bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐performance membranes for pervaporation II. Crosslinked poly(vinyl alcohol)–poly(acrylic acid) blends
Authors: Ping Zhenghua , Nguyen Quang‐Trong , Essamri Azouz , Néel Jean
Published: April 2003

Dense membranes made by crosslinking of poly(vinyl alcohol) (PVA) with poly(acrylic acid) (PAA) were prepared and tested in pervaporation and differential permeation of water–alcohol mixtures. Instead of a decrease of permeation flux as generally observed with most crosslinking agents, an increase in the permeability was observed with PAA crosslinked membranes at low PAA contents. The permeation flux increases with PAA contents in the polymer with no selectivity reduction for membranes containing less than 15 wt. % PAA. The membranes show good performances to water–2‐propanol and water–ethanol mixtures, i.e. high fluxes and high selectivities to pure water. The membranes were stable and highly permeable to water. The enhancement of the permeability of PVA can be explained by a reduced crystallinity and an improved diffusivity due to the presence of PAA.
Poly(butylene terephthalate)–polyarylate blends
Authors: Runt J. , Miley D. M. , Gallagher K. P. , Zhang X. , Barron C. A. , Kumar S. K.
Published: April 2003

In this paper we focus on miscible blends of two engineering polymers: poly(butylene terephthalate) (PBT) and a polyarylate (PAr). The issue of transesterification in these blends will be addressed, followed by a discussion of the crystallization kinetics of PBT, poly(ethylene terephthalate) and several PBT/PAr blends. The ability to estimate polymer–polymer interaction parameters in blends from melting point depression will also be discussed. The amorphous phase behavior of the PBT/PAr blends has been explored primarily using dielectric spectroscopy. For blends in which PBT has crystallized, we observe two relaxations associated with Tg‐like motion, and this behavior is interpreted in light of our recent work on order–disorder interphases in crystalline blends.
Study of the copper electrodeposition process from low molecular weight polymer electrolyte media
Authors: Panero S. , Bardanzellu L. , Scrosati B.
Published: April 2003

The characteristics of the copper deposition process from electrochemical cells using a solution of Cu(CF3SO3)2 in low molecular weight poly(ethylene glycol), PEG, have been investigated by cyclic voltammetry, potential steps and impedance spectroscopy. The results suggest that under non‐equilibrium at the cathodic side the process mainly involves the reduction of Cu(II) ions to copper metal while at the anodic side a chemical reaction competes with the electrochemical dissolution.
Preparation and properties of soluble polyamideimides containing oligo(tetrafluoroethene) segments and application in gas separation
Authors: Steinhauser Norbert , Mülhaupt Rolf , Hohmann Marcus , Springer Jürgen
Published: April 2003

A series of PMDA‐, BTDA‐ and 6F‐polyamideimides containing well‐defined oligo(tetrafluoroethene) segments were derived from N,N′‐bis(aminophenyl)perfluoroalkane‐α, ω‐dicarboxamides with n =1,2,3 tetrafluoroethene units. The influence of the fluorine content, microstructures and the oligo(tetrafluoroethene) segment lengths on phase transition temperatures, thermal degradation, contact angles, pure gas permeabilities and permselectivities was studied.
Interdiffusion of polymer chains during latex coating
Authors: Pekcan Önder , Canpolat Murat
Published: April 2003

The fluorescence method was used to study the interdiffusion of polymer chains during annealing of latex above its glass transition temperature (Tg). The latex film was prepared from mixture of naphthalene (N) (donor) and pyrene (P) (acceptor)‐labeled poly(methyl methacrylate) (PMMA) latex particles. Heptane was used as the coalescent agent. A steady‐state fluorescence technique was employed to measure the amount of direct nonradiative energy transfer from N to P during the interdiffusion of polymer chains across the particle–particle junction. Various latex films with different latex contents were used to measure the percentage critical occupation for the reliable steady‐state fluorescence measurements. Diffusions activation energies in these latex films were measured and found to be around 30 kcal/mol, which was attributed to the backbone motion of PMMA chains.
Approaches to molecular composites from fluorine‐containing bis‐maleimides: Part I
Authors: Tesoro G. C. , Pendharkar S. M.
Published: April 2003

Previous work in our laboratory has shown that covalent bonding of a semiflexible polymer in a bis‐imide matrix prior to thermal polymerization is a promising, although structure‐dependent, approach to the synthesis of molecular composites from organic solvents in thermosets. In the present investigation, the focus has been on the rapid amine‐catalyzed anionic polymerization and crosslinking of fluorine‐containing bis‐maleimides. The objective has been to provide physical entrapment of rigid polymer prior to aggregation. Results have shown that gelation of fluorine‐containing bis‐maleimides initiated by tertiary amines in organic solvent can occur in seconds at moderate temperatures, and thus affords a means of preventing aggregation of rigid polymer prior to crosslinking.
Fluorinated poly(benzoxazole–imide)s
Authors: Bruma Maria , Mercer Frank , Schulz Burkhard , Dietel Reinhard , Neumann Werner
Published: April 2003

New poly(benzoxazole–imide)s have been prepared by polycondensation of bis(o‐aminophenol)s, such as 3,3′ dihydroxybenzidine or 2,2‐bis(3‐amino‐4‐hydroxyphenyl)‐hexafluoropropane, with diacid chlorides containing both imide and hexafluoroisopropylidene groups. The soluble polymer precursor resulting from the first step of polycondensation in N‐methylpyrrolidinone (NMP) at low temperature was processed into thin flexible films, which were then thermally treated to reach the fully cyclized structure of poly(benzoxazole–imide)s, as observed by infrared spectra. An alternative way to produce the cyclization was by heating at reflux the solution of polymer precursor in NMP. Thermal stability, glass transition temperature, dielectric constant and its dependence on relative humidity have been studied and compared with those of related polybenzoxazoles and other heterocyclic Polymers.
Energetic polymers as binders in composite propellants and explosives
Authors: Colclough M. Eamon , Desai Hesmant , Millar Ross W. , Paul Norman C. , Stewart Malcolm J. , Golding Peter
Published: April 2003

