bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nucleic acid base grafted polyethylenimine. Cytosyl pendant groups synthesis and characterization
Authors: Chu V. P. , Overberger C. G. 
Published: April 2003

AbstractPoly(N‐acyl ethylenimine) of various molecular weights was synthesized by the cationic ring‐opening polymerization of 2‐H‐2‐oxazoline and 2‐methyl‐2‐oxazoline. Acid hydrolysis afforded the linear poly(ethylenimine) which was used in the following grafting reactions. Vapor pressure osmometry, gel permeation chromatography and viscosity measurements were used to characterize the polymers synthesized.Potassium 2‐(cytos‐1‐yl)propanoate and potassium 3‐(cytos‐1‐yl)butanoate were synthesized in good yield from the nucleic acid base. These cytosyl pendant groups were grafted onto the poly(ethylenimine) using 4‐chloro‐1‐(4‐chlorobenzenesulfonyl)benzotriazole, 93% graft, and norborn‐5‐ene‐2,3‐carboximido diphenyl phosphate, 70% graft. Grafting of the t‐butoxycarbonyl and n‐butoxycarbonyl protected cytosyl pendant groups resulted in a 47% and 40% graft, respectively.
Quenching of photo‐excited state of copolymer pendant Ru(bpy) complexes with methylviologen
Authors: Hou Xiao‐Huai , Kaneko Masao , Yamada Akira 
Published: April 2003

AbstractCopolymer pendant tris(2,2′‐bipyridine)ruthenium(II) complexes were prepared from the copolymers of 4‐methyl‐4′‐vinyl‐2,2′‐bipyridine with styrene, acrylic acid, methyl methacrylate, hydroxyethyl methacrylate, acrylonitrile, N‐vinylpyrrolidone, 4‐vinylpyridine, and quaternized 4‐vinylpyridine. The quenching of the photo‐excited state of the polymer complexes by methylviologen was studied. Pendant anionic groups such as acrylate enhanced remarkably the quenching of the cationic sensitizer by the cationic substrate, however, pendant cationic groups such as quaternized pyridine did not affect the reaction. The polymer chain showed generally retarding effect on the quenching reaction.
Gold(III) fluorosulfate as an initiator of the polymerization
Authors: Nevius M. , Dreyfuss P. 
Published: April 2003

AbstractGold(III) fluorosulfate was shown to have potential for initiating the polymerization and graft copolymerization of tetrahydrofuran (THF) and similar monomers at room temperature. Addition to THF of either gold(III) fluorosulfate or of gold(III) fluorosulfate and acetyl chloride (a model for a reactive polymer backbone) led to high yields (60–70%) of polytetrahydrofuran. IR, NMR, HPLC, and other studies were used to determine the mechanism of initiation in each case. They showed that in the absence of halide, the gold salt led to hydrogen abstraction from THF and formation of protonic acid, which then initiated polymerization. In the presence of halide, concurrent initiation due to the formation of tertiary oxonium ion by acetylation occurred. Gold(III) chloride precipitated simultaneously.
Synthesis and polymerization of racemic and optically active β‐substituted β‐propiolactones. III. β‐monosubstituted monomers and polymers
Authors: Voyer Richard , Prud'Homme Robert E. 
Published: April 2003

AbstractOptically active β‐(1,1‐dichloroethyl)‐β‐propiolactone (CH3CCl2‐PL), β‐(1,1‐dichloropropyl)‐β‐propiolactone (C2H5CCl2‐PL), and β‐(1,1‐dichlorobutyl)‐β‐propiolactone (C3H7CCl2‐PL) were synthesized with enantiomeric excesses of 100, 100, and 84%, respectively. Polymerization was conducted in bulk and toluene solution, under vacuum, using mainly ZnEt2/H2O as initiator. Osmometry analyses indicate molecular weights in the range 10,000–25,000. The polymers thus prepared are semi‐crystalline and show large optical rotation values.13 C‐NMR was used to show that they have a high degree of isotacticity, indicating that little or no racemization occurs in the course of polymerization. Glass transition, melting and decomposition temperatures are given as a function of the size of the substituent, and their variations are discussed.
Preparation and properties of polyazo Schiff‐bases
Authors: Gopal Jayalakshmi , Srinivasan M. 
Published: April 2003

