bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterocyclic polyamides containing hexafluoroisopropylidene groups
Authors: Bruma Maria , Hamciuc Corneliu , Hamciuc Elena , Mercer Frank , Belomoina Nataliya , Schulz Burkhard 
Published: March 2011

AbstractNew heterocyclic polyamides have been synthesized by solution polycondensation of aromatic diamines containing phenylquinoxaline units with diacid chlorides having both imide and hexafluoroisopropylidene (6F) groups. These polymers are soluble in polar aprotic solvents, such as N‐methylpyrrolidone (NMP) or N, N‐dimethylformamide (DMF), and can be cast into flexible thin films from solutions. They show high thermooxidative stability with decomposition temperatures above 400°C and glass transition temperatures in the range of 225‐300°C. The polymer films exhibit good chemical resistance towards diluted acids and good electrical insulating properties with dielectric constants in the range of 3.2–3.7.
Dodecyl dodecanamide as a model for the study of polyamide n‐chlorination. Unusual behaviors of the reaction system
Authors: Girardon V. , Tessier M. , Maréchal E. 
Published: March 2011

AbstractThe N‐chlorination of dodecyl dodecanamide (DDA) by ter‐butyl hypochlorite (tBuOCl) was carried out at 25°C in methylene chloride. The conversion is determined by 1H‐NMR and iodometric titrations of N‐chlorinated DDA (N‐Cl DDA). Curves of conversion‐time plots present singular profiles whose shapes are strongly depending on the reagent and product concentrations.
New aromatic‐aliphatic polyesters based on N‐alkyl carbazole groups in the main chain. Synthesis‐structure‐properties relationships
Authors: Drzewinski Isabel , Adès Dominique , Bélorgey Georges , Siove Alain 
Published: March 2011

AbstractPolyesters based on N‐butyl or N‐octylcarbazole units in the main chain were synthesized either by direct polycondensation between the carbazole dicarboxylic acids and ethylene glycol or from alcoholysis of the 2‐hydroxyethyl diesters in the presence of different catalytic systems. Depending on the reaction conditions together with the nature and the concentration of the catalyst, diethylene glycol (DEG) is formed as a side‐reaction product. DEG is incorporated in the polyester chain concurrently with EG and leads to the formation of ether links in the spacers. The DEG content as well as the length of the alkyl pendant group of the carbazole unit were found to have a drastical effect on the thermal properties. Furthermore, these materials form charge transfer complexes through carbazole nuclei with electron acceptor and electron donor molecules as well.
Synthesis and structure of elastomeric poly[ester‐block‐ether]s
Authors: Fray Miroslawa El , Slonecki Jerzy 
Published: March 2011

AbstractDifferent poly[ester‐block‐ether] (PEE) elastomers have been prepared in a two‐stage process, namely transesterification followed by polycondensation in the melt. These terpolymers consisted of poly(butylene terephthalate) (PBT), poly(oxytetramethylene) (PTMO) and dimerized fatty acid (DFA). The content of PTMO and DFA blocks was changed at a constant PBT mass ratio of 50. Supermolecular structure of synthesized polymers was investigated using optical microscopy (OM) and transmission electron microscopy (TEM). Thermal and mechanical properties were examined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMTA). An influence of dimerized fatty acid on the segment's comiscibility (phase separation) was estimated.
Synthesis and properties of polyamides derived from 1, 4‐bis(4‐aminophenoxy)‐2‐tert‐butylbenzene
Authors: Liaw Der‐Jang , Liaw Been‐Yang 
Published: March 2011

Abstract1, 4‐Bis(4‐aminophenoxy)‐2‐tert‐butylbenzene was synthesized and used as a monomer to prepare a series of polyamides by the direct polycondensation with various aromatic dicarboxylic acids in N‐methyl‐2‐pyrrolidone using triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.75–1.75 dL g−1. All the polyamides showed amorphous nature and most of them were soluble in polar solvents. Polyamides derived from 4, 4'‐sulfonyldibenzoic acid and 4, 4'‐hexafluoroisopropylidenedibenzoic acid were even soluble in common organic solvent such as THF. All polyamide films could be obtained by casting from their DMAc or NMP solutions. The polyamide films had a tensile strength range of 35–84 MPa, an elongation range at break of 3–7%, and a tensile modulus range of 1.2–2.5 GPa. These polyamides had glass transition temperatures between 203–268°C and 10% mass loss temperatures were recorded in the range of 456–472°C in nitrogen and 453–470°C in air atmosphere.
Chain extension of ketonic resins
Authors: Kizilcan Nilgün , Akar Ahmet 
Published: March 2011

