Synthesis and characterization of controlled molecular weight disulfonated poly(arylene ether sulfone) copolymers and their applications to proton exchange membranes

tert-Butylphenyl terminated disulfonated poly(arylene ether sulfone) copolymers with controlled molecular weights (M_n), 20-50 kg mol⁻¹, were successfully prepared by direct copolymerization of the two activated halides, biphenol and the endcapper, 4-tert-butylphenol. The high molecular weight copolymer (molecular weight over 80 kg mol⁻¹) was also synthesized with 1:1 stoichiometry without an endcapping reagent. The chemical compositions and the molecular weights of the endcapped copolymers were characterized by their ¹H NMR spectra utilizing the 18 unique protons at the chain ends. Modified intrinsic viscosity measurements in 0.05 M LiBr/NMP solution further correlated well with NMR results. Combining the endcapping chemistry with proton NMR end group analysis and intrinsic viscosity measurements, one can demonstrate a powerful tool for characterizing molecular weight of sulfonated poly(arylene ether sulfone) random copolymers. This enables one to further investigate the influence of molecular weight on several critical parameters important for proton exchange membranes, including water uptake, in-plane protonic conductivity and selected mechanical properties. These are briefly discussed herein and will be more fully described in subsequent publications.     

Purity characterization of 3,3′-disulfonated-4,4′-dichlorodiphenyl sulfone (SDCDPS) monomer by UV–vis spectroscopy

The purity of the disulfonated monomer, 3,3′-disulfonated-4,4′-dichlorodiphenyl sulfone (SDCDPS), is very important for obtaining high molecular weight disulfonated poly(arylene ether sulfone) random or block copolymers, which are promising candidates for proton exchange membrane (PEM) fuel cells. For commercialization purposes, direct use of unrecrystallized SDCDPS monomer with known purity in the copolymerization favorably influences its economics relative to the traditional recrystallization purification process. In this paper, a novel method to characterize the purity of the prepared unrecrystallized SDCDPS has been developed using UV–vis spectroscopy. The purity of the comonomer was determined from a Beers Law calibration curve developed using a highly purified SDCDPS sample. High molecular weight poly(arylene ether sulfone) random copolymers, based on this unrecrystallized SDCDPS monomer, 4,4′-dichlorodiphenyl sulfone (DCDPS), and 4,4′-biphenol monomers, were successfully synthesized. The molecular weight obtained from gel permeation chromatography (GPC) (M_n > 45 kg mol^?1) was high enough to allow tough films for PEMs to be solvent cast. This confirmed that the purity characterization method was relatively accurate and applicable. The effect of storage and drying time of SDCDPS were also studied using Beer's Law plots.     

Multiblock poly(arylene ether nitrile) disulfonated poly(arylene ether sulfone) copolymers for proton exchange membranes: Part 1 synthesis and characterization

A series of multiblock copolymers based upon alternating segments of a hydrophilic disulfonated poly(arylene ether sulfone) and a hydrophobic fluorine-terminated poly(arylene ether benzonitrile) (6FPAEB) were synthesized and characterized for use as proton exchange membranes (PEM). The ion-exchange capacity of the block copolymers were varied by utilizing 4,4′-biphenol or hydroquinone in combination with 3,3′-disulfonated-4,4′-dichlorodiphenyl sulfone (SDCDPS) to form the hydrophilic segments. The alternating block copolymer morphology was achieved by using mild temperatures to link the oligomers together and minimize ether–ether interchange reactions. Both the 4,4′-biphenol and hydroquinone based membranes showed high proton conductivity with moderate water uptake and good mechanical properties. The block copolymers displayed nanophase separated morphologies, confirmed by transmission electron microscopy (TEM) and small angle x-ray scattering (SAXS). The strong membrane performance was attributed to the multi-phase morphology.     