AbstractFive colored polymeric Schiff‐bases were synthesized from 4,4′diaminoazo benzene and different dialdehydes and diketones. All the polymers were characterized by UV, IR, and NMR spectroscopy. Their physical properties and thermal characteristics are discussed.
Synthesis of poly(ethylene glycol methyl ether)‐b‐poly(ethylenimine) and its derivatives containing thymine and amino acids as pendants
Authors: Overberger C. G. , Peng L. 
Published: April 2003

AbstractPoly(ethylene glycol methyl ether)tosylate was prepared and used to initiate the polymerization of 2‐methyl‐2‐oxazoline. The resulting poly(ethylene glycol methyl ether)‐b‐poly(N‐acetyl ethylenimine) was hydrolyzed and neutralized to give poly(ethylene glycol methyl ether)‐b‐poly(ethyl‐enimine) (PEO–PEI). 2‐(thymin‐1‐yl)propionic acid, N‐Cbz‐alanine, N‐Cbz‐proline, N‐Cbz‐O‐t‐Bu‐serine. and N‐FMOC‐proline were grafted onto the PEO–PEI copolymer; attempts were then made to remove the Cbz and FMOC protecting groups.
Preparation and characterization of polysuccinimides
Authors: Woo Edmund P. 
Published: April 2003

AbstractA series of polysuccinimides has been prepared from 1,4‐bis(tetrahydrofuran‐2,5‐dion‐3‐yl)benzene and characterized by various thermal and mechanical methods. This new class of polyimides showed excellent solvent and heat resistance, balanced mechanical property profile, and toughness.
Poly(methyl methacrylate‐g‐urethane). II. Thermal and mechanical behavior
Authors: Akcelrud L. , Gomes A. S. 
Published: April 2003

AbstractThe thermal and mechanical behavior of poly(methyl methacrylate‐g‐urethane) has been investigated. Thermal analysis indicated compatibility between the two polymeric segments up to 15% polyurethane content. Tensile tests revealed progressive change in mechanical properties with composition, and the materials varied from glassy to leathery to rubberlike. Thermal and mechanical results suggested a morphological model where a glassy matrix of poly(methyl methacrylate) mixed with polyurethane is the continuous phase up to 25% polyurethane content, when a phase inversion occurs.
Poly(ethylene‐co‐propylene)‐g‐polystyrene through macromer polymerization: Preparation, morphology, and structure–properties relationships
Authors: Ma Jingjing , Pang Deren , Huang Baotong 
Published: April 2003

AbstractGraft copolymers with ethylene‐propylene (EPR) backbone and polystyrene (PS) grafts, EPR‐g‐PS, were prepared by terpolymerization of a PS macromer with ethylene and propylene using a vanadium catalyst, with graft efficiency of up to 80% and PS content in the copolymer 5–45%. Such polymerization parameters as molecular weight and dosage of the macromer, catalyst concentration, and reaction temperature which affect the mobility and hence polymerizability of the macromer may have a marked influence on the polymerization and the structure of the products. The molecular architecture of the copolymers was characterized by osmometry, UV, NMR, and GPC methods. TEM and torsional pendulum studies revealed that EPR‐g‐PS possessed a phase separation morphology with PS domains evenly dispersed in the EPR matrix. The PS content and average number of grafts strongly influence the tensile properties of the copolymers. EPR‐g‐PS graft copolymers prepared by macromer copolymerization exhibit the mechanical properties of a typical thermoplastic elastomer having two or more branches of a certain length.
Catalysis in competing isocyanate reactions. II. Competing phenyl isocyanate reactions catalyzed with N,N′,N″‐pentamethyldipropylenetriamine
Authors: Wong Shaio‐Wen , Frisch Kurt C. 
Published: April 2003