AbstractChain extensions of cyclohexanone‐formaldehyde (CF) and acetophenone‐formaldehyde (AF) resins via their hydroxyl groups were studied. The chain extension was regulated by the ratio of hydroxyl groups/reactive reagents. Dimethyl dichlorosilane, phosphorus oxychloride, toluene‐2, 4‐diisocyanate, phthalic anhydride, tetrahydro phthalic anhydride, trimellitic anhydride, 4, 4'‐oxydiphthalic anhydride were used as chain extender reagent. It has been shown that solubilites, melting point and molecular weight of extended resins depended upon the characteristics of chain extender reagents.
Approach of the mechanism of poly(3‐octyl thiophene) crosslinking under electron beam
Authors: Froyer Gerard , Louarn Gu Y. , Ciprelli Jean Louis , Clarisse Christian 
Published: March 2011

AbstractPoly(3‐octylthiophene) was used as a negative resist in e‐beam microlithography. This conducting polymer fulfills the main requirements placed on materials which can be useful in this type of process. However, chemical modifications leading to crosslinking are not clearly established at this time. Approach of a mechanism is proposed in this paper which is supported by spectroscopic results obtained from the irradiated materials: it seems reasonable that crosslinking might occur between lateral alkyl groups eventually on carbon atoms in allylic position with the formation of a carbon ‐ carbon double bond between locally stacked Poly(3‐octylthiophene) chains.
Synthesis of new haemocompatible phospholipid polyurethanes for biomedical applications
Authors: Li Yu‐Jun , Nakaya Tadao 
Published: March 2011

AbstractA series of new phospholipid polyurethanes with hydrogenated poly (isoprene) glycol and 4, 4'‐methylenediphenyl diisocyanate was synthesized using 2‐[bis(2‐hydroxyethyl)methylammonio]ethylalkylphosphate and 1, 4‐butanediol as chain extender. The polyurethanes exhibited favorable haemocompatibilities and excellent mechanical characteristics.
Synthesis of novel amphiphilic di‐block and multiarmed star‐shaped copolymers based on polyisobutylene and poly(ethylene oxide)
Authors: Lemaire C. , Tessier M. , Maréchal E. 
Published: March 2011

AbstractThe synthesis of polyisobutylene‐b‐poly(ethylene oxide) linear diblock copolymers and multiarmed star‐shaped copolymers (having one‐polyisobutylene‐arm and two, three, or four, ‐poly(ethylene oxide)‐identical length arms) is described. All these different structures were characterized by MALDI‐TOF mass spectrometry and Size Exclusion Chromatography.
Biodegradable synthetic and semisynthetic polymers
Authors: Chiellini Emo , D'Antone Salvatore , Solaro Roberto 
Published: March 2011

AbstractAs a part of our continuing interest in the preparation of multifunctional polymeric materials and evaluation of their potential in pharmaceutical, medical and environmental fields, a survey on new polymeric systems of synthetic and semisynthetic origin, susceptible to bioerosion and/or biodegradation attack is presented. In particular, attention has been focused on the design, preparation and characterization of the following classes of hydrophilic and/or water‐soluble polymeric materials: hydroxyl‐containing poly(ester)s, hydroxyl‐containing poly(amide)s, hydrophilic polymers containing carboxylic groups, perhydroxylated oligo‐ and poly(saccharide)s, oxidized poly(saccharide)s, and hybrid polymeric materials based on blends of carboxyl‐containing synthetic polymers and proteins. The rationale of the research activity undertaken over the years is illustrated by focusing on some specific achievements of practical significance.
Thermoplastic starch revisited. Structure/property relationship for “dialed‐in” biodegradability
Authors: Zdrahala Richard J. 
Published: March 2011

