bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ethynylated N‐phenylbenzimidazoles: Synthesis and thermal properties
Authors: Lau K. S. Y. , Kelleghan W. J. , Boschan R. H. , Bilow N. 
Published: April 2003

AbstractThree diethynylated bisbenzimidazole prepolymers were synthesized and their polymerization characteristics examined. N‐phenyl‐substituted diethynylated bisbenzimidazoles melted between 250 and 265°C and had gel times of several seconds to several minutes. In contrast, an N‐phenoxyphenyl diethynylated bisbenzimidazole melted at a temperature sufficiently low (ca. 150°C) to provide a 5‐min gel time at 170°C and a 4‐min gel time at 210°C. This material showed promise as a potential laminating resin and a brief screening of the prepolymer for this application was carried out. The polymers of both N‐phenyl‐ and N‐phenoxyphenyl‐substituted diethynylated bisbenzimidazoles showed apparent degradation temperatures of 500°C or greater when examined by thermogravimetric analysis.
Properties of polyphenylene films deposited electrochemically in an HF‐benzene system
Authors: Rubinstein Israel 
Published: April 2003

AbstractFree‐standing polyphenylene films, prepared by the electrochemical oxidation of benzene in an HF‐benzene, two‐phase system, were investigated. From electron microscope pictures, x‐ray diffraction patterns, and infrared (IR) spectra of polyphenylene films and commercial polyphenylene powder it is concluded that the films, which are largely para linked, contain in addition a substantial amount of meta and possibly ortho linkages and are amorphous in nature. Doping with AsF5 increases the electrical conductivity of the otherwise insulating films to 10−4−10−2ohm−1cm−1; doped films are relatively stable in air. The lower conductivity of doped films with respect to reported values for chemically synthesized poly‐p‐phenylene appears to be the result of the amorphous nature of the films.
Synthesis of casein‐G‐poly(vinyl acetate). II
Authors: Mohan D. , Radhakrishnan Ganga , Rajadurai S. 
Published: April 2003

AbstractPoly(vinyl acetate) was graft‐copolymerized onto casein in the presence of potassium peroxydisulfate‐ascorbic acid. The effect of synthetic variables on the rates of conversion of monomer (Rp), graft copolymerization (Rg), and homopolymerization (Rh), percent grafting, and grafting efficiency were investigated and the results, compared with the system initiated by peroxydisulfate alone.
Preparation of silicon‐containing polymers. I. Polyimides from dianhydrides and organosilicon diisocyanates
Authors: Ghatge N. D. , Jadhav J. Y. 
Published: April 2003

AbstractNew silicon‐containing polyimides have been prepared by the reaction of pyromellitic dianhydride (PMDA) and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) with organosilicon diisocyanates having the following general structure:
magnified image
where R1 = R2 = CH3 and C6H5. Thermal properties of these polyimides were studied were by TG, DTA, and DTG.
Studies on the role of peroxy and hydroperoxy groups in polymer photodegradation
Authors: Wismontski‐Knittel T. , Kilp T. 
Published: April 2003

AbstractInteractions of carbonyl singlet and triplet excited states with peroxides and hydroperoxides were examined in order to ascertain the reasons why the latter two compounds act as nearly diffusion controlled quenchers of ketone‐containing polymer photodegradation. From singlet state fluorescence quenching and laser flash photolysis measurements of triplet decays, direct interaction with the carbonyl excited states was ruled out. These processes occurred with rate constants at least one to two orders of magnitude below the diffusion controlled limit. Trapping of the 1,4‐biradical precursor to chain scission, thereby preventing its disproportionation was also tentatively eliminated. Results obtained using benzoyl peroxide suggest that quencher photodissociation into alkoxy radicals might represent the key step in the quenching of ketone‐containing polymer photodegradation.
Preparation of polyaryl esters by a new direct polycondensation reaction with arylsulfonyl chlorides in pyridine
Authors: Higashi Fukuji , Akiyama Naoki , Koyama Tsugio 
Published: April 2003

