bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid crystalline networks composed of rigid spacerless monomers: kinetics of network formation, anisotropic structure and mechanical properties
Authors: Braun Dietrich , Frick Gerhard , Grell Martin , Klimes Michael , Wendorff Joachim H. 
Published: April 2003

AbstractRigid isotropic and anisotropic networks were formed by photopolymerization of spacerless liquid crystalline diacrylates and of mixtures of these diacrylates with spacerless monoacrylates in the isotropic and liquid crystalline state. The total conversion of double bonds and the orientational order is strongly restricted for the case of network formation based solely on the diacrylates due to steric constraints. These constraints are considerably relaxed in networks formed from mixtures of di‐and monoacrylates. Such networks display a well defined orientational order. The dynamical mechanical properties were found to correspond to those found for networks based on diacrylates with flexible spacers, the anisotropy of the mechanical properties of oriented networks is weak.
A spin‐probing study of non‐magnetic ionomers: Cu2+ ‐containing polyethylene/methacrylic acid copolymer neutralized with Zn2+
Authors: Yamauchi Jun , Narita Hidehiro , Kutsumizu Shoichi , Yano Shinichi 
Published: April 2003

AbstractA spin‐probing technique was first applied to a study of a non‐magnetic ionomer, polyethylene/methacrylic acid copolymer neutralized with Zn2+ (E‐MAA‐Zn); 2 mol‐% Cu2+ ions were incorporated in replacement of Zn2+, and its ESR spectra were observed in detail at various temperatures in order to obtain physico‐chemical properties of E‐MAA‐Zn, especially its structural changes. We found no significant influence of the 2 mol‐% Cu2+ ‐incorporation upon the properties of the Zn2+ ionomer by differential scanning calorimetry (DSC), which showed two endothermic peaks, (1) an irreversible one at lower temperature which is associated with the ionic aggregate phase in the ionomer, (2) a reversible one at higher temperature with considerable thermal hysteresis which is due to melting of the polymer main chains. ESR hyperfine coupling constants (A∥ and A⊥) of Cu2+ showed no sign of structural changes of the polymer around the phase‐transition temperatures, whereas ESR g‐values (g∥ and g⊥) of Cu2+ proved the onset of the softening of the polymers to be attributable to polymer melting. The latter slope‐changes in the temperature dependences were reversible, although with considerable thermal hysteresis. These findings are compatible with the DSC data. As for the irreversibility regarding the endotherm at lower temperature, broad ESR hyperfine components recovered gradually, indicating an order‐disorder nature of the ionic aggregate phase transition.
New poly(amide‐imide)s synthesis, 16. Preparation and properties of poly(amide‐imide)s derived from 3,3‐bis[4‐(4‐aminophenoxy) phenyl]phthalide and various bis(trimellitimide)s
Authors: Yang Cnin‐Ping , Lin Jiun‐Hung 
Published: April 2003

AbstractA series of novel bis(phenoxy)phthalide‐containing poly(amide‐imide)s 3 were synthesized via direct polycondensation of 3,3‐bis[4‐(4‐aminophenoxy)phenyl]phthalide (BAPP) with various aromatic bis(trimellitimide)s 2 in N‐methyl‐2‐pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. Poly(amide‐imide)s 3 having inherent viscosities up to 1,68 dL/g were obtained in quantitative yields. Most of the resulting polymers showed an amorphous nature and were readily soluble in polar solvents such as NMP and N,N‐dimethylacetamide. All the soluble poly(amide‐imide)s afforded transparent, flexible, and tough films. The glass transition temperatures of these polymers were in the range of 237–292°C and the 10% weight loss temperatures were above 500°C in nitrogen. The properties of poly(amide‐imide)s 3 were compared with those of the corresponding isomeric poly(amide‐imide)s 3′ prepared from 3,3‐[4‐(4‐trimellitimido‐phenoxy)phenyl]‐phthalide and various aromatic diamines.
Divalent cation interactions with a carboxylated derivative of scleroglucan
Authors: Bosco Marco , Sussich Fabiana , Gamini Amelia , Reisenhofer Edoardo , Adami Giampiero , Rizzo Roberto 
Published: April 2003

