Search

Carbon−hydrogen (C−H) and carbon−carbon (C−C) bonds are the main constituents of organic matter. The recent advancement of C−H functionalization technology has vastly expanded our toolbox for organic synthesis1. In contrast, C−C activation methods that allow for editing the molecular skeleton remain limited2–7. To date, a number of methods have appeared for catalytic C−C activation, particularly with ketone substrates, which are typically promoted either by ring-strain release as a thermodynamic driving force4,6 or using directing groups5,7 (DGs) to control the reaction outcome. While effective, these strategies require highly strained ketone substrates or those containing a preinstalled DG, or are limited to more specialist substrate classes5. Here, we report a general C−C activation mode driven by aromatization of an in situ-formed pre-aromatic intermediate. This reaction suitable for various ketone substrates, is catalyzed by an iridium/phosphine combination, and is promoted by a hydrazine reagent and 1,3-dienes. Specifically, the acyl group is removed from the ketone, transformed to a pyrazole, and the resulting alkyl fragment undergoes various transformations. These include the deacetylation of methyl ketones, carbenoid-free formal homologation of aliphatic linear ketones, and deconstructive pyrazole synthesis from cyclic ketones. Given that ketones are prevalent in feedstock chemicals, natural products and pharmaceuticals, these transformations could offer new strategic bond disconnections in the synthesis of complex bioactive molecules.

A new approach to describe the adsorption behavior of liquid mixtures on solid surfaces by use of GE-models is presented. In contrast to the classical formulation of adsorption equilibrium the adsorbed phase is considered to be a mixture containing the adsorbed species (adsorbate) and the adsorbent as additional component. By introducing the Gibbs excess energy GE* for this adsorbate-solid-solution the free energy of adsorption is correlated with the respective activity coefficients of all involved components. This concept, in the following briefly called ASST (adsorbate-solid-solution theory), thus leads to a thermodynamically consistent description of both the adsorption equilibrium and caloric properties.

Both correlation as well as prediction of experimental data for the adsorption of various binary liquid mixtures of alkanes and alkenes on NaX at different temperatures are presented. The theoretical background is based on the adsorbate−solid solution theory which conceives the adsorbed phase to be a mixture of the adsorbed species (adsorbate) and the adsorbent as an additional component. With the introduction of the Gibbs excess energy GE* for this hypothetical mixture, activity coefficients and composition of the adsorbed phase may be calculated. The Gibbs excess energy and thus the activity coefficients of the adsorbed species depend strongly on the energetic heterogeneity of the solid surface which may be described by use of so-called group contribution models. These approaches, until now widely applied to predict fluid-phase equilibrium, are derived from statistical thermodynamics and take into account the energetic interactions between the respective components. For the application of this approach ...

A new mixing rule for the attractive term parameter in the Dohrn-Prausnitz equation of state (DP-EOS) has been developed by combining the EOS with a group contribution GE-model. The application of the Dohrn-Prausnitz perturbation term for the Carnahan-Starling EOS in combination with original- or modified-UNIFAC leads to a new G E EOS model, the predictive-Dohrn-Prausnitz model (PDP), that successfully allows the prediction of phase equilibria of various nonideal systems at low and high pressures without introducing any parameters that have to be fitted to experimental data. Moreover, PDP is excellently suitable to predict both vapor-liquid equilibria (VLE) and vapor-solid equilibria of mixtures containing polar compounds, such as waterethanol, methanolacetone or carbon dioxidenaphthalene. The PDP equation of state can be used for predictions over large range of temperature and pressure and is easily extended to mixtures with supercritical components.

A homologous series of di(4-alkyloxybenzoates) of 4,4′-dimercaptobiphenyl: CH3(CH2) n-1O‒C6H4‒COS‒C6H4‒C6H4‒SOC‒C6H4‒O(CH2) n-1CH3,n=1–7, has been synthesized and the thermotropic liquid-crystalline behaviour investigated. All compounds exhibit enantiotropic mesomorphism over a remarkable temperature range. While the mesophase thermal stability is moderately higher than that found for the corresponding oxygenated analogues, the smectic stability is definitely lower. In fact, all the compounds are nematic but smectic mesomorphism (SC) is observed for n = 7. Compounds with n = 6 or 7 exhibit enantiotropic highly ordered smectic (or disordered crystal) phases, probably SG in type.

