bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, properties and crystallization behavior of poly(ether ether ketone)/poly(phenolphthalein ether sulfone) block copolymers
Authors: Cao Junkui , Su Wencheng , Chen Yan , Wu Zhongwen , Shibata Mitsuhiro , Yosomiya Ryutoku 
Published: April 2003

AbstractPoly(ether ether ketone) (PEEK)/poly(phenolphthalein ether sulfone) (PPES) block copolymers were synthesized by a condensation reaction of fluorine‐terminated PEEK oligomers and hydroxy‐terminated PPES oligomers. The content of PPES in the copolymers was varied from 12 to 44 wt.‐%, and the effect of the compositional variation on the properties was investigated. Microphase separation was not observed and the copolymers formed a homogeneous system having good compatibility. The crystal structure of the copolymers is rhombic, equal to PEEK. The degree of crystallinity of the copolymers was low and decreased rapidly with the increase of PPES content. Concerning the cell parameters of the crystalline unit, a‐ and b‐axes are apparently longer and V is, thus, also larger compared with PEEK. Analyses of the isothermal crystallization kinetics of the copolymers provided an Avrami exponent (n) of 2.0. The glass transition temperature (Tg) of the copolymers greatly rose but the thermal stability became much poorer with the increase of PPES content. PEEK/PPES block copolymers possess good mechanical properties such as high strength and modulus.
Adhesive properties of some pressure‐sensitive adhesive agents containing oligomer additives
Authors: Florián Štefan , Novák Igor 
Published: April 2003

AbstractThis paper deals with the influence of oligomers, namely propylene oil and butylene oil, of different molecular weight on the adhesive properties of atactic polypropylene (aPP) and its mixtures with styrene‐2‐ethylhexyl acrylate (S‐EHA) copolymer. The mechanical work of adhesion Am of the mixture containing atactic polypropylene and oligomer increases with the molecular weight of the oligomer, which was more significant in the case of propylene oil. For ternary mixtures aPP‐S‐EHA copolymer/oligomer a maximum of adhesion can be observed if the content of the S‐EHA copolymer in the mixture reaches about 30 mass‐%. In the absence of oligomers in the mixture a minimum of adhesion can be observed for this composition, which can be attributed to the incompatibility of the remaining components.
Structural changes in poly(methyl methacrylate) during deep‐etch X‐ray synchrotron radiation lithography. Part I: Degradation of the molar mass
Authors: Schmalz Olaf , Hess Michael , Kosfeld Robert 
Published: April 2003

AbstractPoly(methyl methacrylate) is a preferred material used in X‐ray lithography. One effect observed after irradiation is a change of its chemical structure, combined with a decrease of the molar mass. This was analysed quantitatively using size exclusion chromatography combined with multi‐angle laser‐light scattering. Based on a kinetic model, an equation was derived which gives a satisfactory description of the dependence of the molar mass on the radiation dose.
Structural changes in poly(methyl methacrylate) during deep‐etch X‐ray synchrotron radiation lithography. Part II: Radiation effects on PMMA
Authors: Schmalz Olaf , Hess Michael , Kosfeld Robert 
Published: April 2003

AbstractThe irradiation of poly(methyl methacrylate) changes the chemical constitution of the polymer. In addition to a decrease in molar mass further radiation‐induced radical reactions cause changes in the chemical constitution of the polymer. Analysis of the reaction products shows that formation of long‐chain branching can be excluded. Along with degradation of the chain lengths, ester groups in the side chains are attacked. The result is a modified polymer with a physical and chemical behaviour different from that of the starting polymer.
Preparation and uranyl ion adsorptivity of macroreticular chelating resins containing a pair of neighboring amidoxime groups in a monomeric styrene unit
Authors: Park In‐Hwan , Suh Jung‐Mok 
Published: April 2003