AbstractArylsulfonyl chlorides were successfully used as a new condensing agent for the synthesis of polyaryl esters by the direct polycondensation of aromatic dicarboxylic acids and bisphenols. High‐molecular‐weight polymers (Mw = 84,000) were prepared by reacting dicarboxylic acids with the sulfonyl chlorides in pyridine in the presence of LiCI, followed by treating with a pyridine solution of bisphenols. The polycondensation was significantly affected by factors, such as, the kind of arylsulfonyl chlorides, its amount, the conditions of initial reaction of the acids with the sulfonyl chlorides, the amounts of LiCI added, and dropwise addition of bisphenols.
Head‐to‐head vinyl polymers. XI. Preparation and characterization of poly(methyl acrylate) and poly(methyl methacrylate) consisting of head‐to‐head and head‐to‐tail units through cyclopolymerization of acrylic and methacrylic anhydrides
Authors: Ohya Takahiro , Otsu Takayuki 
Published: April 2003

AbstractAcrylic anhydride (AAn) and methacrylic anhydride (MAAn) were polymerized with radical initiator in polar solvents at high temperatures. The polymers obtained were found to consist of five‐and six‐membered ring structures by comparing IR spectra of the polymers with those of model compounds, succinic anhydride, and glutaric anhydride. Hydrolysis and methylation of the polymers gave new polymers composed of head‐to‐head (HH) and head‐to‐tail (HT) methyl acrylate (MA) or methyl methacrylate (MMA) units. The content of HH unit of these HH/HT polymers was determined by 1H‐NMR and 13C‐NMR spectra. The softening, glass transition, and thermal degradation temperatures of the poly(MA) with HH and HT units were found to somewhat increase with increasing of the content of the HH units. On the other hand, the glass transition and thermal degradation temperatures of the poly(MMA) with HH and HT units increased similarly, but the softening temperature decreased as the content of the HH units increased.
Photoresponsive crown ethers. 10. Metal complexation by light‐switched crown ethers immobilized in polymer matrices
Authors: Shinkai Seiji , Kinda Hidefumi , Ishihara Midori , Manabe Osamu 
Published: April 2003

AbstractThe crosslinked polystyrene beads which immobilized two terminal azophenoxide groups of an azobenzene‐crown(24‐crown‐8)‐azobenzene unit were synthesized. The polymer beads adsorbed Cs+ in the dark while they rapidly released Cs+ into the solution under UV‐light irradiation, and the photoresponsive complexation occurred reversibly. On the other hand, the crosslinked polystyrene beads which immobilized one terminal azophenoxide group of an azobenzene‐crown (24‐crown‐8) unit scarcely (or only to a smaller extent) exhibited such a photoresponsive behavior. Similarly, the polymer beads which immobilized two terminal azophenoxide groups of an azobenzene‐crown (18‐crown‐6) azobenzene unit reversibly adsorbed and desorbed K+ in response to UV‐light irradiation. The novel photoresponsive behavior is ascribed to a conformational distortion of the crown rings which induced by the photoisomerization of the azobenzene moiety, although the photoinduced polarity change of the polymer beads is not completely ruled out. The results suggest that the polymer support is useful as a “fixed point” to enforce the conformational changes of immobilized functional molecules.
Water‐soluble copolymers. VII. Cerium (IV) induced graft copolymerization of acrylamide and sodium‐2‐acrylamido‐2‐methylpropane sulfonate onto dextran
Authors: McCormick Charles L. , Park Lee S. 
Published: April 2003

AbstractStudies were conducted on grafting of acrylamide (AM) and sodium‐2‐acrylamido‐2‐methylpropane sulfonate (NaAMPS) comonomers onto dextran utilizing Ce(IV) induced initiation. The effects of reaction temperature, the Ce(IV)/dextran ratio, and the AM/NaAMPS ratio on grafting yield were investigated. The graft copolymerization behavior can be explained by exchange of the AMPS anion with one of the ligands on the Ce(IV) initiator. Oxidative modification of the dextran substrate improved the yield of graft copolymer. The dextran‐g‐poly(acrylamido‐co‐sodium‐2‐acrylamido‐2‐methylpropane sulfonate) samples prepared by this method were characterized as to copolymer composition and molecular weight utilizing elemental analysis, dilute solution viscometry, and aqueous size exclusion chromatography. Relationships of molecular weight and charge density to kinematic viscosity and salt sensitivity are discussed.
Synthesis and attempted polymerization of N‐arylmaleimides substituted with allylamino or cyclopropylamino groups at 2‐position
Authors: Pyriadi Thanun M. , Kaleefa H. 
Published: April 2003

