bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal behavior of polytriazole films: A thermal analysis study
Authors: Gebben B. , Mulder M. H. V. , Smolders C. A. 
Published: April 2003

AbstractThe thermal behavior of poly(1,3‐phenyl‐1,4‐phenyl)‐4‐phenyl‐1,2,4‐triazole has been investigated using different scanning calorimetry (DSC) and thermogravimetry (TG). Processes are studied for this thermally stable polymer that take place between 200 and 500°C. While the polycondensation reaction product in powder from appeared to be partially crystalline, films prepared by casting from a formic acid solution appeared to be completely amorphous. A thermal treatment between Tg(∼ 270°C) and Tm(∼ 430°C) can introduce crystallinity in the films because of the polymer's ability to cold crystallize. The cold crystallization temperature Tc seems to be dependent on the preparation history of the solid polymer phase. Thermal annealing of the films just below Tg does not introduce crystallinity but inhibits subsequent cold crystallization at higher temperatures. Crystallization upon cooling from the crystalline melt has not been observed either. At temperatures just above the crystalline melting point the polymer starts to decompose in an exothermic reaction.
Nafion‐like thin film plasma‐polymerized from perfluorobenzene/SO2 mixture
Authors: Inagaki N. , Tasaka S. , Horikawa Y. 
Published: April 2003

AbstractPlasma polymerization of perfluorobenzene/sulfur dioxide (PFB/SO2) mixture was investigated by elemental analysis, infrared spectroscopy, and XPS. Plasma polymer films like Nafion were obtained from the plasma polymerization of PFB/SO2 mixture. The plasma polymerization deposited fluoropolymers with sulfur moieties including sulfonate and sulfonic acid groups. The elemental composition, F/C, and S/C atomic ratio of the formed plasma polymers were 0.65–0.67 and 0.24–0.27, respectively, which were independent of the starting mixture composition. The polymers showed cation‐exchange ability of which the capacity was 0.49 meq/g polymer, and initiated the polymerization of pyrrole.
Ring‐opening polymerization of α,β‐disubstituted oxiranes by α‐methoxyphenylmethylium hexachloroantimonate
Authors: Iijima Takao , Sashida Nobuyuki , Kakiuchi Hiroshi 
Published: April 2003

Abstractα‐Methoxyphenylmethylium hexachloroantimonate was used as a novel initiator for the polymerization of α,β‐disubstituted oxiranes such as cyclohexene oxide (CHO) and 2‐butene oxide (trans and cis) (2‐BO) at −78°C with dichloromethane or dichloromethane‐toluene mixtures as solvents. The CHO polymerization mixture became turbid and the polymer precipitated in dichloromethane. The CHO polymerization proceed quantitatively in dichloromethane–toluene mixtures. The molecular weight distribution of polyCHO obtained was bimodal regardless of the solvent used. The polymerization of trans‐2‐BO was heterogeneous in both dichloromethane and dichloromethane–toluene mixture. The polymerization mixtures of cis‐2‐BO were transparent but reached a limit yield which was less than the polymer yield of trans‐2‐BO. Furthermore, the microstructure of the poly2‐BOs were analyzed by Vandenberg's method and the results confirmed Vandenberg's finding that inversion of configuration occurs in the propagation step.
Miniemulsion copolymerization of styrene–methyl methacrylate
Authors: Rodriguez Valmore S. , El‐Aasser Mohamed S. , Asua Jose M. , Silebi Cesar A. 
Published: April 2003

AbstractMiniemulsion copolymerization of 50 : 50 weight fraction of styrene–methyl methacrylate monomer, using hexadecane as the cosurfactant, was carried out in both unseeded and seeded polymerizations. Effects of the hexadecane concentration and the ultrasonification time on the conversion–time curves and particle size of the final latex were investigated for unseeded polymerization. The kinetic and particle size distribution results showed that an increase in hexadecane concentration and ultrasonification time cause faster polymerization rate and smaller particle size. The mechanism of mass transport from miniemulsion droplets to polymer particles was also investigated for seeded polymerization. For this purpose a monomer miniemulsion was mixed with a fraction of a previously prepared miniemulsion latex particles prior to initiation of polymerization, using residual oil‐soluble initiator in the seed latex. The concentration of hexadecane and a water‐insoluble inhibitor (2,5 di‐tert‐butyl hydroquinone) in the miniemulsions were the main variables. Seeded polymerizations were also carried out in the presence of miniemulsion droplets containing a water‐insoluble inhibitor and water‐soluble initiator. The inhibitor concentration and the agitation speed during the course of polymerization were the experimental variables. The kinetic and particle size results from these seeded experiments suggested that collision between miniemulsion droplets and polymer particles may play a major role in the transport of highly water‐insoluble compounds.
Synthesis and properties of two new series of isomeric liquid crystalline polyesters with conjugated double bonds
Authors: Navarro Fernando , Serrano José Luis 
Published: April 2003