AbstractA cyanomethylated styrene‐divinylbenzene copolymer was prepared by the reaction of a chloromethylated styrene‐divinylbenzene copolymer with sodium cyanide. A polystyrene‐based macroreticular resin containing a pair of neighboring nitrile groups in each monomeric styrene unit was obtained from the reaction of the cyanomethylated copolymer with 3‐chloropropionitrile under phase transfer conditions. The resin was reacted with hydroxylamine to afford a chelating resin containing a pair of neighboring amidoxime groups in each monomeric styrene unit. The chelating resin showed high adsorption capacity for uranyl ions. It was found that the resin was an effective adsorbent for other heavy metal ions such as Hg2+ and Pb2+.
Le rôle des systèmes photoamorceurs dans l'efficacité de photoréticulation de l'homopolymère dicyclopentadiène acrylate (DCPA) et acrylate d'éthyle (AE) et des dérivés copolymères DCPA/AE
Authors: Eisele Giles , Fouassier Jean‐Pierre , Reeb Roland 
Published: April 2003

AbstractL'efficacité de photoréticulation de toute une série de photoamorceurs commerciaux et de systèmes photosensibles multicomposants a été évaluée sur des matrices acryliques non réticulées. Les polymères utilisés pour cette étude sont des homopolymères et des copolymères d'acrylate de dicyclopentadiène/acrylate d'éthyle de composition variable (100/0, 40/60, 20/80, 0/100) synthétisés en solution par voie radicalaire. Les irradiations ont été effectuées à des grandes longueurs d'ondes (λ ≥ 310 nm). Les systèmes benzophénone/peroxyde de benzoyle ont permis d'obtenir des cinétiques de réticulation très rapides pour des temps d'irradation de 10 min.
Phosphorus‐containing polyurethanes based on bisphenol A via N‐alkylation
Authors: Liaw Der‐Jang , Lin Shiuh‐Ping 
Published: April 2003

AbstractPhosporus‐containing polyurethanes (PU‐P) based on bisphenol A were prepared by N‐alkylation. The structures of N‐alkylated polyurethanes were characterized by IR and 1H NMR spectra. Physical and thermal properties of the phosphorus‐containing polyurethanes were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X‐ray diffraction, tests of solubility, limiting oxygen index (LOI) and reduced viscosity. Tg of the N‐alkylated polymers decreased from 120°C for the starting polymer to 29°C of the 2.0 wt.‐% phosphorus‐containing polyurethanes. The viscosity of N‐alkylated polyurethanes also decreased from 0.36 dL g−1 to 0.24 dL g−1. The thermal stability of polyurethanes decreased on the introduction of phosphorus groups. The LOI values of polyurethanes showed that fire resistance of phosphorus‐containing polyurethanes was enhanced. X‐ray diffraction measurements showed that the increased phosphorus content was accompanied by decreased crystallinity of the polyurethanes. The solubility of PU‐P was improved.
Zur härtung von diandiglycidylether mit anhydridmodifizierten phenolischen härtern und zu vergleichbaren in situ‐reaktionen
Authors: Böschel Dorit , Fedtke Manfred 
Published: April 2003

AbstractDie Härtung von Diandiglycidylether (DDGE) mit hexahydrophthalsäureanhydridmodifiziertem 2,6‐Dimethylol‐p‐kresol (HHPSA‐DMPK) wurde untersucht und mit der in situ durchgeführten Vernetzung von DDGE mit Hexahydrophthalsäureanhydrid (HHPSA) und 2,6‐Dimethylol‐p‐kresol (DMPK) verglichen. Die chemischen Reaktionen wurden durch Titration der Epoxidgruppen und mit verschiedenen spektroskopischen und chromatographischen Methoden untersucht. Es wurde geprüft, ob die weniger aufwendige und daher preiswertere in situ‐Härtung zu Produkten mit gleichen oder besseren Endeigenschaften führt. Weiterhin wurde die Übertragbarkeit der Ergebnisse auf den Einsatz technischer Phenolharzhärter getestet.
Are cured thermoset resins inhomogeneous?
Authors: Dušek Karel 
Published: April 2003

