Synthesis and properties of poly(butylene terephthalate)-poly(ethylene oxide)-poly(dimethylsiloxane) block copolymers

Poly(butylene terephthalate)-poly(ethylene oxide)-poly(dimethyl siloxane)-poly(ethylene oxide) block copolymers, (PBT-PEO-PDMS-PEO)_m, are synthesized by polycondensation (PC) of dimethylterephtalate (DMT), 1,4-butanediol (BDO) and PEO-PDMS-PEO. The soft block has been incorporated from 10 to 70 wt-%; the total molecular weight (MW) of the block-copolymers amounts to 16000 - 20000 g/mol. One major problem of polyether-PBT thermoplastic elastomers is their poor thermo-oxidative stability. Due to the excellent heat stability of PDMS, the resistance of this new thermoplastic elastomer against thermo-oxidative degradation has been increased 80 %! From differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) in the PEO-PDMS-PEO based COPEs, three phases can be distinguished. Besides the crystalline PBT phase, an amorphous mixed phase of PBT and PEO and an almost pure PDMS phase have been found. Due to the high concentration of the mixed PBT-PEO phase, the low temperature modulus and the glass transition temperature, T_g, are not dominated by the pure PDMS phase (T_g = −114°C). Depending on the amount of PBT and PEO present, the main glass transition lies in the range of −50°C to 50°C.     

Synthesis of a novel starch-derived AB-type polyurethane

Starting from 1,4:3,6-dianhydrosorbitol (DAS, 1 ), a five step monomer synthesis led to 2-deoxy-1,4:3,6-dianhydro-2-isocyanato-L -iditol, 9 , which by catalytic polyaddition gave polyurethane 13 . A second route required the synthesis of 2-azido-5-O-chloroformyl-2-deoxy-1,4:3,6-dianhydro-L -iditol, 11 . During catalytic hydrogenation, the intermediate 2-aminochloroformyl derivative 12 underwent spontaneous polycondensation. The structure of 13 was characterized by ¹H and ¹³C NMR, IR spectroscopy and elemental analyses. Gel-permeation chromatography showed M̄_n = 8 000–12 000 corresponding to a degree of polymerisation up to 70. Differential scanning calorimetry revealed the polyadduct to be semicrystalline with a glass transition at T_g = 118°C and a melting range of 190–200°C. The polycondensation product was found to be crystalline with a melting range of 140–180°C.     

Distributions of cyclic oligomers formed by irreversible step-growth polymerisation. Results from kinetic modeling

The distribution of cyclic oligomer concentrations (examined up to the cyclic pentamer) in the process of step-growth polymerisation decreases, in concentrated solution, with i^−2.5 if the chains follow Gaussian statistics (i: degree of polymerization). This picture is analogous to that shown by cyclic oligomer distributions obtained under thermodynamic control and is in contrast with that shown by cyclic oligomer distributions obtained by irreversible chain-growth polymerisation which is characterized by a gradient of −1.5. This result has been initially obtained by numerical integration of the differential rate equations pertinent to a kinetic model relative to the reaction of a bifunctional reactant A—B under batchwise conditions, and then confirmed by analytical integration of the differential rate equations under the condition that propagation is much faster than cyclisation. The case in which the monomeric ring is strained has been also investigated. Also in this case the obtained distribution is analogous to that shown under equilibrium conditions. From an examination of the distributions of the ring yields, the best conditions for the preparation of either the cyclic monomer or the cyclic dimer are suggested.     

Fully aromatic thermotropic liquid crystalline polyesters of 3,4′-dihydroxybenzophenone

A series of fully aromatic, thermotropic polyesters, derived from 3,4′-dihydroxybenzophenone and various aromatic dicarboxylic acids, was prepared by the high-temperature solution polycondensation method and examined for thermotropic behavior by a variety of experimental techniques. The aromatic dicarboxylic acids used in this study were 2,6-naphthalenedicarboxylic acid, 4,4′-bibenzoic acid, and terephthalic acid. The two homopolymers of 3,4′-DHB with either 2,6-NDA or 4,4′-BBA formed nematic LC phases at 285°C and 255°C and also exhibited isotropization transitions (T_i) at 317°C and 339°C, respectively. The copolymer of 3,4′-DHB with 50% TA and 50% 2,6-NDA also formed a nematic LC phase and had a broader range of LC phase than that of its respective homopolymers. Two other copolymers of 3,4′-DHB, both containing 50% 4,4′-BBA, also formed nematic LC phases at low T_f values. All of the thermotropic polyesters had high thermal stabilities. © 1994 John Wiley & Sons, Inc.     