AbstractSeveral N‐substituted chloromaleimides were prepared by dehydrating the corresponding chloromaleamic acids. Treatment of chloromaleimides with allylamine or cyclopropylamine produced N‐aryl‐2‐(allylamino)maleimides and N‐aryl‐2‐(cyclopropylamino)maleimides, respectively. Neither the N‐substituted chloromaleimides nor the N‐aryl‐2‐(allylamino) or N‐aryl‐2‐(cyclopropylamino)maleimides polymerized free radically or anionically. The difficulty of achieving good pi‐pi overlap and stiric effects at the propagation step prevented the cyclopolymerization of the prepared 1,5‐dienes.
Radiolysis of resist polymers. IV. Poly(p‐substituted‐α‐methylstyrene)s
Authors: Babu G. N. , Lu P. H. , Hsu S. L. , Chien James C. W. 
Published: April 2003

AbstractThe effect of parasubstituents on the radiation chemistry of poly(α‐methylstyrene) (PMS) was compared for the fluoro (PFMS), chloro (PCMS), bromo (PBMS), isopropyl (PiPMS), and methoxy (PMeOM) derivatives. Radiolysis yields, ESR spectra, and GCMS analysis of products were obtained. PMS and PFMS have similar low radiolysis yields, products, and product distributions. Only main‐chain radicals which persist to 200° were observed. PCMS has increased values of Gs, Gx, and Gr. The product analysis results suggest that the presence of chlorine contributes to the primary process by dissociative electron capture and enhances the cleavage of α‐methyl group. Irradiation of PBMS caused crosslinking and yielded few volatile products. PMeOMS and PiPMS gel readily by γ‐irradiation and may be useful as negative radiation resists.
The role of oxygen in the ignition of polystyrene by a small flame
Authors: Clark Ferrers R. S. 
Published: April 2003

AbstractThe ignition of slabs of high‐impact polystyrene by a lean hydrogen–oxygen flat flame was studied. The ignition delays and inital rates of flame development after ignition are reported as functions of gas temperature and the separation between flame and polymer surface. The delays follow an Arrhenius‐type expression with an activation energy of 98 ± 18 kJ mol−1. The rates of flame development drop as the gas temperature increases. During long ignition delays the apparent heat transfer coefficient at the sample surface dropped from about 100 W m−2 K−1 to values close to that expected for a hot gas impinging at right angles on a cold surface. For short delays it was higher and more constant at about 100 W m−2 K−1. Although the surface temperature reached before ignition exceeded that required for nonoxidative pyrolysis, the polymer surface charred only when oxygen was present. It is concluded that both oxidative and nonoxidative pyrolysis contribute to the ignition of polystyrene.
System development for aqueous gel permeation chromatography
Authors: Callec G. , Anderson A. W. , Tsao G. T. , Rollings J. E. 
Published: April 2003

AbstractTo devise an improved gel permeation chromatography system for the analysis of macromolecules, with a strongly alkaline solution as eluent, three Fractogel TSK gels were investigated. Because primary standards are usually unavailable, calibration was achieved by using Benoit's universal procedure and polystyrene sulfonates, polyethylene glycols, and dextrans as secondary calibrants. Continuous monitoring of intrinsic viscosity resulted from coupling a viscodetector with a classical differential refractometer. It was found that column efficiency and fractionation range could be extended well beyond those of previously studied systems on a reasonably short period of analysis.
A comparison of theoretically determined and experimentally measured velocity distributions of poly(ethylene terephthalate) flow in a capillary
Authors: Crater Davis H. , Cuculo John A. 
Published: April 2003

AbstractA streak photographic technique was used to determine the velocity distribution in a capillary produced by the flow of poly(ethylene terephthalate) (PET). This uniquely designed quartz die assembly, which was fitted onto a melt extruder, permitted visualization of polymer flow behavior during melt spinning. Aluminum tracer particles were mixed with polymer chips prior to extrusion. A laser beam was directed through a lens system that illuminated the tracer particles in the melt only in a thin, vertical cross section of the transparent quartz die. A pressure‐drop analysis was also performed on PET, under the same experimental conditions, to determine rheological properties of the polymer. By using these rheological properties theoretical velocity distributions were calculated for PET and then compared with the profiles obtained by the streak photographic technique.
Copolymerization of ethylene with higher linear α‐olefins—reactivity ratios
Authors: Kissin Y. V. , Beach D. L. 
Published: April 2003