AbstractThe kinetics of the N,N′,N″‐pentamethyl dipropylene triamine (PMPT)‐catalyzed reaction of phenyl isocyanate with n‐butanol was studied in acetonitrile between 26.5 and 50°C by measuring the NCO disappearance as well as the formation of the various reaction products by means of the standard dibutylamine back‐titration method and the high‐performance liquid chromatography (HPLC) method. The resulting products from the phenyl isocyanate and n‐butanol reaction were found to be N‐butyl phenylcarbamate, N‐butyl‐α,γ‐diphenylallophanate, and triphenylisocyanurate. Trimer formed at the expense of carbamate formation even at a high OH/NCO ratio. Allophanate appeared to be an intermediate in the formation of trimer. PMPT was found to be a urethane and trimerization catalyst for the model reaction of phenyl isocyanate with n‐butanol in acetonitrile. The PMPT‐catalyzed reaction of phenyl isocyanate with n‐butanol in the presence of water in acetonitrile at 50°C was also investigated. The resulting reaction products consisted of n‐butyl phenylcarbamate, n‐butyl‐β,γ‐diphenylallophanate, triphenylisocyanurate, sym‐triphenylbiuret, and N,N′‐diphenylurea. The presence of water retarded the disappearance of NCO groups as well as the trimer formation. Aniline (the product of phenyl isocyanate and water) was detected in the reaction of equivalent amounts of phenyl isocyanate and water in acetonitrile.
Synthesis of block cotelomers involving a perfluorinated chain and a hydrophilic chain. II. Use of fluorinated telogens with iodine or thiol end groups
Authors: Boutevin Bernard , Mouanda Justin , Pietrasanta Yves , Taha Mohamed 
Published: April 2003

AbstractRadical acrylamide telomerization was carried out with three fluorinated telogens, C6F13C2H4I, C6F13I, and C6F13‐C2H4SH with AIBN as initiator. Transfer constants were determined to be 40 × 10−4, 550 × 10−4, and 6500 × 10−4, respectively. Reactions were carried out in butyronitrile, a solvent which also transfers to the growing chain. In the telomerization, the intervention of the solvent, whose transfer constant was also determined, is evaluated quantitatively. Thus the formation of side products, which may reach proportions on the order of 50% compared with the telomer expected, can be explained.
Living cationic polymerization of cis‐ and trans‐ethyl propenyl ethers and synthesis of block copolymers with isobutyl vinyl ether
Authors: Sawamoto Mitsuo , Ebara Kenji , Tanizaki Akio , Higashimura Toshinobu 
Published: April 2003

AbstractThe cationic polymerization of cis‐ and trans‐ethyl propenyl ethers (EPE, CH3CHCHOC2H5), initiated by a mixture of hydrogen iodide and iodine (HI/I2 initiator) at −40°C in nonpolar media (toluene and n‐hexane), led to living polymers of controlled molecular weights and a narrow molecular weight distribution (MWD) (M̄w/M̄n = 1.2–1.3). The geometrical isomerism of the monomer did not affect the living character of the polymerization. 13C NMR stereochemical analysis of the polymers showed that the living propagating end is sterically less crowded than nonliving counterparts generated by conventional Lewis acids (e.g., BF3OEt2). New block copolymers between EPE (cis or trans) and isobutyl vinyl ether were also prepared by sequential living polymerization of the two monomers.
Photocrosslinking of polymers bearing epoxy or epithio groups by quinones in the solid state
Authors: Cha Younsik , Kawasaki Motohiro , Tsunooka Masahiro , Tanaka Makoto 
Published: April 2003