AbstractTwo homologous series of flexible main chain liquid crystalline polyesters with isomeric mesogenic groups containing conjugated double bonds, were synthesized and studied by differential scanning calorimetry and optical microscopy. One series (S1) has the p‐phenylene‐diacryloyloxydibenzoyl moiety as a mesogenic unit. The other (S2) has the terephtaloyl dioxydicinnamoyl moiety as a mesogenic unit. The reactivity of the conjugated double bonds of the p‐phenylenediacryloxy unit, at the temperature of mesophase formation, impedes the stability of liquid crystalline mesophases of polymers of series (S1). Two low molecular weight analogues of polymers were also prepared and their properties compared with those of polymers of similar structure. The two model compounds form stable smectic mesophases over a wide range of temperatures, which shows the high mesomorphogenic ability of both mesogenic units.
Core‐shell type polymer microspheres prepared by domain fixing of block copolymer films
Authors: Ishizu Koji , Onen Aysen 
Published: April 2003

AbstractWell‐defined poly[styrene(S)‐b‐isoprene(I)] diblock copolymers were prepared by sequential anionic addition. The crosslinking reactions of polyisoprene (PI) spherical domains of these block copolymers were carried out in a n‐hexane solution of sulfur monochloride (S2Cl2). Electron micrograph of crosslinked products indicates the structure of core‐shell type polymer microspheres. It is found from NMR and turbi+imetric measurements that the solubility of core‐shell type polymer microspheres depends strongly on that of block chains comprising the shell portion. The particle size of these microspheres shows a narrow distribution.
Silyl enol ethers as monomer. I. Radical copolymerizability of α‐trimethylsilyloxystyrene
Authors: Nagai Katsutoshi , Asada Keisuke , Chiba Keiji , Kuramoto Noriyuki 
Published: April 2003

Abstractα‐Trimethylsilyloxystyrene (TMSST), the silyl enol ether of acetophenone, was not homopolymerized either by a radical or a cationic initiator. Radical copolymerization of TMSST with styrene (ST) and acrylonitrile (AN) in bulk and the terpolymerization of TMSST, ST, and maleic anhydride (MA) in dioxane were studied at 60°C and the polymerization parameters of TMSST were estimated. The rate of copolymerization decreased with increased amounts of TMSST for both systems. Monomer reactivity ratios were found as follows: r1 = 1.48 and r2 = 0 for the ST (M1)–TMSST (M2) system and r1 = 0.050 and r2 = 0 for the AN (M1)–TMSST (M2) system. The terpolymerization of ST (M1), TMSST (M2), and MA (M3) gave a terpolymer containing ca. 50 mol % of MA units with a varying ratio of TMSST to ST units and the ratio of rate constants of propagation, k32/k31, was found to be 0.39. Q and e values of TMSST were determined using the values shown above to be 0.88 and −1.13, respectively. Attempted desilylation by an acid catalyst for the copolymer of TMSST with ST afforded polystyrene partially substituted with hydroxyl groups at the α‐position.
Hydrophobic interactions in the enantioselective solvolyses of optically active activated esters by imidazole‐containing polymeric surfactants
Authors: Cho Iwhan , Lee Burm‐Jong 
Published: April 2003

