bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and photogeneration properties of copolyacrylate having carbazole donor and trinitrofluorenone acceptor chromophores
Authors: Hu Chau Jin , Oshima Ryuichi , Senō Manabu 
Published: April 2003

AbstractNovel copolymers containing both donor and acceptor chromophores have been synthesized by free radical polymerization of 2‐N‐carbazolylethyl acrylate and 2′‐acrylylethyl‐4,5,7‐trinitrofluorenone‐2‐carboxylate. The charge transfer complexation occurs in copolymers in a similar way to poly(2‐N‐carbazolylethyl acrylate) molecularly doped with 2,4,7‐trinitrofluorenone (TNF) and a model compound, ethyl 4,5,7‐trinitrofluorene‐2‐carboxylate (Et‐TNF). Copolymer and doped systems exhibit obvious CT bands in a 440–600 nm region, where the former shows higher absorption than the latter. Glass‐transition temperatures show positive deviations from the weight‐average values of copolymers, indicating the partial interchain interaction of copolymers in solid state. Quantum efficiency of hole photogeneration of the copolymer with the 0.05 to 1.0 molar ratio of TNF to carbazole chromophores is higher than those of the corresponding molecularly TNF‐ and Et‐TNF‐doped poly(2‐N‐carbazolylethyl acrylate), especially at lower electric fields.
The quantitative description of small molecule binding to abiotic polymers
Authors: Charton Marvin 
Published: April 2003

AbstractThe variation of equilibrium constants for the binding of small molecules to abiotic polymers as a function of structure is quantitatively described by the intermolecular force (IMF) equation and relationships derived from it. Structural variations in both the small molecules and in the polymers were studied. The data were taken from the literature. The results obtained suggest that the IMF equation may be generally useful for modelling the effect of structural variation on polymer properties which depend on the difference in intermolecular forces between initial and final states. They also provide a model for nonspecific binding to biopolymers.
New chemically prepared conducting “pyrrole blacks”
Authors: Walker John A. , Warren L. F. , Witucki E. F. 
Published: April 2003

AbstractA series of electrically conducting pyrrole “black” polymers has been prepared by chemical oxidation of pyrrole with a variety of ferric salts. The synthesis and properties of these materials are described and compared with electrochemically‐prepared analogs. Pyrrole “blacks” with strong acid anion “dopants” exhibited the highest conductivities, up to 62 Ω cm−1 for the triflate‐doped polymer. The adjustability and ease of synthesis of the ferric‐derived polypyrroles render these particularly promising for large‐scale processing of conducting polymers.
Mechanism of thermal degradation of poly(alkyl acrylate)s using pyrolysis gas chromatography mass spectrometry
Authors: Haken J. K. , Tan (nee Gunawan) L. 
Published: April 2003

AbstractThe pyrolyses of homologous poly(alkyl acrylate)s is reported with identification of the major pyrolyses products. A mechanism involving random homolytic scission of the chain followed by a series of intermolecular and intramolecular transfer reactions has been proposed for poly(methyl acrylate) by Cameron and Kane and further developed by Haken, Ho, Houghton, and Gunawan. This mechanism is demonstrated to be generally applicable to the poly(n‐alkyl acrylate)s. Reaction mechanisms are postulated for the various products produced and ion fragmentation mechanisms for the mass spectra produced are shown.
Chemical release control: Schiff bases of vinylbenzaldehyde and functional amines
Authors: Kamogawa Hiroyoshi , Sakai Tsuyoshi , Sohma Hirohito 
Published: April 2003

AbstractSchiff base (SB) monomers of vinylbenzaldehyde with functional amines were prepared. Copolymers of SB monomers with N‐vinyl‐2‐pyrrolidone soluble in aqueous solutions were obtained in most cases. However, p‐aminobenzenesulfonamide monomer resulted in gel formation. Thus, the reaction of vinylbenzaldehyde copolymer with the sulfonamide was used instead of the copolymerization. The hydrolytic behaviors of SB monomers and copolymers to liberate respective amines were structure dependent and, for most copolymers, the rates were lower than those of the corresponding monomers.
The crosslinking of epoxy resins at interfaces. V. Amine‐cured resins at carbon and graphite surfaces
Authors: Garton Andrew , Stevenson William T. K. , Wang S. P. 
Published: April 2003

