bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure–property transition‐state model for the copolymerization of ethene and 1‐hexene with experimental and theoretical applications to novel disilylene‐bridged zirconocenes
Authors: Wigum Hanne , Solli Kjell‐Arne , Støvneng Jon Andreas , Rytter Erling 
Published: April 2003

AbstractEthene homopolymerization and copolymerization with 1‐hexene were performed with three new tetramethyldisilylene‐bridged zirconocene catalysts with 2‐indenyl ligand (A), 2‐tetrahydroindenyl ligand (B), and tetramethyl‐cyclopentadienyl ligand (C) and with methylaluminoxane as a cocatalyst. Catalysts A and B showed substantial comonomer incorporation, resulting in a copolymer melting temperature more than 20° lower than that of the corresponding homopolymer. In contrast, catalyst C produced a copolymer with a low 1‐hexene content and a high melting temperature. The reduction in the molecular weight with 1‐hexene addition also correlated well with the comonomer incorporation. For all three catalysts, the homopolymer and copolymer unsaturations indicated frequent chain termination after 1‐hexene insertion and a high degree of chain‐end isomerization during the homopolymerization of ethene. The chain transfer to Al in the cocatalyst also appeared to be important. The comonomer response could be correlated with the structural properties of the catalyst, as derived from quantum chemical calculations. A linear model, calibrated against recent experiments with unbridged (MenC5H5−n)2ZrCl2 catalysts, suggested that the low comonomer incorporation obtained with catalyst C was caused partly by a narrow opening angle between the aromatic ligands and partly by steric hindrance in the transition state of comonomer insertion. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1622–1631, 2003
Novel route to synthesis of allyl starch and biodegradable hydrogel by copolymerizing allyl‐modified starch with methacrylic acid and acrylamide
Authors: Bhuniya Sankar Prasad , Rahman Safikur , Satyanand Anshul J. , Gharia Mahendrasinh M. , Dave Ashok M. 
Published: April 2003

AbstractMaize starch was modified by allyl chloride adopting an interfacial reaction technique with cetyltrimethyl ammonium bromide as a phase‐transfer catalyst and pyridine as an acid acceptor. The degree of substitution was determined from an increasing carbon content of the modified starch. The percentage of carbon and hydrogen of the allyl‐modified starch was estimated by elemental analysis (C, H, and N), and the product characterization was done through 1H NMR and 13C NMR analyses. The allyl‐modified starch was then copolymerized with methacrylic acid and a combination of methacrylic acid and acrylamide at 50 and 70 °C with potassium persulfate as an initiator. The copolymer thus formed swelled in distilled water after neutralization with sodium carbonate. The percentage of absorption capacity of the hydrogels was determined with distilled water and 0.9% NaCl solution. The highest percentage of absorption, 6500%, was achieved for the developed hydrogel containing allyl starch and acrylic monomer in a 1.7:1 w/w ratio and acrylic monomer, namely, methacrylic acid and acrylamide in a 3.2:1 w/w ratio. The study on biodegradability of the developed hydrogel showed that the hydrogel is degradable in the presence of diastase (amylase). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1650–1658, 2003
Nanodroplets of polyisoprene fluid contained within poly(acrylic acid‐co‐acrylamide) shells
Authors: Huang Haiyong , Kowalewski Tomasz , Wooley Karen L. 
Published: April 2003

AbstractThe preparation and characterization of macromolecular nanostructures possessing an amphiphilic core–shell morphology with a hydrophobic, fluidlike core domain with a low glass‐transition temperature are described. The nanostructures were prepared by the self‐assembly of polyisoprene‐b‐poly(acrylic acid) diblock copolymers into polymer micelles, followed by crosslinking of the hydrophilic shell layer via condensation between the acrylic acid functionalities and 2,2′‐(ethylenedioxy)bis(ethylamine), in the presence of 1‐(3′‐dimethylaminopropyl)‐3‐ethylcarbodiimide methiodide. The properties of the resulting shell‐crosslinked knedel‐like (SCK) nanoparticles were dependent on the microstructure and properties of the polyisoprene core domain. SCKs containing polyisoprene with a mixture of 3,4‐ and 1,2‐microstructures underwent little shape distortion upon adsorption from aqueous solutions onto mica or graphite. In contrast, when SCKs were composed of polyisoprene of predominantly cis‐1,4‐repeat units, the glass‐transition temperature was −65 °C, and the nanospheres deformed to a large extent upon adsorption onto a hydrophilic substrate (mica). Adsorption onto graphite gave a less pronounced deformation, as determined by a combination of transmission electron microscopy and atomic force microscopy. Subsequent crosslinking of the core domain (in addition to the initial shell crosslinking) dramatically reduced the fluid nature and, therefore, reduced the SCK shape change. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1659–1668, 2003
Chemistry of alkenyl azlactones. VII. Preparation and properties of multiazlactones derived from mercaptan‐functional compounds and oligomers
Authors: Heilmann Steven M. , Rasmussen Jerald K. , Krepski Larry R. , Smith Howell K. 
Published: April 2003