AbstractEnantioselective solvolyses of optically active activated esters in the aggregate system of optically active polymeric surfactants containing imidazole and benzene moieties were performed. The catalyst polymers [copoly(MHis‐DEVAB)] employed were copolymers of N‐methacryloyl‐L‐histidine methyl ester (MHis) with N,N‐dimethyl‐N‐hexadecyl‐N‐[10‐(p‐vinylcarboxanilido) decyl]ammonium bromide(DEVAB). In the solvolyses of N‐carbobenzoxy‐D‐ and L‐phenylalanine p‐nitrophenyl esters (D‐NBP and L‐NBP) by polymeric catalysts, copoly(MHis‐DEVAB) exhibited not only increased catalytic activity but also enhanced enantioselectivity as the mole percent of surfactant monomers in the copolymers increased. The polymeric catalysts showed noticeable enantioselective solvolyses toward D‐ and L‐NBP of the substrates employed. As the reaction temperature was lowered for the solvolyses of D‐ and L‐NBP with the catalyst polymer containing 4.8 mol% of MHis, an increased reaction rate and enhanced enantioselectivity were observed. The coaggregate systems of the polymer and monomeric surfactants were also investigated. The case of a coaggregate system consisting of 70 mol% of cetyldimethylethylammonium bromide with polymeric catalyst showed maximum enantioselective catalysis, viz., kcat (L)/kcat(D) = 6.68. The catalyst polymers in the sonicated solvolytic solutions were confirmed to form large ordered aggregate structure by electron microscopic observation. From these results, it is concluded that hydrophobic interaction in ordered aggregate structure plays an important role in enantioselective catalysis of optically active imidazole‐containing polymers.
Study of interaction between two oppositely charged polyelectrolytes and formation of polyelectrolyte complexes
Authors: Chatterjee S. K. , Yadav D. , Ghosh Sudipta , Khan A. M. 
Published: April 2003

AbstractPolyelectrolyte complex formation has been studied between oppositely charged polyelectrolytes, e.g., polyethylene‐imine, polymethacrylic acid, and methacrylic acid–methacrylamide copolymer. Formation of complexes could be shown through several experimental techniques, e.g., viscometry, conductometry, potentiometry, and IR spectra. It is suggested that these complexes are perhaps formed as a result of electrostatic cooperative interaction and a “ladder‐like” interaction is likely to be more favorable.
Evidence of formation of radicals in the polystyrene thermodegradation
Authors: Carniti P. , Gervasini A. , Beltrame P. L. , Audisio G. 
Published: April 2003

AbstractThe formation of radicals in the thermal degradation of polystyrene (PS) in tubes sealed under vacuum has been evidenced by using ESR spectroscopy. The radicals were found to be stable for weeks at room temperature. The rate coefficients of the formation of radicals have been evaluated in the temperature range 350–420°C. The reaction kinetically followed has been related to the initiation step of the multi‐step degradation process of PS. The activation energy of this reaction resulted 185 kJ/mol.
Electroinitiated polymerization of acrylamide by direct electron transfer
Authors: Hacioglu B. , Akbulut U. , Toppare L. 
Published: April 2003

AbstractElectroinitiated polymerization of acrylamide was carried out in acetonitrile–tetrabutylammonium fluoroborate by electrolytic reduction of monomer. It was shown by cyclic voltammetry that direct electron transfer from the cathode to the monomer can be achieved in this solvent–electrolyte system. Reduction peak potentials measured by cyclic voltammetry indicated that sodium salts will interfere with such a mechanism. Since the reduction peak potential of sodium salt and dimethylformamide are found to be lower than acrylamide, this couple was not employed for polymerization in this work. Acetonitrile–tetrabutylammonium fluoroborate couple is stable at the reduction peak potential of acrylamide.
Preparation and characterization of thin films of monomeric and polymeric octacyanophthalocyanines
Authors: Ashida Michio , Ueda Yasukiyo , Yanagi Hisao , Sayo Koichi 
Published: April 2003

AbstractThin films were prepared on substrates, cleavage surface of KCl single crystal, and metallic copper, by reaction of 1,2,4,5‐tetracyanobenzene with the substrate at various temperatures. The films were characterized by elemental analysis, IR, and UV/VIS spectroscopies. The films were observed by scanning electron microscopy. The films produced on copper at temperatures between 300 and 400°C consisted of copper octacyanophthalocyanine and its polymer with ladder structure. The ratio of polymer to monomer increased with elevating the reaction temperature. The films were composed of ribbon‐like crystals. The film produced on copper above 450°C was composed of an amorphous and continuous layer of polymeric copper phthalocyanine. The film produced on KCl at temperatures between 250 and 350°C consisted of potassium octacyanophthalocyanine and its polymer with ladder structure. The film produced on KCl above 450°C was polymeric potassium phthalocyanine. Those films contained more metal content than that required stoichiometrical.
Radical desorption in emulsion polymerization
Authors: Asua J. M. , Sudol E. D. , El‐Aasser M. S. 
Published: April 2003