Ipomoea pes-caprae is a medicinal plant used in many countries for the treatment of several ailments, including inflammatory and algesic processes. The present study describes the antinociceptive effects of the methanolic extract and two fractions obtained from aerial parts of this plant. The results indicated that both methanolic extract and two fractions (ethyl acetate and aqueous) exhibited considerable antinociceptive activity against two classical models of pain in mice. Methanolic extract presented a calculated ID50 value of 33.8 mg/kg, i.p. against writhing test and also inhibited both phases of pain (neurogenic and inflammatory) of the formalin test with ID50 of 37.7 and 12.5 mg/kg, i.p. for the first and second phase, respectively. Preliminary phytochemical analysis suggested the presence of steroids, terpenoids, alkaloids and flavonoids. These findings support, at least in part, the popular use of I. pes-caprae to treat dolorous processes.

Bilayers of 40 nm titanium nitride and 500 nm copper were sputter deposited on oxidized silicon substrates. The films were annealed for one hour at temperatures from 400° C to 800° C in either vacuum or Ar/H2, ambients. Neither x-ray diffraction or Rutherford backscattering spectrometry indicated any interaction between the titanium nitride and copper films. While no differences in surface morphology were detected at annealing temperatures of less than 500° C, above this temperature a strong dependence on annealing ambient was found. In the vacuum annealed samples, surface grooves formed at the grain boundaries of the copper film. These grooves became progressively larger as the annealing temperature was increased, eventually leading to void formation. Only small grain boundary grooves were present in the Ar/H2, annealed films regardless of annealing temperature. The driving force for the formation of the grooves is believed to be a difference between the grain boundary and surface energies in the copper films. It is speculated that in Ar/H2 anneals this driving force is reduced because hydrogen segregates to the copper grain boundaries and lowers the grain boundary energy.The formation of grooves was found to retard copper grain growth and texturing. Resistivity of the copper film was also found to increase if the void density was sufficiently high.

Les polythioesters obtenus par polycondensation interfaciale du 4,4'-dimercapto biphenyle avec les dichlorures de diacide ClCO-(CH 2 ) n -COCl (n=10, 10, 13) sont caracterises par FTIR RMN 1 H, GPC et DSC. Les 3 polymeres presentent 2 transitions thermiques, quasi-confondues pour n=13; la premiere transition de phase observee pour n=13 est la fusion; un liquide anisotrope dont la morphologie est caracteristique d'un cristal liquide nematique est obtenu

Stable nitroxide radicals were obtained by the oxidation of 1-hydroxyindolines prepared by allowing the organo-metallic compounds to act upon 2-phenylisatogen and arylimino-derivatives. In both cases nitroxides are obtained with a N of approximately 9 gauss, in agreement with similar known compounds. The ESR spectra of numerous nitroxide radicals are discussed and a number of cases of magnetic non-equivalence of methylenic protons adjacent to asymmetric carbon are brought to light.

The effect of midazolam, a new water-soluble benzodiazepine, on an in vitro slice preparation of the frog spinal cord was investigated using electrophysiological recordings. Midazolam potently (ED 50 = 1 nM) enhanced the depolarizing action of GABA on primary afferent fibres while leaving the depolarizing effect of glutamate, glycine or high K + solutions unchanged. Concentrations of midazolam higher than 100 nM had an antagonistic effect on GABA responses. Ro 14-7437 was a powerful and selective antagonist of the midazolam potentiation without affecting control responses to GABA, glutamate or high K + . The antagonism of GABA responses induced by high doses of midazolam was not sensitive to Ro 14-7437. Our data suggest that midazolam is a very potent and selective modulator of GABA responses: this finding illustrates that electrophysiological techniques can detect specific effects of very low concentrations of benzodiazepines on a CNS since preparation with well preserved architectural organization.

Indolinone nitroxides undergo a homolytic substitution with aroyl oxyl radicals, leading to two isomers, 7-aroyloxy- and 5-aroyloxy-derivative, respectively, whose structures were assigned on the basis of the ESR hfccs and of the 1H NMR spectra of the corresponding amines. The presence of aroyl oxyl radicals in the reaction medium was demonstrated by thermal decomposition of benzoyl peroxide in the presence of aromatic acids.

Stable nitroxide radicals were obtained by the oxidation of 1-hydroxy-2,2-diphenylquinolines prepared by allowing the PhMgBr to act upon a number of 2-phenylquinoline-N-oxides in THF. Methyl-, ethyl- and benzyl-magnesium compounds gave rise to other nitroxides which were identified from their ESR spectra, but not isolated in the solid state. t-Butyl-magnesium chloride reacted with quinoline-N-oxides giving only the deoxidation products. The ESR spectra of numerous nitroxide radicals were interperted and discussed.