AbstractStarch, totally biodegradable polysaccharide biosynthesized by numerous plants, is one of the most abundant renewable resources known to man. Composed mostly from linear amylose and highly branched amylopectin, the starch, in its granular form, is a crystalline material. When mixed with limited amount of water and subjected to heat and shear, starch undergoes spontaneous destructurization. Homogeneous melt, possessing thermoplastic character is formed, called thermoplastic starch. It absorbs between 5 and 30 % of water at relative humidity range 0 to 90 %. Water is principal plasticizer of this material changing its original stiffness from glass‐like to natural gumlike substance. This plasticization is accompanied by significant dimensional changes. Many polymers, both hydrophilic and hydrophobic, were blended with starch to modify its moisture sensitivity. To illustrate influence of admixed polymers on its moisture sensitivity and its effect on properties and biodegradability, poly(vinyl alcohol), poly(ethylene‐co‐vinyl alcohol) and poly(ethylene‐co‐methacrylic acid) were added to potato starch. This paper discusses results and observed trends.
Microbial aspects of the degradation of water‐soluble synthetic polymers
Authors: Kawai F. 
Published: March 2011

AbstractThis paper focuses on microbial aspects of degradation of synthetic polymers, especially of water‐soluble specialty polymers. The polymer structures analogous to natural polymers suggest biodegradability which originates from enzymes which do not discriminate between natural and synthetic polymers. Hydrolysis and oxidation are the primary processes for biodegradation. Assimilation rates are determined by the conversion of the polymer carbons into common metabolic products whether degradation is exogenous or endogenous. Biochemical mechanisms in the degradation of polyethers are summarized. Microbial symbiosis was involved in the degradation of a copolymer and the availability of symbiotic processes is suggested for the degradation of all copolymers. Transportability of PEG 20 000 through cell walls was suggested and a chemical process using hydrogen peroxide and ferric ions is proposed for the depolymerization of PEG with Mn more than 20 000 and its copolymers.
Environmental aspects of photodegradable plastics
Authors: Guillet James 
Published: March 2011

AbstractDuring the latter half of this century the production of synthetic plastics and fibers has grown so that the total volume of plastics produced world–wide now exceeds that of steel. This paper is concerned with theoretical and experimental studies relating to the environmental consequences of such a rapid shift from a technology based primarily on agriculture, forestry and metallurgy to one based on chemical raw materials such as oil, coal and natural gas. It is shown that plastics and synthetic fibers have the lowest energy costs of all comparable materials and cause less environmental pollution in their production and fabrication. They are easily recycled when not contaminated with other materials and can be manufactured in photo‐or biodegradable modifications tailored to highly litter–prone applications. The topics covered include sections on resource costs and renewal, environmental considerations, the technology and role of photodegradable plastics, and experimental studies of the biodegradation of conventional and photodegradable polyethylene, polypropylene and poly(ethylene terephthalate).
New catalytic systems for the manufacture of poly(aspartic acid)
Authors: Ross Robert J. , Batzel Daniel A. , Meah Abdul Rahman , Kneller James F. 
Published: March 2011

AbstractAspartic acid (I), when heated to a temperature in excess of 180 °C, undergoes a solid‐state condensation polymerization to afford the useful polymeric intermediate known as poly(succinimide) (II). Treatment of poly(succinimide) with aqueous base, such as sodium hydroxide, affords sodium poly(α,β‐DL‐aspartate) (III) also known as thermal poly(aspartate) (TPA). Acid catalysts, such as phosphoric acid have been added to the aspartic acid to afford higher‐molecular‐weight poly(succinimide) than is obtained in the non‐catalyzed polymerization. Recently, new sulfur‐based catalysts have been disclosed for the polymerization of aspartic acid. The sulfur‐containing catalysts provide a route to highly biodegradable, low‐color poly(aspartate)s in the molecular weight range of 2 000 to 20 000. A comparison of biodegradability, molecular weight, and spectral characteristics of the poly(succinimide)s and poly(aspartate)s derived from the catalyzed and non‐catalyzed polymerizations is presented.
Light scattering and dielectric relaxation studies of glass forming liquids
Authors: Fischer Erhard W. , Patkowski Adam , Steffen Werner , Gläser Harald , Kanaya Toshiji , Reinhardt Lutz , Reiter Johannes , Thurn‐Albrecht Thomas , Stickel Franz‐Josef , Eckstein Eva 
Published: March 2011