The principles behind the use of polymeric binders in composite propellants and explosives are described with emphasis on the properties which they should possess in order to satisfy the requirements for inclusion in a composition. The desirability of using energetic polymers as binders in terms of both performance and safety, and the problems associated with their preparation and properties, are discussed. The contributions of chemical synthesis within DRA to overcome these problems will be shown. Preparation of energetic polymers both by polymer modification and by polymerization of an energetic monomer is described. We have developed three energetic polymers: poly‐3‐nitratomethyl‐3‐methyloxetane (polyNIMMO), polyglycidyl nitrate (polyG‐LYN) and nitrated hydroxy‐terminated polybutadiene (NHTPB). Two of these (polyNIMMO and polyGLYN) have shown excellent properties in propellant and explosive formulations and proved that low‐vulnerability, high‐performance compositions are possible. The properties of the products from our work are compared with those of other groups and a glimpse of the future in this area is given to show the potential for new energetic polymers.
Bimolecular photoinitiating systems of polymerization: photochemical behavior and radical efficiency
Authors: Mateo José Luis , Bosch Paula
Published: April 2003

A key component in light‐induced radical polymerization is the photoinitiator which produces free radicals through a photochemical reaction. In the first part of this paper, a short analysis of the different steps that take place in the light‐induced radical polymerization using bimolecular photoinitiating systems is made. In the second part, the obtained results in the polymerization of acrylic monomers using conjugated and nonconjugated aminobenzophenones as photoinitiators are shown. A summary of the photochemical behavior of these photoinitiators together with several aspects related to the polymerization kinetics are described. The nature and efficiency of the produced radicals are studied as well as the reactivity of the radicals generated from the substituted dimethylanilines‐camphorquinone photoinitiation systems. Important mechanistic differences were found in the photochemical behavior and radical efficiency for the families of photoinitiators studied.
Approaches to molecular composites from fluorine‐containing bis‐maleimides: Part II
Authors: Pendharkar S. M. , Tesoro G. C. , Levon K.
Published: April 2003

Continuing our research on molecular composites from fluorine‐containing bis‐maleimides (reported in this journal as Part I), we have prepared and characterized experimental composite films from a fluorine‐free bismaleimide (BMI) with Technora® fiber and from a fluorine‐containing system of BMI and rigid rod by rapid amine‐initiated anionic polymerization of the bis‐maleimide. We have also explored the effect of increasing amounts of initiator and of system composition on the film structure.
The first normal stress difference and viscosity in shear of liquid crystalline solutions of hydroxypropylcellulose: new experimental data and theory
Authors: Fried F. , Leal C. R. , Godinho M. H. , Martins A. F.
Published: April 2003

The constitutive equations for liquid crystalline polymers recently proposed by one of us [1] are applied here to interpret the behaviour of the shear viscosity η
$ \dot \gamma $ and the first normal stress difference N1($ \dot \gamma $) measured for liquid crystalline (LC) solutions of hydroxypropylcellulose in acetic acid. N1($ \dot \gamma $) is observed to change from positive to negative and again to positive, as the shear rate $ \dot \gamma $ increases, at lower concentrations, in the LC phase. The $ \dot \gamma $‐values at which N1 changes sign depend on the molecular mass (degree of polymerization) and on the concentration. η $ \dot \gamma $ shows a small Newtonian plateau at low shear rates and a strong shear‐thinning at higher values of $ \dot \gamma $. The rate of decrease of η $ \dot \gamma $ in this region shows an “hesitation” similar to one previously observed in LC solutions of poly‐γ‐benzyl‐L‐glutamate PBLG. All these observations can be rationalized within the frame‐work of Martins' theory. The expressions for N1($ \dot \gamma $) and η $ \dot \gamma $ derived from this theory fit very well (quantitatively) to the experimental data and some fundamental viscoelastic parameters of the system under study are thereby obtained for the first time.
Synthesis and properties of modified aramids
Authors: Berger Werner , Küchenmeister Frank
Published: April 2003

The purpose of this study was to determine the influence of different kinds of main chain modification of aramids on their thermal properties and solubility. The properties of polyamides synthesized by direct polycondensation using phosphorylation reaction depend strongly on the chemical architecture of the macromolecules. Polymers thus obtained were characterized by viscosity measurements, differential scanning calorimetry, thermogravimetry and solubility tests. These polyamides were distinguished by inherent viscosities in the range of 0.12–1.67 dl/g. The thermal transitions decrease in all cases of modification and the solubility is improved. Furthermore, the liquid crystalline properties of the polyamides were investigated. Thermotropic liquid crystalline behavior can be stated for a polyamide composed of 4,4′‐diaminodiphenylmethane (MDA) and sebacic acid (SEB) under shearing. Aromatic polyamides with kinks in their main chain exhibit lyotropic crystalline behavior whereas parallel displacement in the main chain prevent the formation of liquid crystals in solution.
Synthesis and thermal studies of heterocyclic siloxanes containing boron
Authors: Behbehani Haider S. J. , Brisdon Brian J. , McEnaney Brian
Published: April 2003