The mechanisms and kinetics of charge trapping and untrapping have been determined by examining the thermoluminescence and photostimulated emission from benzene. The nature of the electron traps is discussed in terms of dose dependence, action spectrum for stimulated emission and effects of sample treatment prior to irradiation. The emission spectrum is formed from three components; fluorescence from benzene monomer and excimer and phosphorescence from benzene excimer. The emission spectrum varies throughout the glow curve and is shown to depend on the untrapping mechanisms involved.

The reactions of indolinone nitroxides 7 and of the corresponding amine precursors 15 with organic peracids were studied, and were found to give substitution products at the aromatic nucleus, i.e. 5-aroyloxy- and 7-aroyloxynitroxides 8 together with N-oxides 10 and with 7-hydroxynitroxides 9 . Structures were assigned on the basis of ESR and 1 H NMR spectra. A reaction scheme was proposed involving a homolytic substitution which accounts for the products obtained and is supported by an experimental proof.

The recently reported potentiation of γ-aminobutyric acid (GABA) evoked depolarizations by caffeine in the frog spinal cord might involve an interaction with GABA-linked benzodiazepine receptors. This possibility was investigated using a new potent benzodiazepine, midazolam, and a benzodiazepine antagonist, Ro 147437. Caffeine or midazolam enhanced the amplitude of submaximal GABA responses by about 50%; when equieffective enhancing doses of these compounds were simultaneously applied. GABA depolarizations were usually depressed below control levels. It was however possible to detect a narrow range of concentrations of midazolam which had an additive effect to the enhancement by caffeine. Ro 147437 did not block caffeine-induced potentiations of GABA responses. It is suggested that caffeine and benzodiazepines have distinct modes of action in modulating GABA-induced depolarizations in the in vitro spinal cord of the frog.

A parasagittal slice of the frog spinal cord was kept in vitro for electrophysiological recordings from dorsal and ventral roots. Low concentrations of caffeine (50 μM) which had relatively small effects on baseline electrical activity, increased the depolarizing action of GABA on dorsal root fibers by 50%. A similar result was also obtained when GABA motoneuronal responses were tested. On dorsal roots the potentiation of GABA responses by caffeine was reflected by a significant decrease in GABA ED 50 value without change in the maximal response amplitude; this enhancing action of caffeine was not blocked by bicuculline (5 μM) but was abolished by flurazepam (5 μM) or by Ca 2+ antagonists (Mn 2+ and Cd 2+ ). Blockade of interneuronal activity by procaine left the potentiating action of caffeine unchanged. High doses of caffeine (up to 1 mM) produced a seemingly non-competitive antagonism of GABA responses. We suggest that caffeine can modulate GABA responses through two different mechanisms: a potentiation of GABA effects (seen with low doses of caffeine) probably due to Ca 2+ mobilization and on antagonism of GABA responses (typically seen with large doses of caffeine) perhaps caused by block of GABA receptor-activated channels. This novel caffeine-GABA interaction may be useful to interpret some of the effects of caffeine on mammalian behaviour.

The excitatory responses to amino acids were recorded intracellularly from motoneurones in the isolated frog spinal cord and the effect of the antagonist d -α-aminoadipate examined. An unusual profile of antagonism was obtained in that with 50–100 μM d -α-aminoadipate the depolarization to quisqualate was unaffected (or slightly potentiated) while those to l -glutamate, l -aspartate and N-methyl- d -aspartate were all considerably attenuated. d -α-aminoadipate did not influence passive membrane properties although a small hyperpolarization was sometimes evident. Dorsal root evoked excitations of motoneurones, particularly those using low strength stimulation, were also susceptible to antagonism by d -α-aminoadipate. These data suggest a separate neuroeffector/receptor mechanism for quisqualate compared to l -glutamate, l -aspartate and N-methyl- d -aspartate.

The isolated frog spinal cord was used as a test system to investigate the interactions of midazolam and caffeine with GABA-evoked responses recorded from dorsal afferent fibres. Midazolam was a potent stimulator ( ED 50 = 1 nM ) of GABA effectiveness on this preparation since the ED50 value for GABA was nearly halved. The enhancing action of midazolam was apparently produced via activation of benzodiazepine receptor mechanisms with no detectable receptor cooperativity and with a rather high sensitivity to the selective benzodiazepine antagonist Ro 14–7437 (antagonist ED 50 = 2.5 nM ). Responses to glutamate, glycine or high K+ were unchanged in midazolam solutions. When midazolam was applied in concentrations equal or larger than 100 nM, antagonism of GABA responses was evident. Caffeine (50 μM) also potentiated GABA responses through a mechanism distinct from benzodiazepine receptor activation as this action of caffeine was insensitive to Ro 14–7437. Mixtures of low doses of caffeine and midazolam frequently antagonized GABA responses. It is suggested that the blockade of GABA responses by caffeine-midazolam mixtures might account for the reversal of some behavioural actions of these substances even if they probably operate through separate pharmacological mechanisms.