AbstractDivalent cation binding was investigated on a semisynthetic carboxylate derivative obtained from the fungal polysaccharide scleroglucan. Polarography, circular dichroism and isothermal microcalorimetry were used to study both the binding ability of Cu(II), Pb(II), and Zn(II) ions and the macromolecular properties of the systems under investigation. A theoretical model, proposed by Schwarz for the cooperative binding, was used to evaluate binding constants and the parameter σ related to the degree of cooperativity. All findings are discussed in terms of the differences in the binding ability of the different cations investigated. Pb(II) ions exhibit the higher affinity for oxidised scleroglucan and, in addition to this, its binding process is characterised by a cooperative behavior due to the onset of a disorder‐to‐order conformational transition of the polysaccharidic backbone. On the other hand, Cu(II) ions are less effective in the binding and unable to induce the conformational transition.
Association behavior of linear ω‐functionalized polystyrenes in dilute solutions
Authors: Borlenghi Attilio , Pitsikalis Marinos , Pispas Stergios , Hadjichristidis Nikos 
Published: April 2003

AbstractLinear polystyrenes with dimethylamino end groups were prepared by anionic polymerization, using 3‐(dimethylamino)propyllithium as initiator and high vacuum techniques. The amino group was transformed to a sulfozwitterionic moiety by reaction with 1,3‐propanesultone. The dilute solution properties were studied by means of membrane osmometry (MO), low‐angle laser light scattering (LALLS) and viscometry in solvents with different polarity. The amine‐capped polymers, studied by LALLS in tetrahydrofuran (THF), toluene and CCI4 show no evidence of association. In contrast, the zwitterionic samples exhibited a relatively strong association in CCI4 (relative permittivity ε = 2.24), weak in THF (ε = 7.4), and intermediate in toluene (ε = 2.4). The association numbers were lower than those found for linear polyisoprenes and polybutadienes with the same end groups. Viscosity measurements supported the results drawn from LALLS. The results provide strong evidence that the micelles behave hydrodynamically as star polymers. The association behavior is best described by the linear head packing model.
Temperature dependence of the χ‐parameter between polystyrene and polyisoprene
Authors: Rudolf Bernd 
Published: April 2003

AbstractThe temperature dependence of the interaction parameter χ between polystyrene and polyisoprene was investigated. Cloud point, PVT and small angle X‐ray scattering measurements were performed. From various cloud point curves, χ was determined via the Flory‐Huggins theory. Using the PVT‐‐data, χ could be calculated using an equation‐of‐state approach due to Patterson, and the solubility parameter approach. For both methods, the well‐known Berthelot relationship proved to work well, i. e. no adaption of parameters to the experiments was required. Moreover, χ was determined from X‐ray scattering data, using the random phase approximation. Finally these parameters are compared, and in addition parameters determined from X‐ray scattering on diblock copolymers are included. It turns out that the temperature dependence of the χ‐parameters does not depend too much on the method of determination, its absolute value, however, does.
Synthèse d'homopolymères et de copolymères de la N‐acryloyglycine et de l'acide N‐acryloyliminodiacétique, 3. Evaluation de leurs propriétés complexantes vis‐à‐vis de l'ion métallique Cu2+
Authors: Montembault Véronique , Soutif Jean‐Claude , Brosse Jean‐Claude 
Published: April 2003

AbstractHomopolymers and copolymers of N‐acryloylglycine with acrylic acid and acrylamide were synthetized by radical mechanism using azoisobutyronitrile as initiator in dioxane at 80°C. Moreover, hydrolysis conditions of the ester groups of the diethyl N‐acryloyliminodiacetate homopolymers and copolymers with acrylic acid and acrylamide, previously synthetized, have been determined to avoid hydrolysis of the amide functions of the diethyl N‐acryloyliminodiacetate and acrylamide units. The obtained macromolecular structures have a density of complexing groups which varies either in the same unit (one or two aminoacetic groups) or along the polymer chain. The influence of this density on the complexing ability of the synthetized polymers for Cu2+ was investigated by potentiometry and by visible and ultra‐violet absorption spectroscopy.
Preparation and structure‐property relationships of polymeric materials containing arylenevinylene segments — perspectives for new light‐emitting materials
Authors: Greiner Andreas , Bolle Babett , Hesemann Peter , Oberski Josef M. , Sander Roland 
Published: April 2003

AbstractWell defined oligo(arylenevinylene)s were prepared by Pd‐catalyzed coupling of dibromoarenes and styrenes. The mixing behavior of these oligo(arylenevinylene)s with polymers is significantly influenced by the structure of the oligo(arylenevinylene)s. Potential consequences for optical properties are discussed. Segmented polymers with arylenevinylene segments in the main chain are presented and discussed in detail. Light‐emitting thermotropic polymers were obtained with modified distyrylbenzene segments in the main chain. These thermotropic light‐emitting polymers show polarized photoluminescence on orientation on rubbed polyimide substrates. Light‐emitting amorphous polymers with high fluorophore concentrations and high glass transition temperatures were obtained by polymers with arylenevinylene segments in the side chain.
Fabrication of ultrathin film containing bienzyme of glucose oxidase and glucoamylase based on electrostatic interaction and its potential application as a maltose sensor
Authors: Sun Yipeng , Zhang Xi , Sun Changqing , Wang Bo , Shen Jiacong 
Published: April 2003

