bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shell growth mechanism in emulsifier‐free emulsion polymerization: Morphological and kinetic studies
Authors: Chen Show‐An , Lee Song‐Tai , Lee Shien‐Jy 
Published: April 2007

AbstractFor systems of emulsifier‐free emulsion polymerization having particle diameter (Dp) greater than 0.15–0.2μm, a shell‐growth mechanism for particle growth was proposed. According to the mechanism, the polymeric radicals can propagate only within the shell region having a thickness about equal to the most probable end‐to‐end distance of the terminated polymer. This mechanism was considered to result from anchoring of hydrophilic ends of the growing radicals on the particle surface and from a high average number of radicals per particle. The occurrence of limiting conversion for such large particles was attributed to the consequence of shell‐region polymerization characteristic of large emulsion particles and a monomer‐diffusion‐controlled polymerization mechanism within the particles during the high conversion period.
Monodisperse microspheres of copolymers of glycidyl methacrylate and its derivatives as materials for biomedical application
Authors: Hosaka Shuntaro , Murao Yasuo , Tamaki Hideaki , Masuko Sanae , Miura Kumiko , Kawabata Yasuro 
Published: April 2007

AbstractMonodisperse microspheres of copolymers of glycidyl methacrylate were prepared by dispersion polymerization in organic media. The microsphere diameter could be adjusted in the range from 0$md$5 μm to 5μm by changing the monomer concentration, the type of dispersion medium and the content of the comonomers. Terpolymers of glycidyl methacrylate, 2‐hydroxyethyl methacrylate and tri(ethylene glycol) dimethacrylate were analysed by thermal decomposition gas chromatography and the compositions of the polymers agreed well with those of the monomer mixtures. The epoxide of the polymer microspheres was hydrolysed to α,β‐diol with dilute sulphuric acid without side reactions except the slight formation of sulphate. It was confirmed by the 13CFT‐NMR spectrum that the main structure of the hydrolysate was that of poly(glyceryl methacrylate). In the reaction of the epoxide with ammonia, the predominant production of tertiary amine was presumed by the relationship between the conversion of the epoxide and the nitrogen content of the reaction product. The amination of the epoxide with secondary amines resulted in the quantitative formation of the corresponding tertiary amines.
Grafting of polyacrylamide on to guar gum with the redox system potassium bromate/thiomalic acid
Authors: Bajpai U. D. N. , Jain Alka 
Published: April 2007

AbstractThe kinetics of graft copolymerization of polyacrylamide on to a natural polysaccharide guar gum have been studied in aqueous medium at 35 ± 0.2°C. Chemical initiation, using a water‐soluble redox system, potassium bromate/thiomalic acid, was used. This redox pair works in the presence of oxygen and thus makes the whole system cost‐effective. A plausible mechanism of graft copolymerization has been suggested on the basis of the experimental results obtained by varying the parameters.
Synthesis and curing behaviour of urethane‐modified epoxy resin having hydroxymethyl group
Authors: Ohtsuka Keiko , Hasegawa Kiichi , Fukuda Akinori 
Published: April 2007

AbstractSynthesis and curing behaviour of urethane‐modified epoxy resins were studied. The epoxy resins were synthesized by the reaction of 4‐cresol‐type epoxy resin having hydroxymethyl group (EPCDA) with isocyanates. First, as a model compound, EPCDAPI was synthesized by the reaction of EPCDA with phenyl isocyanate (PI). EPCDAPI was heated at 180°C and the reaction products were identified and the reaction mechanism was studied. The following reactions occurred: regeneration of hydroxymethyl group and PI by thermal dissociation of urethane linkage; reaction of epoxide ring and urethane linkage; reaction of epoxide ring and regenerated PI. Urethane‐modified epoxy resin having hydroxymethyl group and urethane linkage (EPCDAMDI) was synthesized by the reaction of EPCDA with 4,4′‐diphenylmethane diisocynate (MDI). The structure was identified by IR, 1H NMR and 13C NMR. The epoxy resin was cured with a mixture of 4,4′‐diaminodiphenylmethane and 1.3‐phenylenediamine (molar ratio 6:4) as a hardener. Curing behaviour of the epoxy resin with hardener was examined by differential scanning calorimetry (DSC). It was found that onset and peak temperatures of the exothermic cure reaction of the EPCDAMDI system were lower than those of the 2‐cresol novolac‐type epoxy resin (EOCN) system, and the rate constant (k) of the cure reaction at 100° C of the former system was about six times larger than that of the latter system and was the same as that of 2‐cresol resol‐type epoxy resin (EOCDA). Viscoelastic properties of the cured resin were studied by dynamic mechanical analysis. It was found that the tan δ of the EPCDAMDI system had two peaks and the lower temperature peak disappeared after further curing over 200° C.
Characterization of crosslinked ethylene—Vinylacetate copolymers
Authors: Huskić Miroslav , Šebenik Anton 
Published: April 2007