AbstractCopolymerization of ethylene with mixtures of linear α‐olefins C6–C36 in the presence of two heterogeneous Ziegler–Natta catalysts, δ‐TiCl3–AlEt3 and TiCl4/MgCl2–AlEt3, at 90°C was studied by the GC method, and reactivity ratios for all paris ethylene–α‐olefin were estimated from the data on olefin consumption in the reactions. In the case of the δ‐TiCl3–AlEt3 system, the r2 value decreases from ca. 0.05 for 1‐decene to ca. 0.02 for α‐C22H44 and then remains approximately constant. This change is similar to the dependence of the modified steric parameter ESC of the olefin alkyl group on the size of the alkyl group. In the case of the supported TiCl4/MgCl2–AlEt3 system a similar variation of r2 with the length of the alkyl group were observed but the absolute values of r2 were six to ten times lower than those for the first catalytic system.
Catalysis of enantiomeric ester hydrolysis in polymer domains: Catalytic effects of N‐decanoyl‐histidine and of dipeptide derivatives containing a histidyl residue
Authors: Kimura Yoshiharu , Tanaka Akihiro , Nango Mamoru , Kuroki Nobuhiko , Ihara Yasuji 
Published: April 2003

AbstractThe catalytic activities of N‐decanoyl‐L‐histidine and its methyl ester and of dipeptide derivatives containing an L‐histidine residue toward the stereoselective hydrolysis of enantiomeric substrates have been studied at pH 7.30 (in 0.01M Bis‐tris buffer) and 25°C in the presence of poly(ethyleneimine) derivatives. The dipeptide catalyst revealed greatest stereoselectivity in a quaternized poly(ethyleneimine) derivative. A comparison of catalytic effects on both the rate constants and stereoselectivities of N‐decanoyl‐L‐histidine and its methyl ester elucidates the cooperative effects of carboxyl groups in the polymer domains. The structure of the substrates influenced both the rate constants and stereoselectivities in polymer domains.
Preirradiation grafting of N‐vinyl‐2‐pyrrolidone onto poly(tetrafluoroethylene) and poly(tetrafluoroethylene‐hexafluoropropylene) films
Authors: Hegazy El‐Sayed A. 
Published: April 2003

AbstractPreirradiation grafting of N‐vinylpyrrolidone (NVP) onto poly(tetrafluoroethylene) (PTFE) and poly(tetrafluoroethylene‐hexafluoropropylene) (FEP) films was investigated. The influence of grafting parameters such as preirradiation dose, monomer concentration, and grafting temperature on the rate and grafting yield was studied. Different solvents were used for diluting the monomer and it was found that the aqueous monomer solution at a concentration of 80 wt% was suitable for this grafting system. However, the graft polymerization of NVP in benzene terminated within a short time without significant grafting yield. The dependence of the grafting rate on preirradiation dose and monomer concentration was 1.2 and 1.07 order, respectively, for grafting onto PTFE films and 1.1 and 1.2 order, respectively, for grafting onto FEP films. Arrhenius plots for grafting onto PTFE films showed a breaking point at ca. 35°C and the overall activation energies were calculated as 23.6 and 9.0 Kcal/mol below and above 35°C, respectively. For grafting onto FEP films, however, no break was observed in the Arrhenius plots; the overall activation energy was 11.9 Kcal/mol. The swelling behavior and electric resistance of the grafted materials were investigated.
Adsorption of methylmethacrylate‐vinylferrocene copolymers at the solution/solid interface
Authors: Diaz‐Barrios Antonio , Rengel Aristides 
Published: April 2003

AbstractA series of methylmethacrylate–vinylferrocene random copolymers was synthesized and characterized. Their adsorption from toluene and chloroform was measured onto pyrogenic silicas. The level of adsorption depended on the solvent, the surface area of the adsorbent, and the copolymer composition. Thus, an inverse adsorption‐solubility relationship for toluene and chloroform was observed. However, in solvents such as tetrahydrofuran, 2‐butanone, and cyclobutanone, which have strong interaction with silica, this trend was not evident. The compositional dependence of the adsorption of these copolymers in toluene and chloroform is similar. Initially, adsorption tends to increase with the vinylferrocene content in the polymer, and at equimolar copolymer compositions the adsorption reaches a maximum which is followed by a decrease in the adsorption values at high vinylferrocene contents. Gel permeation chromatography(GPC) measurements allowed us to conclude that high molecular weight polymer was preferentially adsorbed.
Synthesis and properties of some new polyimidosulfides with highly mobile backbones
Authors: White Jerry E. , Snider Deborah A. , Scaia Mark D. 
Published: April 2003