AbstractAn enzyme multilayer film composed of glucose oxidase and glucoamylase alternating with a bipolar quaternary ammonium salt was achieved on the surface of a quartz slide or a gold electrode and its application as a bienzyme maltose sensor was studied.
Electrochemical dehalogenation polycondensation of 2,5‐dibromopyridine mediated by nickel and palladium complexes
Authors: Yamamoto Takakazu , Saito Nobuo 
Published: April 2003

AbstractDehalogenation polycondensation of 2,5‐dibromopyridine, 2,5‐Br2‐Py, to poly(pyridine‐2,5‐diyl), PPy, has been achieved under electrochemical reductive conditions mediated by various nickel(II) and palladium(II) complexes (nickel‐2,2′‐bipyridine (bpy) and ‐phosphine complexes and palladium‐bpy complexes). PPy is obtained as a thin smooth film on a platinum electrode in high yield, and among the nickel and palladium complexes [Ni(bpy)3]2Br2 serves as the best mediator for the electrochemical reductive polycondensation. Carrying out the electrochemical polycondensation in a two‐compartment cell and in a one‐compartment cell gives almost the same results. The PPy film prepared by using the nickel(II) complex gives the same IR and cyclic voltammogram as chemically prepared authentic PPy shows. When PdCl2(bpy) is used as the mediator, the formation of PPy is accompanied by metalation reaction of palladium to PPy.
High‐pressure free‐radical copolymerization of ethene and butyl acrylate
Authors: Buback Michael , Busch Markus , Lovis Kai , Mähling Frank‐Olaf 
Published: April 2003

AbstractThe free‐radical copolymerization of ethene and butyl acrylate was studied between 130 and 225°C at pressures from 1 500 to 2 500 bar. The reactions which were induced either thermally or laser‐photochemically were run in two types of continuously operated devices. Reactivity ratio data referring to ethene‐rich monomer mixtures are presented. These data allow to estimate the copolymer composition in ethene/butyl acrylate copolymerizations carried out in a wide range of temperatures and pressures.
Competing processes for poly(aryl ether‐ketone) synthesis, 3. Polymerization reactions of 1,3‐bis(4‐chlorobenzoyl)benzene and 1,3‐bis(4‐fluorobenzoyl)benzene in N‐methyl‐2‐pyrrolidinone
Authors: Bhatnagar Atul , Mani Rajrathnam S. , King Brandon , Mohanty Dillip K. 
Published: April 2003

AbstractThe effects of N‐methyl‐2‐pyrrolidinone (NMP) as solvent on the polymerization reactions of 1,3‐bis(4‐chlorobenzoyl)benzene (1,3‐CBB) and 1,3‐bis(4‐fluorobenzoyl)benzene (1,3‐FBB) with 4,4′‐isopropylidenediphenol (bisphenol‐A) were examined. The failure of these reactions to produce high molecular weight polymers in the presence of anhydrous potassium carbonate is due to dehalogenation of 1,3‐CBB via substitution radical‐nucleophilic unimolecular (SRN1) processes. On the other hand, 1,3‐FBB undergoes nucleophilic aromatic substitution reactions (SNAR) with the carbonate anion at elevated temperatures. However, it is possible to synthesize high molecular weight polymers from 1,3‐FBB and bisphenol‐A in NMP either by first forming the bisphenoxide with stoichiometric amounts of aqueous sodium hydroxide or in the presence of anhydrous potassium carbonate at a lower reaction temperature.
Redox polymerization of 2‐hydroxyethyl methacrylate, 2. Kinetics, mechanism and solvent effect using manganese triacetate/cyanoacetic acid as the redox system
Authors: Mathew Jainamma , Mahadevan Venkatanarayana 
Published: April 2003

