Synthesis and characterization of novel polyarylates bearing NLO moieties

A series of thermally stable second‐order nonlinear optical polyarylates containing azo side‐chain groups have been obtained by interfacial polycondensation. Theoretical calculations of the static hyperpolarizabilities, first‐ and second‐order hyperpolarizability, were carried out. The structures of the obtained monomers and polymers were confirmed by infrared, ¹H NMR and ultraviolet spectroscopies. Thermal and optical properties of the obtained polymers were evaluated. The investigations show that some of the new polymers obtained in this study may find use in optical applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2195–2201, 2006     

Synthesis and Optical Properties of Nonlinear Optical Polyarylates

Several polyarylates based on bisbenzylidenoketones have been synthesized by interfacial polycondensation. Two distinct types of polymers have been obtained: guest-host systems and polyarylates with NLO (nonlinear optical) side chains. The dispersion of the linear refractive index (n ₀) is measured over the wavelength range from 800 to 2000 nm. The Holing formula, based on a semiclassical model of a simple harmonic oscillator, is used to calculate the NLO susceptibility X⁽³⁾.     

Variability of water uptake studies of biomedical polymers

Water uptake influences many properties of polymers and has been widely studied. In the context of polymeric biomaterials, several publications reported an unusual high variability of analytical results, without further investigating the cause for this phenomenon. Using selected polymers from the library of L ‐tyrosine‐derived polyarylates and poly(D ,L lactic acid), we showed that nonaged and nonannealed compression molded film samples exhibit the typical large variation in water uptake observed in previous reports. The introduction of an annealing step allows accurate and reproducible water uptake measurements for these polymers. We evaluated the use of ³H‐radiolabeled water for the determination of water uptake, finding that the use of radiolabeled water yields statistically indistinguishable measurements, compared to gravimetric methods, while providing significant advantages in throughput and sensitivity. Using the recommended methods of annealing and ³H‐radiolabled water, the water uptake profiles of 24 polymers of the library of L ‐tyrosine‐derived polyarylates are reported. This article addresses experimental concerns related to water uptake studies and may assist other researchers in improving the accuracy of their water uptake results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Dynamic mechanical analysis and interpretation of molecular motions in polyarylates

Molecular motions in polyarylates synthesized from substituted bisphenols have been investigated by dynamic mechanical analysis. Substitution at the ring carbon atom results in a more pronounced enhancement in glass transition temperature (T_g) as compared to substitution at the bridge carbon atom. The enhancement in mono and disubstituted polyarylates is more consistent than that in the case of polycarbonates and polysulfones. The β transition has been shown to result from defects in the polymer samples. The molecular motion responsible for the τ transition in polyarylates has been shown to be more iocalized than in the case of polycarbonates. Introduction of the phthalide ring in the isopropylidene unit of bisphenol-A molecule results in splitting of the τ transition peak into two. The results have been compared with those reported for other bisphenol-based polymers, viz. polycarbonates and polysulfones, and explained on the basis of the structural attributes of the polymers. © 1994 John Wiley & Sons, Inc.     

Synthesis and properties of aromatic polyesters and brominated polyesters derived from α,α′-bis(4-hydroxyphenyl)-1,4(or 1,3)-diisopropylbenzene

The interfacial polycondensation technique was used for the preparation of polyarylates and brominated polyarylates. Polyarylates and brominated polyarylates were prepared by mixing a solution of diacid chloride such as terephthaloyl chloride, isophthaloyl chloride, or their mixture in dichloromethane with an aqueous alkaline solution of ,-bis(4-hydroxyphenyl)-1,4(or 1,3)-diisopropylbenzene or ,-bis(4-hydroxy-3,5-dibromophenyl)-1,4(or 1,3)-diisopropylbenzene using triethylbenzylammonium chloride as the phase transfer agent. Moderate to high molecular weight polyarylates with _inh up to 1.27 dL/g were obtained, and most of them could be cast into tough and flexible films depending on the polymer composition. In general, polymers containing more 1,3-isomer or isophthaloyl chloride moieties gave transparent and flexible films and had lower glass transition temperatures and higher solubility. Although these polymers have two isopropylidene linkages in their repeating units, they still exhibit moderately high thermal stability and show no obvious weight loss before 400 °C. The introduction of bromine on the polymer backbone caused a decrease of inherent viscosity, crystallinity, and thermal stability of the polyarylates, while causing an increase in glass transition temperature and a great enhancement of fire retardancy.     