AbstractThe derivation of a radical desorption coefficient in emulsion polymerization is presented, which takes into account the possible reactions of the desorbed radical in the aqueous phase as well as the competition between desorption and termination in polymer particles containing more than one radical. This model overcomes some important limitations of the previous models and is able to explain previously reported experimental results that the other models were unable to explain.
Acetylene–norbornene copolymers
Authors: Ramakrishnan S. , Hirsch J. A. , Martinez J. R. , Chien J. C. W. 
Published: April 2003

AbstractMetathesis ring opening polymerization has been used to copolymerize norbornene and 7,8‐bis(trifluoromethyl)tricyclo[4,2,2,02,5]deca‐3,7,9‐triene. Subsequent thermal elimination of the precursor copolymers yielded acetylene–norbornene copolymers. The undoped copolymers were found to have electrical conductivity, spin concentration, and EPR linewidths which vary with composition. The location of the trans‐CH out‐of‐plane vibration, however, was invariant at 1010cm−1 indicating that conjugation length of n > 4 are present even at 40% acetylene content in the copolymer. The copolymers containing 79 mol % of acetylene units attained a doped conductivity of 0.02 S/cm with a dopant concentration of 6 mol % of I per sp2 carbon.
Aqueous polymerization on clay surfaces. III. The polymerization of methyl methacrylate by montmorillonite/thiourea initiating system
Authors: Bhattacharya J. , Chakravarti S. K. , Talapatra S. , Saha S. K. , Guhaniyogi S. C. 
Published: April 2003

AbstractInitiation of polymerization of methyl methacrylate with redox system montmorillonite (with lattice Fe3+)–thiourea has been achieved. The rates are dependent on both clay mineral and thiourea. Amidosulfenyl radicals are believed to initiate the polymerization on the clay surface. The polymerization produced nonextractable clay–polymer adduct up to an extent of 70 wt %. The pH of the medium (in the acidic range) did not affect the polymerization rate.
Synthesis of polynucleotide analogs by grafting optically active adenine, cytosine, and hypoxanthine derivatives onto polytrimethylenimine
Authors: Overberger C. G. , Chang Ji Young 
Published: April 2003

AbstractA new family of polynucleotide analogs were prepared by grafting nucleic acid base derivatives onto polytrimethylenimine. Several new optically pure α‐nucleic acid base substituted propanoic acids were prepared as pendant groups. The (R)‐ethyl adeninylpropanoate was obtained from adenine and (S)‐ethyl lactate by utilizing a diethyl azodicarboxylate‐triphenyl phosphine method. Subsequent hydrolysis of the ester in aqueous acid gave the (R)‐adeninylpropanoic acid without racemization. The reaction of cytosine sodium salt with (S)‐ethyl 2‐[(methylsulfonyl)oxy] propanoate produced the 20% racemized (R)‐ethyl 2‐(cytosin‐1‐yl)propanoate. The optically pure ester was obtained by recrystallization from ethyl alcohol, which was hydrolyzed in aqueous acid to give the (R)‐acid with 66% enantiomeric excess. The (R)‐2‐(hypoxanthin‐9‐yl)propanoic acid was prepared by reaction of (R)‐2‐(adenin‐9‐yl)propanoic acid with sodium nitrite. The pendant groups were allowed to react with N‐hydroxy compounds in the presence of dicyclohexylcarbodiimide to give the active esters. These active esters underwent reaction with N,N‐dipropylamine to provide monomer model compounds. The pendant groups were grafted onto polytrimethylenimine by using the active ester method. The racemization reactions were observed in the grafting reactions. The resulting polymers showed a range of percent grafting from 60 to 80%.
Photocrosslinking of polyethylene. II. Properties of photocrosslinked polyethylene
Authors: Chen Yong Lie , Rånby Bengt 
Published: April 2003

AbstractSome properties of photocrosslinked high density polyethylene (2 mm thick sheets) have been studied. The homogeneity of the network is greatly improved by the application of triallylcyanurate (TAC) as crosslinking agent. The role of TAC in promoting the crosslinking is discussed. The crosslinked PE is found to be durable towards immersion in boiling water. Oxygen permeability increases while density and melting point decrease with increasing degree of crosslinking. The network chain density is obtained using conventional swelling method in boiling xylene, which together with data from melting point depression show that contribution of chain entanglement is insignificant to the gel formation of PE in this work.
Terpolymerization of maleic anhydride with vinyl monomers
Authors: Florjańczyk Zbigniew , Krawiec Włodzimierz 
Published: April 2003

