bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strontium‐based initiator system for ring‐opening polymerization of cyclic esters
Authors: Tang Zhaohui , Chen Xuesi , Liang Qizhi , Bian Xinchao , Yang Lixin , Piao Longhai , Jing Xiabin 
Published: May 2003

AbstractAn amino isopropoxyl strontium (Sr‐PO) initiator, which was prepared by the reaction of propylene oxide with liquid strontium ammoniate solution, was used to carry out the ring‐opening polymerization (ROP) of cyclic esters to obtain aliphatic polyesters, such as poly(ε‐caprolactone) (PCL) and poly(L‐lactide) (PLLA). The Sr‐PO initiator demonstrated an effective initiating activity for the ROP of ε‐caprolactone (ε‐CL) and L‐lactide (LLA) under mild conditions and adjusted the molecular weight by the ratio of monomer to Sr‐PO initiator. Block copolymer PCL‐b‐PLLA was prepared by sequential polymerization of ε‐CL and LLA, which was demonstrated by 1H NMR, 13C NMR, and gel permeation chromatography. The chemical structure of Sr‐PO initiator was confirmed by elemental analysis of Sr and N, 1H NMR analysis of the end groups in ε‐CL oligomer, and Fourier transform infrared (FTIR) spectroscopy. The end groups of PCL were hydroxyl and isopropoxycarbonyl, and FTIR spectroscopy showed the coordination between Sr‐PO initiator and model monomer γ‐butyrolactone. These experimental facts indicated that the ROP of cyclic esters followed a coordination‐insertion mechanism, and cyclic esters exclusively inserted into the Sr–O bond. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1934–1941, 2003
Densely grafted polyisocyanides synthesized by two types of polymerization techniques
Authors: Tian Yanqing , Li Yi , Iyoda Tomokazu 
Published: May 2003

AbstractA series of novel polyisocyanide‐graft‐polystyrenes and polyisocyanide‐graft‐[polystyrene‐block‐poly(butyl acrylate)]s were synthesized through the grafting‐through and grafting‐from routes with two types of living polymerization techniques: polymerization with the Pd–Pt μ‐ethynediyl dinuclear complex as the initiator and catalyst for the polyisocyanide backbone and atom transfer radical polymerization for the grafted side chain. Through the introduction of a chiral center at the side chain of the polyisocyanide backbone, helical grafted and graft block polyisocyanides were prepared through the grafting‐from method. All of the obtained polymers exhibited polydispersities in the range of 1.07–1.41. This might have been the first time grafted polyisocyanides were prepared, especially helical grafted polyisocyanides, through the operation of two living polymerization techniques. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1871–1880, 2003
Complexation of linear and poly(ethylene oxide)‐grafted poly(methacryl oxyethyl trimethylammonium chloride) with poly(ethylene oxide‐block‐sodium methacrylate)
Authors: Andersson Toni , Holappa Susanna , Aseyev Vladimir , Tenhu Heikki 
Published: May 2003

AbstractThe interactions between oppositely charged polyelectrolytes were studied in saline aqueous solutions as functions of the temperature and the salt and polymer concentrations. The polyanion was a diblock copolymer composed of a poly(ethylene oxide) block and a poly(sodium methacrylate) block. Two polycations were used, the homopolymer poly(methacryl oxyethyl trimethylammonium chloride) and its poly(ethylene oxide)‐grafted analogue. By dynamic light scattering and turbidity measurements, it was observed that the salt concentration, temperature, and counterion size had a significant effect on the formation of the polymer complexes in aqueous solutions. At a fixed salt concentration and a fixed temperature, it was possible to form completely soluble complexes of an ionic polymer in aqueous solutions between poly(ethylene oxide)‐grafted poly(methacryl oxyethyl trimethylammonium chloride)and the polyanion with a poly(ethylene oxide) block at a 1:1 anion/cation ratio. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1904–1914, 2003
Preparation and characterization of highly polar polymeric sorbents from styrene–divinylbenzene and vinylpyridine–divinylbenzene for the solid‐phase extraction of polar organic pollutants
Authors: Fontanals Núria , Marcé Rosa Maria , Galià Marina , Borrull Francesc 
Published: May 2003