Eight‐ and six‐membered cycloborasiloxanes containing two and one boron atoms respectively are strained ring compounds which undergo ring opening polymerization and ring–ring transformation reactions on thermolysis. Prolonged heating at 200°C results in volatilization of the cyclic boroxine (PhBO)3, whereas rapid heating of either compound to 1500°C in an inert atmosphere does not result in loss of boron, but affords instead an amorphous residue containing silicon carbide, boron oxide and carbon. Upon further pyrolysis at 1700°C the final product consists of microcrystalline silicon carbide in which are embedded large crystals of boron carbide.
Adsorption of bovine serum albumin to acrylamide–itaconic acid hydrogels
Authors: Karadaǧ Erdener , Saraydin Dursun , Öztop H. Nursevin , Güven Olgun
Published: April 2003

In this study, acrylamide–itaconic acid hydrogels containing different amounts of itaconic acid prepared by irradiating with γ radiation are discussed. They have been used in experiments of swelling, diffusion and bovine serum albumin (BSA) adsorption. Maximum and minimum swellings were observed with water (1520%) and BSA (890%), respectively. Diffusion of water, NaCl and BSA within hydrogels were found to be non‐Fickian in character. In the experiments of BSA adsorption, type III adsorption was found. The hydrogel prepared with 60 mg itaconic acid and irradiated at 2.00 kGy was found to be the best adsorption system for BSA. The adsorption capacity of acrylamide–itaconic acid hydrogel was found to exceed that of acrylamide hydrogel by more than 80–100%.
Cooperative self‐assembling in statistical copolymers: a new approach to high‐temperature thermoplastic elastomers
Authors: Hellmann Jörg , Hilger Christopher , Stadler Reimund
Published: April 2003

Based on previous work, where it was shown that 4‐urazoylbenzoic acid (U4A) groups, which are attached statistically to polybutadiene, form ordered supramolecular arrays in the unpolar polymer matrix, the present work describes the synthesis of a new molecular building block capable of self‐assembling in the unpolar polymer matrix. 5‐Urazoylisophthalic acid (U35A) groups attached to 1,4‐polybutadiene chains cause the formation of a thermoplastic elastomer of improved properties. The clusters of functional groups show an endothermic transition. The melting temperature increases for low levels of modification from 130°C up to 190°C. The mechanical properties (stress–strain and dynamic mechanical) reveal excellent rubbery characteristics and a rubbery plateau which is considerably flatter than those of technical grade thermoplastic elastomers. The IR data indicate that the U35A groups are tetrafunctional with respect to supramolecular self‐assembling. Based on detailed knowledge of the structure of the self‐assembled domains in U4A groups, a model is developed which describes the observed material properties qualitatively.
Mesomorphic flexible chain polymers based on silicon
Authors: Out G. J. J. , Siffrin S. , Frey H. , Oelfin D. , Kögler G. , Möller M.
Published: April 2003

Poly(dialkylsiloxane)s and poly(dialkylsilane)s form a similar type of columnar mesophase. Although, the polysilanes are stiffer than polysiloxanes, both classes of polymers may be considered to be flexible due to the ability to form chain‐folded crystals. Chain flexibility rather than the presence of chain stiffness determines whether the columnar mesophase is formed. A certain amphiphilic character does not appear to be required, as polysiloxanes with short side groups, e.g. polydiethylsiloxane display the same mesophase behaviour as polydialkylsilanes with long side chains and other nonpolar flexible chain molecules. The importance of the entropy gain upon conformational disordering is reflected in the increase in temperature stability with increasing alkyl side group length and the absence of mesophase behaviour in the case of the dimethyl substituted polymers
Chemical modification of polymer surfaces: a review
Authors: Penn L. S. , Wang H.
Published: April 2003

The main approaches that have been taken to chemically modify polymer surfaces are introduced and reviewed. These are wet chemical oxidation, plasma treatment, classical organic chemistry, and attachment of polymer chains. The extent to which each of these approaches can produce the specific modifications desired is discussed, and any unwanted effects that commonly occur are cited. Finally, the need for using several methods of surface analysis in concert to obtain adequate surface characterization is described.
Doping of polyaniline with polymeric dopants in solid state, gel state and solutions
Authors: Liao Yun‐Hsin , Levon Kalle
Published: April 2003

Polystyrene with different degrees of sulfonation was empolyed as a polymeric dopant for polyaniline. The purpose of using a polymeric dopant is to avoid the migration of a small molecule dopant to increase stability of the doped complex. We applied the polymeric dopant to polyaniline in three different ways: in solid state, in solution and in gel state. In solid state, the conducting form was achieved only through a novel thermal doping method with the increase in temperature and pressure. In solution, the doping process was shown to be dependent on the nature of the solution and also on the molecular weight of the polymer. In the gel form of polyaniline, a polymeric dopant with a surprising low degree of sulfonation was found to be successful in the doping process.
Mechanistic study of thermal behavior and combustion performance of epoxy resins: I homopolymerized TGDDM
Authors: Levchik Sergei V. , Camino Giovanni , Luda Maria Paola , Costa Luigi , Costes Bruno , Henry Yves , Morel Emile , Muller George
Published: April 2003

Tetraglycidyl 4,4′‐diaminodiphenylmethane (TGDDM) undergoes homopolymerization on heating. Intramolecular reactions which compete with crosslinking favor the formation of cyclic structures with increasing thermal and fire resistance of the resin, whereas physical mechanical properties tend to decrease.