Synthesis and photophysical properties of novel organo-soluble polyarylates bearing triphenylamine moieties

Two series of new blue photoluminescent aromatic polyesters (polyarylates) were synthesized from 4,4′-dicarboxytriphenylamine and 4,4′-dicarboxy-4″-methyltriphenylamine with various bisphenols by the diphenylchlorophosphate (DPCP) activated direct polycondensation in a medium of pyridine and lithium chloride. These polymers were amorphous and readily soluble in various common organic solvents including DMAc, THF, and chloroform, and could be cast from their chloroform solutions into transparent films due to their excellent solubility. These polyarylates exhibited moderately high T _g values (186–264 °C) and thermal stability. In THF solution, these triphenylamine-containing polyarylates showed UV-Vis absorption bands at 359–365 nm and photoluminescence peaks around 427–451 nm in the blue region. Figure Two series of new blue photoluminescent aromatic polyesters (polyarylates) were synthesized from 4,4’-dicarboxytriphenylamine and 4,4’-dicarboxy-4”-methyltriphenylamine with various bisphenols by the diphenylchlorophosphate (DPCP) activated direct polycondensation in a medium of pyridine and lithium chloride. These polymers were amorphous and readily soluble in various common organic solvents including DMAc, THF, and chloroform, and could be cast from their chloroform solutions into transparent films due to their excellent solubility. These polyarylates exhibited moderately high Tg values (186-264 oC) and thermal stability. All the PL spectra of these polymers showed a blue shift when the solvent was changed from NMP to THF or chloroform. Solvation should increase the interaction between polymer chain and solvent, which may consume certain excitation energy and lead to increase on the emission wavelength.     

Synthesis and characterization of readily soluble polyarylates derived from either 1,1‐bis(4‐hydroxyphenyl)‐1‐phenylethane or tetramethylbisphenol A and aromatic diacid chlorides

A series easily soluble polyarylates were synthesized from either 1,1‐bis(4‐hydroxyphenyl)‐1‐phenylethane or tetramethylbisphenol A with various aromatic diacid chlorides by the two‐phase interfacial polycondensation. These polyarylates have the inherent viscositiesin the range of 0.36–0.97 dL/g, and their number‐average and weight‐average molecular weights determined by gel permeation chromatography are 14,200–43,200 and 31,900–102,500, respectively. All these polyarylates are readily soluble in a wide range of organic solvents, thus these polymers can be convenient to process into heat resistance films by cast, spin‐ or dip‐coating. The polyarylates have the glass transition temperatures in the range of 165.0–201.6°C. The pendent phenyl‐containing polyarylates reveal excellent thermal stability, and their initial degradation temperatures are all above 480°C and char yields at 700°C are 37.97–40.53% in nitrogen atmosphere. However, the polymers prepared from tetramethylbisphenol A have a large decrease in thermal stability, and their initial degradation temperatures in nitrogen are only about 440°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Functional polyesters and copolyesters based on the 4,4′-dihydroxy-α-methylstilbene

Liquid crystalline (LC) thermotropic main-chain polyesters and copolyesters based on 4,4′-dihydroxy-α-methylstilbene (mesogen) and azelaoyl chloride (flexible spacer) and 10,12-docosadiynedioyl chloride [ultraviolet (UV)-crosslinkable moiety] were synthesized by interfacial polymerization. Improvement of molecular weight was achieved by the modification of interfacial polymerization. Molecular weights of the LC polymers ranged from 13,000 to 56,500 g/mol⁻¹, depending on composition of the LC polymers. Mesomorphic properties of these polymers were studied, and phase diagrams were established. Polymers showed nematic and smectic mesophases, depending on the flexible spacer composition. UV-crosslinking of the LC polymers containing UV-sensitive diacetylenic groups was attempted, and crosslinked LC polymer films were obtained. Mechanical properties of LC polymer films were also studied with a dynamic mechanical analyzer. The storage moduli of the polymer films, depending on the molecular weight of the polymers, increased by the UV-crosslinking. Higher molecular weights and crosslinking were favorable for the higher storage moduli of the films. The effect of orientation on the mechanical properties was also studied, and it was found that orientation induced the increase of the moduli of the films. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 387–393, 1998     

One-pot melt synthesis of resorcinol based polyarylates for UV-stable coatings

A new one-pot method for the melt synthesis of polyarylates based on resorcinol and phthalic acids has been developed. The method consists in the reaction of diphenyl carbonate, phthalic acids and resorcinol using titanium butoxide as catalyst. Model reactions have shown that the diaryl ester is generated in situ by reaction of the aromatic diacid and of the aromatic diol with diphenyl carbonate. It is thus possible to obtain polymers with tailored end-groups and molecular weight, by changing the molar ratio of the monomers and the reaction conditions. More specifically, we applied this method to the synthesis of low molecular weight polymers with carboxylic end-groups, suitable for powder coating applications. The literature actually reports that resorcinol based polyarylates present an outstanding long-term UV stability and therefore COOH terminated oligomers are highly promising materials for the preparation of super-durable powder coatings.     