AbstractThe effects of carbon blacks, chopped carbon fibers, and crushed carbon fibers on the crosslinking chemistry of a diglycidyl epoxy resin/m‐phenylenediamine system were examined by infrared (IR) spectroscopy and differential scanning calorimetry (DSC). The carbon and graphite surfaces were given oxidizing and reducing treatment to simulate the surface treatment of carbon fibers used in the manufacture of composites. The oxidized carbon surfaces initially accelerated epoxy–amine reactions but inhibited the later stages of the reaction such that the final extent of cure was reduced. The oxidized carbons also preferentially adsorbed the amine curing agent, resulting in a stoichiometric imbalance at the interface.
Characterization of poly(carboxylic acid)/poly(ethylene oxide) blends formed through hydrogen bonding by spectroscopic and calorimetric analyses
Authors: Jeon Seung Ho , Ree Taikyue 
Published: April 2003

AbstractThe solid state of the complex between poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO), and that between poly(methacrylic acid) (PMAA) and PEO formed via hydrogen‐bonding was studied by differential‐scanning calorimetric (DSC) and by Fourier‐transform infrared (FT–IR) spectroscopic measurements. Melting temperature Tm and the degree of the crystallinity Xc of PEO in the systems PAA (or PMAA)/PEO blends obtained from aqueous or dimethyl sulfoxide (DMSO) medium were measured in various unit mol % of PEO ([PEO]100/{[PAA(or PMAA)] + [PEO]}) where [ ] is the unit mole concentration. It was found that 50 unit mol % of PEO is a critical composition, which gives new evidence for the 1 : 1 complex formation between PAA (or PMAA) and PEO. From the FT–IR spectroscopic analysis in conjunction with DSC measurements we also found that the effects of solvent and of hydrophobic interaction (due to the α‐methyl group of PMAA) are the important factors controlling the complexation in the solution and solid systems. These factors also affect the crystallization behavior and the microstructure of the PAA (or PMAA)/PEO blend in solid state.
Reactivities of sulfur‐centered radical toward polyisoprenes and polybutadienes studied by flash photolysis method
Authors: Ito Osamu , Tamura Saburo , Matsuda Minoru , Murakami Kenkichi 
Published: April 2003

AbstractThe kinetic behavior of the thiyl radical in the solution containing polyisoprenes and polybutadienes has been studied by the flash photolysis method. For benzothiazole‐2‐thiyl radical, the addition rate constants toward these polymers and the model compounds of the polymers were evaluated. The relative reverse rate constants and equilibrium constants were also estimated. The addition rate constants decrease with an increase in the degree of polymerization; the ratio of the addition rate constant for polyisoprene (3.1 × 104M−1s−1(in monomer unit);Mv= 674,000) to that for 2‐methyl‐2‐butene (1.5 × 105M−1s−1) is about 1/5. This indicates that the polymer chain effect appears in the free‐radical addition reaction. The relative reverse rate constants for the polymers are also smaller than those for 2‐methyl‐2‐butene, suggesting a kind of polymer effects; i.e., it can be presumed that the bonded‐thiyl radicals migrate very rapidly to the neighboring double bonds in the polymer. Significant differences in the rate parameters were observed between polyisoprene and polybutadiene, betweencis‐ andtrans‐polyisoprenes, and between 1,4‐ and 1,2‐polybutadienes.
Emulsion polymerization: Theory of particle size distribution in copolymerization system
Authors: Chen Show‐An , Wu Kuo‐Wei 
Published: April 2003

AbstractA mathematical model for describing the particle size distribution (PSD) in emulsion copolymerization system is developed by analogy to that in emulsion homopolymerization system as proposed by Lichti and co‐workers. By use of the appropriate combinations of the kinetic parameters of the comonomers, the complicated equations for copolymerization systems can be reduced to simpler equations identical to those of homopolymerization systems. The two calculation examples, styrene–methyl methacrylate and styrene‐butadiene systems, are given to demonstrate the applicability of the proposed theory. The conditions for producing bimodal PSD from a seeded emulsion polymerization are discussed.
Stereoregularity of poly(methyl methacrylate) prepared by aqueous polymerization and catalyzed by corundum
Authors: Moustafa A. B. , Ellatif Z. H. Abd , Amer L. I. 
Published: April 2003

