Mitica Sava

Symmetric Liquid Crystal Dimers Containing a Luminescent Mesogen: Synthesis, Mesomorphic Behavior, and Optical Properties

New thermotropic liquid crystalline dimers containing chromophoric units into calamitic mesogens have been synthesized and studied. Cyan, pyrrole, indole and diphenyl moieties were chosen as chromophoric units. The thermotropic behavior of the dimers was monitored by polarized light microscopy, differential scanning calorimetry, and variable temperature X-ray diffraction measurements. The photophysical properties were studied by UV-vis and photoluminescence spectroscopy. All the dimers have mesomorphic behavior and emit violet, indigo, or blue light, in solution and film.

New symmetric azomethinic dimer: the influence of structural heterogeneity on the liquid crystalline behaviour

The paper deals with the study of the thermotropic liquid crystalline properties of a new azomethinic symmetric dimer and some of its structural heterogeneous mixtures with one of its reagents. Their thermotropic behaviour was monitored by polarised light microscopy, differential scanning microscopy and variable temperature X-ray diffraction measurements. The influence of the structural heterogeneity on the mesomorphic behaviour was established and some similarities with the mesomorphic behaviour of the polydisperse polymers were underlined.

Bismaleimide Resins Containing Urethanic Moieties

Abstract A series of novel bismaleimide (BMIs) resins were prepared from 4-maleimidophenyl isocyanate and oligoether diols and oligoester diols. All the BMIs were characterized by IR, 1H-NMR spectra and elemental analysis. DSC studies indicated that the thermal polymerization of the BMIs carried out in the 80–260°C range, and their curing behavior was significantly affected by the molecular weight of the BMIs. The poly(aminobismaleimide) resins (V1a-e, V2a-e) obtained by Michael addition of 4,4′-diaminodiphenylmethane and 4,4′-oxydianiline in 1-methyl-2-pyrrolidinone, led to elastic films showing good mechanical properties and better thermal stability than the traditional polyurethane elastomers.

Polyimides Containing 1, 4-Dithiine Units and their Corresponding Thiophene 2, 3, 4, 5 Tetracarboxylimide Units

Polyimides containing 1, 4-dithiine units and corresponding thiophene units were synthesized by the nucleophilic substitution reaction of bis(dichloro-maleimide) arylene derivatives with sodium sulfide. Their structures were confirmed by IR and UV spectroscopy and elemental analysis. The polymers were characterized by viscosimetric measurements, softening points and thermogravimetric data.

Synthesis, Characterization and Stability of Bismaleimides Containing Ester Groups in the Backbone

Abstract A new series of bismaleimides containing ester groups in the backbone were synthesized from maleimido benzoic acid via its acid chloride with 4,4′-(hexa-fluoroisopropilidene)diphenol, 2,7-dihydroxynaphtalin, 1,3-dihydroxy-benzene and 4-hydroxyphenyl sulfone by simple condensation reaction. The monomers are characterized by IR, 1H-NMR and elemental analysis. DSC studies of these bismaleimides indicated a curing exotherm in the temperature range 260–306°C with polymerization heat 92.9–139.6 J/g. Thermogravimetric analysis of the monomers showed high thermal stability for all bismaleimides.

Synthesis and Characterization of Poly(Maleimide-Ethers) from the Reaction of Bisdichloromaleimides with 4,4′-(Hexafluoroisopropylidene)diphenol

Abstract New poly(maleimide-ethers) containing chlorine and fluorine were synthesized and characterized. They were prepared by reacting bisdichloromaleimides with 4,4′-(hexafluoroisopropylidene)diphenol. Polymers were characterized by inherent viscosity measurements and infrared (IR) spectroscopy. Thermal characterization of monomers and polymers were accomplished by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). GPC was employed for characterization of polymer Illb. In addition, the thermal stability of the polymers was evaluated by isothermal gravimetric analysis (IGA). The properties of these polymers are discussed and compared with polymers derived from bisphenol A.

Synthesis and Characterization of Novel Arylidene and Cardo Ester Bismaleimides and Poly(aminoaspartimide)s Therefrom

Six new bismaleimides (BMIs) having arylidene or cardo cycloaliphatic internal moieties were prepared by reacting 4-maleimidobenzoyl chloride with various arylidene or cardo bisphenols. The structures of BMIs were confirmed using elemental analysis data and spectroscopic (IR, 1H-NMR) characterizations. Two poly(aminoaspartimide)s (PAAs) were synthesized to exemplify one of the post-reaction abilities of the BMIs. Thermotropic liquid crystalline behavior was observed by differential scanning calorimetry and polarized light microscopy. The thermal stability of BMIs and PAAs was determined by thermogravimetric analysis and they showed good thermal stability except BMI 10, containing a cyclopentanone unit, which decomposed around 235°C. In this paper, we discuss the synthesis and characterization of these materials.

Heterocyclic Poly(bismaleimide)s. I. Synthesis and Characterization of New Poly(amino-bismaleimide)s Containing Parabanic Rings

Abstract New poly(ether-bismaleimide)s containing parabanic rings were obtained by the nucleophilic substitution reactions of 1,3-bis(4-dichloromaleimido-phenyl)parabanic acid (4) with various bisphenols. The structures of the resulting polymers were confirmed by IR and elemental analysis. The polymers are soluble in aprotic dipolar solvents and showed lower thermal stability than other polymers without parabanic rings.

New poly(4-Dichloro)maleimides: III. Synthesis and characterization of poly(ether-ester-azomethine-(4-chloro) maleimides) and poly(azomethin ester-aspartimides)

New poly[(N-ester-azo)-3-ether-4-chloro)maleimides] and poly(azomethin-ester-aspartimides) were synthesized by the reaction of N-[4-(formylphenoxy carboxylphenyl)]-3-(4-formylphenoxy)-4-chloromaleimide (3a) or N-[4-formylphenoxycarbonylphenyl)maleimide (3b) with various diamines. IR and elemental analyses confirmed the structures of the resulting polymers. A series of model compounds were synthesized to facilitate confirmation of the polymer structures. The polymers possess inherent viscosities in the range 0.17–0.42 dl g−1, solubility in aprotic dipolar solvents and 5% weight loss at temperatures above 300 °C.

SYNTHESIS, CHARACTERIZATION, AND POLYMERIZATION OF BISMALEIMIDES CONTAINING ESTER GROUPS IN THE BACKBONE AND CHLORINE ATOMS

New chlorinated bismaleimides with ester units were synthesized by the reaction of 3(4)-maleimido benzoic acid chloride [3(4)-MBAC] with 2,2-bis(3,5-dichloro-4-hydroxy-phenyl)-pro-pan and 2,2-bis(3,5-dichloro-4-ethanol phenoxy)propan using chloroform as solvent and triethylamine (TEA) as acid acceptor. The bismaleimides were polymerized with 1,2-bis[2-(4-aminophenoxy)ethoxy]ethane (BAPEE). The relationship between the structure and the properties of the obtained bismaleimides and reaction conditions for the synthesis of resin were studied. The properties of these monomers and polymers were compared with those of monomer and polymer derived from bisphenol A.