AbstractTwo types of ethylene‐vinylacetate copolymers, containing 16% and 9% of vinylacetate, respectively, were crosslinked with dicumyl peroxide in a Brabender plastograf. The time of the torque maximum was proportional to the degree of crosslinking. The degree of crosslinking was determined by extraction and depended on the concentration of the crosslinking agent and of vinylacetate in the copolymer, and on the crosslinking temperature and time. It was found by DSC and by solid‐state CP‐MAS 13C NMR that with the progress of crosslinking the crystalline phase of the copolymers changed to the amorphous phase. Crosslinking took place mostly on the acetate groups.
Electrochemical, FTIR and morphological study of polypyrrole—Polystyrenesulphonate conducting films
Authors: González‐Tejera M. J. , De Plaza M. A. La , Sánchez La Blanca E. De , Hernández‐Fuentes I. 
Published: April 2007

AbstractThe electrochemical behaviour, FTIR spectrum and the morphology of polypyrrole‐polystyrenesulphonate (PPy‐PSS) films obtained potentiostatically at 0.6 V in a 0.05m Py + 1.7 × 10−2m NaPSS medium have been analysed. Different electrochemical parameters have been modified in order to establish the first polaron formation, the reversibility of the redox process and the doping mechanism.The FTIR spectrum confirms the existence of CO groups in the film structure and two possible explanations are suggested. SEM reveals a higher homogeneity in these films than in PPy films doped with smaller counterions.
Alginate polyelectrolyte lonotropic gels. XIII geometrical aspects for chelation in metal alginate complexes related to their physico‐chemical properties
Authors: Hassan Refat M. 
Published: April 2007

AbstractElectrical conductance measurements showed that monovalent, trivalent and tetravalent metal alginate complexes possess electrical conductivities in the order of semiconductors, whereas divalent and hexavalent metal alginate electrical conductivities lic in the range of insulators. X‐Ray diffraction indicated that these metal alginate complexes are amorphous in nature. Two geometrical structures for chelation between the functional groups and the interdiffused metal ions have been suggested: a non‐planar geometrical structure for the mono‐, tri‐ and tetravalent metal alginates, and a planar geometry for the divalent and hexavalent metal alginates.
Particulate composites from epoxy resin and fly‐ash for the confinement of medium and low level radwastes
Authors: Rinaldi G. , Rossi D. 
Published: April 2007

AbstractWater resistance of particulate fly‐ash‐epoxide composites, cured at low temperature by means of synthetic polyalkylenepolenepolyaminophenolic products, was tested at room temperature. Siliceous fly‐ash (20% w/w) as filler reduces water penetration into the matrices, while saturation with water does not strongly affect the properties of the composites. The low value of the water diffusion coefficient through the material and the high mechanical properties of the particulate composites suggest further experimentation for its application in the confinement of low and medium activity nuclear wastes or of toxic chemical wastes.
N,N′‐Methylenebisacrylamide polymerization initiated by Ce(IV)—Malic acid redox system—A kinetic study
Authors: Das Rima , Behari Kunj , Agrawal Uma 
Published: April 2007

AbstractFree‐radical‐initiated linear cyclopolymerization of a symmetrical non‐conjugated divinyl monomer, viz. N,N'‐methylenebisacrylamide, was carried out using cerium sulphate as initiator and malic acid as activator, in an inert atmosphere at 25 ± 0.1°C. A gel‐free polymer was formed under the experimental conditions. The order with respect to malic acid and monomer was found to be 1 and 2, respectively. The rate of polymerization was found to be inversely proportional to the concentration of Ce(IV). The overall energy of activation was found to be 25.5 kJ mol−1. An intramolecular cyclization prior to propagation is proposed in formulating a suitable mechanism to explain the kinetic results.
Polymer surface modification due to excimer laser radiation—Chemical and physical changes in the surface structure of poly(ethylene terephthalate)
Authors: Watanabe Hirosuke , Takata Tadahiko , Tsuge Masuo 
Published: April 2007