AbstractThe reaction of polymercaptans and 2‐alkenyl azlactones has been further investigated, and several new multiazlactones which are liquids at room temperature have been prepared and characterized. Michael addition yielding the multiazlactones was found to take place slowly in the absence of and rapidly in the presence of acid catalysts. If basic impurities capable of forming mercaptide ion were present, however, the reaction underwent a substantially different course producing primarily ring‐opened products. A source of these basic impurities was determined to be the method of preparation of the alkenyl azlactone itself. When the azlactone was prepared from its acyclic N‐substituted aminoacid precursor by cyclodehydration by use of ethyl chloroformate and triethylamine, a small amount of triethylamine remained that dramatically altered the course of reaction. Nonbasic cyclodehydration agents such as dicyclohexylcarbodiimide were effective at eliminating this side reaction, as well as was the practice of adding excess acid to the reaction system to neutralize the basic impurities.
Functional polymers and sequential copolymers by phase‐transfer catalysis. 16. Influence of sequence distribution on the mesomorphic properties of thermotropic copolyethers containing 4,4′‐dihydroxybiphenyl
Authors: Shaffer Timothy D. , Jamaludin Mustafah , Percec Virgil 
Published: April 2003

AbstractRandom and alternating thermotropic liquid‐crystalline copolyethers have been synthesized from 4,4′‐dihydroxybiphenyl and a 1/1 mol ratio of 1,5‐dibromopentane and α,ω‐dibromoalkanes by a two‐phase (organic solvent‐aqueous NaOH) phase‐transfer‐catalyzed polyetherification. Random copolyethers were prepared from α,ω‐dibromoalkanes having six to twelve methylene units. Their phase behavior was compared with those of the perfectly alternating copolyethers containing five methylene units in one spacer and eight, nine, or eleven methylene units in the other, respectively. An odd‐even dependence in thermal transitions has been observed in both oligomeric systems. In all cases, alternating copolyethers, even though comparatively lower in molecular weight, have given rise to higher melting and isotropization temperatures. Since the increase in the melting temperature is larger than the increase in the isotropization temperature, the thermal stability range of the mesophase has narrowed for alternating copolyethers with respect to their random copolyether counterparts.
Functional monomers and polymers. CXIX.. Synthesis and photochemical reaction of polymethacrylate derivative containing 6‐cyanouracil
Authors: Inaki Yoshiaki , Fukunaga Shin‐Ichi , Suda Yasuo , Takemoto Kiichi 
Published: April 2003

AbstractA polymethacrylate derivative containing 6‐cyanouracil was prepared, and its photochemical reaction was studied. The 6‐cyanouracil derivative was found to show high reactivity for the photochemiccal reaction. The photochemical‐reaction product was identified as a cyclobutanetype photodimer, and the photodimer was formed in high yield even from the monomeric compound of 6‐cyanouracil under UV irradiation in low concentration. The quantum yield of the photodimerization of the 6‐cyanouracil derivative was greater than that of the thymine derivative. The photodimerization of the 6‐cyanouracil derivative could not be quenched by usual triplet quenchers, but was found to be quenched by the polymeric derivative of adenine, suggesting a specific interaction.
Synthesis of poly dithioesters and cyclization to 1, 3‐dithiolium (dithiafulvenium) salts
Authors: Mulvaney J. E. , Figueroa Francisco R. 
Published: April 2003

AbstractPiperidinium dithiobenzoate and piperidinium tetrathioterephthalate react with α‐halo carbonyl compounds to give small molecules and polymers which, upon dehydrative cyclization with H2SO4, yield materials containing the 1,3‐dithiolium ring. Maximum yields are obtained by use of phase‐transfer techniques and the solvent system H2O/CH2Cl2. The cyclized polymers are soluble in sulfuric acid, and films can be made from (CF3)2 CHOH solutions.
Polynuclear and halogenated structures in polyphenylenes synthesized from benzene, biphenyl, and p‐terphenyl under various conditions: Characterization by laser desorption/fourier transform mass spectrometry
Authors: Brown Charles Eric , Kovacic Peter , Wilkie Charles A. , Kinsinger James A. , Hein R. E. , Yaniger Stuart I. , Cody Robert B. 
Published: April 2003