Macrocycles 25. Cyclic poly(ether sulfone)s derived from 4-tert-butylcatechol

Poly(ether sulfone)s were prepared by polycondensation of silylated 4-tert-butylcatechol and 4,4′-difluorodiphenylsulfone in N-methylpyrrolidone. The feed ratio and the reaction time were varied to study the influence of stoichiometry and conversion on molecular weight and extent of cyclization. Molecular weights and molecular weight distributions (MWD)s were characterized by SEC measurements calibrated with polystyrene. Light scattering confirmed that calibration with polystyrene gives reasonable results and revealed a tendency towards a bimodal MWD for the samples rich in cycles. The MALDI-TOF mass spectrometry indicated that the extent of cyclization increased with higher conversion and with optimization of the stoichiometry. This interpretation was confirmed by ¹H NMR endgroup analyses. For the samples with the highest molar masses only mass peaks of cycles were found, which were detectable up to 20 000 Da before and up to 27 000 Da after fractionation. Via the pseudo-high dilution method low molar mass poly(ether sulfone) containing more than 95 mol% of cycles were prepared, and even these low molar mass samples had broad MWDs. DSC measurements indicated that the glass transition temperatures depend on the structure of the endgroups and increase with higher fractions of cycles.     

Synthesis and characterization of poly(aryl ether sulfone) copolymers containing terphenyl groups in the backbone

A linear rigid bisphenol monomer, 4,4′-dihydroxyterphenyl (DHTP), has been incorporated into poly(aryl ether sulfone)s (PAESs) in a study to impart crystallization to these amorphous polymers. The PAES made from DHTP and dichlorodiphenylsulfone (DCDPS) is semi-crystalline but not soluble or thermally processable. Three bisphenols, 4,4′-isopropylidenediphenol (BPA), 4,4′-(hexafluoroisopropylidene)diphenol (BPAF) and 4,4′-dihydroxybiphenyl (BP), have been copolymerized with DHTP and DCDPS in order to study the effect of structure on crystallinity and processability. Both random and segmented copolymers containing different amounts of DHTP have been prepared via standard solution nucleophilic aromatic substitution polymerization technique. Only segmented polysulfone containing 50% BP and 50% DHTP was found to be semi-crystalline. This PAES had a melting temperature (T_m) 320 °C in the first heating cycle of a DSC measurement and the presence of crystallites was confirmed by wide angle X-ray diffraction (WAXS).     

Synthesis and properties of polyimides from isomeric bis(dicarboxylphenylthio)diphenyl sulfone dianhydrides

4,4′-Bis(3,4-dicarboxyphenylthio)diphenyl sulfone dianhydride(4,4′-PTPSDA) and 4,4′-bis(2,3-dicarboxyphenylthio)diphenyl sulfone dianhydride(3,3′-PTPSDA) were synthesized from chlorophthalic anhydrides and bis(4-mercaptophenyl)sulfone. Their structures were determined via IR spectra, ¹H NMR and elemental analysis. A series of polyimides were prepared from isomeric PTPSDAs and aromatic diamines in 1-methyl-2-pyrrolidinone (NMP) via the conventional two-step method. Polyimides based on 4,4′-PTPSDA and 3,3′-PTPSDA have good solubility in polar aprotic solvents and phenols. The 5% weight-loss temperatures of isomeric polyimides were near 500 °C in N₂. DMTA and DSC analyses indicated that the glass-transition temperatures of polyimides from 3,3′-PTPSDA are higher than those of polyimides from 4,4′-PTPSDA. The wide-angle X-ray diffraction showed that all polyimides are amorphous. The polyimides from 3,3′-PTPSDA showed higher permeability but lower permselectivity compared with those from 4,4′-PTPSDA.     