AbstractPhotocrosslinking of poly(glycidyl methacrylate) (PGMA) and a copolymer of 2,3‐epithiopropyl methacrylate and methyl methacrylate [P(ETMA‐co‐MMA)] was studied in the solid state in the presence of various quinones. The efficiency of photocrosslinking was strongly dependent upon the structures of quinones and the kinds of polymers. For example, the alkyl‐substituted quinones such as 2‐ethyl‐p‐benzoquinone (EQ), 2‐tert‐butyl‐p‐benzoquinone (tBQ) and 2,5‐di‐tert‐butyl‐p‐benzoquinone (2,5‐dtBQ) did not induce photocrosslinking of poly(methyl methacrylate) (PMMA), whereas they acted as efficient photocrosslinking agents in PGMA and P(ETMA‐co‐MMA). The formation of charge transfer complexes did not play a principal role in this effective photocrosslinking, because the order of the photocrosslinking efficiency [EQ > tBQ > 2,5‐dtBQ > p‐benzoquinone (Q)] was not in agreement with that of the magnitude of the electron affinities of quinones, i.e., Q > EQ > tBQ > 2,5‐dtBQ. Photopolymerization of propylene sulfide (PS) in the presence of tBQ or Q was also investigated. The presence of tBQ induced polymerization of PS upon UV irradiation. From these results, it was deduced that the photocrosslinking of P(ETMA‐co‐MMA) film containing tBQ proceeds via a cationic polymerization of epithio groups. A similar mechanism should be applicable to the photocrosslinking of PGMA film containing tBQ.
Equilibrated radical polymerization of acrylic propionic anhydride as a mono‐ene counterpart of acrylic anhydride
Authors: Matsumoto Akira , Funamoto Hisashi , Oiwa Masayoshi , Butler George B. 
Published: April 2003

AbstractRadical polymerization of acrylic propionic anhydride (APA) as a mono‐ene counterpart of acrylic anhydride (AA) was investigated in order to obtain supporting evidence for a previously proposed mechanism based on polymerization equilibrium for the cyclopolymerization of AA. The deviation from first‐order dependence of the rate of polymerization Rp on monomer concentration was enhanced by a decrease in monomer concentration. The Arrhenius plot of lnRp vs. 1/T was clearly curved in a highly dilute system. These results suggest increased significance of the depropagation reaction equilibrated with propagation under polymerization conditions favorable to five‐membered ring formation in cyclopolymerization of AA. Under these conditions, the disproportionation reaction of APA became important and the liberated AA was incorporated into the polymer chain through copolymerization with APA, resulting in poly(APA‐co‐AA) having five‐membered anhydride units.
SN‐conducting polymers with heterocyclic spacer groups
Authors: Chien James C. W. , Zhou Mei‐Ying 
Published: April 2003

AbstractPolymer‐containing alternating sulfur nitrogen moieties separated by heterocyclic groups have been synthesized and characterized. The polymers have undoped conductivities of 10−6 to 10−9 (Ω cm)−1; the intrinsic carriers are negatively charged as shown by thermopower coefficient of −1.4 × 103 to −1.9 × 103 μV K−1. The polymers are degraded by AsF5 and cannot be doped by iodine. Exposure to bromine resulted in reversible p‐doping of the SN polymers to the thermopower values of +400 to +820 μV K−1 and conductivities of 0.01 to 0.002 (Ω cm)−1. Removal of dopant by evacuation returns most of the properties of the polymers to the undoped states. Magnetic properties of the materials have been studied.
Gamma‐ray polymerization of phospholipids having diene or triene groups as liposomes
Authors: Ohno Hiroyuki , Ogata Yoshitaka , Tsuchida Eishun 
Published: April 2003