Synthesis of aromatic polyamide-phthalimidines from chloroformylphthalides and aromatic diamines

New polymer-forming monomers, 3-benzylidene-5-chloroformylphthalide and 3-benzylidene-6-chloroformylphthalide, were synthesized by the Perkin reaction of trimellitic anhydride with phenylacetic acid, followed by chlorination. The polycondensation of these monomers with aromatic diamines in N-methyl-2-pyrrolidone at 200°C afforded aromatic polyamide-phthalimidines having inherent viscosities of 0.2-0.5 dL/g. All the polymers were readily soluble in m-cresol, pyridine, dimethylformamide, and dimethyl sulfoxide. Glass transition temperatures of some of the polymers were in the range of 255–282°C. The polyamide-phthalimidines began to lose weight at around 300°C in both air and nitrogen atmospheres, with 10% weight losses being recorded at 435–475°C in nitrogen by thermogravimetry.     

Real-time X-ray scattering study of thermal expansion of poly(butylene terephthalate)

Real-time x-ray scattering at elevated temperatures has been used to investigate the thermal expansion characteristics of poly(butylene terephthalate), PBT. Changes in the six lattice parameters of the α-form of PBT were obtained from wide-angle x-ray scattering over the temperature range from 35 to 215°C. The linear thermal expansion coefficients relating the unit cell parameters at temperature T to their values at 0°C are found to be The temperature dependence of both the long period and the lamellar thickness of semicrystalline PBT were determined from real-time small-angle x-ray scattering analysis of the one-dimensional electron density correlation function. The long period, lamellar thickness, and degree of crystallinity increase as the temperature increases. We find an average linear thermal expansion coefficient of the bulk material to be α_ave = 5.0 × 10⁻⁴°C⁻¹. © 1992 John Wiley & Sons, Inc.     

Analysis of photocurrent spectra at polybithienyl film coated on Pt

Photoelectrochemical measurements have been performed at a polybithienyl (PBT) film (doping level of 1 × 10¹⁸/cm³) deposited on a platinum electrode. The cathodic photocurrents and negative slope of the Mott-Schottky plot indicate that the PBT film has the features of a p-type semiconductor. The cathodic photocurrents are interpreted in terms of the Gaertner-Butler model on the basis of the theory of the semiconductor|solution interface. The (i _ph hν)^2/n vs. hν plots taken from the photocurrent spectra show two linearities for n=1 in the wavelength range from 460 nm to 490 nm and for n=4 in the wavelength range λ > 490 nm. The band gaps of the PBT film were determined to be 2.05 ± 0.05 eV for n=1 and 1.55 ± 0.05 eV for n=4. The flat-band potential is 0.33 V (vs SCE). From the slope of the Mott-Schottky plot at the modulation frequency of 3 kHz, the dielectric constant ɛ of the film and the thickness of the depletion layer W ₀ of the PBT film were determined to be 7.4 and 0.29 μm, respectively. Received: 6 January 1999 / Accepted: 6 June 1999     

Synthesis and characterization of polyesteramides derived from an oxazoline-functional alcohol and dicarboxylic acid anhydrides

Novel polyesteramides were synthesized by copolymerization in bulk of 5-(4,5-dihydro-1,3-oxazol-2-yl)-1-pentanol and various cyclic dicarboxylic acid anhydrides at temperatures varying between 120 and 200°C. The polymers resulting from polycondensation were characterized by means of ¹H–NMR, FTIR, MALDI–TOF–MS, SEC, and DSC. The glass transition temperatures, T_g, of the copolymers were varied between −28 and +31°C as a function of the anhydride type. Molecular weights, M_w, were dependent on reaction temperature, reaction time, and anhydride type. Spectroscopic investigation of reaction products and esteramide model compounds provided evidence for imide by-product formation, which accounts for the low degree of polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3367–3376, 1999     

Direct observation and stability of active species in cationic polymerization: A reexamination of the polymerization of styrene initiated by triflic acid