Synthesis and characterization of polyimides and co-polyimides having pendant benzoic acid moiety

A novel diamine monomer, 2,4-diamino-4′-carboxy diphenyl ether had been synthesized. Several polyimides were prepared by reacting this diamine with commercially available dianhydrides, such as benzophenone tetracarboxylic acid dianhydride (BTDA), 4,4′-bis{hexafluoroisopropylidene bis (phthalic anhydride)}(6-FDA), oxydiphthalic anhydride (ODPA) and 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA). Furthermore, copolymers from the resulting diamine and oxydianiline (ODA) with 6 FDA were also synthesized. The inherent viscosities of the polymers were 0.42-0.67 dl g⁻¹. The polymers have good solubility in polar aprotic solvents, high thermal stability up to 410 °C in nitrogen and high glass transition temperatures (T_g) ranging from 260-330 °C. These polymers formed tough flexible films by solution casting.     

An examination of the thermorheological and drug release properties of zinc tetraphenylporphyrin-containing thermoresponsive hydrogels, designed as light activated antimicrobial implants

This study describes the thermorheological, mechanical and drug release properties of novel, light-activated antimicrobial implants. Hydrogels, based on N-isopropylacrylamide (NIPAA) and hydroxyethylmethacrylate (HEMA) and either devoid of or containing zinc tetraphenylporphyrin, were prepared by free radical polymerisation and characterised using oscillatory rheometry and texture profile analysis. Drug release was studied at both 20 and 37 °C. Hydrogels containing NIPAA exhibited a sol-gel temperature (Tm), which increased as the proportion of HEMA increased and was . The viscoelastic properties (storage modulus G^′, loss modulus G^″, loss tangent and dynamic viscosity η^′) were affected by hydrogel composition and temperature, with the copolymers exhibiting lower values of G^′,G^″ and η^′ values than either homopolymer. Similar relationships between the composition of the hydrogels and the textural/mechanical properties were observed. At 37 °C rheological structuring (increased G^″,G^″,η^′ and reduced loss tangent) occurred for all NIPAA-containing polymers and increased as the NIPAA content increased. At 20 °C drug release was diffusion controlled, the rate of which was similar for all NIPAA-containing polymers and was lower than drug release from p(HEMA), despite the greater elasticity of this homopolymer. At 37 °C drug release from the NIPAA-containing hydrogels was initially non-diffusion controlled, following which drug release levelled. Drug release decreased as the NIPAA content increased and correlated to hydrogel elasticity. It is suggested that the ability to engineer the release of Zn-TPP from these hydrogels, in conjunction with their acceptable mechanical properties, may be clinically advantageous for the treatment of infection.     

Shear thickening behavior of dilute poly(diallyl dimethyl ammonium chloride) aqueous solutions

Using dynamic light scattering (DLS) and capillary dynamic viscoelasticity (DVE) analyzer, we investigated dilute (0.5 mg/ml) poly(diallyl dimethyl ammonium chloride) (PDADMAC) aqueous solution properties for three different molecular weights of PDADMACs mixed with various concentrations of NaCl. The dependence of PDADMAC molecular chain conformations in aqueous solutions on polymer molecular weight and NaCl concentration were studied. By analyzing dynamic shear viscosity η′(ω), viscoelastic relaxation times t_r, and shear rate at tube wall ?_a(ω) of PDADMAC aqueous solutions in oscillatory flows, we proposed that polymer chain conformations varied with increasing shear frequency ω via the following steps: intra-polymer associations, dissociation of intra-polymer associations, stretching of polymer chains, inter-polymer aggregations, and dissociations of inter-polymer aggregations. The intra-polymer associations lowered the n′ exponent of storage modulus G′(ω) (G′(ω) ∼ ω^n′) with n′ < 2, and the polymer chain stretching and inter-polymer aggregations caused shear thickening (i.e. upturn of η′(ω)) of PDADMAC aqueous solutions. The behaviors of the lowering of n′ exponent with n′ < 2 and the shear thickening were favored by increasing ionic strength of solutions. By comparing η′(ω) data with DLS hydrodynamic radii (R_h) data, we also confirmed the possibility of inter-polymer aggregations in dilute solutions when polymer chains were stretched in oscillatory flows.     