AbstractThis article explores the synthesis of styrene–divinylbenzene resins with different surface areas and the influence of these surface areas on their performance in the solid‐phase extraction of polar compounds from water samples. As expected, increasing the surface areas increases the retention capability of polar compounds. To improve the retention properties, we have used 4‐vinylpyridine instead of styrene in the polymerization and evaluated the influence of the sorbent polarity and surface area on the retention properties. We have found that a compromise is required between the percentage of 4‐vinylpyridine, which increases the polarity of the sorbent, and the percentage of divinylbenzene, which increases the surface area. In the solid‐phase extraction of polar compounds, the results are best for a polymer containing 2.14% N and having a surface area of 710 m2/g. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1927–1933, 2003
Sulfuration and reversion reactions of brominated poly(isobutylene‐co‐isoprene)
Authors: Parent J. Scott , White Greg D. F. , Thom Darren J. , Whitney Ralph A. , Hopkins William 
Published: May 2003

AbstractThe sulfuration and reversion products of brominated poly(isobutylene‐co‐isoprene) (BIIR) were characterized through the use of a model compound, brominated 2,2,4,8,8‐pentamethyl‐4‐nonene (BPMN). The reaction of BPMN with S8 produced bisallylic polysulfides of various ranks, yielding sulfur bromide intermediates that likely contributed to the rapid oxidation of allylic sulfides into thiophenes. Reductive cure reversion to pentamethylnonene was also observed in the latter stages of vulcanization. The reaction of 2,2′‐dithiobisbenzothiazole with BIIR and BPMN produced a stable adduct that reduced the concentration of allylic bromide available for vulcanization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1915–1926, 2003
Assembly of amphiphilic poly[2‐(methacryloyloxy)ethyl phosphorylcholine] with cholesteryl moieties as terminal groups
Authors: Sugiyama Kazuo , Shiraishi Kohei , Matsumoto Takako 
Published: May 2003

AbstractPoly[2‐(methacryloyloxy)ethyl phosphorylcholine]s (PMPCs) with one pendant cholesteryl moiety at the polymer end (PMPC‐Chol‐I and PMPC‐Chol‐II) and two pendant cholesteryl moieties at both polymer ends as terminal groups (PMPC‐2Chol‐I and PMPC‐2Chol‐II) were prepared by the radical polymerization of 2‐(methacryloyloxy)ethyl phosphorylcholine initiated with 4,4′‐azobis[(3‐cholesteryl)‐4‐cyanopentanoate] in the presence of 2‐mercaptoethanol or thiocholesterol as chain‐transfer reagents, respectively. The self‐organization of PMPC‐Chol and PMPC‐2Chol was analyzed with fluorescence and 1H NMR measurements. The critical micelle concentrations of PMPC‐Chol‐I with a degree of polymerization (Pn) of 91 and of PMPC‐2Chol‐I with a Pn value of 165 were 250 and 27 mg L−1, respectively. The blood compatibility of PMPC‐2Chol was evaluated from the Michaelis constant (Km) for the enzymatic reaction of thrombin and a synthetic substrate, S‐2238, in the presence of PMPC‐2Chol. Km was 0.07, 0.05, and 0.56 for PMPC‐2Chol‐I with Pn = 165, PMPC‐2Chol‐II with Pn = 38, and PMPC (an intrinsic viscosity of 0.54 dL g−1) initiated with 2,2′‐azobisisobutyronnitrile in the absence of chain transfer agent, respectively. A mixture of PMPC‐2Chol‐II and cholesterol as a drug model formed a lamellar type of complex with an interplanar spacing of d = 35.2 Å. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1992–2000, 2003
Synthesis of autophotosensitive hyperbranched polyimides based on 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride and 1,3,5‐tris(4‐aminophenoxy)benzene via end capping of the terminal anhydride groups by ortho‐alkyl aniline
Authors: Chen Huan , Yin Jie 
Published: May 2003

AbstractBenzophenone‐containing, anhydride‐terminated hyperbranched poly(amic acid)s were end‐capped by ortho‐alkyl aniline in situ and then chemically imidized, yielding autophotosensitive hyperbranched polyimides. The polyimides were soluble in strong polar solvents, such as N‐methyl‐2‐pyrrolidone, N‐dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. Thermogravimetric analysis revealed their excellent thermal stability, with a 5 wt % thermal loss temperature in the range of 527–548 °C and a10 wt % thermal loss temperature in the range of 562–583 °C. The strong absorption of the polyimide films in ultraviolet–visible spectra at 365 nm indicated that the hyperbranched polyimides were patternable. Highly resolved images with a line width of 6 μm were developed by ultraviolet exposure of the polymer films. A well‐defined image with lines as thin as 3 μm was also patterned, but the lines were rounded at the edges. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2026–2035, 2003
Synthesis and characterization of novel fluorinated polyimides based on 2,7‐bis(4‐amino‐2‐trifluoromethylphenoxy)naphthalene
Authors: Hsiao Sheng‐Huei , Yang Chin‐Ping , Chung Cheng‐Lin 
Published: May 2003