AbstractThe aqueous polymerization of methyl methacrylate was carried out in the absence and in presence of corundum or carborundum at 25 and 80°C. In the absence of corundum and carborundum, it has been found that rising the polymerization temperature from 25 to 80°C resulted in changing the tacticity of the obtained polymers. At 25°C the isotactic triad was 26% while the heterotactic triad was 33.5% and the syndiotactic one was 40.5%. Increasing the polymerization temperature to 80°C resulted in a decrease of the isotactic structure to 0% and increased the heterotactic structure and syndiotactic structure to 48 and 52% respectively. Polymerizing at 25°C in presence of corundum (0.5 g) an increase in the syndiotactic triad took place from 40.5 to 50.7% while the isotactic triad decreased from 26 to 22.2% and the heterotactic structure decreased from 33.5 to 27%. Raising the polymerization temperature to 80°C in the presence of the same amount of corundum resulted in an increase in both the isotactic and heterotactic triads to 35 and 32.7%, respectively. Polymerizing at 80°C in presence of corundum (0.5 g) resulted in nearly an equal percentage of each triad 33%.
Polyurethane cationomers. I. Structure–properties relationships
Authors: Al‐Salah H. A. , Xiao H. X. , McLean Jr. J. A. , Frisch K. C. 
Published: April 2003

AbstractPolyurethane (PU) cationomers have been synthesized by quaternizing tertiary amine‐containing linear polyurethanes using different quaternizers containing acid groups. The effect of chemical structure of PU cationomers on the physical properties was studied. The mechanical properties of PU cationomers were improved with decreasing molecular weight of poly(caprolactone) glycol, and increasing concentration of quaternary ammonium. Decreasing the carbon number in the alkyl group of the N‐alkyl diethanol‐amine chain‐extenders, and using rigid symmetrical diisocyanates, the mechanical properties of the PU cationomers were increased. The effects of these factors on the glass transition temperature of PU cationomers were also examined. The mechanical properties of the PU cationomers decreased by immersion in water and recovered after removal of the water.
New polymer syntheses. XIX. Syntheses of aromatic polyesters from phenoxyterephthalic acid
Authors: Kricheldorf Hans R. , Schwarz Gert , Ruhser Frank 
Published: April 2003

AbstractThe synthesis of bisphenol‐A phenoxyterephthalate was chosen as model system to find the optimum method for polycondensations of aryloxyterephthalic acids. It is demonstrated that phenoxyterephthalic acid or its acid chloride may cyclize at temperatures above 180°C yielding anthrone‐3‐carboxyclic acid which causes termination steps. The highest yield and molecular weight was obtained by interfacial polycondensation of phenoxyterephthaloylchloride.
Stereoselective substitution on PVC using phase transfer catalysts
Authors: Martíanez G. , Mijangos C. , Terroba P. , Millán J. 
Published: April 2003

AbstractThe nucleophilic substitution with sodium benzenethiolate in aqueous suspension in the presence of a phase‐transfer catalyst has been studied for two samples of PVC of different tacticities. The kinetics shows two well‐defined periods: one period is very fast and involves low conversions that are greater as the isotactic content of PVC increases, while another steady period is slow and its slope seems to depend on physical features, e.g., molecular weight and crystallinity, which would affect the accessibility of nucleophile. The evolution of unreacted syndio, iso, and heterotactic triad contents with degree of substitution has been followed by 13C‐NMR spectroscopy. Since the content of syndiotactic triads does remain unreacted at the end of the reaction and that of isotactic and heterotactic triad decreases, but at a different rate, the reaction is proved to proceed by a stereospecifically controlled mechanism. The influence of degree of substitution on both the thermal degradation rate and the evolution of UV–Visible spectra of equally degraded samples has been also studied; the highest stability in terms of degradation rate and content of short polyenes is obtained when a specific fraction of isotactic triads has reacted. From the correlation between the results of this work and those previously obtained in solution, some enlightening conclusions about the reaction mechanism are drawn.
Synthesis and characterization of polyazo(amine‐imide)s
Authors: Thanuja J. , Srinivasan M. 
Published: April 2003

AbstractAromatic polyamine‐imides were synthesized from N,N′‐bismethylolazobenzenetetracarboxylic diimide and various diamines. Polycondensations were carried out in DMAc containing 1% water. The linear polyamine‐imides obtained varied in color and had inherent viscosities in the 0.25–0.35 dL/g range. These polymers were characterized by physical and thermal methods.
Preparation and properties of polyamides from 2,8‐phenoxathiin‐bis‐(γ‐ketobutyric acid), 2,7‐thianthrene‐bis(γ‐ketobutyric acid), and aromatic diamines
Authors: Reddy T. Ashok , Srinivasan M. 
Published: April 2003