AbstractThis question was addressed using various methods to monitor the process of curing and state of the final network. Attention was particularly focused on the possible inhomogeneous network formation as a consequence of the crosslinking process. An analysis of experimental data has revealed that some cured resins can be considered as homogeneous as the corresponding uncrosslinked materials. Resins cured by simple stepwise alternating chemistries, with good compatibility of components, usually fulfill the criterion of homogeneity. A family of epoxy resins cured with polyamines belongs to this category. Nodular structures seen by electron microscopy are a result of interaction of the electron beam or etching. Such structures are also observed for uncrosslinked polymers investigated under the same conditions. Formation of inhomogeneities in a number of thermoset systems is due to (a) chainwise mechanism of network formation with fast propagation inducing cyclization and steric volume exclusion and (b) poor compatibility of components of the system made stronger by increasing molecular weights and crosslinking during curing. Networks formed by freeradical polymerization and copolymerization of polyvinyl monomers can serve as an example of crosslinking‐driven formation of inhomogeneities.
Effect of aramid‐CTBN block copolymer on phase structure and toughness of cured epoxy resins modified with carboxy‐terminated butadiene acrylonitrile copolymer (CTBN)
Authors: Ochi Mitsukazu , Mimura Kenji , Kiyohara Osamu , Tagami Toshio 
Published: April 2003

AbstractAn Aramid‐CTBN block copolymer was added to a Bisphenol‐A type epoxy resins modified with CTBN. With the addition of the copolymer, the impact strength of the CTBN‐modified systems was about twelve times higher than that of the unmodified system. Transmission electron micrographs of the block copolymer‐epoxy system showed that the diameter of CTBN‐dispersed phase decreased and a number of fine CTBN phases were dispersed in the matrix. The deformability of matrix in these systems increased with a dispersion of the fine CTBN phase. It is concluded that the improvement of toughness of the cured resins is due to the increases in the ductility of epoxy matrix by the incorporating of the dispersion of the fine CTBN phase in the matrix.
The curing of dicyanate ester liquid crystalline thermosets
Authors: Ober Christopher K. , Körner Hilmar , Shiota Atsushi , Laus Michele 
Published: April 2003

AbstractThe attractive physical properties of cyanate ester resins make these materials an important class of high‐performance polymer thermosets for applications such as electro‐optic coatings and thin film dielectrics. Triazine networks have been used as insulating materials for over 25 years; however, in order to meet future requirements such materials must exhibit appropriate glass transition temperatures, high thermal stability, high moduli, good adhesion at elevated temperatures, low dielectric losses, and a low coefficient of thermal expansion (CTE). With our approach to thermoset design and processing we are able to directly control their mechanical and physical properties by curing new liquid crystalline cyanate ester resins in electric fields. Combining new LC materials with non‐LC cyanate monomers leads to a variety of novel ordered network structures and is a convenient method for modifying and controlling their chemical and physical properties. Studies of the new LC thermosets and their mixtures with non‐LC materials will be described.
Design of network polymers by photopolymerization
Authors: Crivello James V. 
Published: April 2003

AbstractThe base and transition metal catalyzed isomerization of allyl and crotyl ethers affords a facile, high yield route to the preparation of a variety of mono‐, di‐, and multifunctional 1‐propenyl and 1‐butenyl ethers. Employing this novel method, monomers containing epoxide, ester, ether carbonate and urethane groups can be prepared from their readily available allyl and crotyl precursors. In general, these monomers display very high reactivity in cationic polymerizations. In our work, we have focused on photoinduced cationic polymerizations of these monomers using diaryliodonium and triarylsulfonium salt photoinitiators. To study these very fast photopolymerizations, extensive use of real‐time infrared spectroscopy was made. Employing this technique, the effects of monomer and photoinitiator structure on the rates of polymerization were studied.
Synthesis and properties of acrylic/silicone polymer networks by hydrosilylation reaction
Authors: Tanabe Hisaki , Ohsugi Hiroharu , Takarada Mitsuhiro 
Published: April 2003

AbstractThe present investigation concerns acrylic/silicone polymer networks formed by the hydrosilylation reaction. Acrylic polymers containing alkenyl groups have been obtained by radical polymerization of a monomer having an alkenyl group and other vinyl monomers. Also a silicone polymer containing SiH groups has been prepared by the equilibrium reaction in presence of sulfuric acid. They are compatible with each other and can be crosslinked by the hydrosilylation reaction. The cured films are approximately of uniform structure and their acid resistance is excellent.
Microgels 4: The preparation of novel microgels and their applications
Authors: Graham Neil B , Mao Jianwen , Urquhart Alison 
Published: April 2003