Polyarylates (polyesters from aromatic dicarboxylic acids and bisphenols)

After a short review on the literature of aromatic polyarylates synthesis the following aspects are described: preparation of some monomers; preparation of the polymers by different chemical processing routes; physical properties; moulding behaviour. Amorphous polymers are especially considered. Figures on continuous melt condensation via the diphenylester route are given. Some polyarylates have attractive mechanical and electrical properties. Injection moulding is only possible if the glass temperature is not too high (≤200°C), and even with these polymers thermal decomposition during injection moulding is a limiting factor for their technical use. The weak point is the ester group. Extrusion, pressing, and solution casting are technically feasable.     

Ionic conductivity,dielectric behavior,and HATR–FTIR analysis onto poly(methyl methacrylate)–poly(vinyl chloride) binary solid polymer blend electrolytes

Solid polymer electrolytes comprising blends of poly(vinyl chloride) (PVC) and poly(methyl methacrylate) (PMMA) as host polymers and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) as dopant salt were prepared by solution‐casting technique. The ionic conductivity and dielectric behavior were investigated by using AC‐impedance spectroscopy in the temperature range of 298–353 K. The highest ionic conductivity of (1.11 ± 0.09)×10^?6 S cm^?1 is obtained at room temperature. The temperature dependence of ionic conductivity plots showed that these polymer blend electrolytes obey Arrhenius behavior. Conductivity–frequency dependence, dielectric relaxation, and dielectric moduli formalism were also further discussed. Apart from that, the structural characteristic of the polymer blend electrolytes was characterized by means of horizontal attenuated total reflectance–Fourier transform infrared (HATR–FTIR) spectroscopy. HATR–FTIR spectra divulged the interaction between PMMA, PVC, and LiTFSI. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dielectric properties of polymers containing dispersed TCNQ salts

Tetracyanoquinodimethane salts have been incorporated into insulating polymers to raise their dielectric constants. Cast films prepared from mixtures of insulating polymers and tetracyanoquinodimethane salts in a solvent show a high dielectric constant (>20). The dielectric constant of the films varies with the tetracyanoquinodimethane salts. High values were attained with the films containing high-conducting tetracyanoquinodimethane salts. These values remain constant over a range of frequencies (10²–10⁴ Hz). Dissipation factors and electric strength values of the films are also reported.     

Molecular modeling and synthesis of polymers for use in applications requiring a low-k dielectric

As integrated circuits have become more and more complex and with smaller and smaller feature sizes several limitations have become apparent. One of these is the need for low-k dielectric materials as insulating layers. Recent work has reported promising materials for such insulators that include some fluorinated polymers. These dielectric materials were further improved by introducing porosity into the polymer films. One of the key factors in the dielectric constant of a material is its density. As the polarization of the material is related to the number of bonds, the dielectric constant will scale with the density. In this paper a series of molecular modeling calculations were conducted on various fluorine substituted polymers in order to predict their densities. A surprising result of these calculations was the prediction that some of the polymers would have densities less than 1 g/cm³. One of these polymers was synthesized and the density determined. The calculated density was in extremely good agreement with the experimental density. This paper will present the details of the molecular modeling technique as well as the synthesis and characterization of one of the polymers of interest.     

Synthesis and characterization of polyazomethine conducting polymers and oligomers

Conjugated polyazomethine polymers were prepared from the polycondensation of terephthalaldehyde with 4,4′-thiodianiline, and 4,4-thiodibenzaldehyde with 4,4′-thiodianiline, 4,4′-phenylenediamine and benzidine. The polymers showed good stability in air and were soluble in many organic solvents. The electrical conductivities of the undoped and doped (H₂SO₄ and I₂) polymers were studied. Doping the polymers markedly increased their conductivities from 10^?8 ? 10^?11 S cm^?1 (dielectric region) to 10^?3 ? 10^?5 S cm^?1 (semiconducting region). The polymers were characterized by IR spectroscopy, elemental analyses, viscosity measurements and X-ray diffraction. Furthermore, polyazomethine oligomers were prepared and a comparative study of the physical properties of the oligomers and their corresponding polymers was performed. The electrical behavior of the oligomers was studied. It was found that oligomers with a minimum of eight aromatic (Ar) rings gave almost the same electrical conductivities as long-chain polymers.     

Dielectric and Thermal Behavior of Ethyl and Butyl Methacrylate and N-p-cyano-phenyl Maleimide Copolymers

N-p-Cyano-phenyl maleimide PCPMI was prepared and copolymerized with ethyl and butyl methacrylate in order to study the effect of introducing a strong dipole along the polymer backbone. The copolymer composition was determined by elemental analysis and ¹H NMR spectroscopy. The molecular mass of the copolymers was determined by GPC. The glass transition temperature was measured and it was found to correlate well with the chemical structure, and increases with the increase of the maleimide content. The dielectric behavior of the homo methacrylate polymers and the copolymers was measured in the frequency range of 0.01 Hz to 10 MHz at different temperatures. The dielectric data were compared with the two Cole–Cole parameters equation. The glass transition temperature obtained from DSC measurements agreed well with the dielectric relaxation data.     

