Synthesis and properties of some polyesterimides

New polyesterimides have been obtained by condensation of pyromellitic dianhydride with various aromatic diamines and by esterifying, before the actual dehydration, some carboxyl groups of polyamic acid with 4,4′bis (2-hydroxyethoxy) dinaphthyl 1,1′. Some new polyesterimides containing polynaphthalene rings in the side chain have thus been obtained. Thermal properties of the new polymers were studied by thermogravimetric analysis. Investigations were carried out by determining the decomposition temperatures and measuring the weight losses on heating polymer samples under atmospheric conditions in the presence of air. The influence of the structure of the polymers on their properties was investigated.     

Model quantum chemical studies of the electronic structure and aspects of reactivity of diol epoxides of aromatic hydrocarbons

This paper offers a unified presentation of the main ring conformers of the diol expoxides, triol carbonium ions, and tetrols related to the “bay-region” benzo ring of carcinogenic metabolites of PAH and brings forward quantitative information through ab initio SCF computations about their relative energies. It substantiates and evaluates the energy of the syn epoxide-OH4 hydrogen bond and, on the contrary, refutes the significance of an O ?H? O or an O^? ?H? O bond in the triol carbonium ions. It provides an explanation for the similar rates of acid-catalyzed hydrolysis of the syn and anti diol expoxides. It evaluates the stabilization of the triol carbonium ions due to the presence of a neighboring double bond and accounts for the spontaneous opening of protonated epoxides. Finally it accounts for cis hydrolysis of the syn diol epoxide and trans hydrolysis of the anit diol epoxide under acid conditions.     

Influence of temperature on thermodynamic properties of substituted aromatic compounds

This work presents experimental liquid densities and ultrasonic velocities for a collection of substituted aromatic compounds (isobutylbenzene, 1,3,5-trimethylbenzene, butylbenzene, isopropylbenzene, p-xylene, m-xylene and o-xylene) at the range of temperature 278.15–323.15 K and atmospheric pressure of a collection of halogenated and aromatic hydrocarbons. Fitting equations were applied to data in order to correlate for later computer-based design. The estimation of the studied properties was made by the application of different theoretical procedures. An equation of state based on the generalised Van der Waals theory which combines the Staverman–Guggenheim combinatorial term of lattice statistics with an attractive lattice gas expression and the free length theory (FLT) showed a good response at the studied conditions.     

Synthesis and properties of aromatic polyamides containing the cyclohexane structure

1,1-Bis[4-(4-carboxyphenoxy)phenyl]cyclohexane (III) and 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane (V) were prepared in two main steps starting from the aromatic nucleophilic substitution of p-fluorobenzonitrile and p-chloronitrobenzene, respectively, with 1,1-bis(4-hydroxyphenyl)cyclohexane in the presence of potassium carbonate in N,N-dimethylformamide (DMF). Using triphenyl phosphite and pyridine as condensing agents, two series of polyamides with cyclohexylidene cardo groups were directly polycondensated from dicarboxylic acid III with various aromatic diamines or from diamine V with various aromatic dicarboxylic acids in an N-methyl-2-pyrrolidone (NMP) solution containing dissolved calcium chloride. The polyamides exhibited inherent viscosities in the range of 0.45 to 1.78 dL/g. Almost all of the polymers were readily soluble in polar aprotic solvents such as NMP and N,N-dimethylacetamide (DMAc) and could afford transparent, flexible, and tough films by solution casting. The glass transition temperatures (T_g) of these aromatic polyamides were in the range of 180–243°C by DSC, and the 10% weight loss temperatures in nitrogen and air were all above 450°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3575–3583, 1999     

Structure-reactivity indices for the hydrolysis of diol epoxides of polycyclic aromatic hydrocarbons

Several different computational parameters have been used in an attempt to predict relative reactivity of carcinogenic bay-region diol epoxides. The correlation of experimentally observed hydrolytic reactivity with these parameters is described.     

Influence of the molecular structure on the phase transition temperatures of mononuclear aromatic compounds

Boiling and melting points in relation to the molecular structure were examined for 60 mononuclear aromatic compounds. Phase transition temperatures were analyzed as influenced by the structural isomerism and symmetry of the molecules.     

Synthesis,structure, and properties of aromatic polysulfides

Polycondensation of haloaromatics and sodium sulfide has been studied. An increase in reactivity of functional groups, a change of the composition of the elementary polymeric unit with a change of the relative amounts of the monomers, and a key role of side-reactions, i.e. intra(molecular) and macrocyclisation, have been revealed. Low-melting isomeric poly(phenylene sulfides), as well as their derivatives, reactive telechelic oligomers, have been prepared. New methods of preparation of poly(arene sulfides) by transarylation of diphenyl sulfide, polymerisation of cyclic aromatic sulfides, or by direct polycondensation of arenes with sulfur under the action of AlCl₃, as well as by polycondensation of aniline with sulfur in the absence of catalysts have been suggested. Structures and properties of newly prepared polymers have been studied.     

Influence of additives on the structure and properties of polymers

Investigations into the transformation of hexagonal into monoclinic modification in isotactic polypropylene (iPP) were carried out. The hexagonal phase () was obtained by crystallization from a melt of iPP samples containing small molecular compounds (additives). A decline in the amount of-modification and changes of dimensions of ordering areas, perpendicular to the chain axes of iPP, was analysed at various temperatures and times of heating.The interdependence between the structure of additives and the amount of-phase occurring and also the stability of this modification during thermal treatment was observed.Obtained results indicated that only some additives play the role of moderating agents for the phase transition process.A preliminary report of this work has been presented at XIII Congress of the International Union of Crystallography (9–18 August 1984).     