AbstractAromatic‐aliphatic polyamides containing phenoxathiin and thianthrene heterocyclic units were prepared by the direct polycondensation of 2,8‐phenoxathiin‐bis(γ‐ketobutyric acid) (I) or 2,7‐thianthrene‐bis(γ‐ketobutyric acid) (II) with various aromatic diamines in a triphenylphosphite‐pyridine system. Prior to polymer synthesis two model diamides were prepared by condensing γ‐keto acid I or II with p‐toluidine. The model diamides and polyamides were characterized by spectral methods and elemental analysis. The polyamides, obtained in 56–90% yields, had inherent viscosities in the 0.82–1.1 dL/g range in concentrated H2SO4 at 30°C. The effect of heterocyclic units on polymer properties, such as solubility, crystallinity, and thermal stability has been discussed.
Hydrogen bonding on accessible surfaces of cellulose from various sources and relationship to order within crystalline regions
Authors: Rowland Stanley P. , Howley Phyllis S. 
Published: April 2003

AbstractCelluloses from a variety of common sources were analyzed for availabilities of O(2)H, O(3)H, and O(6)H in order to estimate the extent of hydrogen bonding on accessible fibrillar surfaces. Celluloses from flax, ramie, sisal, and wood (both cellulose I and II from wood) together with liquid NH3‐swollen cotton and NaOH‐swollen cotton (cellulose II) had relative availabilities similar to those of native cotton. Celluloses from Valonia centricosa and in rayon samples stood apart from each other and from the “cotton family.” The difference between Valonia and cotton celluloses appears to result, in addition to the accepted smaller, less perfect crystallites in cotton, from an O(2)H hydrogen bond which is likely the intramolecular bond between O(2)H and O(6′)H that is present in Valonia and absent in cotton. Rayon samples also showed evidence of similar bonds involving O(2)H on accessible surfaces. Since the regenerated rayons had relative availabilities different from those of mercerized cotton and wood cellulose samples, it is proposed that chain packing arrangements are not the same in these two types of cellulose II.
Benzocyclobutene in polymer synthesis. I. Homopolymerization of bisbenzocyclobutene aromatic imides to form high‐temperature resistant thermosetting resins
Authors: Tan Loon‐Seng , Arnold Fred E. 
Published: April 2003

AbstractA series of new bisbenzocyclobutene‐terminated aromatic imide monomers has been synthesized from the condensation reaction of 4‐aminobenzocyclobutene and the perspective dianhydride in refluxing acetic acid/toluene. The differential scanning calorimetric studies of the foregoing monomers indicated that polymerization exotherms began at 229–250°C and reached their maxima at 258–263°C. The cured samples (250–254°C; N2; 8 h) were surprisingly stable toward thermo‐oxidative degradation; only 7–10% weight loss was observed after 200 h (in air) at 314°C (600°F). At higher temperatures (650 and 700°F), the most rigid structure was the most thermo‐oxidatively stable. An approach to enhance both the final glass‐transition temperature (Tg cure) and the thermo‐oxidative stability of the bisbenzocyclobutene system was to dilute the cure‐site density since the cure‐site structure is the weakest part of the polymeric structure. Therefore, a series of bisbenzocyclobutene‐terminated aromatic imide oligomers were prepared, using various aromatic amines as the chain‐extending agents. Meta‐phenylenediamine was apparently the most effective in the advancement of both the Tg (cure) and thermo‐oxidative stability.
Emulsion polymerizations. I. A novel approach to the evaluation of the molecular weight distributions
Authors: Giannetti Enzo , Storti Giuseppe , Morbidelli Massimo 
Published: April 2003