Low-swelling proton-conducting copoly(aryl ether nitrile)s containing naphthalene structure with sulfonic acid groups meta to the ether linkage

Wholly aromatic poly(aryl ether ether nitrile)s containing naphthalene structure with sulfonic acid groups meta to ether linkage (m-SPAEEN), intended for fuel cells applications as proton conducting membrane materials, were prepared via nucleophilic substitution polycondensation reactions. The incorporation of rigid naphthalene structure with meta-sulfonic acid groups was with the intent of improving the aggregation of hydrophilic and hydrophobic domains and to increase the acidity and conductivities. m-SPAEEN copolymers were readily synthesized by potassium carbonate mediated nucleophilic polycondensation reactions of commercially available monomers: 2,6-difluorobenzonitrile (2,6-DFBN), 2,8-dihydroxynaphthalene-6-sulfonate sodium salt (2,8-DHNS-6), and 4,4′-biphenol (4,4′-BP) in dimethylsulfoxide (DMSO) at 160-170 °C. The sulfonic acid group content (SC), expressed as a number per repeat unit of polymer, ranged from 0 to 0.6 and was readily controlled by changing the feed ratio of 2,8-DHNS-6 to 2,6-DFBN. High thermal stability of m-SPAEEN copolymers was indicated by observed glass transition temperatures (T_gs) ranging from 223 to 335 °C in sodium salt form and from 230 to 260 °C in acid form (m-SPAEENH) and decomposition temperatures (T_d)s over 250 °C in acid form and over 350 °C in sodium form in both nitrogen and air. All m-SPAEENH copolymers exhibited reasonable flexibility and tensile strength in the range of 39-78 MPa, indicating they were mechanically stronger than Nafion^®117, which had an approximate value of 10 MPa under the same test conditions. As expected, m-SPAEENH copolymers showed considerably reduced moisture absorption compared to previously prepared sulfonated hydroquinone based poly(aryl ether nitrile). m-SPAEENH copolymers also showed improved proton conductivities. Proton conductivity curves parallel to that of Nafion 117 were obtained with proton conductivity of 10⁻¹ S/cm at equivalent ion exchange capacities (IEC) of 1.6 and 1.9, comparable to Nafion^®117. The best compromise combining PEM mechanical strength, water swelling and proton conductivity, was achieved at SC of 0.5 and 0.6.     

Electrosynthesis and structural characterization of a novel aryl ether trimer

The structure of a novel trimer formed by three p-tert-butyl anisole moieties via the controlled potential electrolysis of p-tert-butyl anisole was determined by X-ray diffraction method. By cyclic voltammetry, we report a multistep electron transfer, each followed by a chemical reaction, resulting in an ECECEC mechanism. Preparative scale oxidation of p-tert-butyl anisole in dry acetonitrile leads to its two first oligomers. The symmetrical dimer, 2,2′-dimethoxy-5,5′-di-tert-butylbiphenyl, shows that the favored coupling sites are those in the ortho position of the methoxy group. The title compound, namely the 1-methoxy-bis-2,3-(2′-methoxy-5′-tert-butylphenyl)-4-tert-butylbenzene crystallizes in triclinic space group P-1 with a = 10.571(3) Å, b = 11.739(1) Å, c = 12.733(2) Å, α = 74.64(1)°, β = 88.71(2)°, γ = 76.58(2)°, V = 1480.8(5) Å³, and Z = 2. The structural analysis reveals that two p-tert-butyl anisole moieties are linked in ortho position on a third p-tert-butyl anisole fragment.     