AbstractThe effects on chemical and physical properties of PET (poly(ethylene terephthalate)) film surfaces as a result of microstructuring induced by KrF‐laser (248 nm) radiation were investigated. On irradiation, the properties of film surfaces changed in proportion to radiation flux intensity. Close to threshold values, bulbous swellings appeared on the surface, which showed hydrophilic properties. At the threshold and above, regular rippling was seen, and the surface showed hydrophobic properties. Excimer laser irradiation induced chemical modification of the surface, decrease in the O/C ratio, dissociation of ester binding and amorphism as observed by X‐ray‐induced photoelectron spectroscopic and Fourier‐transform infrared analysis.
Studies on the kinetics of radical initiated photocopolymerisation of di(vinyl 2‐hydroxy propanoate) ether of bisphenol‐A and monomers
Authors: Chandra R. , Soni R. K. , Murthy S. S. 
Published: April 2007

AbstractDi(vinyl 2‐hydroxy propanoate)ether of bisphenol‐A (DEBA) was prepared by reacting diglycidyl ether of bisphenol‐A (DGEBPA) with acrylic acid using triphenyl phosphine as catalyst. Divinylester monomer was copolymerised with four different monomers, viz. methyl methacrylate (MMA), n‐butyl acrylate (BA), vinyl acetate (VAc) and acrylic acid (AA), using benzoin as photoinitiator. The kinetics of radical initiated photocopolymerisation were studied by differential photocalorimeter (DPC). The thermogram data obtained from DPC were used to calculate kinetic parameters, order of the reaction (n), independent order to encompass autocatalytic reaction (m) and the apparent rate constant (k) for the copolymerisation at different temperatures for each monomer. A change in the kinetic model from autocatalytic to Nth order was observed with increase in the fraction of conversion. A comparison of rate of conversion for copolymerisation with different monomers reveals that acrylic acid has a tendency to undergo faster copolymerisation whereas methyl methacrylate has relatively less tendency to copolymerise with DEBA.
The intrinsic viscosity of poly(acrylic acid) and partially neutralized poly(acrylic acid) by isoionic dilution
Authors: Staikos Georges , Bokias Georges 
Published: April 2007

AbstractThe isoionic dilution method has been used to measure the intrinsic viscosity, [η], of a poly(acrylic acid) (PAA) sample as a function of neutralization degree, i, at low ionic strength, I = 1.0 × 10. The results obtained for the counterion activity are in close agreement with Manning's theory for counterion condensation. The influence of the ionic strength, I, on [η] and on the Huggins coefficient, k', was also examined and the exponents of the scaling laws relating these two parameters with I were found.
Raman spectroscopic analysis of the microstructures of butadiene—Acrylonitrile copolymers
Authors: Edwards H. G. M. , Johnson A. F. , Lewis I. R. , Cowie J. M. G. 
Published: April 2007

AbstractA quantitative Raman spectroscopic study has been made for the first time of the polybutadiene microstructures of a number of copolymers of butadiene and acrylonitrile and a comparison made with IR studies of these copolymers. The intensities of the v(C°C) and the v(CN) bands have also been used to determine the amount of each monomer in the copolymer.
Free radical copolymerization in the presence of lewis acids. II. Alternating copolymerization of styrene with butyl acrylate in the presence of SnCl4
Authors: Yuan Yumin , Song Hong , Xu Guojin 
Published: April 2007

AbstractThe mechanism of alternating copolymerization of butyl acrylate (BA) with styrene (St) in the presence of SnCl4, photo‐initiated by Mn2(CO)10‐CCl4, has been investigated. The results show that the rate of copolymerization is proportional to [BA‐SnCl4] [St]0, which is in agreement with the cross‐propagation mechanism. The apparent rate constant, which can be conveniently obtained by measuring the rate of polymerization as a function of [SnCl4], is found to be 3.25 × 10−1. Alternating copolymers are obtained over a wide range of reactant composition. The solvent effect shows that the reaction in tetrachloro‐ethylene (TCE) is more advantageous to alternation than is that in toluene (TOL). 13C‐NMR spectrum confirms that the copolymers obtained have strict alternating structure.
Solvatochromic properties of long alkyl chain π* indicators: comparison of N,N‐dialkyl‐4‐nitroanilines and alkyl 4‐nitrophenyl ethers
Authors: Helburn R. , Bartoli M. , Pohaku K. , Maxka J. , Compton D. , Creedon B. , Stimpson C. 
Published: April 2007