AbstractA new trifluoromethyl‐substituted bis(ether amine) monomer, 2,7‐bis(4‐amino‐2‐trifluoromethylphenoxy)naphthalene, was synthesized. It led to a series of novel fluorinated polyimides by thermal and chemical imidization routes when reacted with various commercially available aromatic tetracarboxylic dianhydrides. Most of the polyimides obtained from both routes were soluble in many organic solvents, such as N,N‐dimethylacetamide. All the polyimides could afford transparent, flexible, and strong films with low moisture absorptions of 0.3–0.6%, low dielectric constants of 2.52–3.27 at 10 kHz, and an ultraviolet–visible absorption cutoff wavelength at 377–436 nm. The glass‐transition temperatures of the polyimides were in the range of 244–297 °C, and the 5% weight‐loss temperatures were higher than 550 °C. For a comparative study, a series of analogous polyimides based on 2,7‐bis(4‐aminophenoxy)naphthalene were also prepared and characterized. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2001–2018, 2003
Dark‐cure studies of cationic photopolymerizations of epoxides: Characterization of the active center lifetime and kinetic rate constants
Authors: Sipani Vishal , Scranton Alec B. 
Published: May 2003

AbstractWe have characterized the effective rate constants for termination/trapping (kt/t) and propagation (kp) for solvent‐free cationic photopolymerizations of phenyl glycidyl ether for conversions up to 50%. We have performed dark‐cure experiments in which active centers are produced photochemically for a specified period of time until the initiating light is shuttered off, and then the polymerization rate is monitored in the dark. This method is especially well suited for characterizing cationic polymerizations because of the long active center lifetimes. Our analysis provides profiles of the instantaneous kinetic rate constants as functions of conversion (or time). For photopolymerizations of phenyl glycidyl ether initiated with iodonium photoinitiators, kt/t and kp remain essentially invariant for conversions up to 50%. For the photoinitiator (tolycumyl) iodonium tetrakis (pentafluorophenyl) borate (IPB), the values of kt/t at 50 and 60 °C are 0.027 and 0.033 min−1, respectively. The corresponding values of kt/t for diaryliodonium hexafluoroantimonate (IHA) are 0.041 and 0.068 min−1. The values of kp at 50 °C for IPB and IHA are 0.6 and 0.4 L mol−1 s−1, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2064–2072, 2003
Cocrystallization phenomena in piperazine‐based copolyamides as examined by differential scanning calorimetry, wide‐angle X‐ray diffraction, and solid‐state NMR
Authors: Vanhaecht Bert , Devroede Jan , Willem Rudolph , Biesemans Monique , Goonewardena Wyjayanthi , Rastogi Sanjay , Hoffmann Sven , Klein Philip G. , Koning Cor E. 
Published: May 2003

AbstractCopolyamides 2.14/piperazine.14 with variable built‐in ratios of 1,2‐ethylenediamine (1,2‐EDA) and piperazine (pip) were synthesized by solution polycondensation. The built‐in ratio of both diamine comonomers was determined with solution 13C NMR analysis. The gradual replacement of 1,2‐EDA units by cycloaliphatic pip units in polyamide 2.14 resulted in a progressively decreased melting (Tm) and crystallization temperature of the obtained copolyamides. Apparently, the Tm raising effect of the incorporation of rigid cycloaliphatic moieties is overruled by the simultaneous Tm reduction caused by a decreasing hydrogen‐bond density. Indications for cocrystallization of 2.14 and pip.14 repeating units were obtained by the thermal analysis of copolyamides 2.14/pip.14 and of a blend of both homopolyamides. A preliminary wide‐angle X‐ray diffraction study pointed to the same conclusion. Solid‐state NMR spectroscopy was used to investigate the influence of the composition on the percentage of the rigid phase of the copolyamides and delivered additional indications for cocrystallization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2082–2094, 2003
Metal‐template synthesis of cyclic epoxide–amine oligomers: Uncrosslinked epoxide–amine addition polymers, 47
Authors: Klee Joachim E. , Hägele Klaus , Przybylski Michael 
Published: May 2003