Polymerization of styrene initiated by triflic acid in CH₂Cl₂ solution was reexamined, using a new stopped-flow device working in high purity conditions over a wide temperature range. Monomer and styryl cation were followed simultaneously through their respective absorbances at 290 and 340 nm. Initiation is very rapid, and cations concentration reaches a plateau the duration of which is depending on temperature. In our conditions (I₀ = 0.5 − 9.10⁻³M, M₀/I₀ = 1 to 20), cations concentration is so low at room temperature that it is almost unmeasurable. At −65°C, it is 100 times higher, remains constant for several seconds and complete termination takes place within a minute or more. Such a profile of cation evolution agrees with an equilibrium situation between initiation and a much more temperature-dependent backward deprotonation. Apparent initial rate of initiation is first order with respect to monomer, but the order with respect to initiator was found very high and variable with temperature (from 4.5 at −65°C to 3 at −20°C). This supports the presence, even if they are in low concentration, of acid high agregates, the reactivity of which increases with size. A first order monomer consumption is observed during the plateau, which leads to k_p values ranging from 10³ at −65°C to 9.10⁴ M⁻¹.s⁻¹ at −10°C (Ep^# = 43 kJ.mol⁻¹). The disappearance of cations, which follows the plateau, slows down and becomes unimolecular when monomer consumption is complete, and k_t values range from 6.10⁻²s⁻¹ at −65°C to 1.2s⁻¹ at −23°C (E_t^# = 33 kJ.mol⁻¹).     

Preparation and properties of aromatic polyamides from 2,2′-bis(p-aminophenoxy) biphenyl or 2,2′-bis(p-aminophenoxy)-1,1′-binaphthyl and aromatic dicarboxylic acids

New aromatic diamines having kink and crank structures, 2,2′-bis(p-aminophenoxy)biphenyl and 2,2′-bis(p-aminophenoxy)-1,1′-binaphthyl, were synthesized by the reaction of p-fluoronitrobenzene with biphenyl-2,2′-diol and 2,2′-dihydroxy-1,1′-binaphthyl, respectively, followed by catalytic reduction. Biphenyl-2,2′-diyl- and 1,1′-binaphthyl-2,2′-diyl-containing aromatic polyamides having inherent viscosities of 0.44–1.18 and 0.26–0.88 dL/g, respectively, were obtained either by the direct polycondensation or low-temperature solution polycondensation of the diamines with aromatic dicarboxylic acids (or diacid chlorides). These polymers were readily soluble in a variety of organic solvents including N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide, m-cresol, and pyridine. Transparent, pale yellow, and flexible films of these polymers could be cast from the DMAc or NMP solutions. These aromatic polyamides containing biphenyl and binaphthyl units had glass transition temperatures in the range of 215–255 and 266–303°C, respectively. They began to lose weight at ca. 380°C, with 10% weight loss being recorded at about 470°C in air. © 1993 John Wiley & Sons, Inc.     

Polymerization in the crystalline state. X. Solid-state conversion of 6-aminocaproic acid to oriented nylon 6

When single crystals of 6-aminocaproic acid (ACA) are heated about 30°C below their melting point, polycondensation to nylon 6 takes place. The polymer crystallites are biaxially oriented towards each other and the relation between their orientation and that of the parent monomer crystal has been clarified. The kinetics of the process are characterized by three stages, (a) an induction period, (b) a stage in which monomer disappears at a constant rate while polymer of relatively low molecular weight is formed, and (c) a slow polycondensation of the polyamide chains after exhaustion of the monomer. Oligomer concentrations were below detectable limits at all stages of the process. Addition of monomer to the polyamide was retarded when ACA was kept from reaching its equilibrium vapor pressure (0.12 mm Hg at 170°C) by condensation on a cool surface or when an inert gas was admitted to the system. This was interpreted as suggesting that ACA is transported through the vapor phase to the propagating polyamide. A number of surfaces catalyzed the polycondensation of ACA vapor, but nylon 6 formed in this way on KCl crystals exhibited no preferred orientation. The linear dimer and trimer of ACA were also found to condense to nylon 6 in the crystalline state, although at a slower rate than the monomer. The solid-state polycondensation of these oligomers was accelerated when they were exposed to the vapor of the monomer. Solid-state polycondensation of single crystals of the linear dimer led also to biaxially oriented nylon 6.     

Synthesis and characterization of N-phenylated aromatic polyamides from N-silylated dianilino compounds and aromatic diacid chlorides

N-Phenylated aromatic polyamides of high molecular weights were synthesized by the hightemperature solution polycondensation of N,N′ -di(trimethylsilyl)-substituted dianilino compounds derived from p-dianilinobenzene, bis(4-anllinophenyl) ether, and α,α′-dianilino-p-xylene, with isophthaloyl and terephthaloyl chloride. Almost all of the N-phenylated polyamides were amorphous, and soluble in a variety of organic solvents including dimethylformamide, m-cresol, and chloroform. Transparent and flexible films of these polymers could be cast from the dimethylformamide solutions. Four wholly aromatic polyamides had glass transition temperatures in the range of 195–255°C, and began to lose weight around 400°C in air.     