AbstractPolyphenylenes made by reaction of benzene, biphenyl, or p‐terphenyl with metal halide catalyst–oxidant systems are complex mixtures of dissimilar oligomers, which include halogenated and polynuclear structures, according to positive and negative‐ion laser desorption/Fourier transform mass‐spectral analyses. Polymerization of benzene with metal‐chloride salts that terminate chain elongation by chlorination of the end rings appears to decrease formation of polynuclear structures by providing a competing pathway for chain termination. Polynuclear structures occur to a greater extent with oligomerization of biphenyl than with benzene, presumably because of isomerization and increased opportunity for π overlap during propagation. Electrical conductivities of polyphenylenes made by various routes should not be discussed solely in terms of the linear poly(p‐phenylene) structure.
Direct mass spectrometry of polymers. XIV. Thermal fragmentation processes in poly‐schiff bases
Authors: Ballistreri Alberto , Garozzo Domenico , Giuffrida Mario , Maravigna Pietro , Montaudo Giorgio 
Published: April 2003

AbstractThe thermal fragmentation processes in poly‐Schiff bases have been investigated by direct pyrolysis–mass spectrometry. The mass spectral data show that the thermal fragmentation occurring in the polymers under investigation is characterized by hydrogen transfer reactions. In the case of a totally aromatic poly‐Schiff base (polymer I), the thermal fragmentation process involves hydrogen transfer irom the methyne group with formation of fragments bearing nitrile and/or phenyl end groups. In the case of aromatic‐aliphatic poly‐Schiff bases (polymers II–IV), the hydrogen transfer process occurs from the aliphatic methylene groups. The latter process involves a lower energy and therefore occurs at lower temperatures with respect to the totally aromatic polymer I, with formation of thermal fragments bearing olefin and/or imine end groups. Beside these fragments, several thermal fragmentation compounds are also evolved by multiple hydrogen transfer reactions.
Antiinflammatory polymer‐bound steroids for topical applications II. Controlled release of the steroids
Authors: Vu Khue Nguyen , Jung L. , Coupin G. , Poindron P. 
Published: April 2003

AbstractThe release of hydrocortisone and dexamethasone due to hydrolysis of the carbonate linkage from the polymeric supports of poly(oxyethyleneglycol), hydroxypropyl cellulose, and N‐vinylpyrrolidone/hydrocortisone–21CH2–vinylcarbonate copolymer was observed in a living system, by induction of αGPDH activity in rat C6 glial cells, and in vitro by a kinetic study of release in aqueous sodium phosphate buffer medium. The glucocorticoid release is pH and temperature dependent and highly sensitive to steric hindrance. In vivo testing on antiinflammatory activity in rats with poly(oxyethyleneglycol) and hydroxypropyl cellulose bound dexamethasone was performed. However, it produced negative results probably due to difficulty in splitting the carbonate linkage in the inflammatory region of acidic pH values.
Inverse emulsion polymerization of acrylamide. I. Contribution to the study of some mechanistic aspects
Authors: Graillat C. , Pichot C. , Guyot A. , El Aasser M. S. 
Published: April 2003

AbstractThe inverse emulsion polymerization of aqueous solution of acrylamide in toluene has been studied at 40°C using a blend of surfactants as emulsifying system and oil soluble azo initiators. The azo compound partition between the phases has been measured and the effects of their nature and concentration on the polymerization kinetics have been investigated. The influence of other parameters on the kinetics and particle size of the inverse latex have also been investigated: the nature and amount of the emulsifier system, the stirring rate, and the presence of oil‐soluble inhibitor. The particle‐size analysis using electron microscopy or dynamic light‐scattering methods showed the presence of two populations of particles in the initial monomer emulsion and in the final inverse latex: one with very tiny particles (20 nm diam) and the other with larger particles (80–400 nm diam) which is highly polydispersed. The average size of these large particles undergoes a sharp decrease at a certain percent conversion depending upon the stirring rate. The evolution of the particle size distribution may result from a balance between coalescence and dispersion of the emulsion droplets under the effect of prevailing shear rate due to agitation.Concerning the initiation process, the very low solubility of the azo compound in the aqueous solution, together with the effect of the stirring rate and the presence of an oil‐soluble inhibitor on the polymerization kinetics lead to the conclusion that most of the initiaton originates from the capture of radicals or oligomeric radicals produced in the oil phase or in the interfacial layer.
Aromatic polyisophthalamides with oxybenzoyl pendent groups
Authors: De Abajo J. , Guijarro E. , Serna F. J. , De La Campa J. G. 
Published: April 2003