Copolyesters containing rigid aromatic units based on 4,4'-sulfonylbisphenol (bisphenol S) have been prepared by melt mixing poly(propylene terephthalate) (PPT) with an ethoxylated bisphenol S (sulfonyldiphenol). The insertion of the bisphenol units inside the polymer chain occurred quantitatively and no side reaction has been observed. The copolymers displayed good thermal stability. The main effect of copolymerization was a lowering in the degree of crystallinity and a decrease of the melting temperature with respect to PPT. On the contrary, an increment of T-g as the content of bisphenol S units increased due to the stiffening effect of the moieties deriving from bisphenol S. The Wood equation described well the correlation between T-g and composition.

Imidazolium poly(butylene terephthalate) ionomers with ionic groups located randomly along the polymer chain or selectively as end-groups (telechelic) have been prepared in order to determine their antimicrobial (AM) activity. Two different approaches have been followed for the linkage of the imidazolium to the polymer backbone: a covalent bond and an ionic aggregation to sulfonated groups covalently bonded to the polymer. The ionic groups have been linked to the polymer in order to improve the long-term AM activity since the low molecular weight additives commonly used tends to migrate toward the surface during use. We have found that imidazolium ionomers present AM activity comparable with that of commercial antimicrobial agents such as Triclosan. The AM activity depends on the polymer architecture, the telechelic approach being more active compared to the random approach. We have proved that imidazolium ionomers retain their high AM activity even after 6 days in water at 60 °C while Triclosan consistently loses his activity.

Recent regulation IEC 60335-1 ed.4 (2008) was introduced for materials used in electric appliance, establishing new limits in glow wire ignition temperature (GWIT) performance for materials used for electric connectors. Development of new products with high GWIT is possible, but the main issue is to keep good mechanical properties and processability, as well as tracking resistance (CTI). Only few patents and no scientific publication exist about glow wire test performance of polymers. In this work we report GWIT and CTI properties for three engineering thermoplastic polymers (PBT, PET and PC). We have also studied the phenomena involved in this test, treating the phenomena with the parameterization approach already used in the studies of the fire behaviours of polymers. PC, PBT and PET filled with 30% w/w glass fibres have been tested, and material properties that can be related to GWIT and CTI performance have been measured by TGA, Laser flash, Py-GC/MS. CTI seems to be predictable with the char formation tendency of the materials, so PBT show a higher tracking resistance than PET and PC. Polycarbonate is the only that pass the test glow wire (GWIT higher than 775°C) but generally GWIT performance is not directly related with degradation temperature, since PET is more thermal stable compared with PBT, but less stable in glow wire test. The ignition process, together with the unsteady heat and mass transfer process characteristic of glow wire test, are affected by many parameters at the same time. That’s why it is not easy to relate results of TGA, Laser flash, Py-GC/MS with the glow wire ignition temperature of the materials tested, but the whole of these properties can give useful indication.

Aliphatic poly(butylene 1,12-dodecanedioate) is an interesting biodegradable polyester characterized by high thermal stability and high crystallinity, but low melting temperature. In order to improve the performances of this polymer some novel fully aliphatic random copolyesters have been prepared starting from 1,4-butanediol and different molar ratio of 1,12-dodecanedioc acid and 1,4-cyclohexanedicarboxylic acid. The copolymers have a notable resistance to thermal degradation, thermal properties which vary as a function of the composition, and maintain the mechanical characteristics of the poly(alkylene dicarboxylate). In particular, the copolymer containing the 70 mol% of 1,4-cyclohexanedicarboxylate units improves the thermal properties of the poly(butylene 1,12-dodecanedioate) and presents a very high biodegradation rate, higher than those of the two parent homopolymers. This behavior has been correlated to the low level of crystallinity of the sample and to the composition of the amorphous phase. Therefore, these novel fully aliphatic copolymers represent an interesting new class of copolyesters which can balance good physical properties and high biodegradability.