AbstractExtended Abstract: Glass forming organic liquids and polymers exhibit long range density fluctuations with correlation length ξ in the range of 10–300 nm at temperatures above Tg (1 ‐ 6). This follows from dynamic and static light scattering experiments revealing some unexpected features, which cannot be explained on the basis of conventional liquid state theories: (i) In static light scattering the intensity I(q → 0) is no longer proportional to the isothermal compressibility, (ii) This excess scattering Iexc shows a strong q‐dependence (q = (4π/Λ.)sin(θ/2)) corresponding to a correlation length ξ in the above mentioned range, (iii) The Landau‐Placzek ratio IRayleigh/2IBrillouin is much too high compared with the results of light scattering theories, (iv) In photon correlation spectroscopy a new ultraslow hydrodynamic mode (Γ ˜ q2) is detected with relaxation rates Γ about 10−6 to 10−9 lower than those of the α‐process at a given temperature.In order to explain these observations, a two‐state fluid model is proposed, which starts from the coexistence of “liquid‐like” and “aperiodic solid‐like” regions within the liquids. Such ideas have been discussed many times before, so for example A.R. Ubbelohde (7) speculates about “anticrystalline” clusters in liquids. Molecular dynamics simulations of atomic liquids showed that long range orientational fluctuations appear upon supercooling (8). A preferred icosahedral ordering is observed (9) and the number of icosahedral clusters increases with decreasing temperature (10). In connection with the interpretation of the dynamics of supercooled liquids different “two‐state” models have been proposed (11 ‐ 15).For the explanation of the light scattering results we propose that the molecules in the different dynamic states (“liquid” or “solid”) aggregate during annealing of the liquid at temperatures above Tg. Experiments showed that the equilibration times can be rather long (3 ‐ 5), but nevertheless the liquids exhibiting long range density fluctuations are in the state of lowest free energy. We claim that our observations are the first experimental proof of the existence of such different dynamic states, which have been discussed many times before. The extended secondary clusters can also be detected by ultra small angle X‐ray scattering.
Computational modelling of declination loops under shear flow
Authors: Lavine Marc S. , Windle Alan H. 
Published: March 2011

AbstractOptical observations of sheared lyotropic and thermotropic liquid crystals have shown them to have a rich microstructure dominated by disclination loops and networks. In thermotropic liquid crystalline polymers it has been possible to freeze in the microstructures, which are then sectioned and analysed by optical and electron microscopy, to enable the identification of the predominant types of disclinations.In this work a computational model is presented which simulates the development of texture in liquid crystalline materials. The model has been designed so that it is possible to study large localised distortions which are subjected to a flow field. In the aspect of the work reported here, simulations have been used to study the influence of simple shear on individual disclination loops placed in an otherwise undeformed sample. The subsequent deformation of the loop is shown to be dependent on the angle that the rotation vector of the loop makes with the vorticity direction.
Polymer crystallisation: Role of metastability and the confluence of thermodynamic and kinetic factors
Authors: Keller A. , Rastogi S. , Hikosaka M. H. 
Published: March 2011

AbstractConsideration is given to the effect of size on the thermodynamic stability in situations where two or more phase variants compete in the course of a phase transformation. It is found that, pending on material parameters, a situation can arise where the stabilities of the competing phases invert with size. Such a size induced stability inversion can have a profound influence on phase development in general connecting also with the kinetics of the phase transformation. Specifically, this newly considered combination of interrelated thermodynamic (stability) and kinetic (rates) factors can provide an explanation for the frequently experienced dominance of metastable phases (the century old Ostwald Stage Rule). When applied to polymers, as in the example of polyethylene, it provides a new outlook for polymer crystallisation. Amongst others it creates a unified approach for the two, so far largely disconnected areas of chain folded and extended chain type crystallisation incorporating (not contradicting!) existing approaches within a widened framework.
Macromolecular aggregation: Complexation due to hydrogen bonding and hydrophobic association
Authors: Jiang Ming , Li Mei , Liu Lu , Xiang Maoliang , Zhu Lei 
Published: March 2011

AbstractThis paper reports the main results of the studies carried out in our laboratory on various kinds of polymer aggregation in aqueous and organic solutions. (1) In solutions of a polymer blend with controllable hydrogen bonding, a transition from individual polymer coils to intermolecular complex is observed as the hydrogen bonding interaction increases to a certain level. This is found to be a general phenomenon of polymer blends in which hydrogen bonding is adjustable. (2) A new kind of aggregation behavior of block ionomers based on SEBS is found and studied by fluorospectroscopy. The results explore that the block ionomer can form dispersion of hydrophobic aggregates in water stabilized by rare ionic groups. (3) Fluorocarbon‐containing PNIPAM in water establishes hydrophobic association. Fluorocarbon‐modified pyrene (PycoRf) is found to be qualified to serve as a fluorescent probe to monitor the association.
Failure modes in vapor‐deposited organic led's
Authors: Antoniadis Homer , Hueschen Mark R. , Miller Jeffrey N. , Moon Ronald L. , Roitman Daniel B. , Sheats James R. 
Published: March 2011