AbstractA series of polyisophthalamides containing pendent oxybenzoyl groups were prepared from 5‐oxybenzoyl‐isophthaloyl chloride and aromatic diamines. The analogous unsubstituted polyisophthalamides were also prepared in order to compare the two series and to determine the effect of oxybenzoyl pendent groups on the properties of aromatic polyamides. The modified polymers exhibited better solubility than, and approximately the same glass transition temperatures (in the range 260–290°C) as, the parent unsubstituted polymers. The mechanical strength of polymer films was affected only to a small extent by the presence of side groups, but the thermal resistance was negatively affected, with the result that polyisophthalamides with oxybenzoyl pendent groups began to decompose at about 360°C (TGA), 60–100°C lower than the unsubstituted polyisophthalamides. By means of an appropriate thermal treatment, crosslinking of the modified polymers was achieved and their thermal resistance significantly enhanced.
Binding of methyl orange and its homologs by powdered nylon 66
Authors: Lim Yong Jin , Kim Sung Hoon , Hamano Hiromitsu , Takagishi Toru , Kuroki Nobuhiko 
Published: April 2003

AbstractPowdered Nylon 66 was prepared as a model of amorphous polymers. The resultant powder polyamide was composed of only amorphous regions. The extent of uptake of the acid azo dyes, a homologous series of methyl orange derivatives, by the polymer was measured in an aqueous solution. The first binding constants and the thermodynamic parameters in the course of the binding were evaluated. The thermodynamic behaviors obtained are very similar to those of crosslinked polyvinylpyrrolidone. The favorable free energy of the binding is accompanied by an entropy gain and an exothermic enthalpy change. The shorter the alkyl chain of the dyes, the more negative is the enthalpy change and, hence, the smaller is the entropy change. The thermodynamic data for butyl orange showed that the binding process is athermal and is wholly an entropic effect. The binding of the dyes to the matrix is entropically favorable as a result of the operation of the hydrophobic effect. In addition, an electrostatic force is operative between the sulfonate group on the dyes and the terminal amino groups on the polyamide.
Investigation of polymer miscibility by spectroscopic methods. III. Labeling of poly(vinyl chloride), poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile) with fluorescent chromophores for nonradiative energy transfer studies
Authors: Albert B. , Jerome R. , Teyssie P. , Selb J. 
Published: April 2003

AbstractPoly(vinyl chloride) (PVC) is generally recognized as miscible with s.poly(methyl methacrylate) (s.PMMA), poly(ϵ‐caprolactone) (PCL) and poly(styrene‐co‐acrylonitrile) copolymer (SAN) containing 27 wt % AN. Nonradiative energy transfer (NRET) is a very sensitive technique in the investigation of the polymer miscibility. To compare by NRET the actual degree of miscibility of the PVC/s.PMMA, PVC/PCL, and PVC/SAN polymer pairs, each polymer is to be labeled with a fluorescent chromophore to an extent of 1 or 2 mol %. This paper reports efficient pathways to attach anthracene (acceptor) or naphthalene (donor) onto preformed PVC, s.PMMA, and SAN samples. All the attempts for grafting carbazole (donor) moieties have failed, as well as any labeling of PCL whatever the nature of the chromophore.
Extent of complex participation in the rate of copolymerization of styrene with maleic anhydride in methyl ethyl ketone
Authors: Fujimori Kiyohisa , Craven Ian E. 
Published: April 2003

AbstractGeorgiev and Shirota's simplified terminal complex model was applied to the dilatometrically measured initial rate of copolymerization of sytrene (ST) with maleic anhydride (MA) in methyl ethyl ketone (MEK) at 50°C. The rate was maximum at the feed MA mole fractions of 0.752, 0.769, and 0.806 at the total monomer concentrations of 2M, 1.5M, and 0.5M, respectively. Shirota's method gave the following ratios of propagation rate constants: βA=kAC/kAD = 8.25 and βD = kDC/kDA = 2.70. Georgiev's method gave βA = 14, βD = 2.7, and α = kAD/kDA = 22. The equilibrium constant of the donor‐acceptor complexation between ST and MA in MEK was measured to be 0.045 dm3/mol at room temperature.
Polymers from 4,4′‐sulfonyldiphenol
Authors: Mulvaney J. E. , Figueroa Francisco R. , Wu S. J. 
Published: April 2003