AbstractThe relative reactivity of vinyl monomers characterized by electron donor and electron acceptor properties in free radical terpolymerization with maleic anhydride has been compared on the basis of product composition analysis. Terpolymers containing ca. 50 mol % of maleic anhydride were obtained in systems containing two electron donor monomers and the relative reactivity of them increases in the following order: 1‐hexene < propylene ≈ isobutylene < styrene < isoprene < 1,3‐butadiene. In systems consisting of an electron donor monomer and two electron acceptor monomers (i.e., maleic anhydride and an acrylic monomer), the composition of the terpolymers formed depends essentially on the resonance stabilization of the electron donor monomer. With a rise of their resonance stabilization, the content of acrylic monomeric units decreases and the share of alternating sequences of the electron donor and maleic anhydride monomeric units increases. It was found that the relative reactivity of maleic anhydride in all such systems is much greater than that predicted on the basis of reactivity ratios determined in binary systems. The relative reactivity of the studied acrylic monomers decreases in the order: methyl methacrylate > methyl acrylate > acrylonitrile. In the presence of catalytic amounts of ZnCl2 the content of acrylic monomeric units clearly increases in the products obtained, mainly as a result of homopropagation. The results obtained are discussed in terms of the classical mechanism of propagation and the complex participation model.
Dynamic mechanical and dielectric properties of epoxidized SBS triblock copolymer
Authors: Hsiue Ging‐Ho , Huang Wen‐Kuei , Hou Wei‐Hsin 
Published: April 2003

AbstractThe morphological and dynamic properties of epoxidized styrene–butadiene–styrene block copolymers were studied and compared with their parent styrene–butadiene–styrene block copolymer (SBS). Two peaks were observed in the mechanical loss (tan δ) curve which can be attributed to segmental motion of epoxidized polybutadiene (EPPB) and polystyrene. Analysis by DSC thermograms also showed the linear increase of glass transition temperature for EPPB domain with the epoxy group content. Phase separated structures of epoxidized SBS as observed by TEM suggests a considerable degree of mixing occurred between phases after 80 mol % of the double bonds in SBS were epoxidized. The interfacial region displays a third peak and causes much steeper drop in modulus at higher temperature than Tg of EPPB. Parallel dielectric relaxation measurements were also made in the frequency range of 30 Hz–1 KHz as a function of temperature. In each dielectric constant (ϵ′) curve, there is a maximum near the Tg of EPPB determined from the dielectric loss tangent curve. The shift in Tg of EPPB versus epoxy group content was consistent with that measured by the thermal and dynamic mechanic analysis. These findings indicated an 8°C shift in glass transition temperature as the epoxy group content in EPPB increased 10%.
Anionic syntheses of terminally functionalized ethylene oligomers
Authors: Bergbreiter David E. , Blanton J. R. , Chandran R. , Hein M. D. , Huang K.‐J. , Treadwell D. R. , Walker S. A. 
Published: April 2003

AbstractSynthetic procedures for preparation of terminally functionalized linear ethylene oligomers are described. The preferred synthetic method is anionic oligomerization of ethylene with n‐butyllithium–tetramethylethylenediamine and electrophilic substitution of the living oligomer so‐formed. Conditions and procedures for subsequent chemistry to elaborate the end groups of these oligomers are described. These procedures afford strictly linear ethylene oligomers which contain a wide variety of end groups and which range in molecular weight from 1000 to 4500 (Mn). The product oligomers were characterized spectroscopically as toluene‐d8 solutions at 110°C using multinuclear NMR, FT‐IR, fluorescence, and UV‐visible spectroscopies as appropriate. Alternative stepwise approaches to such oligomers are also discussed.
Kinetic analysis of the transesterification of dimethyl terephthalate with ethylene glycol in a semibatch reactor
Authors: Barandiarán M. J. , Asúa J. M. 
Published: April 2003

AbstractThe kinetic analysis of the transesterification of ethylene glycol (EG) and dimethyl terephthalate (DMT) was studied in a semibatch reactor under nonisothermal conditions. The effect of the temperature profile, EG/DMT ratio, and catalyst concentration on the reaction rate was studied. Models were fitted by using an algorithm of parameter estimation in differential equations based on the Gauss–Newton method improved with the Marquardt extension. It was found that, unlike previous authors, the reaction rate was not a classical third order reaction of first order with respect to EG, DMT, and catalyst concentration, but the EG reaction order was 0.6 and a hyperbolic function was found to fit the relationship between reaction rate and catalyst concentration. Also, it was found that, at high conversions, the effect of the reverse reaction should not be neglected.