Gamma irradiation has been used as an alternative way of curing diol-diisocyanate by means of specific catalysts and/or elevated temperatures. A mixture of toluene diisocyanate (TDI) and hydroxy terminated polybutadiene (HTPB) oligomer were irradiated over a dose range of 0–720 kGy using a 5 kCi60Co -source. Various compositions were formulated and also suitable additives were incorporated. Disappearance of the isocyanate peak in the IR spectra was considered as a measure of its consumption. The conversion characteristics showed a profound influence of irradiation. A suitable mechanism is envisaged.
Authors:Oana Ştefănescu, Corneliu Davidescu, Mircea Ştefănescu, and Marcela Stoia
In this paper we present a study regarding the obtaining of iron oxides embedded in silica matrix, using a modified sol-gel
method. This method consists in the formation, inside the silica matrix, of some Fe(III)-carboxylate compounds, resulted in
the redox reaction between Fe(NO3)3 and diol.
We have synthesized four gels, starting from tetra-ethyl orthosilicate, Fe(NO3)3·9H2O and different diols: ethylene glycol, 1,2-propanediol, 1,3-propanediol and 1,4-butanediol, for a final composition 50% Fe2O3/50% SiO2. The obtained gels have been thermally treated at 130°C, when the redox reaction Fe(NO3)3-diol took place with formation of the precursors in the xerogels pores. The thermal decomposition of all four precursors
took place up to 300°C.
The samples obtained by annealing at 300, 500, 700°C of the four xerogels lead to crystalline phases inside the amorphous
silica matrix. γ-Fe2O3/SiO2 may be obtained as unique phase depending on the diols nature. The formation of the precursors inside the silica matrix and
the evolution of the crystalline phases were analyzed by thermal analysis, FTIR spectrometry and XRD.
New polyurethanes with mesogenic units in the main chain due to the use of a liquid crystalline chain extender were synthesized
from 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI)using diisocyanates of different trans, trans isomer content, a low molecular diol4,4'-bis(6-hydroxyhexoxy)biphenyl (BHHBP) and a high molecular poly(hexyleneadipate)diol
(PHA). The growth of trans, trans isomer content in HMDI used to syntheses of PU induces monotonic growth of melting point, rectilinear growth of crystallization
temperatures and the growth of crystallization enthalpy, both for hard segment polyurethanes and block polyurethanes. The
increase of trans, trans isomer content in HMDI increases also glass transition temperatures and dynamic storage modulus of the polyurethanes.
Authors:Oana Ştefănescu, Marcela Stoia, Mircea Ştefănescu, and Titus Vlase
Hybrid organic–inorganic materials, silica–diol, were synthesized by the sol–gel process from mixtures of tetraethylorthosilicate
(TEOS) and diols: ethylene glycol (HO–CH2–CH2–OH) and 1,3 propane diol (HO–CH2–CH2–CH2–OH), in acid catalysis. The gels have been synthesized for a molar ratio H2O:TEOS = 4:1 and different molar ratios diol/TEOS: 0.25; 0.5; 0.75; 1.0; 1.25 and 1.5. The resulting gels were studied by
thermal analysis and FT-IR spectroscopy, in order to evidence the interaction of diols with silica matrix. Thermal analysis
indicated that the condensation degree increases with the molar ratio diol/TEOS until a certain value. The thermal decomposition
of the organic chains bonded within the silica network in the temperature range 250–320 °C, leaded to a silica matrix with
modified morphology. The adsorption–desorption isotherms type is different for the samples with and without diol. Thus, the
specific surface areas have values <11 m2/g for the samples without diol and >200 m2/g for the samples with diols, depending on the annealing temperature.