AbstractThis paper describes studies on the formation of microgels from high functionality mixtures of monomers which are able to polymerise by a step‐growth process to polyurethanes in the specially selected solvent butan‐2‐one. Using the reactants poly(ethylene glycol) 6000, 1,2,6‐hexanetriol and biscyclohexylmethane‐4,4′‐diisocyanate in formulations made to comprise exactly one isocyanate group per hydroxyl, it was found that microgels of number average molecular weight, as determined by Gel Permeation Chromatography, of less than 20,000 were obtained up to the Critical Gelation Concentration which ranged from w/w reactant to solvent concentrations of from ∼ 0.24 to 0.74 at PEG/HT ratios of 1:4 to 4:4 respectively. These polymerisations surprisingly, went to complete conversion without gelation and produced 95 – 99% yields of microgel product after precipitation into a non‐solvent. Intrinsic viscosity determinations on the microgels dissolved in chloroform were determined and used to obtain estimates of the swollen coil densities at infinite dilution from which the critical packing concentration of these swollen coils in the solvent used for the solvent could be estimated. The critical packing concentration was in all cases well below the Critical Gelation Concentration. It was thus clearly demonstrated that the formation of “soluble” microgels is progressing in spite of the system being critically packed. This is a surprising observation and especially so when it is combined with the very low measured weight average molecular weights and high conversions of the products in the critically packed region. The GPC molecular weights decreased at the higher concentrations which is contrary to expectations. The ability to form microgels above critical packing confirms the results obtained and reported previously by us, that a similar phenomenom occurs in the case of the polymerisation of polyfunctional free‐radically polymerised monomer systems. These observations will need to be taken into account when formulating mathematical analyses of the gelation process. This class of products are able to be crystallised from organic solvents and are soluble in water. They are potentially useful as components of pharmaceutical formulations for the controlled release of drugs, high molecular weight active materials and living microorganisms.
Volume phase transition of spherical microgel particles
Authors: Wu Chi , Zhou Shuiqin , Au‐yeung Steve C. F. , Jiang Suhong 
Published: April 2003

AbstractThe volume phase transition of poly(N‐isopropylacrylamide) (PNIPAM) spherical microgel particles was studied by static and dynamic laser light scattering (LLS). The results were compared with the coil‐to‐globule transition of individual long linear PNIPAM chains. The microgel particles have a higher transition temperature, but a less sharp phase transition, in comparison with that of long linear chains. This difference has been attributed to both the short length and the broad length distribution of the subchains inside the microgels. A combination of static and dynamic LLS results revealed that even in a highly collapsed state the microgel particles retained ∼70% of water and the density of the microgel networks increased from 0.021 g/cm3 to ∼0.30 g/cm3 during the phase transition. The temperature‐dependence of the NMR spin‐lattice relaxation times T1 of PNIPAM indicate an association between water and the CH proton on the N‐isopropyl group. Our results also showed that the transition was strongly influenced by the presence of surfactant. Addition of anionic surfactant, such as sodium dodecyl sulfate (SDS), promotes the swelling of the particles and shifts the transition to a higher temperature, while the addition of a cationic surfactant, such as dodecyl pyridine bromide (DPB), has less effects on the swelling and phase transition, which has been attributed to the electron‐rich amide group in PNIPAM. Moreover, a two‐step phase transition was observed for the first time in the presence of SDS. The dynamic LLS results demonstrates that SDS is expelled gradually from the microgel in the first‐step volume phase transition.
Unsaturated polyester diol‐polyurethane composite networks
Authors: Xu M. X. , Liu W. G. , Yao K. D. 
Published: April 2003

AbstractThis article introduced the formation of an unsaturated polyester/diol‐polyurethane hybrid polymer networks(UP/PU HPNs). The phase behavior was examined by the dynamic mechanical properties and the morphology was investigated by transmission microscope(TEM) and atomic force microscopy(AFM). The effect of phase separation on mechanical properties is briefly described as well.
Molecular design of novel network polymers
Authors: Endo Takeshi , Sanda Fumio 
Published: April 2003