AbstractA simple, probabilistic approach describing the number distribution of the molecular weight (MWD) of polymers formed by emulsion polymerization is presented. The radical populations of the reacting system are formally split into infinite, quickly convergent series of particularly tagged radical populations. These populations are characterized by the nature and the number of the state transitions of the associated latex particles. For each kind of single radical or radical pairs a distribution function is then defined. These functions can be specified on the basis of αi and Qi, the growth probabilities, within a latex particle in state i, of a single radical and a radical pair respectively. The overall MWDs are then given by summation over all the distributions of the radical populations and over all the allowed states. Only one set of ordinary differential equations (the Smith–Ewart equations) are involved in the mathematical formulation, single distribution functions being obtained by solving simple exponential‐type integrals. In this paper, analytic solutions are presented for the zero‐one, zero‐one‐two and general systems. Analogies and differences between our approach and previously reported treatments are critically discussed.
Characterization of polyethylene terephthalate by gel permeation chromatography (GPC)
Authors: Weisskopf Klaus 
Published: April 2003

AbstractThe use of the solvent mixture chloroform/hexafluoroisopropanol (98 : 2 vol %) in the GPC‐analysis of polyethylene terephthalate (PET) is described. PET‐samples of different molecular weight have been prepared and characterized by light scattering, viscometry, and improved techniques of osmometry and end group titration. These well characterized samples were used in calibrating the GPC. The calibration with polydisperse standards was found superior to the universal calibration procedure in the solvent system chosen.
Polyarylates. V. The influence of phase transfer agents on the interfacial polycondensation
Authors: Lee Yu‐Der , Tsai Hong‐Bing , Jeng Jaw‐Tarng 
Published: April 2003

AbstractThe effect of various phase transfer agents on the interfacial polycondensation of bisphenol A with isophthaloyl chloride was investigated. It was found that the transfer rate of bisphenolate and, thus, the reaction rate of polycondensation were increased with an increasing lipophilicity of the phase transfer agent, i.e. TBAC > TEBAC > TEAC, whereas the equilibrium of bisphenolate between the organic phase and the aqueous phase was hardly affected. Moreover, experimental evidence indicated that a phase transfer agent of high lipophilicity reduced the hydrolysis of the acid chloride, an important aspect in interfacial polycondensation.
Radical cyclopolymerizations of diallylsilanes and triallylsilanes
Authors: Saigo Kazuhide , Tateishi Kazuo , Adachi Hiroshi 
Published: April 2003

AbstractThe radical polymerizations of diallylsilanes such as diallyldimethylsilane (1) and diallylmethylphenylsilane (2) have been conducted. Both poly(diallyldimethylsilane) (3) and poly(diallylmethylphenylsilane) (4) are soluble in benzene, methyl ethyl keton (MEK), and chloroform, slightly soluble in acetone, and insoluble in methanol and ethanol. No insoluble fraction of either polymer was obtained. Very little evidence of vinyl protons in the 1H‐NMR spectra can indicate that both polymerizations predominantly proceed with intramolecular cyclization. In order to study the ring size of cyclic structure in the repeating unit of the polymers, a model compound, allyl(2‐chloropropyl)dimethylsilane (5), was synthesized and cyclized with Bu3SnH in the presence of azobisisobutyronitrile (AIBN) in benzene, under similar condition of those for the cyclopolymerizations. The product was analyzed with GC–MS which showed that the five‐membered ring compound, 1,1,3,4‐tetramethylsilacyclopentane, was not formed. From the result of the cyclization of the model compound, it can be suggested that the polymerizations undergo with only h–t intramolecular cyclization to form a six‐membered ring in the repeated unit. The 13C‐NMR spectra of 3 and 4 were measured to study the ring size and the configuration of the cyclic structures. The two peaks at −1.6 and −3.4 ppm of the spectrum of 3 show that there are two kinds of methyl carbons in the repeating unit. From consideration of the model reaction and the number of the peaks of the NMR spectrum, it can be considered that the polymer main chain is assembled with the six‐membered ring in cis‐form, and the two signals are assigned to equatorial and axial methyl carbons, respectively. The two peaks at ‐1.5 and ‐5.1 ppm of the 13C‐NMR spectrum of 4 can be assigned similarly. The radical cyclopolymerizations of triallylsilanes such as methyltriallylsilane (6) and phenyltriallylsilane (7) were conducted. The 1H‐NMR spectra of poly(methyltriallylsilane) (8) and poly(phenyltriallylsilane) (9) show broad peak around 5 ppm for vinyl protons and around 2 ppm for alkyl protons. Comparisons of the relative intensities of the peaks indicate that both polymerizations undergo with single ring closure to form a polymer with monocyclic structure moiety, cyclosilahexane, and an allyl group in a repeating unit of 8 and 9.