AbstractSmall unilamellar liposomes were prepared in an aqueous medium by the sonication of phospholipids containing diene or triene groups in their hydrocarbon acyl chains. These liposomes were polymerized by gamma‐ray irradiation. Conversion of polymerization was successively followed by UV spectrometry. Diene‐type lipid liposomes were revealed for which a gamma‐ray dose of 0.8 Mrad was required for complete polymerization and which were polymerized more easily than triene‐type lipid liposomes. Triene‐type lipids required 2.3 Mrad gamma ray to polymerize them completely. Contrary to UV‐irradiation polymerization, there was no concentration dependence on the polymerization. Structure of the polymerized liposomes were confirmed by electron microscopy as small unilamellar liposomes. Study on the leakage of fluorescein from inner aqueous phase of the polymerized liposomes revealed that polymerized triene‐type liposomes were relatively more stable than the polymerized diene‐type liposomes.
Solid‐state thermolysis of poly(p‐t‐butoxycarbonyloxystyrene) catalyzed by polymeric phenol: Effect of phase separation
Authors: Ito Hiroshi 
Published: April 2003

AbstractThermolysis of poly(p‐t‐butoxycarbonyloxystyrene) (PBOCST) catalyzed by polymeric phenol in the solid state is very much dependent on the extent of phase separation. Poly(p‐hydroxystyrene) (PHOST, a thermolysis product of PBOCST) is not miscible with PBOCST. Therefore, this phenolic resin can not effectively catalyze the solid‐state thermolysis reaction when simply blended with PBOCST. However, if the phenolic functionality is forced to be in the vicinity of the t‐butoxycarbonyl (tBOC) group, the thermolysis takes place facilely at 130°C. The effect of casting solvent on thermolysis in PBOCST/Varcum films is also discussed.
Uniform polymer particles by dispersion polymerization in alcohol
Authors: Tseng C. M. , Lu Y. Y. , El‐Aasser M. S. , Vanderhoff J. W. 
Published: April 2003

AbstractUniform polystyrene particles in 1–10 μm size range and up to 40% solid contents have been prepared by polymerizing styrene in ethyl alcohol with azo‐type initiators and a polymeric stabilizer polyvinylpyrrolidone along with an anionic, nonionic, or comonomeric co‐stabilizer. Effects of polymerization parameters, such as monomer concentration, type of co‐stabilizer, initiator type and concentration, crosslinking monomer, and diluent on average particle size and size distribution have been studied. Functional groups such as hydroxyl, carboxyl, amine, amide, silane, polydimethylsiloxane, and silacrown have been successfully incorporated onto the particles by copolymerization. A mechanism for particle formation and growth in dispersion polymerization is presented.
Synthesis and properties of eighteen‐arm polybutadienes
Authors: Toporowski P. M. , Roovers J. 
Published: April 2003

AbstractA series of eighteen‐arm regular star polybutadienes with molecular weights between 9.9 × 104 and 1.9 × 106 were prepared and characterized. Evidence is presented for the expanded configuration of the large eighteen‐arm stars in a θ solvent. The intrinsic viscosities of the eighteen‐arm stars gave g′ = [η]/[η]l = 0.284 in dioxane at 27°C (θ solvent) and 0.225 in toluene at 35°C (good solvent). The linear viscoelastic properties of the melts were also determined. The plateau modulus, GN°, is the same as for linear polybutadiene. The zero‐shear viscosities (η0) and the longest relaxation times (Tmax) increase exponentially with the arm molecular weight Ma and are identical to those of four‐arm polybutadienes with the same Ma. The zero‐shear recoverable compliance (Je°) increases linearly with molecular weight. v′ in Je°GN° = v′Na, where Na is the number of entanglements per arm, is 0.95 slightly larger than 0.66 for four‐arm polybutadienes. Similarly, g2 is higher than calculated from the Rouse–Ham theory.
Kinetic study of the reaction between hydroxylated polybutadienes and isocyanates. II. Reaction with 3‐isocyanatomethyl‐3,5,5‐trimethylcyclohexylisocyanate (IPDI) and dimer diacid diisocyanate (DDI)
Authors: Coutinho Fernanda M. B. , Rezende Luiz Cláudio , Quijada Juan Raul 
Published: April 2003