AbstractPolymerization of 2‐hydroxyethyl methacrylate (HEMA) initiated by the redox system manganese triacetate (Mn)(III)/cyanoacetic acid (CAA) was investigated kinetically in DMF and in HOAc/water (80 : 20 v/v). Monomer (M) conversion was followed gravimetrically. Polymerization was carried out at 31°C and at 41°C. The rate of polymerization Rp in DMF is expressed by the equation, RP, ∝ [M]1,4 [Mn(III)]0,4 [CAA]0,4. In HOAc/water, the polymerization exhibited a strong dependence on the concentration of Mn(III). That is, at low concentrations of Mn(III), the rate variations are [M]1,0, [CAA]0,5 and [Mn(III)]0,5, while at high Mn(III) concentration the polymerization rates are independent of [Mn(III)] and vary as a function of [M]1,5 and [CAA]0,5. Enhanced oxidation of the primary radicals by Mn(III) at higher concentrations has been elicited to explain the observed orders. The degree of polymerization was found to increase with increase in concentrations of monomer and decrease in concentrations of CAA and Mn(III). The polymerization rates as well as the molecular weights of the polymers are higher in HOAc/water than in DMF. The enhanced polymerization rates have been attributed to the increased propagation and the reduced termination rates.
Conformational effects on electrical and spectroscopic properties of 1,2‐di(2‐thienyl)ethylenes and corresponding poly[(2,2′‐dithienyl)‐5,5′‐diylvinylenes]
Authors: Benincori Tiziana , Brenna Elisabetta , Sannicolò Franco , Trimarco Licia , Schiavon Gilberto , Zecchin Sandro , Zotti Gianni 
Published: April 2003

Abstract1,2‐Dialkyl‐substituted 1,2‐di(2‐thienyl)ethylenes have been synthesized and investigated by cyclic voltammetry. The bulk of the alkyl substituents was modulated in order to progressively increase the torsional angle between the thiophene rings and the plane of the olefinic bond, from a fully planar structure to highly twisted systems. Distortion markedly affects the UV spectra and the oxidation peak potentials of the monomers. The electro‐chemical polymerization experiments gave the following results: (i) (E)‐ and (Z)‐dithienyl‐ethylene systems produced polymers with identical properties; (ii) progressive deviation from planarity increased the oxidation peak potential of the monomer, as far as the polymerization was inhibited; (iii) long and rigid monomeric units reduced chain flexibility, leading to materials with low conductivity and unsatisfactory mechanical properties.
New poly(amide‐imide) syntheses, 19. Preparation and properties of poly(amide‐imide)s derived from N‐phenyl‐3,3‐bis[4‐(4‐aminophenoxy)phenyl]‐1‐oxoisoindoline and various bis(trimellitimide)s
Authors: Lin Jiun‐Hung , Yang Chin‐Ping 
Published: April 2003

AbstractA series of novel bis(phenoxy)‐1‐oxoisoindoline‐containing poly(amide‐imide)s 3 were synthesized by the direct polycondensations of N‐phenyl‐3,3‐bis[4‐(4‐aminophenoxy)‐phenyl]‐1‐oxoisoindoline (1m, NPBA) with various aromatic bis(trimellitimide)s 2 in N‐methyl‐2‐pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. Poly(amide‐imide)s 3 having inherent viscosities up to 1,06 dL/g were obtained in quantitative yields. Most of the resulting polymers showed an amorphous nature and were readily soluble in polar solvent such as NMP and N,N‐dimethylacetamide. All of the soluble poly(amide‐imide)s afforded transparent, flexible, and tough films. The glass transition temperatures of these polymers were in the range of 277–327°C, and the 10% weight loss temperatures were above 500°C in nitrogen. The properties of poly(amideimide)s 3 were compared with those of the corresponding isomeric poly(amide‐imide)s 3′ prepared from NPBA and various aromatic diamines.
Miscibility and crystallization behavior of thermosetting polyimide/thermoplastic polyimide blends
Authors: Tang Hao , Dong Lisong , Zhang Jin , Ding Mengxian , Feng Zhiliu 
Published: April 2003

AbstractCompatibility, morphology, crystalline structure and mechanical properties of the blends of a thermosetting polyimide with thermoplastic polyimides consisting of dianhydrides of different lengths have been studied by the use of dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and small angle X‐ray scattering (SAXS) techniques. The results of our research show that the blends change from compatible to semi‐compatible when the difference between the length of the dianhydrides of the two components increases. Addition of a thermoplastic polyimide inhibits the crystallization of the thermosetting component. However, this effect decreases with increasing length of the dianhydrides and the distribution of the molecules of the thermoplastic polyimide component changes from interlamellar to interfibrillar. Impact strength and morphology of the fractured surfaces indicate that among the semi‐interpenetrating polymer networks (semi‐IPN) obtained the toughening effect of the partially compatible one is the best. The results are discussed in terms of charge transfer interaction between imide group and p‐phenylene group.
Miscibility and specific interactions in blends of poly(2‐ethyl‐2‐oxazoline) with hydroxylated polymethacrylates
Authors: Isasi José R. , Meaurio Emilio , Cesteros Carlos , Katime Issa 
Published: April 2003