The influence of the structure of aromatic diisocyanates on the preparation and the properties of polyurethanes

The comparative reactivities of the following aromatic diisocyanates were studied: 4,4′-stilbene diisocyanate-trans, 4,4′-diisocyanatodiphenyl ether, methylene-bis-(4-phenylisocyanate), 4,4′-bibenzyl diisocyanate and 1,5-naphthalene diisocyanate. Polyurethanes were prepared from ethylene glycol and these diisocyanates. The more reactive was the diisocyanate, the less stable was the polyurethane to thermal degradation and ultraviolet radiation.     

Analysis of the relationship between the structure and aromatic properties of chemical compounds

This paper presents the results of research on the relationship between the structure and odour properties of a selection of chemical compounds. The research concerns five groups of esters, each with a different smell: almond, apricot, apple, pineapple and rose. The supposed relationship between the smell and certain selected attributes of each molecule was examined by various pattern recognition techniques using programs developed in the Department of Computer Chemistry at Rzeszów University of Technology.     

Influence of structure on the properties of polypropylene copolymers and terpolymers

Several Ziegler-Natta copolymers of iPP with ethylene or 1-butene, and terpolymers with both counits have been characterized, devoting special attention to the effect of composition and processing conditions on the crystal structure and final properties. DSC and X-ray diffraction were used to study the polymorphism of copolymers and terpolymers. Comonomer insertion interrupts the isotactic sequences, acting as a structural defect, and the formation of γ form is enhanced. Moreover, crystallinity decreases and crystal structure is modified. Comonomer type and concentration determine the extent of these modifications, resulting in important changes in macroscopic properties. In particular, the excellent optical properties of the analyzed terpolymers make them very attractive for applications such as transparent film or packaging.     

Electrostatic potential mapping of polycyclic aromatic hydrocarbon diol epoxides using a dipole

Electrostatic potential maps of benz(a)anthracene diol epoxide, benzphenanthrene diol epoxide, chrysene diol epoxide, and tryphenylene diol epoxide, which are ultimate carcinogens derived from the corresponding polycyclic aromatic hydrocarbons, have been studied using a dipole of length 1 Å and strength 1 Debye. The net charge distributions in the molecules were obtained using the MNDO molecular orbital method. The maps were drawn for two closest distances of approach between the charged ends of the dipole and atoms of the molecules. Using the electric field directions and values of electrostatic potentials, reactive sites and relative reactivities of these molecules have been examined. Existence of a bay region appears to be important for the carcinogenic activity of a diol epoxide in this class of carcinogens.     

Influence of the structure of medium-sized aromatic precursors on the reactivity of their dications towards rare gases

The gas-phase reactivity of dications generated by dissociative electron ionization of several aromatic C_mH_nN_o precursors with 4 ≤ m ≤ 13, 4 ≤ n ≤ 21, and 0 ≤ o ≤ 2 with rare gases is investigated. Whereas most of these reactions lead to monocations via simple electron transfer, proton transfer, or Coulomb explosion, the formation of organo rare-gas dications is observed in a few cases. Specifically, dications generated from 2,4,6-trimethylpyridine react with krypton and xenon to form organo rare-gas species as major products and under maintenance of the two-fold positive charge. Such a reactivity is not observed in the presence of lighter rare gases. The formation of organo rare-gas dications are also observed for dications generated from 3-vinylpyridine, N,N-dimethylaniline, isopropylbenzene, and 4-ethyltoluene as neutral precursors. In some cases, isomeric dications are characterized by very different reactivity toward rare gases, suggesting that the structure of the precursors is crucial and that electron ionization does not lead to a total scrambling of the structures of the doubly charged ions obtained.     

Influence of the amine structure on the polymerization of methyl methacrylate photoinitiated by aromatic ketone/amine

The polymerization of methyl methacrylate photoinitiated by 2‐chlorothioxanthone in the presence of amines of different structures has been investigated. The photoinitiation efficiency of these systems is highly dependent on the structure of the amine. The polymerization rate increases with the amine concentration, reaching a constant value in an amine concentration range of 10–30 mM. At these amine concentrations, aliphatic hydroxyalkyl amines are more efficient photoinitiators than the corresponding alkyl‐substituted compounds. Dimethylanilines with electron‐acceptor substituents in the 4‐position give higher polymerization rates than electron‐donor‐substituted anilines. The photophysics of these photoinitiation systems has been studied in the polymerization medium. These data show that the singlet and triplet excited states of thioxanthones are efficiently deactivated by the amine. Rate constants are well correlated to the oxidation potential of the amine. These studies have allowed us to simulate the dependence of the photoinitiation efficiency with the amine concentration and indicate that the active radicals are produced from the interaction of the ketone triplet with the amine. Also, photochemical studies have allowed us to establish that the dependence of the polymerization rate on structural features of amines is mainly due to differences in the fraction of produced active radicals that add to the monomer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2888–2893, 2002     

Relationship between chromatographic properties of aromatic carboxylic acids and their structure

The retention of aromatic carboxylic acids and their esters in reversed-phase HPLC is proportional to the sum of their partition coefficients in octanol-water system and retention increments. This equation can be used for the identification of various side-products formed in monomer production.     

Influence of monomer structure on the properties of blue phase liquid crystal

In this paper, four kinds of polymer-stabilized blue phase liquid crystals (PS-BPLCs) with different monomer were designed and prepared. The morphology, temperature ranges and electro-optical properties of the blue phase were studied and discussed. The temperature ranges of four BPLCs are more than 90°C, and all samples can be stabilized well at room temperature. Referring to electro-optical performance, on-state voltage for mono-functional monomers systems is reduced from 75 V to 65 V at 497 nm. On-state voltage for tri-functional monomers systems is reduced from 107 V to 85 V at 497 nm. These results are helpful to the application of display and photonic devices.