Detection of secondary relaxation in polyacetal,polycarbonate and polyether–sulfone by ultrasonic and dielectric methods

The ultrasonic pulse echo technique in the range of frequencies between 1 and 5.7 MHz and temperatures between 170 and 360 K is used to detect the secondary relaxations in polyacetal, polycarbonate, and polyether–sulfone. The activation energies and the relaxation frequencies were calculated and they were found to be comparable in value. The dielectric permittivity ε′ and loss factor tan δ for such polymers were also studied over a frequency range from 10² and 10⁵ Hz and temperatures between 30 and 80°C. At higher temperatures, the polymers possess better dielectric properties.     

Thermal properties and enthalpy relaxation of tyrosine-derived polyarylates

Sixteen degradable, tyrosine-derived polyarylates with well-defined chemical structures were used to study the effect of polymer structure on the glass transition temperature and enthalpy relaxation kinetics (physical aging). These polyarylates compose a model system where the number of methylene groups present in either the pendent chain or the polymer backbone can be altered independently and in a systematic fashion. Quantitative differential scanning calorimetry was employed to measure the glass transition temperature and the enthalpy relaxation kinetics. Correlations between these material properties and the polymer structure were established. The glass transition temperature of this family of polymers ranged from 13 to 78°C. The addition of methylene groups to either the pendent chain or the polymer backbone made a fairly constant contribution to lowering the glass transition temperature. The rate of enthalpy relaxation increased with an increasing number of methylene groups in the polymer backbone, but was independent of the number of methylene groups in the pendent chain. This observation indicated that the rate of enthalpy relaxation in these polymers was limited by the mobility of the polymer backbone. The enthalpy relaxation data was fitted to the Cowie-Ferguson model and the relaxation times obtained ranged from 44 min to about 100 min. Although these structure-property correlations facilitate the design of new materials with predictable thermal properties, they are rarely investigated for biomedical polymers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1441–1448, 1997     

DC Conductivity of some Polyazomethines

Eight polyazomethine polymers were synthesized with different backbone structures and side groups attached. Five of these polymers, with high melting point, were subjected to DC conductivity (σ) measurements versus temperature change (300–500K). The annealed samples show consistent behaviour. The [log σ] versus [1/T] curves for the undoped polymers can be divided into two parts: a nearly independent (low temperature) region, and an activated (high temperature) region with an activation energy of about 0·5eV. The values of σ for the undoped polymers lie in the dielectric domain (σ≃10^-11–10^-10Scm^-1). Iodine and concentrated sulphuric acid were used as dopants. The doped polymers show a sudden dramatic increase in σ up to 10^-7–10^-6Scm^-1, which brings the doped polymers into the semiconductor domain. This was sometimes accomplished in steps. All the results are interpreted by the energy band model with the formation of bipolarons. © of SCI.     

Synthesis and Structure-Property Study of Polyarylates Derived from Bisphenols with Different Connector Groups

Several polyarylates were synthesized from the interfacial or high-temperature solution polycondensation reactions of four bisphenols including 2,2-bis(4-hydroxyphenyl)propane (BPA), 2,2-bis(4-hydroxyphenyl)hexafluoropropane (BPAF), 1,1-bis(4-hydroxyphenyl)-1-phenylethane (BPAP), and 1,1-bis(4-hydroxyphenyl)-1-phenyl-2,2,2-trifluoroethane (BPAPF) with various aromatic diacyl chlorides. The basic properties such as inherent viscosity, film-forming capability, crystallinity, and mechanical and thermal properties and the “structure-property” relationships of these polyarylates were investigated. The polyarylates derived from asymmetric BPAP and BPAPF had lower crystallinity and higher solubility and glass-transition temperature (T_g) than the corresponding counterparts based on symmetric BPA and BPAPF. The fluorinated polyarylates revealed higher T_g values and decomposition temperatures than the corresponding nonfluorinated polyarylates.     

An infra-red investigation of cardo polymer solutions

Intermolecular interaction of certain cardo polyarylates, polyamides, polyimides with solvents such as chloroform, sym.-tetrachloroethane, m-cresol, has been investigated. Integrated intensities for the carbonyl stretching bands point to the formation of hydrogen bonds with solvent molecules. The lactone carbonyl is most capable of forming such a bond. The formation of hydrogen bond in polyamides is weakened by the polymer interchain interaction. The proportion of the solvated lactone carbonyls decreases when passing to polymers with more rigid chains.