AbstractHydrophobic forms of the N,N‐dialkyl‐4‐nitroaniline (DNAP) (p‐O2NC6H4NR2) (1a–f) and alkyl‐4‐nitrophenyl ether (p‐O2NC6H4OR) (2a–c) solvatochromic π* indicators have been characterized and compared with respect to: (a) solvatochromic bandshape, (b) sensitivity expressed as −s, (${\rm d}\bar v_{\max } $/dπ *), and (c) trends in −s with increasing length of alkyl chain(s) on the probe molecule. Octyl 4‐nitrophenyl ether (p‐O2NC6H4OC8H17) (2b) and decyl 4‐nitrophenyl ether (p‐O2N C6H4 OC10H21) (2c) were synthesized and their solvatochromic UV/Vis absorption bands were found to maintain a Gausso‐Lorentzian bandshape for the indicators in non‐polar and alkyl substituted aromatic solvents, for example, hexane(s) and mesitylene. Corresponding absorption bands for 1a–f display increasing deviation from a Gausso‐Lorentzian shape in the same solvents as the alkyl chains on the indicator are increased in length all the way to C10 and C12, for example, N,N‐didecyl‐4‐nitroaniline (p‐O2NC6H4N (C10H21)2) and N,N‐didodecyl‐4‐nitroaniline (p‐O2NC6H4N (C12H25)2) (1d–f). A plot of −s versus Cn follows a 1st order decay for the DNAP indicators but is linear for the alkyl 4‐nitrophenyl ethers. A discussion of how the long alkyl chains on the two types of indicators affect the orientation and overlap of n and π* orbitals, and resulting solvatochromic bands is presented. For DNAP, overextending the alkyl chains to obtain greater hydrophobic character may cause the alkane component to dominate solute‐solvation processes at the expense of the probe's fundamental solvatochromic character. Copyright © 2007 John Wiley & Sons, Ltd.
Depolymerization kinetics of di(4‐tert‐butyl cyclohexyl) itaconate and Mark‐Houwink‐Kuhn‐Sakurada parameters of di(4‐tert‐butyl cyclohexyl) itaconate and di‐n‐butyl itaconate
Authors: Szablan Zachary , Huaming Ming , Adler Martina , Stenzel Martina H. , Davis Thomas P. , Barner‐Kowollik Christopher 
Published: April 2007

AbstractMultipulse pulsed laser polymerization coupled with size exclusion chromatography (MP‐PLP‐SEC) has been employed to study the depropagation kinetics of the sterically demanding 1,1‐disubstituted monomer di(4‐tert‐butylcyclohexyl) itaconate (DBCHI). The effective rate coefficient of propagation, k, was determined for a solution of monomer in anisole at concentrations, c, 0.72 and 0.88 mol L−1 in the temperature range 0 ≤ T ≤ 70 °C. The resulting Arrhenius plot (i.e., ln k vs. 1/RT) displayed a subtle curvature in the higher temperature regime and was analyzed in the linear part to yield the activation parameters of the forward reaction. In the temperature region where no depropagation was observed (0 ≤ T ≤ 50 °C), the following Arrhenius parameters for kp were obtained (DBCHI, Ep = 35.5 ± 1.2 kJ mol−1, ln Ap = 14.8 ± 0.5 L mol−1 s−1). In addition, the k data was analyzed in the depropagatation regime for DBCHI, resulting in estimates for the associated entropy (−ΔS = 150 J mol−1 K−1) of polymerization. With decreasing monomer concentration and increasing temperature, it is increasingly more difficult to obtain well structured molecular weight distributions. The Mark Houwink Kuhn Sakurada (MHKS) parameters for di‐n‐butyl itaconate (DBI) and DBCHI were determined using a triple detection GPC system incorporating online viscometry and multi‐angle laser light scattering in THF at 40 °C. The MHKS for poly‐DBI and poly‐DBCHI in the molecular weight range 35–256 kDa and 36.5–250 kDa, respectively, were determined to be KDBI = 24.9 (103 mL g−1), αDBI = 0.58, KDBCHI = 12.8 (103 mL g−1), and αDBCHI = 0.63. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1931–1943, 2007
Synthesis and electrochromism of novel organosoluble polyarylates bearing triphenylamine moieties
Authors: Liou Guey‐Sheng , Chang Cha‐Wen , Huang Huang‐Ming , Hsiao Sheng‐Huei 
Published: April 2007