Poly(butylene 1,4-cyclohexanedicarboxylate), an aliphatic polyester with favorable properties, such as resistance to weather and potential biodegradability, has been synthesized with different cis/trans ratio of the 1,4-cyclohexylene ring. The samples show high degradation temperatures, independent of the stereochemistry of the aliphatic ring. Instead, glass transition temperature, crystallization and melting behavior are strongly influenced by the cis/trans ratio. The trans isomer, more rigid and symmetric than the cis, favors higher transition temperatures and crystallizability. The DMTA spectra present two secondary relaxations, attributed to the -(CH 2 )- unit and aliphatic ring motions, which can be beneficial for improving impact resistance properties. The physical properties are compared with those of PBT and PCCD.

Poly(butylene terephthalate) (PBT) and poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) (PCCD) ionomers containing terminal ionic units, derived from a novel sodiosulfonate epoxy molecule, were synthesised using an end capping technique in solution. The sulfonated epoxide has the fundamental feature of selectively reacting with the polymer carboxylic terminal groups and therefore, creating polymers with terminal ionic groups. The presence of the sodiosulfonate end groups was confirmed by 1 H NMR spectroscopy and titration of carboxyl end groups. Differential scanning calorimetry (DSC) indicated that the presence of ionic end groups has a different effect on the crystallisation process. In particular in PBT the ionic groups cause an increment of the crystallisation rate, whereas, in PCCD the opposite effect is observed.

Aliphatic poly(alkylene dithiocarbonate)s are an interesting class of potentially biodegradable and biocompatible materials in analogy with their homologous poly(alkylene carbonate)s. In this paper, the properties of poly(hexamethylene dithiocarbonate) (SSR6) are compared to those of poly(hexamethylene carbonate) (HMC) in order to study the effect of the substitution of oxygen atoms with sulphur atoms in the polymer backbone. SSR6 presents a higher level of crystallinity and a faster crystallisation rate with respect to HMC. The melting temperature in SSR6 is about 60 °C higher, due to a solid–solid transition between phase I, stable at room temperature, and phase II, present at high temperature. HMC crystallises only in phase I and melts at a relatively low temperature (30 °C). The capacity of SSR6 to crystallise in phase II has been attributed to the higher flexibility and mobility of the chains containing –S–CO–S– groups with respect to the chains containing –O–CO–O– groups. The pure phase II in SSR6 has been obtained in isothermal conditions and its crystallisation rate and mechanism have been analysed.

Copolyesters of terephthalic acid with bis-(hydroxyethyl ether) of bisphenol A (BHEEB) in different molar ratios have been synthesized by reactive blending from terephthalate polyesters and by melt polycondensation from the monomers. By this way, bisphenol A groups were inserted in the polyester chains with the aim to obtain polyesters with improved mechanical properties. The insertion of the BHEEB into the polyester backbone is quantitative and does not give rise to side reactions. These copolyesters can be obtained by the chemical recycling of commercial polymers; indeed BHEEB can be synthesized by chemical recycling of bisphenol A polycarbonate and may be incorporated in the polyester by reactive blending with recycled terephthalate polyesters. A new method for BHEEB synthesis by chemical recycling of PC is also presented

Poly(butylene terephthalate) ionomers with imidazolium groups selectively located as end-groups (telechelic) have been prepared by melt polycondensation adding a hydroxyl derivatized imidazolium salt at the beginning of the polymerization process. The design of the chemical structure of the imidazolium salt is of fundamental importance in order to achieve the synthesis of ionomers with good thermo-mechanical properties. The final ionomers present high molecular weight, good color, transparency and thermal stability. Imidazolium ionomers present good antimicrobial (AM) properties comparable with those of commercial AM agents. The incorporation of the ionic groups in the polymer chain prevents their migration during use and therefore the antimicrobial activity can be preserved for longer time.

International audience; Anatase-structured TiO2 films were deposited on a commercial fluorinated polymer (FEP) with a treated surface, by means of a sol-gel dip-coating technique. Two different curing temperatures were investigated and the film microstructures were characterized by X-ray diffraction, atomic force microscopy and scanning electron microscopy analyses. The prepared samples presented very high performances in terms of photocatalytic activities, analyzed by the degradation of an organic dye in a liquid medium, and of bactericidal activities, tested on Staphylococcus aureus (S. aureus, a Gram positive bacterium) and Escherichia coli (E. coli, a Gram negative bacterium).

