Mihaela Simionescu

New poly(amide-imide) siloxane copolymers by polycondensation

Abstract Some new poly(amide-imide) siloxane copolymers have been synthesized by solution polycondensation of some aromatic diamines with siloxanic diacids having preformed imide rings. Two polycondensation techniques were used: polycondensation of aromatic diamines with diacid chlorides and direct polycondensation of aromatic diamines with diacids in the presence of organic phosphites, following the Yamazaki–Higashi phosphorylation technique. In all cases the reactions were carried out using equimolecular amounts of the two monomers, in polar aprotic solvents and inert atmosphere. The obtained compounds were characterized by elemental C, H and Si analysis, solubility tests, IR and 1H-NMR spectrometry. Thermogravimetric curves were also recorded. All data agree with the proposed structures.

Synthesis of polysilane–bis(salicyliden)ethylenediamine Ni(II) complex

Abstract This paper describes the synthesis of a new coordination polymer prepared through the polycondensation reaction of α,ω-bis(chloromethyl)-polymethylphenylsilane with the Ni(II) complex of bis(salicylidene)ethylenediamine (salen). For this purpose, a new preparation method of the chloromethylated polysilane was presented along with the synthesis and characterisation of the polymer–metal complex. IR, 1 H-NMR and UV–Vis spectral analyses as well as GPC and TGA were used to investigate the new chemical structures.

Poly(siloxaneimide)s 2. Polycondensation of some imidic diacid chlorides with aminoalkylsiloxanes

Abstract Some new poly(siloxaneimide) copolymers with good solubilities have been synthesized by solution polycondensation of aromatic diacid chlorides containing preformed imide rings with disiloxanes and siloxane oligomers having α,ω-aminopropyl functionalities. The polycondensation reactions were carried out using equimolecular amounts of the two monomers, in polar aprotic solvents and inert atmosphere. The obtained compounds were characterized by elemental C, H, and Si analysis, solubility measurements, IR and 1 H-NMR spectrometry. Thermogravimetric curves were also recorded. All data agree with the proposed structures.

GDP and Net Migration in Some Eastern and South-Eastern Countries of Europe. A Panel Data and Bayesian Approach

This paper analyzes the relationship between the GDP and the net migration using the comparative approach represented by the panel data and Bayesian analysis.

Incorporation of the siloxanes in hydrolytically degradable organic structures. II. Segmented siloxane-imide poly(anhydride)S

ABSTRACT New segmented poly(anhydride)s containing pre-formed siloxane-imide sequences have been synthesized. The synthetic strategy involves the preparation of α, ω-bis(3-aminopropyl)oligodimethylsiloxane having certain molecular weight, their chemical modification by reaction with trimellitic anhydride, and subsequent polycondensation of the obtained diacid macromers in solution. The acetylation method was used for the in situ activation of the diacids. The structures of partial and final products and their degradability were confirmed by IR and 1H NMR spectroscopy.

Polyhydrosilanes I. Synthesis

Abstract Using the well known Wurtz coupling technique, polyhydrosilanes copolymers with diphenyl - and methyl(phenyl) - sequences, were synthesised. This work describes the possibility to maintain stable Si-H group and to obtain in good yields, soluble, high molecular, functional polysilanes. IR, 1-NMR, 13C, UV spectral data, quantitative elemental Si and H (from Si-H) analyses and indirect molecular weight investigation sustain the molecular structure of the copolysilanes.

THE USE OF VARMA MODELS IN FORECASTING MACROECONOMIC INDICATORS

Although the scalar components methodology used to build VARMA models is rather difficult, the VAR models application being easier in practice, the forecasts based on the first models have a higher degree of accuracy. This statement is demonstrated for variables like the 3-month Treasury bill rate and the spread between the 10 year government bond yield, where the quarterly data are from the U.S. economy (horizon: first quarter of 2001 - second quarter of 2013). It was used a better measure of accuracy than those used in literature till now, the generalized forecast error of second moment, that was adapted to measure relative accuracy.

Polysilane—Metal Complexes for Organic Semiconductors

New polysilane-metal complexes structures were obtained by the polycondensation reaction of α,ω-bis(chloromethyl)-polymethylphenylsilane with the Ni (II) complex of bis(salicylidene)ethylenedia-mine (salen). The chloro-functionalized polysilane was obtained by a modified Wurtz coupling procedure at low temperatures. To obtain the polymer-metal complex the resulted macroligand was complexed with metal cations. This structure is characterized by a highly localized electroactivitry in the redox moiety combined with a specific σ conjugative effect in the polysilane chain. Infrared, 1H NMR and UV-vis spectral analysis as well as gel permeation chromatography and thermogravimetric analysis were used to investigate the new chemical structures.

Synthesis and Characterization of New α,ω-Bis(Maleimide-Ester) Substituted Siloxane Oligomers

Abstract Organofunctional siloxane oligomers containing maleimide were synthesized by condensation reaction of α. ω-hydroxypropylsiloxane oligomers with n-[4-(chlorocarbonyl)phenyl]maleimide. A model compound [bis(maleimide-ester)disiloxane] was obtained to facilitate the characerization of the oligomers. Then, the heterogeneous catalyzed ring-opening cationic polymerization technique was applied to obtain an oligomer starting from the model compound and octamethylcyclotetrasiloxane. The structures of the resulting oligomers were confirmed by elemental analysis, IR and 1H-NMR spectroscopy. They were characterized by determining softening points, solubility and studying their thermal behavior by thermogravimetric (TGA and differential scanning calorimetry (DSC) measurements.

Microwave-Assisted Synthesis of Functional Polysilanes

The presence of reactive Si–H groups in polyhydrosilanes allows to obtain different polysilane structures with various functionalities through catalytic addition of unsaturated organic compounds. An efficient synthesis method of such functional polysilanes has been achieved using a conventional method as well as microwave irradiation. The effect of microwave irradiation on chemical reactions is generally evaluated by comparing the time needed to obtain a desired yield of final products with respect to conventional thermal heating. Research in the area of chemical synthesis has shown some potential advantages in the ability not only to drive chemical reactions but to perform them in reduced time-scale. Comparison of microwaveassisted synthesis of functional polysilanes with the conventional synthetic method demonstrates advantages related to shorter reaction times, better reaction yields and milder reaction conditions, a fact that allows a better protection of polysilane chemical structure.