Synthesis and characterization of soluble copoly(arylene ether sulfone phenyl-s-triazine)s containing phthalazinone moieties in the main chain

A series of new poly(arylene ether sulfone phenyl-s-triazine) copolymers containing phthalazinone moieties in the main chain (PPESPs) were prepared by a direct solution polycondensation of 4-(4-hydroxylphenyl)(2H)-phthalazin-1-one (HPPZ) with 2-phenyl-4,6-bi(4-fluorophenyl)-1,3,5-triazine (BFPT) and 4,4′-dichlorodiphenyl sulfone (DCS). Model reactions monitored by HPLC indicated that BFPT had slightly higher reactivity than DCS in nucleophilic displacement reactions. The obtained random copolymers were characterized by FTIR, NMR, elemental analysis and GPC. The presence of sulfone and phthalazinone in the polymer chain results in an improvement in the solubility of poly(arylene ether phenyl-s-triazine)s in common organic solvents, such as N-methylpyrrolidone, N,N-dimethyl acetamide (DMAc), chloroform, sulfolane and pyridine. Thermal analysis reveal that the copolymers exhibit high glass transition temperatures (T_gs) ranging from 271–300 °C, and excellent thermal stability associated with decomposition temperatures for 5% mass-loss exceeding 503 °C. All copolymers are amorphous except PPESP28 as evidenced by WAXD. Their T_gs and solubility increase with an increase in sulfone content in the polymer backbone, while the crystallinity and overall thermal stability appear to decrease. This kind of phthalazinone-based copoly(arylene ether sulfone phenyl-s-triazine)s may be considered a good candidate for using as high-performance structural materials.     

Synthesis and characterization of polyoxazoline-polysulfone triblock copolymers

Amphiphilic triblock poly(2-ethyl-2-oxazoline-b-sulfone-b-2-ethyl-2-oxazoline) (PEOX-b-PSF-b-PEOX) and poly(2-ethyl-2-oxazoline-co-ethyleneimine-b-sulfone-b-2-ethyl-2-oxazoline-co-ethyleneimine) (PEOXcoPEI-b-PSF-b-PEOXcoPEI) copolymers were synthesized for potential use as water purification membranes. Poly(arylene ether sulfone) (polysulfone) oligomers of controlled molecular weight were prepared by nucleophilic step polymerization of 4,4′-dichlorodiphenyl sulfone with a molar excess of bisphenol-A. The phenolate endgroups were then reacted with ethylene carbonate to afford telechelic aliphatic hydroxyethyl groups. These were tosylated to produce macroinitiators for ring-opening cationic polymerization of 2-ethyl-2-oxazoline. Subsequently, the pendent amides on the hydrophilic PEOX blocks were also hydrolyzed to generate positively charged PEOXcoPEI-b-PSF-b-PEOXcoPEI copolymers. Compositions with high polysulfone compositions relative to the hydrophilic blocks were of particular interest because they maintained good mechanical integrity in water. Water uptake at room temperature increased up to 18 wt% for copolymers with 22 wt% of the hydrophilic components. Solid-state thermal properties suggested some phase mixing of the components in the PEOX-b-PSF-b-PEOX copolymers but better phase separation of the blocks in the partially hydrolyzed PEOXcoPEO-b-PSF-b-PEOXcoPEI materials.     

The synthesis of tetrahedral bipyridyl metallo-octupoles with large second- and third-order nonlinear optical properties

Two new 4,4′-bis(donor)-6,6′-diphenyl- 2,2′-bipyridine ligands and their corresponding D_2d (Cu^I, Ag^I, Zn^II) octupolar metal complexes were synthesized, and their linear and nonlinear optical properties were investigated. A single crystal X-ray structure was also determined for the bis[4,4′-bis(diethylaminostyryl)-6,6′-diphenyl-bipyridine]copper(I) complex, which revealed a distorded pseudo-tetrahedral geometry. Molecular second-order nonlinear optical properties were determined for the complexes using the Harmonic Light Scatterring technique at 1.91 μm. These metallo-chromophores display large first hyperpolarizabilities β_1.91 in the range of 211-340 × 10⁻³⁰ esu, which increase with the Lewis acidity of the metal ion. The two-photon absorption properties of the bipyridyl ligands and related complexes were determined using either the two-photon emission method for fluorescent compounds or the open aperture Z-scan technique for non emissive ones. The complexes display red-shifted two-photon absorption bands compared to their metal-ion free chromophores, as well as a large increase of the maximum two-photon absorption cross-sections.     