Surface coatings of pretreated poly(fluoroethylene propylene) (FEP) films by UV-induced graft copolymerization with 2-hydroxyethyl methacrylate (HEMA) and an antimicrobial agent, 3-hexadecyl-1-vinylimidazolium bromide (VIB), have been carried out. Surface chemical and morphological modifications were investigated with spectroscopic analysis using attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR), scanning electron microscopy (SEM) and X-ray diffraction distribution map of bromide atoms. Fluorescein dye absorption studies were performed in order to quantify the amount of reacted VIB. Antibacterial activities were assayed with Staphylococcus aureus ( S. aureus , a Gram positive bacterium) culture on HEMA-VIB modified FEP specimens, prepared with different amounts of the antimicrobial agent. In addition to bactericidal properties, the functionalized FEP surface also prevented the adhesion of microorganisms to the film.

International audience; The synthesis of novel poly(butylene dodecanoate)s containing different percentages of glycerol was successfully carried out. The polyesters are characterized by branched or cross-linked molecular structures, according to the glycerol content. The modification of the linear backbone of the poly(butylene dodecanoate) increases the rigidity and induces significant changes in the polymer behavior toward photodegradation with respect to UV irradiation. Such a result could be very significant for specific outdoor applications of the novel polyesters

Poly(butylene terephthalate) (PBT) is widely used for electrical and electronic devices as insulating material. For these applications PBT has to combine both good flammability and electrical properties (tracking resistance) measured, respectively, by UL94 and Comparative Tracking Index (CTI) tests. In this paper a simultaneous study of UL94 and CTI performances has been conducted on different PBT formulations with the addition of halogen-free flame retardants (diethylphosphinic acid aluminium salt (AlPi) and melamine polyphosphate (MPP)). A thermosetting resin (Ultem) has also been added. FTIR and TGA analyses have been used in order to relate the action of these additives to flammability and electrical properties. AlPi shows the best flame results achieving a V0 classification in UL94 test. On the other hand, melamine has the best performances in CTI tests. TGA and FTIR analyses show that AlPi acts in the condensed phase forming a consistent amount of char, while melamine acts in the gas phase and is not able to protect PBT during combustion.

Bisphenol A polycarbonate telechelic sulfonated ionomers have been prepared by melt polycondensation using bis(methyl salicyl) carbonate (BMSC), bisphenol A (BPA) and the sodium salt of sulfobenzoic acid phenylester (SBENa). Using an activated carbonate such as BMSC it is possible to decrease both reaction temperature and time respect to a standard polycondensation that use diphenylcarbonate (DPC) as carbonate precursor. Using the activated carbonate, ionomers with low Fries by-products and with good color have been obtained. The addition of SBENa permits the preparation of telechelic ionomers with ionic contents up to 3 mol%. All the properties of the telechelic ionomer obtained using BMSC are superior respect to those of the telechelic ionomers obtained using DPC. In particular, the ionomers prepared using BMSC are stable up to 400 °C and present higher glass transition temperature and storage modulus respect to standard PC.

Novel copolyesters have been prepared by polycondensation and by melt mixing of poly(butylene terephthalate) with an ethoxylated bisphenol S. No side reactions occur during the synthesis of the samples, as proved by NMR analysis. The polyesters were examined by TGA and DSC. The insertion of the bisphenol S (sulfonyldiphenol) group significantly improved the thermal stability of the polymer. The thermal analysis carried out using DSC technique showed that the T m of the copolymers decreased with increasing co-unit content, differently from T g , which on the contrary increased, exceeding in some cases 100 °C, and crystallization rate decreased. A polymer containing only terephthalate moieties and ethoxylated bisphenol S has been prepared for the first time.

High-performance materials in the optical field, with special reference to optical limiting applications, can be obtained by combining nonlinear optical (NLO) active molecules with high optical quality hosts. An interesting method is the synthesis of fullerene–polymer systems. In this paper novel fullerene–polysulfone samples were obtained by direct fullerenation between a commercial sample of polysulfone and fullerene, using electrophilic aromatic substitution reactions in the presence of AlCl 3 as catalyst. The synthesis was successful; the molecular structures of the samples, confirmed by 1 H NMR, IR, and UV analyses, indicate that fullerene is covalently bonded to the polysulfone chains. C 60 is random distributed along the macromolecules, in amounts varying from 0.5 to 3.2 mol%. The C 60 –polysulfone materials show a very high thermal stability, a glass transition temperature depending on the C 60 content, and interesting optical limiting properties.