Palladium complexes with biological ligands—I. Equilibrium and reaction mechanism of Pd(II) complexes with ethionine

An equilibrium study has been carried out on the interaction of ethionine(eth) with Pd(II) in aqueous solution at I = 0.16 M (Cl⁻ and 25°C using potentiometic methods. It has been concluded that five complex species exist in the pH range 2.8–4.8. these species are: PdCl₃(Eth0H⁰₂, PdCl₂(Eth)⁻, PdClOH(Eth)⁻, Pd(Eth)₂(H)²⁺₂ and Pd(Eth)⁰₂. In addition, the stopped-flow method has been used to study the reaction kinetics of Pd(II) with Eth. Three kinetic steps were observed in the pH range 1–5.5. These steps are dependent on the total concentration of Eth (T_Eth) as well as the pH of the medium. The observed pseudo-first order rate constants for the three reaction kinetic steps at constant pH are expressed empirically by kⁱ_obs = m_i + m′_iT_Eth. The parameters m_i and m′_i are pH-dependent. It has been concluded that PdCl²⁻₄ and PdCl₂OH²⁻ species play an important role in the complex formation reactions with Eth. The data were interpreted in terms of the complex species obtained from the equilibrium study. cis-trans substitution reactions have been suggested to account for some kinetic steps.     

Aromatic and rigid rod polyelectrolytes based on sulfonated poly(benzobisthiazoles)

Aromatic polyelectrolytes based on sulfonated poly(benzobisthiazoles) (PBTs) have been synthesized by a polycondensation reaction of sulfo-containing aromatic dicarboxylic acids with 2,5-diamino-1,4-benzenedithiol dihydrochloride (DABDT) in freshly prepared polyphosphoric acid (PPA). Several sulfonated PBTs, poly[(benzo[1,2-d:4,5-d′]bisthiazole-2,6-diyl)-2-sulfo-1,4-phenylene] sodium salt (p-sulfo PBT), poly[(benzo[1,2-d:4,5-d′]bisthiazole-2,6-diyl)-5-sulfo-1,3-phenylene] sodium salt (m-sulfo PBT), their copolymers, and poly[(benzo[1,2-d:4,5-d′]bisthiazole-2,6-diyl)-4,6-disulfo-1,3-phenylene] potassium salt (m-disulfo PBT), have been targeted and the polymers obtained characterized by ¹³C-NMR, FT-IR, elemental analysis, thermal analysis, and solution viscosity measurements. Structural analyses confirm the structures of p-sulfo PBT and m-disulfo PBT, but suggest that the sulfonate is cleaved from the chain during synthesis of m-sulfo PBT. m-Disulfo PBT dissolves in water as well as strong acids, while p-sulfo PBT dissolves well in strong acids, certain solvent mixtures containing strong acids, and hot DMSO. TGA indicates that these sulfonated PBTs are thermally stable to over 500°C. Free-standing films of p-sulfo PBT, cast from dilute neutral DMSO solutions, are transparent, tough, and orange in color. Films cast from basic DMSO are also free standing, while being opaque and yellow-green. p-Sulfo PBT was incorporated as the dopant ion in polypyrrole, producing conductive films with conductivities as high as 3 S/cm and electrical anisotropies as high as 10. © 1996 John Wiley & Sons, Inc.     

Diffusion and reaction in polyester melts

An understanding of the physical and chemical processes involved in the melt polymerization of polyesters in the higher inherent viscosity ranges is of fundamental importance in polyester preparation. For example, the volatile condensation product must diffuse to a polymer–vapor interface before polymerization can take place. Thus, the rate of polymerization of a polyester may be dependent not only upon the chemical kinetics of the polymerization reaction but also upon the diffusion of the condensation product through the polymer melt. The objective of the work presented in this paper was to determine to what degree diffusion or reaction kinetics, or both, limit the melt polycondensation of poly(ethylene terephthalate). Degrees of polymerization in melts between 0.0285 and 0.228 cm in depth at 270°C were measured for various reaction times and were compared with the predictions of mathematical models. The polycondensation rates under these conditions depend upon both the polycondensation rate constant k₁ and the diffusivity D of ethylene glycol through the melt. Estimates of the values to these parameters are: k₁ = 0.0500 (moles/mole of repeat unit)^?1 sec^?1; D = 1.66 × 10^?4 cm²/sec.     