AbstractThe addition reaction of 2,2‐bis‐[4‐(2,3‐epoxypropoxy)‐phenyl]‐propane (DGEBA) and preformed complexes of metal ions and disecondary diamines led to a large quantity of cyclic epoxide–amine oligomers. As shown by gel permeation chromatographic analysis, cycles of n = 1, 2, and 3 were formed. Functional epoxide end groups of the prepared oligomers were completely missing in the IR and 1H NMR and 13C NMR spectra. In the fast atom bombardment and matrix‐assisted laser desorption/ionization mass spectra, the molecular ions of the n = 1, 2, 3 cycles of DGEBA and N,N′‐dibenzyl‐5‐oxanonanediamine‐1,9 were detected at m/z = 680, 1361, and 2042. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2047–2052, 2003
Reverse atom transfer radical polymerization of methyl methacrylate initiated by p‐chlorobenzenediazonium tetrafluoroborate
Authors: Ucan Recep , Tunca Umit , Hizal Gurkan 
Published: May 2003

AbstractThe controlled polymerization of methyl methacrylate (MMA) in bulk was initiated with p‐chlorobenzenediazonium tetrafluoroborate (1) and Cu(II) or Cu(I)/Cu(II)/N,N,N′,N″,N″‐pentamethyldietylene triamine (PMDETA) complex system at various temperatures (20, 60, and 90 °C). The proposed polymerization mechanism is based on the Meerwein‐type arylation reaction followed by a reverse atom transfer radical polymerization. In this mechanism, aryl radicals formed by the reaction with 1 and Cu(I) and/or PMDETA initiated the polymerization of MMA. The polymerization is controlled up to a molecular weight of 46,000 at 90 °C. Chain extension was carried out to confirm the controlled manner of the polymerization system. In all polymerization systems, the polydispersity index and initiator efficiency ranged from 1.10–1.57 to 0.10–0.21, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2019–2025, 2003
Highly active methyl methacrylate polymerization catalysts obtained from bis(3,5‐dinitro‐salicylaldiminate)nickel(II) complexes and methylaluminoxane
Authors: Carlini Carlo , Martinelli Marco , Raspolli Galletti Anna Maria , Sbrana Glauco 
Published: May 2003

AbstractThe homopolymerization of methyl methacrylate was investigated with bis(salicylaldiminate)nickel(II) complexes, such as bis[3,5‐dinitro‐N(2,6‐diisopropylphenyl)salicylaldiminate]nickel(II) (IIIa) and bis[3,5‐dinitro‐N(phenyl)salicylaldiminate]nickel(II) (IIIb), and with methylaluminoxane (MAO) as an activator. In particular, the effect of the Al/Ni molar ratio on the catalytic activity and on the properties of the resulting poly(methyl methacrylate) (PMMA) was checked. The maximum activity was ascertained when an Al/Ni molar ratio equal to about 100 was used. However, the productivity of the catalytic systems was rather low. When the IIIa/MAO catalytic system was prepared under an ethylene atmosphere, an extremely high activity was observed, a productivity value of up to around 150,000 g of PMMA/(mol of Ni × h) being obtained, the highest ever found with nickel‐based catalysts. No appreciable presence of ethylene counits in the polymeric products was also ascertained. When the IIIb/MAO system was used, similar results were found, and high molecular weight PMMAs were obtained, despite the absence of bulky isopropyl substituents in positions ortho and ortho′ to the N‐aryl moiety of the salicylaldiminate ligand. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2117–2124, 2003
A Re‐Evaluation of the Particle Size of Dow “Monodisperse” Latex Samples After an Elapsed Time of 47–54 Years
Authors: Davidson John A. , Ramic Anthony J. , Kornbrekke Ralph 
Published: May 2003