Weatherable semicrystalline polyesters based on 1,4-cyclohexanedimethanol, 1,4-cyclohexanedicarboxylic acid (CHDA) or dimethyl 1,4-cyclohexane dicarboxylate (DMCD) can be prepared under normal melt-phase conditions, using titanium tetrabutoxide as catalyst. The effect of monomer ratio, reaction temperature and catalyst loading on the final polymer properties was studied. Under the proper polymerization conditions, poly(1,4-cyclohexylenedimethylene-1,4-cyclohexanedicarboxylate) polymers with high molecular weight can be obtained. During polymerization, isomerization can occur towards the thermodynamically stable cis-trans ratio of 34–66 mol%. Carboxylic acid end groups can catalyze the isomerization and therefore the polymerization is more critical starting from CHDA rather than DMCD. Moreover, temperature control becomes a key factor to avoid or to limit isomerization. The study of the isomerization of the different monomers permitted a better understanding of the isomerization and therefore of the polymerization process. Copyright © 2011 Society of Chemical Industry

In this work we present a three-dimensional numerical simulation technique for the study of ion permeation through ion channels embedded in silicon membranes, that can be exploited for sensor applications. The results of this work clarify how the charges embedded in the protein forming the ion channel can influence ionic conductance through silicon membrane slabs, controlling the channel conductance and selectivity with respect to ionic species.

The synthesis of poly(butylene terephthalate) (PBT) nanocomposites by in situ polymerisation method using an organo-modified layered doubled hydroxide is described. 4-Sulfobenzoic acid potassium salt, sodium dodecyl sulfate and dimethyl 5-sulfo isophthalate sodium salt were used as intercalating compounds to improve clay exfoliation. The thermal and dynamic mechanical properties of the nanocomposites prepared were investigated and compared to those of montmorillonite-type nanocomposites prepared by similar synthetic route. The nanocomposites obtained, independent of the degree of exfoliation, showed better dynamic mechanical properties respect to PBT homopolymer while improvements in thermal stability were achieved when dimethyl 5-sulfo isophthalate was used as intercalating agent, highlighting the importance of the interactions of ionic groups covalently linked to the polymer with the charged clay platelets.

In order to improve the thermal and mechanical properties of the poly(butylene 1,12-dodecanedioate), some novel aliphatic-aromatic random copolyesters have been prepared by starting from 1,4-butanediol and different molar ratio of 1,12-dodecanedioc acid and terephthalic acid. The samples were characterized by 1 H NMR and the molecular structure was correlated with the crystalline phase present, the level of crystallinity, the glass transition temperature, the mechanical behavior, and the biodegradability. In particular, the copolymer containing the 70 mol% of PBT repeating units notably improves the thermal and mechanical properties of the poly(butylene 1,12-dodecanedioate) towards those of PBT and maintains a very high thermal stability, but loses the biodegradability of the poly(alkylene dicarboxylate). Therefore, for this class of aliphatic–aromatic copolymers the chemical composition must be carefully chosen to reach a compromise between good thermal and mechanical performances and biodegradability, according to the necessity.

This study investigates on the preparation and characterisation of new random copolymers containing the monomeric units of a poly(arylene ether ketone) (PEAEK) and a poly(arylene thioether ketone) (PTATK) previously synthesised by our group. The syntheses were performed using a one-pot polymerisation method starting from 4,4′-difluorobenzophenone, bis(N,N-dimethyl-S-carbamate) of 2,2-bis(4-mercaptophenyl)propane (MBTA) and bisphenol A (BPA). Different mole percentages of BPA with respect to MBTA, varying from 20% to 80%, were used. The copolymers, obtained in good yields, have molecular weights in the range from 19,000 to 32,000 as determined by GPC. The structural proof is provided by 1H NMR spectroscopy. The TGA analysis shows that the high stability of PEAEK is only slightly affected by the introduction of the PTATK co-units in the chain. Indeed, the presence of sulphur atoms induces an initial degradation process at temperatures slightly lower than that of PEAEK, but in a second stage tends to improve the formation of crosslinkings. Moreover, the copolymers with an amount of PEAEK equal to 40 and 20 mol% show a small crystallinity, due to the presence of PTATK units. The Tg values are not affected by the composition of copolymers. Therefore, the presence of sulphur atoms in the polymer backbone does not significantly modify the PEAEK characteristics, whereas can induce important new properties, such as better flame resistance or higher refractive index.