The mechanism of thermal decomposition of TGDDM is studied by thermogravimetry, differential scanning calorimetry and thermal volatilization analysis with characterization of volatiles evolved and residue left. Thermal degradation of poly‐(TGDDM) starts at 260°C with elimination of water from secondary alcoholic groups which is a typical pathway for epoxy resin degradation. Resulting unsaturations weaken bonds in the β‐position and provoke the first chain breaking at allyl–amine and allyl–either bonds. With increasing temperature, saturated alkyl–ether bonds and alkyl carbon–carbon bonds are broken first, followed by the most stable alkyl–aryl bonds at T>365°C. The combustion performance of TGDDM is discussed on the basis of the thermal degradation behavior.
Synthesis and characterization of thermoplastic copolyesters containing copolymerized azoic dyes
Authors: Po Riccardo , Bornengo Giorgio , DiStefano Letterio , Cavagna Carla , Occhiello Ernesto , Garbassi Fabio
Published: April 2003

Poly(ethylene terephthalate) and a series of other amorphous copolyesters based on ethylene glycol and terephthalic/isophthalic or 2,6‐naphthalenedicarboxylic/isophthalic acid mixtures were prepared by melt polycondensation. Comonomers consisting of azoic dyes having two polymerizable functions on the aromatic rings (either one alcoholic and one carbomethoxyl, two alcoholic or two carbomethoxyl groups) were also added, in amounts lower than 1% mol with respect to the sum of diesters used as starting monomers. In these conditions (P<0.1 torr and T=280°C), only few azoic dyes were found to be stable.

Among the prepared polymers, those based on dyes having sufficient thermal stability were characterized by differential scanning calorimetry and solution properties. Inherent viscosities suggest that molecular weights are high. Glass transition and melting temperatures as well as mechanical properties of colored polyesters are not affected by the presence of the azoic comonomers. UV–visible spectra of copolyester solutions were registered, and absorption coefficients were correlated with the amount of dye.
Fabrication and spectroscopic characterization of the nanocrystals of poly[5,7‐dodecadiyn‐1,12‐diol bis(n‐butoxycarbonylmethyl urethane)]
Authors: Nalwa Hari Singh , Kasai Hitoshi , Okada Shuji , Matsuda Hiro , Oikawa Hidetoshi , Minami Nobutsugu , Kakuta Atsushi , Mukoh Akio , Ono Katsumichi , Nakanishi Hachiro
Published: April 2003

A novel wet water–ethanol‐borne technique of preparing nanocrystals of the poly[5,7‐dodecadiyn‐1,12‐diol bis‐(n‐butoxycarbonylmethyl urethane)], oxoreferred to as poly(4‐BCMU), is reported for the first time. The fabrication of poly(4‐BCMU) nanocrystals with sizes ranging from a few to hundreds of namometers is presented. The spectroscopic analysis of the poly(4‐BCMU) nanocrystals using nuclear magnetic resonance, infrared, optical absorption spectroscopy, gel permeation chromatography and scanning electron microscopic techniques is discussed. A structural characterization at molecular level of the poly(4‐BCMU) constituting the nanocrystals evidences the maintenance of the molecular integrity of the polydiacetylene backbone.
Phthalocyanines and related macrocycles for multi‐electron transfer in catalysis, photochemistry and photoelectrochemistry
Authors: Wöhrle Dieter , Schlettwein Derck , Schnurpfeil Günter , Schneider Gerhard , Karmann Elfriede , Yoshida Tsukasa , Kaneko Masao
Published: April 2003

At different phthalocyanines and related macrocycles it is shown that one‐step, multi‐electron transfer and one‐step, multi‐change of oxidation states occur. At first, the catalytic oxidations of thiols and sulfide in the presence of different Co(II)phthalocyanines are discussed. Thiolates are oxidized to disulfides via a two‐electron transfer whereas the reduction of O2 occurs via a two‐ or four‐electron transfer to H2O2 or H2O. Zn(II) and Al(III)phthalocyanines are efficient sensitizers for the conversion of triplet to singlet dioxygen under illumination with visible light. In the presence of thiolates or sulfides an efficient photo‐oxidation to sulfonic acids or sulfate is observed. The oxidation state of sulfur changes from −2 to +4 or +6, respectively. This process of singlet oxygen reactions finds application in the photodynamic therapy of cancer. The unsubstituted zinc(II)‐phthalocyanine as p‐type molecular semiconductor can efficienfly reduce O2 in photoelectrochemical experiments whereas zinc(II)phthalocyanines with electronwithdrawing groups as n‐type conductors are active in the photoelectrochemical oxidation of thiols. All processes include multi‐electron transfer. The electrocatalytic reduction of CO2 is investigated at electrodes modified with Co(II)phthalocyanine. In particular, the phthalocyanine in a polyvinylpyridine membrane is active, so the CO2 is reduced to CO by multi‐electron transfer. In addition, two photon excitations of a Mg(II)phthalocyanine are presented and some examples are reviewed.
Multi‐electron transfer process of vanadyl complexes for oxidative polymerization of diphenyl disulfide
Authors: Yamamoto Kimihisa , Oyaizu Kenichi , Tsuchida Eishun
Published: April 2003

Oligo(p‐phenylene sulfide) is synthesized by oxidative polymerization of diphenyl disulfide with oxygen catalyzed by vanadyl acetylacetonate under strongly acidic conditions. The mechanistic studies reveal that the redox cycles of the vanadyl complexes give rise to catalysis through a two‐electron transfer between diphenyl disulfide and molecular oxygen. The VO catalysts act as an excellent electron mediator to bridge a 1.0 V potential gap between the oxidation potential of disulfides and the reduction potential of oxygen. The VO‐catalyzed oxygen‐oxidative polymerization provides pure oligo(pphenylene sulfide)s containing an S–S bond. The polymeric product is of low molecular weight due to the insolubility under these conditions.