AbstractThe particle size of Dow polystyrene latex 580G lot #3584, LS‐057‐A, and LS‐063‐A were recently redetermined by electron microscopy. Sample 580G had been polymerized in 1948, while both LS‐057‐A and LS‐063‐A date back prior to 1955. The lot 580G material that we examined had gradually increased in size over the years and was badly contaminated. A second generation of fine particles was present which may be of non‐latex origin. On the other hand, both LS‐057‐A and LS‐063‐A showed no change in particle diameter. Both of these samples had been stored at high dilution (ca. 1.5×10−4 g/cm3) and at room temperature. This work suggests that a low solids level is very important for archival storage, in so far as it essentially negates water loss through evaporation. The “drying out” of standard latex samples supplied in 10 cm3 or similar quantities has long been known to limit their shelf life, and consequently the utility of these materials. Sample LS‐057‐A was also examined by QELS, which gives a measurement of particle diameter that is sensitive to agglomeration. This technique yielded a diameter ca. 18% larger than that obtained by TEM. However, upon re‐dispersion using ultrasonication, very good agreement was obtained. Two badly sedimented Duke monodisperse latexes also gave satisfactory agreement with the manufacturer's stated diameter after ultrasonic re‐dispersion, suggesting the utility of this method of re‐dispersion.
Application of the Maximum Entropy Formalism on Sprays Produced by Ultrasonic Atomizers
Authors: Dumouchel Christophe , Sindayihebura Daniel , Bolle Léon 
Published: May 2003

AbstractA recent application of the Maximum Entropy Formalism on liquid atomization problems led to the development of a mathematical volume‐based drop‐size distribution. This function, which depends on three parameters, is a reduction of the four‐parameter generalized Gamma function. The aim of the present work is to investigate the relevance of the three parameters in the characterization of liquid atomization processes. To achieve this, a variety of experimental drop‐size distributions of ultrasonic sprays were analyzed with the mathematical function. Firstly, it is found that the mathematical drop‐size distribution is very suitable to represent the volume‐based drop‐size distribution of ultrasonic sprays. Furthermore, it is seen that when considering the three parameters introduced by the function, one of them is constant for all the situations investigated, and the other two are linked to a non‐dimensional group that includes the main parameters controlling the drop production. These results are very important, since they suggest a possible development of physical models of primary atomization based on the M.E.F., which would allow for the prediction of the spray drop‐size distribution. Thusfar, such a model does not exist.
Characterization of Nano‐Particles Using Laser‐Induced Incandescence
Authors: Leipertz Alfred , Dankers Stefan 
Published: May 2003

AbstractLaser‐induced incandescence (LII) is introduced as a valuable tool for the characterization of nanoparticles. This optical measurement technique is based on the heating of the particles by a short laser pulse and the subsequent detection of the thermal radiation. It has been applied successfully for the investigation of soot in different fields of application, which is described here in the form of an overview with a focus on work done at the LTT‐Erlangen during the last 10 years. In laboratory flames the soot primary particle size, volume concentration, and relative aggregate size have been determined in combination with the number density of primary particles. Furthermore, the primary particle sizes of carbon blacks have been measured in situ and online under laboratory conditions and also in production reactors. Measurements with different types of commercially available carbon black powders, which were dispersed in a measurement chamber yielded a good correlation between LII results and the specified product properties. Particle diameters determined by LII in a furnace black reactor correlate very well with the CTAB‐absorption number, which is a measure for the specific surface area. It turned out that the LII method is not affected by variations of the aggregate structure of the investigated carbon blacks. The LII signal also contains information on the primary particle size distribution, which can be reconstructed by the evaluation of the signal decay time at, at least, two different time intervals. Additionally, soot mass concentrations have been determined inside diesel engines and online measurements were performed in the exhaust gas of such engines for various engine conditions simultaneously providing information about primary particle size, soot volume, and number concentration. The LII results exhibit good correlation with traditional measurement techniques, e.g., filter smoke number measurements. In addition to the soot measurements, primarily tests with other nanoparticles like TiO2 or metal particles are encouraging regarding the applicability of the technique for the characterization of such different types of nanoparticles.
The Fundamentals of Particle Size Analysis by Transmission Fluctuation Spectrometry.
Authors: Shen Jianqi , Riebel Ulrich 
Published: May 2003

AbstractA transmission signal measured on a flowing suspension of particles with a high spatial and temporal resolution shows significant fluctuations, which contain the complete information on particle size distribution and particle concentration. In Parts 1 and 2, the basic properties of signal fluctuations were studied for temporal averaging by a gliding time window and for spatial averaging by a circular beam of uniform intensity. However, the experimental implementation of such conditions is difficult. Now, the theory is extended for Gaussian beams of variable diameter and averaging by signal filtering in the frequency domain. This provides the basis for an experimental implementation by transmission of a laser beam and analog signal processing by an array of low pass filters.