A series of new aliphatic polyesters derived from 1,12-dodecanedioic acid and different diols with an even number of methylene units have been studied to assess the effect of the chemical structure on the final thermal properties of the materials. The polyesters have high thermal stability and are fast crystallizing polymers, with crystallization rate similar to that of polyethylene (PE). This behavior is connected to the fact that long aliphatic chains assume conformational characteristics very similar to that of PE. However, the polyester prepared from ethanediol shows a peculiar behavior (for example, double melting peak, melting and crystallization temperatures, which do not fit the trend of those of the other samples and ringed spherulites) owing to a probable different conformation, deviating from the all-trans planar typical of PE. In the isothermal crystallization studies, a bell-shape trend has been found for the crystallization rate as a function of the number of (CH2) units in the diol. The high crystallization rate of the sample with long (CH2) sequences has been attributed to the high chain flexibility and, thus, high mobility in the molten state and ease of chain folding. By reducing the aliphatic sequence length, instead, implications of the structural characteristics of the samples are probably involved. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1053–1067, 2007

A series of novel poly(arylene ether-thioether ketone) random copolymers were synthesised by copolymerisation of 4,4′-difluorobenzophenone with bis(N,N-dimethyl-S-carbamate) of 2,2-bis(4-mercaptophenyl)propane (MBTA) and 4,4′-dihydroxybiphenyl (BP). The syntheses were performed using a one pot polymerisation method starting from different mole percentages of BP with respect to MBTA, varying from 20% to 80%. The copolymers were obtained in good yields and had molecular weights in the range 10,000–17,000 as determined by GPC. The structural proof was provided by 1H-NMR spectroscopy. In order to study the effect of the copolymerisation on the thermal properties and crystal behaviour, also the poly(ether biphenyl ether ketone) homopolymer (PEBEK) has been synthesised using the same polymerisation method. The TGA analysis shows that the high stability of PEBEK is only slightly affected by the introduction of co-units in the chain. The copolymers with an amount of PEBEK variable from 80 to 50 mol% are crystalline, with percentage of crystallinity and melting temperature which decrease as the co-unit content increases. The samples with lower amount of PEBEK (40 and 20 mol%) are amorphous. The Tg values tend to decrease with the reduction of the percentage of PEBEK units.

Poly(propylene terephthalate/2,6-naphthalate) random copolyesters (PPT-PPN) were synthesized and characterized from the molecular and thermal point of view. All the polymers showed a good thermal stability. The main effect of copolymerization was a lowering in the crystallinity and a decrease of Tm respect to homopolymers. WAXD measurements indicated that PPT-PPN copolymers are characterized by isodimorphic cocrystallization. The defect free energies, calculated on the basis of the inclusion model proposed by Wendling and Suter, indicated that the amount of PT units incorporated in the poly(propylene 2,6-naphthalate) (PPN) β crystals is higher than the amount of PN units which cocrystallizes in the poly(propylene terephthalate) (PPT) crystalline phase, probably due to the larger molar volume of PN units compared to PT ones. Amorphous samples showed a monotonic increment of Tg as the content of PN units is increased, due to the stiffening effect of naphthalene rings in the chain. Finally, the Fox equation described well the Tg-composition data.

Novel poly(arylene thioether)s were synthesised using the one pot polymerisation method from the bis( N,N -dimethyl-S-carbamate) of 2,2-bis(4-mercaptophenyl)propane and activated difluoro aromatic compounds. Each of the polymers, obtained in good yields and with fairly high molecular weights, were characterised by IR, GPC and NMR analyses. In particular, the NMR characterisation was performed using 1 H NMR, 13 C NMR, DEPT, 2D COSY and 2D HSQC experiments. To study the effect on the thermal properties of replacing the ethereal oxygen atoms with sulfur atoms, we have synthesised the counterparts, the poly(arylene ether)s, with similar molecular weights. We observed that the substitution of the ethereal oxygen atoms with sulfur atoms results in a slightly lower thermal stability for the poly(thioether ketone)s, both under nitrogen and in air, and does not modify the T g values. For the poly(thioether sulfone), on the other hand, the thermal stability is equal to that of the poly(ether sulfone), while the T g is 10 °C lower. Furthermore, each sample is completely amorphous, with the exception of one of the poly(thioether ketone)s (sample 1b), which shows the capacity to crystallise, even if with a very slow crystallisation kinetics.

New telechelic poly(butylene terephthalate) (PBT) ionomers, characterized by the presence of some aliphatic sulfonated chain ends, were prepared by reaction with the 1,4-butane sultone. Two methods of synthesis were compared and the final polymers, containing different percentages of ionic groups, were characterized, with particular attention to the thermal properties. Thermogravimetric analysis shows that the presence of ionic groups does not modify the thermal stability of PBT. The differential scanning calorimetry indicates that the crystalline phase and the crystallinity degree of PBT do not change in the presence of ionic chain ends, whereas the crystallization rate was found to be strongly modified. The ionomers crystallize at very high rate, due to the nucleating effect of the ionic aggregations formed in the melt.