AbstractA comparative kinetic study of the reaction of three different hydroxylated liquid poly‐butadienes (M̄n ⋍ 3000)–R‐45M, R‐45HT and H‐034–with 3‐isocyanatomethyl–3,5,5‐trimethylclohexylisocyanate (IPDI) and dimer diacid diisocyanate (DDI) was carried out in toluene solution. An analytical method was used to follow the kinetics of the reactions, at four different temperatures. In the second‐order plots, a discontinuity was observed in the reaction with IPDI, in contrast to the reactions with DDI which showed straight‐line plots. In all studied reactions, the R‐45M polybutadiene was about twice as reactive as R‐45HT and H‐034. The latter hydroxylated polybutadienes (R‐45HT and H‐034) showed similar reactivities.
A positron annihilation lifetime study of isotactic polypropylene
Authors: Lind John H. , Jones Phillip L. , Pearsall George W. 
Published: April 2003

AbstractPositron lifetime studies were performed on well‐characterized annealed and quenched samples of isotactic polypropylene. The positron experiments were conducted from −20 to 110°C as a function of both heating and cooling. Of the three decaying exponential components resolved from the lifetime spectra, only the long‐lifetime ortho‐positronium (o‐Ps) pickoff component was affected by the changes in temperature. The behavior of both the lifetime and intensity of the o‐Ps component was interpreted with the aid of x‐ray diffraction, densitometry, and optical microscopy examinations and results from previously reported investigations of the thermal transition behavior of polypropylene. The present experiments demonstrate that o‐Ps lifetimes were similar for both the annealed and quenched samples, independent of thermal cycling, while the o‐Ps component intensity was significantly larger for the quenched material during heating, with both sample types exhibiting a significant hysteresis upon cooling. These results suggest that the mean free‐volume cavity size is independent of prior thermal treatment, while the density of free‐volume sites is a sensitive function of structure and prior thermal history. The variations of lifetime and of intensity with temperature have provided insight into polypropylene's glass transition phenomena.
The nature and properties of giant‐orbital polymers
Authors: Pohl Herbert A. 
Published: April 2003

AbstractIn the course of studying the properties of highly conjugated polymers, we found that long‐range orbital delocalization conferred unexpected properties. The giant electronic orbitals made these materials electroactive yet very stable. A new mode of electronic polarizability, a giant nomadic polarization, resulted, making these organic polymers among the most polarizable materials ever observed. In addition, remanent magnetization, high conductivity, and unusual pressure sensitivity could be achieved. The giant‐orbital concept opens new vistas of materials properties.
Post‐gamma‐irradiation grafting of polypropylene. Part II. Butadiene: E.S.R. experiments
Authors: Busfield W. Ken , Buchanan Tracey Morley , Pomery Peter J. 
Published: April 2003

AbstractESR spectra of gamma irradiated annealed and quenched forms of polypropylene film have been studied at the temperatures used for post‐irradiation grafting experiments with butadiene, described in Part I. On warming from low temperature there is radical loss by termination and some radical transformation to radicals with optimum stability in annealed polypropylene at approximately 45°C. These radicals, which may be allyl type, are sited at the crystal faces, and decay more rapidly at higher temperatures in annealed polypropylene; in quenced polypropylene their concentration never exceeds one third the optimum observed in annealed polypropylene. Correlation with the grafting experiments suggests that allyl radicals are important for long‐term grafting. Effects on the ESR spectrum of adding butadiene to the system show that in the long‐term butadiene adds exclusively to the allyl radicals and that alkyl radicals still present at that stage are precursors to the allyl radicals. They do not react directly with butadiene presumably because they are sited in the inaccessible crystal core. Experiments at lower temperature show that butadiene does react with alkyl radicals in accessible regions.
Linear aminophenol polymers using the mannich reaction
Authors: Hodgkin Jonathan H. 
Published: April 2003

AbstractMannich reactions were used to prepare a series of low‐molecular‐weight linear polymers from substituted phenols, formaldehyde, and secondary diamines. The physical and spectroscopic properties of these new aminophenol polymers are described and compared with those of the bisphenolic diamines formed as an intermediate step in the polymerization process. The polymers were found to give coloured, water‐soluble, metal complexes with copper and iron salts.