AbstractCationic, anionic, and radical ring‐opening polymerization of spiro and bicyclic monomers, and their application to network polymers have been developed. Bicyclo orthoesters (BOEs), spiro orthoesters (SOEs), and spiro orthocarbonates (SOCs) were polymerized by cationic double ring‐opening. Bicyclobis(γ‐butyrolactone)s and spirobis(γ‐butyrolactone)s were copolymerized with epoxides by anionic alternating ring‐opening. Polymers from SOCs bearing exomethylene groups consisted of ring‐opened and vinyl polymerized units. The degree of ring‐opening of SOCs depended upon the number of rings and steric hindrance. The radical polymerization of vinylcyclopropanone cyclic acetals depended on the ring‐size. With the monomers bearing 5‐ and 6‐membered acetal rings, single ring‐opened polymers were obtained. With the monomer bearing 7‐membered acetal ring, the polymer mainly consisted of double ring‐opened unit. These monomers could be crosslinked by bifunctionalization. Poly(cyclic orthoester)s linked by covalent bonds with dithiols to bifunctional SOEs were crosslinked by acid catalysts, and the reversible crosslinking‐depolymerization system could be controlled by temperature.
Computational study of network formation of phenolic resins
Authors: Yamagishi Tada‐Aki , Nakatogawa Takuji , Ikuji Masaki , Nakamoto Yoshiaki , Ishida Shin‐ichiro 
Published: April 2003

AbstractThe network formation of phenol‐formaldehyde resin was investigated by the Monte Carlo (MC) simulation technique. The observed value of the gel point, pc, was exactly determined as a critical extent of reaction, where the Mw/Mn in soluble parts is maximum. The MC simulation with the cubic percolation theory was applied to the gelation of phenolic resins and gave an exact gel point, which was in excellent agreement with the observed value of pc. The simulation showed that the intramolecular reaction occurred frequently with increasing the gel fraction beyond the gel point. The structural analysis of the maximum cluster with the computer strongly supported the contribution of the intramolecular reaction to the network formation of the gel.
Characterization of polyurethane network elastomers
Authors: Furukawa Mutsuhisa , Komiya Masaru , Yokoyama Tetsuo 
Published: April 2003

AbstractPolyester urethane network elastomers with incorporated hard segment oligomers have been prepared by poly(ethylene adipate)glycol (PEA), 2,4‐tolylene diisocyanate (TDI), and 1,4‐butanediol (BD). These hard segment oligomers were hydroxy‐terminated oligomers ([BD‐TDI]n‐BD; n=1,3), obtained by reacting BD with TDI. Concentrations of allophanate as a cross‐linking site were determined by the amine degradation method. Hard segment moieties were obtained by a novel selective hydrolysis of soft segments in the elastomers. Molecular weight distributions of hard segment were measured by means of GPC. Mechanical and thermal properties were measured. Dependence of rubber elasticity on physical cross‐linking between normal elastomers and the elastomers with incorporated hard segment oligomers were discussed.
PH‐induced structure change of poly(vinyl alcohol) hydrogel crosslinked with poly(acrylic acid)
Authors: Hirai Toshihiro , Okinaka Toshihiro , Hayashi Sadao , Amemiya Yoshiyuki , Kobayashi Katsumi , Hirai Mitsuhiro 
Published: April 2003

AbstractThe structure of the hydrogel of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) was investigated by small angle X‐ray scattering (SAXS) of synchrotron radiation. A physically crosslinked blend gel, which was prepared by repetitive freezing and thawing of an aqueous solution of PVA and PAA, could be chemically crosslinked by esterfication of PVA with PAA even in the hydrogel state. The chemical crosslinking induced the destruction of physical crosslinks into a folded structure, indicating that the chemical crosslinking proceeds at the sites around the physical crosslinks that contain PVA and PAA in much higher concentration than other portion of the gel. The pH‐induced structure changes of the PVA hydrogels, chemically crosslinked with poly(acrylic acid) (PAA) were investigated by SAXS on the samples of various chemical crosslinking time. The gels were shrunk at pH4, and swollen at pH8. The results of SAXS showed, that the Porod slope changed with chemical crosslinking time from ‐3.5 to −2.9 at pH4, and from −2.9 to −2.4 at pH8. The results suggest that a folded structure as a structural domain, which is characterized by fractally rough interface, tends to change into the structure that corresponds to percolation cluster, particularly at pH8. The gels immersed in pH8 showed a remarkable structure change accompanying swelling. The results revealed that a conformational change of PAA chains, induced by the pH change, can be explained by the presence of a structural domain in the gel network, where both PVA chains and PAA chains get entangled and partially form a interpenetrating polymer network(IPN).