Poly(arylene ether sulfone) multi-block copolymers bearing perfluoroalkylsulfonic acid groups

Poly(arylene ether sulfone) (PAES) multi-block copolymers bearing perfluoroalkylsulfonic acid moieties were prepared from hydrophilic and hydrophobic prepolymers. The latter were synthesized by reaction of N,N-diisopropylethylammonium 2,2-bis(p-hydroxyphenyl)pentafluoropropanesulfonate (HPPS) with bis-(4-fluorophenyl) sulfone (FPS), and biphenol (BP) with FPS, respectively. Prepolymers and multi-block copolymers were prepared at 180 °C in N,N-dimethylacetamide in the presence of K₂CO₃. The prepolymers were reacted overnight; the multi-block copolymers were reacted only 80 min to minimize transetherification. Prepolymers and multi-block copolymers were characterized using ¹H and ¹³C NMR. ¹⁹F NMR provided molecular weight of hydrophilic prepolymers bearing aryl fluoride end groups. GPC was used to characterize the multi-block copolymers. Copolymer block lengths were determined by quantifying ¹³C NMR peak areas of quaternary carbon atoms adjacent to sulfur in FPS moieties. Hydrophilic and hydrophobic block lengths were in the range 9.4-23.4 and 4.4-11.8 repeating units, respectively. AFM showed phase separation for all block lengths. Conductivity at 80 °C and 100% relative humidity ranged from 6.2 to 34.3 mS/cm, with the best value obtained for hydrophilic/hydrophobic block lengths of 13.3/6.0.     

Synthesis of amphiphilic ethyl cellulose grafting poly(acrylic acid) copolymers and their self-assembly morphologies in water

Amphiphilic ethyl cellulose (EC)-g-poly(acrylic acid) (PAA) copolymers were synthesized by atom transfer radical polymerization (ATRP). Firstly, ethyl cellulose macro-initiators with the degree of the 2-bromoisobutyryl substitution of 0.04 and 0.25 synthesized by the esterification of the hydroxyl groups remained in EC macromolecular chains and the 2-bromoisobutyryl bromides. Secondly, tert-butyl acrylate was polymerized by ATRP with the ethyl cellulose macro-initiator and EC-g-PtBA copolymers were prepared. Finally, the EC-g-PAA copolymers were prepared by hydrolyzing tert-butyl group of the EC-g-PtBA copolymers. The grafting copolymers were characterized by means of GPC, ¹H NMR and FTIR spectroscopies. The molecular weight of graft copolymers increased during the polymerization and the polydispersity was low. A kinetic study showed that the polymerization was first-order. Meanwhile, EC-g-PAA copolymers were self-assembled to micelles or particles with diameters of 5 nm and 100 nm in water (pH = 10) when the concentration was 1.0 mg/ml.     

Synthesis and characterization of thermotropic liquid crystalline poly(azomethine ether)s

Two series of monomers, namely 4,4′-diformyl-α,ω-diphenoxydecane and 4,4′-diformyl-3,3-methoxy-α,ω-diphenoxydecane, were prepared from 1,10-dibromodecane with p-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde (vanillin), respectively. The poly(azomethine ether)s were prepared by solution polycondensation using 4,4′-diformyl-α,ω-diphenoxydecane, 4,4′-diformyl-3,3-methoxy-α,ω-diphenoxydecane with various diamines. The monomers and polymers were characterized by intrinsic viscosity, FT-IR, ¹H, and ¹³C NMR spectroscopy. The thermogravimetric analysis reveals that the polymers are stable up to 320-500 °C and decomposed with good char yield. The thermotropic liquid crystalline properties of the polymers were examined by differential scanning calorimetry (DSC) and their textures observed under hot stage optical polarized microscopy (HOPM). All the polymers were exhibited thermotropic liquid crystalline properties except tetramethylene diamines-based polymers.     