Synthesis,liquid crystallinity,and mechanical properties of thermotropic polyquinolines

Thermotropic liquid-crystalline polyquinolines with high molecular weights, i.e., poly[2,2′-(α,ω-dioxyphenylene (or -dioxybiphenylene) alkane)-6,6′-(4,4′-dioxybiphenyl)-bis(4-phenylquinoline)]s (P-H-B1Mns or P-H-B2Mns), were synthesized by polycondensation of 4,4′-bis(4-amino-3-benzoylphenoxy)biphenyl and α,ω-bis(4-acetophenoxy (or -acetobiphenoxy))alkanes. For P-H-B1Mn series, the T_m and T_i were in the range of 129–230°C and 156–254°C, respectively, while for the P-H-B2Mn series, those were 182–275°C and 217–309°C, respectively. The introduction of both the dioxybiphenylene group and an alkylene spacer induced thermotropic liquid crystallinity in the polyquinoline, although the introduction of the alkylene spacer alone did not induce it. In addition, polyquinolines substituted with methyl, methoxy, and chloro groups exhibited larger mesophase temperature ranges as well as higher T_ms and T_is than the unsubstituted ones. Tensile strengths of these thermotropic polyquinolines were considerably high in the range of 770 to 1170 kgf/cm². © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 749–759, 1998     

Excess Molar Volumes and Partial Molar Volumes of Dipropylene Glycol Monomethyl Ether + n-Alkanol Mixtures at 25°C

The excess molar volumes V^E for binary liquid mixtures containing dipropylene glycol monomethyl ether and methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, and 1-heptanol have been measured using a continuous dilution dilatometer over the whole mole fraction range at 25°C at atmospheric pressure. V^E are negative over the whole composition range except for the systems containing 1-pentanol, 1-hexanol, or 1-heptanol which are positve at every composition. V^E increases in a positive direction with increase in chain length of the n-alcohol. The results have been used to estimate the excess partial molar volumes V_i^E of the components. The change of V^E and V_i^E with composition and the number of carbon atoms in the alcohol molecule are discussed as a basis to understand some of the molecular interactions present in the mixtures:     

Chain-growth polycondensation of potassium 3-cyano-4-fluorophenolate derivatives for well-defined poly(arylene ether)s

Polycondensation normally proceeds in a step-growth reaction manner to give polymers with a wide range of molecular weights. However, the polycondensation of potassium 2-alkyl-5-cyano-4-fluorophenolate ( 1 ) proceeded at 150°C in a chain polymerization manner from initiator, 4-fluoro-4′-trifluoromethyl benzophenone ( 2 ), to give aromatic polyethers having controlled molecular weights and low polydispersities (M_w/M_n ⩽ 1.2). The resulting polycondensation of 1 had all of the characteristics of living polymerization and displayed a linear correlation between molecular weight and monomer conversion, maintaining low polydispersities. Sulfolane was a better solvent for chain-growth polycondensation of 1 than other aprotic solvents. The polyether from 1 with a low polydispersity showed higher crystallinity than that with a broad molecular weight distribution, obtained by the conventional polycondensation of 1 without 2 .     

Polymerisation of methyl methacrylate with tert-butyllithium and triisobutylaluminium in toluene: mechanism of initiation and termination by matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI TOF MS)

The polymerisation of methyl methacrylate (MMA) using triisobutylaluminium/tert-butyllithium in hydrocarbon at 0°C and −78°C has been investigated by matrixassisted laser desorption ionisation time-of-flight mass spectrometry (MALDI TOF MS). Although the system gives extremely good control over molecular weight and narrow molecular weight distribution, initiation of polymerization can be complicated by formation of small amounts of tert-butyl isoprenyl ketone ( 1 ), and termination of polymerization can occur by end cyclisation of the end unit of 3 . Both complications in initiation and termination can be avoided by suitable reaction conditions. Incorporation of 1 is suppressed by increasing the alkylaluminium content and by higher temperature. Termination by cyclisation has been found to occur over much longer time scales than propagation and can therefore be avoided by controlled termination after the appropriate reaction time.     

On some problems in quantum pharmacology I. The partition functions

We performed an analysis of the drug-receptor equilibrium constant, K_i = {Q_DiRQ_Di^?1Q_R^?1} exp (?Δ_εi/kT). It is shown that, for a group of nonrotating molecules we may consider the product of the partition functions as constant if log(mass) = constant for all the molecules.