105Rh[1,5,9,13-tetrathiacyclohexadecane-3,11-diol] is a promising drug precursor for targeted radiotherapy. Nevertheless, the
axial position of chloride ions in the complex structure and their weak binding to rhodium centre, due to HSAB concept, make
such a complex subject to modifying action of certain sulphuric ligands, like human plasma thiol antioxidants: glutathione
and cysteine. Experiments were performed with both radioactive 105Rh and inactive rhodium. The complexation of rhodium with 1,5,9,13-tetrathiacyclohexadecane-3,11-diol (16S4diol) resulted in three distinct peaks seen on UV, radiometric and MS chromatograms. The substitution of chlorides was noted
in over 80% of 105[Rh(16S4diol)Cl2]+ units after incubation with glutathione, and less than 10% of complex units after incubation with cysteine (24 h, 37 °C).
Reaction of 105[Rh(16S4diol)Cl2]+ with 1,8-octandithiol and 1,9-nonandithiol resulted in disappearance of the complex peak and occurrence of two new peaks.
Product of RhCl3 and 16S4diol reaction is a mixture of three distinct forms having different number of chlorine atoms. Our in vitro experiments suggest
that the substitution of axial chlorides with glutathione and cysteine might also occur in vivo in human plasma. Glutathione
shows higher reactivity than cysteine in replacement reaction. Axial positions in precursor might be effectively blocked by
1,8-octandithiol and 1,9-nonandithiol.
Authors:Marcela Stoia, Mircea Stefanescu, Mirela Barbu, Paul Barvinschi, and Lucian Barbu-Tudoran
III (NO 3 ) 3 , this diol is oxidized at malonic acid, which coordinates to these cations forming polynuclear malonates, as previously reported in the literature [ 6 , 7 ]. This reaction takes place in a similar way when the reacting mixture is
Authors:M.A. Hawrył, M. Niemiec, K. Słomka, M. Waksmundzka-Hajnos, and G. Szymczak
Micro-thin-layer chromatography in two dimensional (2D-mTLC) mode in normal and reversed phase systems by use of diol bonded stationary phase was applied to make fingerprints of 11 species of Mentha genus and two finished pharmaceutical products.
Nonaqueous eluents (propan-2-ol or ethyl acetate dissolved in n-heptane) were used in normal phase systems. Mixtures of acetonitrile with water were used in reversed phase chromatographic systems.
Optimization of one dimensional systems was performed by determining of RF vs. composition of mobile phases dependencies for standards occurring in various species of Mentha. Most selective eluents were chosen to optimize two-dimensional systems by creating RF in normal-phase (NP) systems vs. RF in reversed-phase (RP) systems correlations.
2D-mTLC on diol polar bonded stationary phase were optimized to separate phenolic compounds and make fingerprints of examined plant materials and this method was never applied earlier in the chromatographic analysis.
The structures of the inclusion compounds formed by the host 9,9’-(ethyne-1,2-diyl)bis(fluoren-9-01) with pyridine and picolines are similar and display tubular topology. The host discriminates poorly between
these guests. The kinetics of desorption of the pyridine compound is governed by the Avrami-Erofe’ev equation A2, with an
activation energy of 111(7) kJ mol−1.
The soft segment crystallinity and morphology of poly(ester-urethanes) (PEUs) based on poly(&-caprolactone) (PCL) as a soft
segment and an aliphatic diisocyanate in the hard segment were studied. It was found that the restriction of the crystallization
of the PCL soft segment depends on the hard segment concentration, the length of the soft segment, and the total molecular
mass of the PEUs. The PEU based on a low molecular mass PCL (M=2000) is an amorphous elastic material during a long time after
casting from solution or after melt crystallization. A soft-hard segment endothermal mixing transition (Tmix) of about 70-80C is observed in the DSC curves of this PEU sample.
Authors:Mircea Stefanescu, Marcela Stoia, Oana Stefanescu, and Paul Barvinschi
coordination compounds formed in the redox reaction between NO 3 − (from Fe(III), Ni(II), Zn(II) nitrates) and ethylene glycol (EG) [ 20 ].
This article presents a study on obtaining Ni–Zn ferrite nanoparticles using other polyols: 1,2-propane diol (1