at least qualitatively correlated with the MD findings. However, the lack of explicit solvent representation in PM3 calculations can constitute a major drawback in evaluating the relative energies of complexation of different inclusion modes.