Water resistant sulfonated polyimides based on 4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride (BNTDA) for proton exchange membranes

A series of sulfonated polyimides (SPIs) were synthesized in m-cresol from 4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride (BNTDA), 4,4′-diaminodiphenylether-2,2-disulfonicacid (ODADS), and 4,4′-diamino-diphenyl ether (ODA) in the presence of triethylamine and benzoic acid. The resulted polyimides showed much better water resistance than the corresponding sulfonated polyimides from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) and ODADS, which is contributed to the higher electron density in the carbonyl carbon atoms of BNTDA. Copolyimides S-75 and S-50 maintained their mechanical properties and proton conductivities after aging in water at 100 °C for 800 h. The proton conductivity of these SPIs was 0.0250-0.3565 S/cm at 20 °C and 100% relative humidity (RH), and increased to 0.1149-0.9470 S/cm at 80 °C and 100% RH. The methanol permeability values of these SPIs were in the range of 0.99-2.36 × 10⁻⁷ cm²/s, which are much lower than that of Nafion 117 (2 × 10⁻⁶ cm²/s).     

Prediction of the density and viscosity in biodiesel blends at various temperatures

Biodiesel defined as mono-alkyl esters of vegetable oils and animal fats, has had a considerable development and great acceptance as an alternative fuel for diesel engines. Density and viscosity are two important physical properties to affect the utilization of biodiesel as fuel. In this work, mixtures of biodiesel and ultra low sulfur diesel (ULSD) were used to study the variation of density (ρ) and kinematic viscosity (η) as a function of percent volume (V) and temperature (T), experimental measurements were carried out for six biodiesel blends at nine temperatures in the range of 293.15-373.15 K. Both, density and viscosity increases because of the increase in the concentration of biodiesel in the blend, and both of them decrease as temperature increases. One empirical correlation was proposed to estimate the density: ρ = α·V + β·T + δ; and three empirical correlations were developed to predict the kinematic viscosity: η = exp[ln(γ) + ?·V + ω/T + λ·V/T²], η = exp[ln(γ) + ω/T + λ·V/T²] and η = exp[ln(γ) + ω/T + λ·V/T]. The corresponding parameters were optimized by the Levenberg-Marquardt method. The estimated values of density and viscosity are in good agreement with the experimental data because absolute average prediction errors of 0.02% and 2.10% were obtained in the Biodiesel(1) + ULSD(2) system studied in this work.     

Synthesis and characterization of poly(ether sulfone) copolymers

Poly(ether sulfone) copolymers I–V were synthesized by the nucleophilic substitution reaction of 4,4-dichlorodiphenyl sulfone with varying mole proportions of 4,4-isopropylidene diphenol (bisphenol A) and 4,4-dihydroxydiphenyl sulfone (bisphenol S) using sulfolane as the solvent in the presence of anhydrous K₂CO₃. The polymers were characterized by different physicochemical techniques. The glass transition temperature was found to decrease with increase in the concentration of bisphenol A units in the polymers. All polymers were found to be amorphous. Thermogravimetric studies showed that all the polymers were stable up to 400°C with a char yield of about 36% at 900°C in a nitrogen atmosphere. ¹³C-NMR spectral analysis reveals that bisphenol S-based triads are preferentially formed compared to bisphenol-A triads, indicating greater reactivity of bisphenol S toward dichlorodiphenyl sulfone. The overall activation energy for the thermal decomposition of bisphenol A-based polymer (1) is much higher than that of bisphenol S-based polymer ( II ). This was attributed to the modification of the backbone of polymer I during the initial cleavage of the C—CH3 bond of the isopropyledene group. Polymer II decomposes by cleavage of the C—SO2 bond. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 743–750, 1998