AbstractA study of the main failure mechanisms in vacuum vapor‐deposited organic light‐emitting diodes (LED's) is presented. Three degradation modes were identified for a prototype bilayer ITO/TPD/Alq3/Mg/Ag device: a) formation and growth of black non‐emissive spots, b) abrupt ceasing of light emission associated with catastrophic failures caused by electrical shorts, and c) long term wearout associated with the decrease of quantum efficiency and luminance along with an increase in voltage, while the device is stressed under constant current.
Photoluminescence enhancement in organic microcavity structures
Authors: Dirr Siegfried , Wiese Stefan , Johannes Hans‐Hermann , Böhler Achim , Ammennann Dirk , Kowalsky Wolfgang 
Published: March 2011

AbstractWe have studied the photoluminescence properties of the metal chelates aluminum‐tris(8‐hydroxychinoline) (Alq3) and tris(4,4,4‐trifluoro‐1‐(2‐thienyl)‐1,3‐butanediono)‐1,10‐phenanthroline europium(III) (Eu(TTFA)3Phen) sandwiched between a planar Fabry‐Perot microcavity structure. A strong influence of the position of the emission thin film on the luminescence spectra has been observed. The emission intensity normal to the substrate surface is drastically enhanced by an order of a magnitude if the active layer is placed at the antinode of the standing wave in the cavity. In comparison to non‐resonant Alq3 structures, the FWHM of the spectrum is reduced from 100 nm to about 20 nm. We also show that the Eu(TTFA)3Phen luminescence is spacially directed due to the inherent linewidth of only Sum.
New luminescent polymers for leds and LECS
Authors: Hwang Do‐Hoon , Chuah Beng Sim , Li Xiao‐Chang , Kim Sung Tae , Moratti Stephen C. , Holmes Andrew B. , De Mello John C. , Friend Richard H. 
Published: March 2011

AbstractStatistical copolymers 5 containing poly(2‐dimethyloctylsilyl‐1,4‐phenylenevinylene) (DMOS‐PPV) and poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) have been synthesized using the dehydrohalogenation condensation route. The copolymers show a shift of photoluminescence maxima to longer wavelengths as the proportion of the MEH‐PV unit increases. This trend is accompanied by reduced efficiencies and lower turn‐on voltages in single layer electroluminescent devices. Light‐emitting electrochemical cells (LECs) have been prepared using a blend of DMOS‐PPV 1 with poly(ethylene oxide)/lithium triflate and the homopolymer poly[2‐methoxy‐5‐(triethoxymethoxy)‐1,4‐phenylene vinylene] (MTEM‐PPV) 9 with lithium triflate. In comparison with single‐layer devices which were fabricated using the homopolymers 1 and poly[2,5‐bis(triethoxymethoxy)‐1,4‐phenylene vinylene] (BTEM‐PPV) 10, the LEC devices showed lower turn‐on voltages.
Synthesis and characterization of a soluble blue light emitting alternating copolymer
Authors: Cho Hyun Nam , Kim Jai Kyeong , Kim Dong Young , Kim Chung Yup 
Published: March 2011

AbstractAn alternating copolymer with monomer units of fluorene and phenylenedivinylene was synthesized by reaction between n‐hexyl fluorene phosphonium salt and isophthalic aldehyde based on the Wittig reaction. The polymer solution in chloroform was made into a film with a very fine surface by spin‐casting on indium‐tin oxide (ITO) coated glass to fabricate a light emitting diode (LED) with an aluminum negative electrode. The optical absorption spectrum of the solid film shows a peak at 370 ran while the PL spectrum has the main peak at 560 nm with a secondary peak at 440 nm and the EL spectrum has a single peak at 560 nm showing the Stokes shift of 190 nm. The peak in the PL spectrum shifts to 420 nm with a vibronic structure at 440 nm on either dilution by chloroform or blending with polyvinylcarbazole (PVK). The emissive polymer bulk seemed to generate sites for excimers and molecular aggregates which were diminished on the dilution or blending. The peak in the EL spectrum also shifts to 440 nm on blending of 20% of the copolymer with PVK. Further dilution to 10% of the copolymer shifts the EL peak to 420 nm with the onset potential of 15 V and the highest quantum efficiency of 0.01% in this series. The concentrated channels were developed in the blends with severe phase separation to show a lower onset potential but poor quantum efficiency.