(N,N′‐ethylenebis(salicylideneaminato))oxovanadium‐(IV), VO(salen), was used as an inert model compound to elucidate the redox chemistry of the vanadium complex. VO(salen) reacts with trifluoromethanesulfonic acid (CF3SO3H) or triphenylmethyl tetrafluoroborate (ϕ3C(BF4)) to form a deoxygenated complex, VIV(salen)2+, and a μ‐oxodinuclear complex, [(salen)VOV(salen)]X2, (X = CF3SO3− or BF4−). The dimerization of VO(salen) is initiated by deoxygenation to produce V(salen)2+ which enters into an equilibrium with a second VO(salen) complex to produce the μ‐oxo dimer. The two‐electron transfer of the μ‐oxo dinuclear vanadium complex is elucidated.
Dipole moments and structure of poly(epoxypropylcarbazole)
Authors: Kuliešius F. , Kriščiūnas V. , Mačkus P.‐K.
Published: April 2003

The mean‐square molecular dipole moments 〈μ2〉 of carbazole, N‐ethylcarbazole and of the sequence of poly(epoxypropylcarbazole) (PEPCa) oligomers of various molecular weights have been evaluated in solutions of these organic compounds in dioxan. For PEPCa the values of 〈μ2〉 have also been determined in the solid state. On the basis of the experimental results and of molecular mechanics calculations it has been shown that the orientation of the lateral group of PEPCa favors noninteracting racemic dyads. The temperature‐dependence of the effective dipole moment of solid PEPCa follows the Onsager theory above 295 K.
Synthesis and structure–property relationships of acrylic core–shell particle‐toughened epoxy networks
Authors: Bécu L. , Sautereau H. , Maazouz A. , Gérard J. F. , Pabon M. , Pichot C.
Published: April 2003

The use of emulsion polymerization to prepare core–shell rubber (CSR) toughening particles with different shell thickness‐to‐core diameter ratios is described. The conditions leading to controlled particle size and morphology are discussed. The particle shell is crosslinked during the synthesis so that its integrity and morphology are maintained upon curing of the epoxy network. The mixing of the CSR particles with the reactive epoxy and the processing of toughened‐epoxy networks are described. The characteristics of each phase and the mechanical properties of the materials are reported. The fracture parameters (Klc, Glc) are discussed in relation to the structure of the CSR‐particles.
Nanocomposite materials from latex and cellulose whiskers
Authors: Favier V. , Canova G. R. , Cavaillé J. Y. , Chanzy H. , Dufresne A. , Gauthier C.
Published: April 2003

Composite materials were processed by casting a mixture of aqueous suspensions of latex and microfibrils. These microfibrils, or whiskers, are extracted from a sea animal and are monocrystals of cellulose, with an aspect ratio around 100 and an average diameter of 20 nm. It has been found that the mechanical properties (shear modulus) are increased by more than two orders of magnitude in the rubbery state of the polymeric matrix, when the whisker content was 6% (w/w). This very large effect is discussed on the basis of different types of mechanical models and it is concluded that these whiskers form a rigid network, probably linked by hydrogen bonds. The formation of this network is assumed to be governed by a percolation mechanism.
Electrically conducting polymer colloids and composites
Authors: Vincent Brian
Published: April 2003

The preparation, characterization and properties of aqueous dispersions of electrically conducting polymer particles are described. Three types of such particles have been prepared: polyacetylene, polypyrrole and polyaniline. Particles in the size range 50–500 nm (diameter) and with conductivities generally ≃ 1–10 S cm may be made. Composites of such particles, dispersed in a matrix polymer which is non‐conducting, are also described.
Morphology and properties of semi‐IPNs of polyetherimide and bisphenol A dicyanate
Authors: Lee Bong Keun , Kim Sung Chul
Published: April 2003

Semi‐interpenetrating polymer networks (semi‐IPNs) were synthesized from mixtures of polyetherimide (PEI) and bisphenol A dicyanate (BPACY) at different compositions and different cure temperatures. The phase separation behavior during cure was analyzed in terms of glass transtion temperature (Tg) behavior of fully cured semi‐IPNs and the morphology–property relationship was also studied. The mixtures of PEI and BPACY monomer showed upper critical solution temperature behavior and their semi‐IPNs showed sea‐island morphology in 1–14 wt% PEI composition, dual‐phase morphology in 15–19 wt% PEI composition and nodular morphology in 20–60 wt% PEI composition, respectively. The sea‐island morphology was formed via nucleation and growth, while the other morphologies were predominantly formed via spinodal decomposition. Cure temperature did not influence the macroscopic morphology, but the domain size changed with temperature. As cure temperature was increased, the PEI domain size in the sea‐island morphology decreased, while the BPACY nodule size increased in the nodular morphology. Mechanical and thermal properties were so strongly dependent upon the morphology that they changed dramatically near the phase inversion point.
Block copolymers prepared by emulsion polymerization with poly(ethylene oxide)–azo‐initiators
Authors: Tauer K.
Published: April 2003

Poly(ethylene oxide)‐b‐poly(styrene) block copolymers were prepared in the form of latex particles by emulsion polymerization of styrene with poly(ethylene glycol)–azo‐initiators as well as with the redox initiation system poly(ethylene glycol)/Ce4+. The emulsion polymerization can be carried out in the absence of additional stabilizers if the chain length of the poly(ethylene glycol) is greater than 40. The latex particles as well as the copolymers were characterized by capillary hydrodynamic fractionation, 13C‐nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy. By 13C‐NMR spectroscopy a side reaction of the primary radicals arising from the azo‐initiator was found which can contribute to the low efficiency of azo‐initiators in emulsion polymerization.
Polymeric surfactants in latex technology: polystyrene–poly(ethylene oxide) block copolymers as stabilizers in emulsion polymerization
Authors: Mura Jean‐Luc , Riess Gérard
Published: April 2003

Polystyrene–poly(ethylene oxide) PS–PEO di‐ and triblock copolymers have been used as stabilizers in the emulsion polymerization of styrene and styrene–butylacrylate for the preparation of “hairy latexes”. The polymerization kinetics and the efficiency of these polymeric surfactants were correlated with the molecular characteristics of the block copolymer. It was shown that the efficiency decreased with increasing molecular weight and PS content of the block copolymer.