AbstractVarious alkanedithiols [HSRSH; R = (CH2)3–6 orCH2CH2OCH2CH2] add to the carbon‐carbon double bonds of N,N′‐bismaleimido‐1,8‐octane (1) at room temperature in m‐cresol that contains triethylamine as a catalyst to produce the corresponding polyimidosulfides (3) in yields of 75–86% and with inherent viscosities (ηinh) of 0.30–1.05 dL/g. In general (3) are amorphous, elastomeric materials that undergo glass transitions (Tg) within the range of 6.5–13°C but product (3a) [R = (CH2)6] is a tough, leatherlike polymer that exhibits Tg = 35°C and a melting transition at 77°C. X‐ray analysis indicates that (3a) is ca. 37% crystalline. In addition to further details of the synthesis and properties of polyimidosulfides (3), comparisons are made between crystalline (3a) and a structurally analogous but morphologically dissimilar, elastomeric polyaspartimide synthesized earlierJ. E. White, M. D. Scaia, and D. A. Snider, J. Appl. Polym. Sci., in press.
from (1) and N,N′‐dimethyl‐1,6‐hexanediamine.
The photoelectrochemical initiation of polymerization of styrene
Authors: Funt B. Lionel , Tan Shu‐Rong 
Published: April 2003

AbstractA TiO2 semiconductor was immersed in a solution that contained styrene monomer and a supporting electrolyte. Polymer was formed when light was focused on the semiconductor. The yield was a function of the bias level maintained at the semiconductor elecotrode. With methylmethacrylate monomer direct photoinitiation of the monomer occurred, but the polymer yield could be reduced by varying the electrode potential.
Modification of an epichlorohydrin polymerization
Authors: Morse S. D. , Wilson T. D. , Merrill C. I. 
Published: April 2003

AbstractThe acid‐catalyzed polymerization of epichlorohydrin was modified by the addition of 1,4‐butanediol diglycidyl ether to the reaction. The amount of diepoxide added and the method of addition were varied to produce a series of polymers with increased molecular weight, broad molecular weight distributions, and variations in hydroxyl functionality. Polyurethane networks were prepared from these polyols for the evaluation of elastomeric properties. The most obvious result was the lack of elastomeric network formation in the unmodified material when modified polyols produced elastomeric properties under the same conditions. Differences in properties between samples with more diepoxide added in the original polymerization generally showed trends to lower elongation and higher modulus. Changes in the method of addition of the diepoxide produced great differences in the toughness of the elastomers formed in the cure process.
Synthesis of high molecular weight polyester carbonates via interfacial phosgenation of aromatic dicarboxylic acids and bisphenols
Authors: Keohan F. L. , Freelin R. G. , Riffle J. S. , Yilgör İ. , McGrath J. E. 
Published: April 2003

AbstractThe synthesis of bisphenol A poly(carbonate–ester) copolymers was studied by phase‐transfer catalysis and modified interfacial polymerization. Only low molecular weight copolymers were prepared directly from dicarboxylic acids, phosgene, and bisphenol A by an interfacial process that involves the use of pyridine as catalyst, HCl acceptor, and weak base. To avoid the use of tertiary amines, which can be difficult to remove from the polymer products, and to produce higher molecular weight copolymers from the same dicarboxylic acid precursors another synthetic method was developed. This more effective method required careful pH control that was achieved by the selective use of the weak‐base potassium carbonate in the first stage of the process. Moreover, elevated reaction temperatures (∼65–70°C) and phase‐transfer catalysis were used. The carbonate–ester copolymers prepared by this technique had consistently high intrinisic viscosities, little or no anyhydride microstructure, and higher degrees of ester unit incorporation than those produced by the pyridine‐catalyzed method. These copolymers also had glass transition temperatures (Tg) 20–30°C higher than bisphenol A polycarbonate homopolymer. An analytical method for determining quantitatively the amount of ester units in the bisphenol A poly(carbonate‐esters) was developed by using Fourier transform infrared spectroscopy (FT‐IR). Agreement between this FT‐IR method and a quantitative nuclear magnetic resonance (NMR) method was found to be reasonable, especially for copolymers with ester unit percentages lower than 40%.