AbstractThe compatibility of blends of poly(2‐ethyl‐2‐oxazoline) (PEOX) with poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly(2‐hydroxypropyl methacrylate) (PHPMA) was investigated by means of differential thermal analysis and infrared spectroscopy. Calorimetric results show single glass transition temperatures in the entire range of compositions for both systems. S‐shaped curves are obtained when plotting the glass transition temperatures vs. blend compositions. IR analysis of blends reveals the existence of specific interactions via hydrogen bonding between the carbonyl and hydroxyl groups of PHEMA and PHPMA. The association phenomena were quantitatively studied from room temperature up to 180°C with the aid of spectral subtraction techniques.
One‐pot synthesis of a new hyperbranched polyester containing 3,6‐di‐acceptor‐substituted carbazole chromophores for nonlinear optics
Authors: Zhang Yadong , Wang Liming , Wada Tatsuo , Sasabe Hiroyuki 
Published: April 2003

AbstractThe preparation of a new AB2 monomer and a precursor of AB2 monomer bearing carbazole chromophores is described. A new hyperbranched polymer containing carbazole substituted with two acceptor groups for nonlinear optical materials has been synthesized starting from the precursor of AB2 monomer 3,6‐diformyl‐9‐(11‐hydroxyundecyl)carbazole via Knoevenagel condensation and ester exchange condensation in a one‐pot reaction. This hyperbranched polymer with a mass‐average molar mass of about 20000 g/mol is soluble in common organic solvents. The thin polymer films could be obtained from chloroform solution by spin coating. Differential scanning calorimetry analysis showed no crystalline transitions for this hyperbranched polymer and the glass transition temperature of the polymer is about 97,6°C. The resulting thin and glassy polymer films were shown to exhibit reasonably second harmonic generation efficiencies (d33 = 7 pm/V) after electric corona poling at about 100°C.
Side chain pendant non‐linear optically active polymers synthesised by grafting reactions on maleic anhydride copolymers
Authors: McCulloch Iain , Demartino Ronald , Keosian Richard , Leslie Thomas , Man Hong‐Tai 
Published: April 2003

AbstractThe synthesis of well defined, high molecular weight polymers for non‐linear optical (NLO) applications has been carried out in an effort to improve the film properties of waveguides fabricated from these materials, Free radical methods of polymerisation result in molecular weight limitations due to the chain transfer nature of the NLO active chromophores, and therefore, in order to prepare a high molecular weight polymer, a post polymerisation grafting method was chosen to incorporate side chain pendant chromophores onto a preformed polymer. Alcoholysis of anhydride copolymers resulted in chromophore incorporation levels of up to 90% of available reactive sites. Additional branching of the linear anhydride prepolymers was also carried out using polytetrahydrofuran but this was not shown to improve the mechanical properties of the fabricated films. Since the anhydride opens to an ester and an acid, in order to reduce the ionic content of the final polymer, further reaction of the generated carboxylic acid group was attempted, resulting in partial diester formation, and an improvement in film quality. Electrical field poling at temperatures close to the glass transition was only successful at low electrical field strengths, allowing electrooptic coefficients of values of up to 2.4 pm/V at a poling field of 80 V/μm to be obtained.
Synthesis and properties of highly gas permeable poly(amide‐imide)s
Authors: Fritsch Detlev , Avella Nicola 
Published: April 2003

AbstractSeven dicarboxylic acids containing one or two preformed imide rings were prepared by condensation of trimellitic anhydride with 3‐amino‐4‐methylbenzoic acid or with the diamines 2,4,6‐trimethyl‐1,3‐phenylenediamine, 3,3′‐dimethoxybenzidine, 3,3′,5,5′‐tetramethyl‐benzidine, 3,3′‐dimethyl‐1,1′‐binaphthalene or by condensation of 2,2‐hexafluoroisopropylidenebis(phthalic acid anhydride) (6FDA) with 2 mol of 3‐aminobenzoic acid or 3‐amino‐4‐methylbenzoic acid. Polycondensation was performed directly in N‐methyl‐2‐pyrrolidone (NMP)/triphenyl phosphite/lithium chloride with oxydianiline, 2,2‐bis(4‐aminophenyl)‐perfluoropropane or 3,3′,5,5′‐tetramethylbenzidine. All the resulting polymers are soluble in NMP, some in tetrahydrofuran (THF) and could be cast to transparent, flexible and tough films. The helium permeability as a probe for diffusivity improves with increasing fluorine content and non‐linearity in the repeating unit.