The PEO frige, with a thickness of 4–25 nm, on the latex particle surface could be characterized and it was shown by differential scanning calorimetry (DSC) that water is strucured in that PEO layer. Film formation with “hairy latexes” was also examined both by DSC and thermomechanical analysis. The properties and application possibilities, such as in controlled latex flocculation, have been reviewed.
Protein adsorption on polystyrene latex particles
Authors: Norde Willem , Gonzalez Francisco Galistéo , Haynes Charles A.
Published: April 2003

Protein adsorption is the net result of various types of interaction between the different components present in the system, i.e. the sorbent surface, the protein(s), the solvent and any other solutes such as low molecular weight electrolyte. In this paper methods and techniques will be discussed to study the mechanism of protein adsorption on, in particular, colloidal particles. The discussion is based on experimental data obtained with relatively simple systems that contain one well‐defined protein and well‐characterized polystyrene latexes. Thus, the adsorption behavior of lysozyme and α‐lactalbumin are compared, emphasizing the role of structural rearrangements in the protein molecule.
The effect of pigments on the crystallization and properties of polypropylene
Authors: Silberman A. , Raninson E. , Dolgopolsky I. , Kenig S.
Published: April 2003

The effect of pigments of different chemical compositions on the crystellization process of PP was studied by means of differential scanning calorimetry in isothermal mode. The Avrami equation was applied to obtain the crystallization parameters of polypropylene with different pigments.

Lipatov's equations were applied for evaluation of the thickness and volume content of the transition layers. Results show that pigments affect not only the degree of crystallinity but also the structure of the amorphous phase and the integrity of the crystalline/amorphous interphase. Finally, the morphology and mechanical properties of pigmented polypropylene were studied in view of the different chemical compositions of the various pigments.
Making polymer concrete and polymer mortar using synthesized unsaturated polyester resins from poly(ethylene terephthalate) waste
Authors: Abdel‐Azim Abdel‐Azim A. , Attia Ibrahim A.
Published: April 2003

Depolymerization of poly(ethylene terephthalate), PET, waste was studied in the presence of manganese acetate catalyst and propylene glycol (PG) at different weight ratios. The glycolyzed products were analyzed for hydroxyl value and the amount of free glycol. A series of unsaturated polyesters based on the glycolyzed products, maleic anhydride and styrene, were prepared. Molecular weights and curing behavior of these polyesters were determined. Polymer concrete (PC) and polymer mortars (PM) made with these resins were investigated for their compressive strength. It has been found that the properties of PC and PM obtained from resins based on recycled PET are comparable to PC and PM made from virgin materials.
Electrochemical study of the nitroxyl radical derivatives built in the π‐conjugated poly(phenylenevinylene) skeleton
Authors: Toriu Shuichi , Kaneko Takashi , Nishide Hiroyuki , Tsuchida Eishun
Published: April 2003

The electrochemical oxidation and reduction of the stable neutral nitroxyl radical gave the oxoaminium salt and hydroxylamine or nitroxyl anion, respectively. The electrochemical behavior of the N‐butylnitroxyl radicals or N‐butylhydroxylamines built in to various phenylenevinylene species were discussed in connection with its developed π‐conjugated structure based on cyclic voltammetric measurements. The aromatic nitroxyl radical showed two pairs of oxidation–reduction waves, but the acidic proton (hydroxylamine) changed its cathodic peak to a broad one with a shift to the anodic side. The π‐conjugated poly(phenylenevinylene) backbone and mobile proton of the hydroxylamine unstabilized the nitroxyl radical by retaining the energy gap.
Chitin–cellulose blends: phase properties in dimethylacetamide–LiCl
Authors: Bianchi E. , Marsano E. , Baldini M. , Conio G. , Tealdi A.
Published: April 2003

Chitin–cellulose blends dissolved in dimethylacetamide containing LiCl (7% w/w) have been studied in a wide concentration range, from very dilute solutions to medium concentrations and up to solid films (absence of diluent).

The intrinsic viscosities at various chitin–cellulose ratios, as well as the phase diagram behavior, imply a good compatibility between the components. The result is confirmed by the infrared measurements on solid films. The lack of anisotropic phase formation in chitin–diluent binary solutions and the anomalous trend of v′CH–CE line on the phase diagram are both interpreted on the basis of aggregation phenomena.
Characterization of low‐density polybutadiene latexes by sedimentation field–flow fractionation
Authors: Blanda Marco , Reschiglian Pierluigi , Dondi Francesco , Beckett Ronald
Published: April 2003

A procedure based on sedimentation field–flow fractionation for physical characterization of polydisperse latexes is presented. The particle density, dimensions, polydispersity, size distribution and aggregation can be determined for both narrow and wide polydispersities. The procedure is applied to the sample case of polybutadiene latexes with density lower than water. The results are compared with independent measurements obtained by electron microscopy. The relevance of significant steps of the procedure, such as the nonequilibrium corrections, are discussed.
Liquid crystalline poly(enamine ketone)s formed through hydrogen bonding
Authors: Yandrasits Michael A. , Zhang Anqiu , Bruno Katie , Yoon Yeocheol , Sridhar Krishnamurthy , Chuang Yuhway , Harris Frank W. , Cheng Stephen Z. D.
Published: April 2003

