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1
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Mechanical, thermal and surface properties of polyacrylamide/dextran semi-interpenetrating network hydrogels tuned by the synthesis temperature

100%
Dinu M., Cazacu M., Drăgan E.
Open Chemistry
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2013
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vol. 11
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issue 2
248-258
EN
The mechanical, rheological, thermal, and surface behaviors of three polyacrylamide/dextran (PAAm/Dx) semi-interpenetrating polymer network (semi-IPN) hydrogels, prepared at 22°C, 5°C and −18°C, were investigated. The results were compared with those obtained on cross-linked PAAm without Dx synthesized under the same conditions. Hydrogels prepared at the lowest temperature were the most mechanically stable. The thermal stability of the semi-IPN hydrogels is slightly lower than the corresponding PAAm gels, irrespective of preparation temperature. The water vapor sorption capacity depended on the presence of Dx as well as preparation temperature, which determines the network morphology. [...]
2
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A silica-silver nanocomposite obtained by sol-gel method in the presence of silver nanoparticles

100%
Racles C., Nistor A., Cazacu M.
Open Chemistry
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2013
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vol. 11
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issue 10
1689-1698
EN
Silver nanoparticles (AgNPs) were obtained by a redox reaction, using a glucose-containing cyclosiloxane as a reduction agent and stabilizer. Then the AgNPs aqueous solution was used as the reaction medium for the sol-gel process, starting from tetraethylorthosilicate (TEOS) as silica precursor. The nanocomposite material resulted (SilAg) after solvent removal, aging and calcination and was investigated by infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy coupled with energy dispersive X-ray system (SEM/EDX), transmission electron microscopy (TEM), energy-dispersive X-ray fluorescence spectroscopy (EDXRF), X-ray diffraction (XRD) and dynamic vapor sorption (DVS). The results were compared to model silicas obtained without silver. A higher condensation degree in SilAg was obtained due to the basic medium used in the first step and was confirmed by a sorption capacity lower than for the model silicas. The solid surface area calculated with GAB analysis using DVS data for the water vapors is 210 m2 g−1. The nanocomposite showed good catalytic activity for hydrogen peroxide decomposition. [...]
3
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Fuzzy modeling applied to optical and surface properties of a ferrocenylsiloxane polyamide solution

100%
Pislaru M., Curteanu S., Cazacu M.
Open Chemistry
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2012
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vol. 10
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issue 1
194-204
EN
A fuzzy model was designed to predict changes in surface tension and maximum absorbance due to self-assembly in a DMF solution of poly{1,1′-ferrocene-diamide-[1,3-bis(propylene) tetramethyl-disiloxane} as a function of temperature and concentration. The building of fuzzy rule-based inference systems appears as a grey-box because it allows interpretation of the knowledge contained in the model as well as its improvement with a-priori knowledge. The method provides accurate results and increases the efficiency of utilizing the available information in the model. Small mean squared errors (0.0064 for absorbance and 0.79 for surface tension) and strong correlations between experiment and simulated results (0.93 and 0.97, respectively) were found during model validation. The results showed that it is feasible to apply a Mamdani fuzzy inference system to the estimation of optical and surface properties of a ferrocenylsiloxane polyamide solution.
4
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New iron-cobalt clusters with silicon-containing dicarboxylic acids

100%
Cazacu M., Vlad A., Turta C., Lisa G.
Open Chemistry
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2012
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vol. 10
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issue 4
1079-1086
EN
For the first time, silicon-containing dicarboxylic acids were used to prepare two new heterotrinuclear carboxylates of the composition [Fe2IIICoIIO(Bcpdps)3(H2O)3], I, where H2Bcpdps ≡ HOOC-C6H4-Si(C6H5)2-C6H4COOH, and [Fe2IIICoIIO(Ipds)3(H2O)3], II, where H2Ipds ≡ [HOOC-C6H3(CO)2N-(CH2)3-(CH3)2Si]2O. The precursor for these two complexes was trinuclear µ3-oxo-hexaacetate triaqua diiron(III)cobalt(II) cluster, {Fe 2 CoO}, in which the acetate anions were subsequently substituted by silicon-containing dianions. The resulting products were characterized by elemental analysis, thermogravimetry, Fourier Transform Infrared (FTIR), Energy-Dispersive X-ray Fluorescence (EDXRF), and Mossbauer spectroscopies (MS). The investigation by MS revealed the presence of the iron(3+) ions in high spin state and having the close environment. Thermogravimetric analysis results indicated an improving in the thermal stability by replacing acetate anions with silicon-containing carboxyl ligands. This widens the temperature range in which such compounds can be used in practical applications. [...]
5
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Preparation and characterization of new hydrogels based on poly(vinyl alcohol)/phosphoester - chondroitin sulphate

76%
Vlad-Bubulac T., Serbezeanu D., Oprea A.-M., Carja I.-D., Hamciuc C., Cazacu M.
Open Chemistry
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2013
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vol. 11
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issue 3
446-456
EN
Abstract New polymer hydrogels based on partially phosphorylated poly(vinyl alcohol) (PVA/Phosphoester) have been prepared. Fourier transform infrared spectroscopy (FT-IR) was employed to confirm PVA/Phosphoester formation. Contact angle measurements were performed to evaluate the surface characteristics of the hydrogels. The PVA/Phosphoester hydrogels were co-networked with Chondroitin sulfate (CS) in various ratios by chemical crosslinking. The synthetic-natural mixed resulted semi-IPN hydrogels were structurally and morphologically investigated by ATR - FT-IR spectroscopy and scanning electron microscopy, respectively. The swelling behavior and dynamic moisture sorption capacity of the PVA/Phosphoester (p-methyl-phenyl phosphonic dichloride) (P3)-CS semi-IPN hydrogels were followed. It was found that the performance of the semi-IPN hydrogels was influenced by the CS. By kinetic studies, it has been shown that the swelling processes occurred by an anomalous transport mechanism. Graphical abstract [...]
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