AbstractSeveral polymers have been prepared from 4,4′‐sulfonyldiphenol (SDP) or its bis‐phenate salt as the nucleophile in condensation polymerizations. Ester‐sulfone‐amic acid polymers were of fairly high molecular weight, and could be imidized. Soluble film‐forming poly ether‐ester‐sulfones were prepared from diphenyl ether diacid chloride.
Oxygen diffusion in poly(dimethyl siloxane) using fluorescence quenching. I. Measurement technique and analysis
Authors: Cox M. E. , Dunn B. 
Published: April 2003

AbstractThe transport properties of oxygen in poly(dimethyl siloxane) have been measured using the method of quenching of fluorescence. This paper discusses the uniqueness of this method and its use in measuring the diffusion coefficient of oxygen in unfilled PDMS. The results show (1) a large value for the diffusion coefficient of oxygen in pure PDMS at 25°C, D = 3.55 × 10−5 cm2/s, (2) a low value of the acitivation energy, ED = 4.77 kcal/mole, which was not temperature dependent in the ranges evaluated, and (3) a large value of the preexponential term, D0 = 0.115 cm2/s. The diffusion coefficient was found to be independent of both the oxygen concentration and fluorophor concentration in the pressure and temperature ranges used in these experiments. The import of these experiments lies in their application to a unique biomedical oxygen sensor which is fast, sensitive, and does not consume oxygen.
Mechanism of plasma‐initiated polymerization: Concerning the nature of solvent effects on the lifelike polymerization of water‐soluble vinyl monomers
Authors: Kuzuya Masayuki , Kawaguchi Tohru , Yanagihara Yasukichi , Nakai Sachihiko , Okuda Takachiyo 
Published: April 2003

AbstractTo provide a satisfactory basic understanding of the solvent effect of plasma‐initiated polymerization, we have carried out several kinds of polymerizations of various water‐soluble vinyl monomers. It has been shown that aqueous solution of such vinyl monomers underwent the polymerizations induced by methyl isobutyrate (MIB) plasma‐exposed glass surface. The invisible ultrathin polymer film trapping an active radical species deposited on the plasma‐exposed glass surface apparently induced the polymerizations. The efficiency, however, was largely dependent on the solvent used: the solvent can be considered to act as “an initiation‐activator” for the lifelike postpolymerization. The nature of the solvent effect was ascribed to the physicomechanical property such as swelling ability and/or solubility toward the ultrathin film formed on the glass surface. Thus it has been suggested that the choice of good‐balanced combination between the structural feature of the plasma‐induced ultrathin polymer film and the solvent as an initiation‐activator is important to achieve activity of a desired solution polymerization.
Kinetic study of the reaction between hydroxylated polybutadienes and isocyanates. 1. Reaction with tolylene diisocyanate (TDI)
Authors: Coutinho Fernanda M. B. , Rezende Luis C. , Quijada Raul 
Published: April 2003

AbstractA comparative kinetic study of the reaction of three different hydroxylated liquid polybutadienes (Mn ⋍ 3000) — R ‐ 45M, R‐45HT, and H‐034—and tolylene diisocyanate (TDI), was carried out in toluene solution. An analytical method was used to follow the kinetics of the reactions at four different temperatures. The reactions presented an apparent second‐order rate law. In the second‐order plots, a discontinuity was observed. The R‐45M polybutadiene was about twice more reactive than R‐45HT and H‐034; these latter two polybutadienes presented similar reactivities.
Cerium (IV)‐2‐chloroethanol redox‐pair initiated polymerization of acrylamide in aqueous medium
Authors: Gupta K. C. , Behari K. 
Published: April 2003

AbstractThe kinetics of acrylamide polymerization has been investigated by employing cericammoniumnitrate‐2‐chloroethanol redox pair under nitrogen atmosphere at 30 ± 1°C. The rate of monomer disappearance is directly proportional to the concentration of 2‐chloroethanol (1.0 × 10−2 − 10.0 × 10−2 mol. dm−3) and is inversely proportional to the ceric ion concentration (2.5 × 10−3 − 10.0 × 10−3 mol. dm−3) but shows square dependence to the concentration of monomer (5.0 × 10−2 − 25.0 × 10−2 mol. dm−3). The rate of ceric ion disappearance is directly proportional to the initial concentration of ceric ion and 2‐chloroethanol but independent of acrylamide concentration. The viscometric average molecular weight (Mv) decreases on increasing the concentration of ceric ion and increases on increasing the concentrations of acrylamide and 2‐chloroethanol. A tentative mechanism has been proposed.