A series of poly(enamine ketone)s (PEAKs) which exhibit liquid crystalline phases has been synthesized. The enamine ketone groups are able to exist in the cis and trans conformations. Molecular modelling results show that the cis conformation is energetically more favorable due to intramolecular hydrogen bonding. Model compound studies indicate that the formation of the mesogen requires the cis conformation in the enamine ketones to stabilize the liquid crystalline phase. This liquid crystalline phase is nematic for the model compound and the polymers. The heats of liquid crystal transition in the model compound and in PEAKs are very close (4.7 kJ/mol in model compound and 4.0 kJ/mol of repeating units in polymers). This is not only an indication of a similar percentage of the cis conformation in both cases, but also an example that the flexible ethyleneoxy spacers in the polymers do not contribute to the orientational order of this liquid crystalline phase. PEAKs can crystallize through either quenching from the isotropic melt or from the liquid crystalline phase. Crystallization kinetics exhibit the effect of pre‐ordering when these two different kinetics are compared.
Influence of the molecular weight of ionenes on the cobaltphthalocyanine‐catalysed autoxidation of mercaptoethanol
Authors: Schipper Eugène T. W. M. , Roelofs Alexander H. C. , Piet Pieter , German Anton L.
Published: April 2003

In order to study the promoting effect of polycations on the cobalt(II)phthalocyanine‐tetrasodiumsulphonate (CoPc(NaSO3)4)‐catalysed autoxidation of thiols, it is imperative to know the molecular weight dependence of the polymer. Monodisperse oligomers can often supply a lot of information. To elecidate the mechanism of the promoting effect of 2,4‐ionene, a poly(quaternary ammonium)salt, on the CoPc(NaSO3)4‐catalysed autoxidation of 2‐mercaptoethanol, a series of monodisperse 2,4‐ionene oligomers were prepared. Trimeric 2,4‐ionenes, containing two quaternary ammonium groups separated by four methylene groups, showed a high co‐catalytic activity, and active Co‐aggregates were detected with visible light spectroscopy. The spectroscopic behaviour was in close agreement with that of high molecular 2,4‐ionene/CoPc(NaSO3)4 complexes. In order to achieve this aggregation several oligomeric ionenes have to act concertedly. If the distance between the ionic sites is short the trimer acts as a simple salt in stablizing the aggregates. With respect to the catalytic activity the optimum polycation/catalyst ratio, expressed as the N+/Co ratio, decreased with increasing chain lenght and reached a constant level of 50 at a 2,4‐ionene nonamer. For the trimers and pentamers this ratio is affected by the type of end‐group. All synthesized 2,4‐ionene oligomers exhibited excellent co‐catalytic properties at the optimum N+/Co ratio, with maximum turnover frequencies of 4600 mol thiol/(mol Co s), i.e. 50 times higher than those obtained for the polymer‐free system. In the case of monodisperse 2,4‐ionene pentamer with bromo end‐groups, double Michaelis–Menten kinetics were observed, as also was exhibited by high molecular weight ionene.
Modelling studies of the controlled anionic copolymerization of butadiene and styrene
Authors: Chang C. C. , Halasa A. F. , Miller J. W. , Hsu W. L.
Published: April 2003

The anionic polymerization of isoprene with n‐butyl lithium and polar modifier such as TMEDA and tripiperdinophosphine oxide were studied and kinetic and reactor models are proposed for these systems. Reactor conversion, molecular weight distribution and polymer glass transition temperature had been calculated from the model and compared favorably to the actual data for various combinations of reactor systems and operating conditions. Simulations of the model can be used to design reactor systems and predict polymer properties of large‐scale operations from results of small scale batch reactor runs.
Synthesis of stereoblock poly(methyl methacrylate) via transformation of isotactic‐specific living polymer anion to syndiotactic‐specific anion
Authors: Kitayama Tatsuki , Fujimoto Nobutaka , Yanagida Takatsune , Hatada Koichi
Published: April 2003

Polymerization of methyl methacrylate (MMA) by isotactic poly(methyl methacrylate) (PMMA) living anion, prepared with t‐C4H9MgBr in toluene at −60°C, was carried out at −78°C in the presence of trialkylaluminiums (R3Al; R = CH3, C2H5, and n‐C4H9) to obtain a stereoblock PMMA, isotactic PMMA‐block‐syndiotactic PMMA. Among the R3Als, (CH3)3Al gave most effectively the steroblock PMMA with narrow molecular weight distribution. The fraction of rr triad in the syndiotactic PMMA block increased with increase in the ratio of Al/Mg and reached about 76% at a ratio of Al/Mg ≥ 6. The method was also used to prepare stereoblock copolymer comprising isotactic PMMA block and syndiotactic block of butyl methacrylate. Stereocomplex formation and solution viscosity of the stereoblock PMMA were also studied.
Dipole moments of styrene/4‐vinylpyridine copolymers—II: Relation to microstructure
Authors: Yilmaz Elvan , Küçükyavuz Zühal
Published: April 2003

Mean‐square dipole moment values of styrene/4‐vinylpyridine (S4VP) copolymers determined at 25–60°C in 1,4‐dioxane solutions were related to the microstructure of the chains. Data on the synthesis and dipole moments of S4VP copolymers were used to calculate the distribution of triad fractions and effective dipole moments of styrene, S‐centred, and 4‐vinylpyridine, V‐centred, fractions in the copolymer chains. The relative magnitudes of the effective dipole moment values calculated for each type of triad reflect the effect of dipole–dipole interactions on these values.
Performance of polysulfone/carboxylated polysulfone membranes
Authors: Lau Wayne W. Y. , Jiang Youqing
Published: April 2003

Membranes were made from miscible blends of polysulfone (PSf) and carboxylated polysulfone (CPSf) having an average of 0.45 and 0.87 COOH groups per repeated unit. Membranes made from PSf and CPSf alone showed low separation for NaCl, glucose, polyethylene glycol (PEG) of various molecular weights and bovine albumin, from aqueous solutions under an applied pressure of 50 psig and higher. Membranes made from PSf/CPSf of varied blend composition showed higher separation factors for the above solutes. Highest separation was observed in membranes made from an 80/20 wt% PSf/CPSf 0.45 blend, which yielded a separation factor of 0.60 for NaCl, 0.97 for glucose, 0.98 for PEG and 0.99 for bovine albumin under an applied pressure in the range 50–150 psig. This higher performance is believed to be a result of a synergism between PSf and CPSf 0.45 to give a membrane morphology unique among the PSf/CPSf membranes.
The study of complex mineral silicates by trimethylsilylation
Authors: ap Kendrick Dafydd , Montecinos Marcia , Parsonage John R.
Published: April 2003

The Lentz trimethylsilylation technique has been applied to study four micas: biotite, phlogopite, muscovite and suzorite. The Lentz derivitisation technique is shown to be independent of the exact amount of phase transfer agent (propan‐2‐ol or ethanol) present in the trimethylsilylation of the micas as long as the ratio of mineral to hexamethyldisiloxane is held constant. The polyorganosiloxane product distribution is shown to be largely dependent on the amount and distribution of Al3+ present in the tetrahedral layers of the micas.
Acoustical studies on polyvinylchloride in dimethylformamide
Authors: Sundaresan B. , Srinivasarao A.
Published: April 2003

Ultrasonic velocity studies were undertaken on solutions of polyvinylchloride (PVC) in dimethylformamide (DMF) in the concentration range 0–3% by weight, at an RF frequency of 2 MHz at three different temperatures, 303 K, 313 K and 323 K. The observed non‐linear increase in ultrasonic velocity with increase of PVC concentration is attributed to the segment–segment interaction which causes molecular association between PVC and DMF.
Combined electrochemical and chemical synthesis of thick polypyrrole layers and their characterization
Authors: Omastová Mariá , Lazár Milan , Košina Stanislav
Published: April 2003

The presence of pyridinium chlorochromate as an oxidizing agent in acetonitrile solution containing the monomer and the doping agent significantly accelerates electrochemical polymerization of pyrrole. The thickness of poly pyrrole layers produced by this combined electrochemical and chemical synthesis reaches several milimetres for the 60 min polymerization reaction.

The influence of pyridinium chlorochromate concentration on the rate of polymer formation and the amount of released gas was investigated during the combined synthesis of polypyrrole. The polypyrrole prepared was characterized by ESCA analysis.
Properties of carbon fibers modified by oxygen plasma
Authors: Jin Byung Suk , Lee Kwang Hee , Choe Chul Rim
Published: April 2003

Oxygen plasma treatment was used to introduce functional groups on the surface of polyacrylonitrile‐based carbon fibers. The fiber surface was examined by X‐ray photoelectron spectroscopy after treatment. The amount of functional groups on the fiber surface initially increased with increasing treatment time up to 2 min, thereafter remaining constant. The variation of surface energy with plasma treatment showed a similar trend. The plasma treatment affected the surface area and the mechanical properties of carbon fibers. The surface area increased but the mechanical properties decreased with increasing treatment times. The plasma treatment also changed the morphology of the fiber surface.
pH‐dependent hydrolysis and drug release of chitosan/polyether interpenetrating polymer network hydrogel
Authors: Yao Kang‐de , Peng Tao , Xu Mei‐xuan , Yuan Chen , Goosen Mattheus F. A. , Zhang Qi‐qing , Ren Lei
Published: April 2003

This paper describes a novel hydrogel based on crosslinked chitosan with glutaraldehyde interpenetrating polyether polymer network. The gel can hydrolyse in acid at 37°C due to the cleavage of imine bonds within the network. At pH≥7, there is no hydrolysis. The pH‐dependent release of cimetidine from the gel was also investigated.
Pigments, dyes and fluorescent brightening agents for plastics: An overview
Authors: Christie Robert M.
Published: April 2003

Articles manufactured from plastic materials are generally enhanced visually by the incorporation of pigments, dyes and fluorescent brightening agents. This article provides an overview of the requirements of these colouring materials for use in plastics and of the structures and properties of the most important products in commercial use.
Synthesis, characterisation and catalytic activity of styrene–divinylbenzene copolymer (XAD‐2) bound palladium (II) complex
Authors: John Jacob , Ram R. N.
Published: April 2003

Polymer‐anchored Pd(II) complex catalyst was sythesised by sequential attachment of 1,2‐diaminopropane as a ligand to the chloromethylated commercially available styrene‐divinylbenzene copolymer (XAD‐2). The catalyst was characterised using techniques such as FTIR, SEM, EPR, and UV‐VIS reflectance spectroscopy. Other physicochemical properties, such as bulk density, moisture content, swelling and surface area by the BET method at low temperature by nitrogen adsorption, were also studied. The catalyst was tested for the rate of hydrogenation of cyclohexene. The influence of various factors such as temperature, concentration of catalyst, substrate, and quantity of solvent have been determined. The results are compared with the homogeneous analogue. The recycling efficiency of the catalyst was also studied.