AbstractA series of novel aromatic polyarylates with triphenylamine units in the main chain and as the pendent group were prepared from the dicarboxylic acid monomer, N,N‐bis(4‐carboxyphenyl)‐N′, N′‐diphenyl‐1,4‐phenylenediamine (1), and various bisphenols. These polyarylates were amorphous and readily soluble in common organic solvents. They had excellent levels of thermal stability associated with moderately high Tg values (182–263 °C). These polymers exhibited strong UV–vis absorption bands at 357–360 nm in toluene solution and the photoluminescence spectra showed maximum bands around 493–503 nm in the green region. The hole‐transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyarylates exhibited two reversible oxidation redox couples in acetonitrile solution at Eonset 0.77–0.79 V and 1.12–1.14 V, respectively. The typical polymer 3b film revealed good stability of electrochromic characteristics, with color change from colorless to green and blue at applied potentials ranging from 0.00 to 1.24 V. These anodically polymeric electrochromic materials not only showed excellent reversible electrochromic stability with good green coloration efficiency (CE = 159 cm2/C) and blue coloration efficiency (CE = 154 cm2/C) but also exhibited high contrast of optical transmittance change (ΔT%), 54% in 895 nm for green color and up to 84% in 595 nm for blue color. After over 100 cyclic switches, the polymer films still exhibited excellent stability of electrochromic characteristics. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2004–2014, 2007
Helping Her Heal: a pilot study of an educational counseling intervention for spouses of women with breast cancer
Authors: Lewis Frances Marcus , Cochrane Barbara B. , Fletcher Kristin A. , Zahlis Ellen H. , Shands Mary Ellen , Gralow Julie R. , Wu Salene M. , Schmitz KrisAnn 
Published: April 2007

AbstractBreast cancer is known to cause substantial anxiety, depressed mood, and diminished marital functioning in the diagnosed woman's spouse. Despite the scope and magnitude of these issues, few intervention studies have included spouses or addressed the causes of their lower functioning. The purpose of this pilot study was to evaluate the short‐term impact of a 5‐session, clinic‐based, educational counseling intervention for spouses whose wife was recently diagnosed with early stage breast cancer. The goals of the intervention were to enhance spouses' skills and confidence to communicate and interpersonally support his wife about the breast cancer as well as improve spouses' self‐care, depressed mood, anxiety, and marital adjustment. Pre–post‐test results obtained from 20 spouses from valid and reliable standardized questionnaires showed significant improvements in spouses' depressed mood, anxiety, skills, self‐confidence, and self‐care. Confidential post‐intervention interviews with spouses and wives included detailed examples of positive changes in the spouse's communication and support to his wife about the breast cancer, diminished tension in the spouse, and improved quality in the couple's relationship. Further evaluation of the Helping Her Heal Program is warranted within a clinical trial. Copyright © 2007 John Wiley & Sons, Ltd.
Investigation of the Decomposition Mechanism and Thermal Stability of Nitrocellulose/Nitroglycerine Based Propellants by Electron Spin Resonance
Authors: Chin Anton , Ellison Daniel S. , Poehlein Sara K. , Ahn Myong K. 
Published: April 2007

AbstractNitrocellulose based (NC) and nitroglycerin based (NG) propellants often have a fixed acid and water content during the manufacturing time. After manufacture, the quantity and ratio of acid/water will continue to vary depending upon the conditions of storage and operation. The level of variation depends on many factors such as loading density, temperature, volume of ullage and sealing condition of the containing cartridge, just to name a few. As described in this paper and other literature, the degradation mechanisms and aging processes of NC/NG based propellants are extremely complicated. This paper describes the details of the application of Electron Spin Resonance (ESR) to study if the free‐radical mechanism is involved in the decomposition of nitrocellulose and nitroglycerin. Due to the high free‐radical intensity possessed by the propellant composition, we believe that a π complex intermediate may be formed between DPA and NG and/or NC. The formation of a π complex intermediate is not preferred because it may enhance the rate of decomposition of nitrate esters.
Triphenylamine – a ‘New’ Stabilizer for Nitrocellulose Based Propellants – Part I: Chemical Stability Studies
Authors: Wilker Stephan , Heeb Gerhard , Vogelsanger Beat , Petržílek Jan , Skládal Jan 
Published: April 2007

AbstractTriphenylamine (TPA) was used for the first time in France in 1937 as a stabilizer for propellants. The stability of those samples was described as ‘good’. Around 1950 an American group produced TPA stabilized propellants and investigated the decomposition mechanism. Apart from one single experiment in the 1970s no further attempts were made to take TPA as a stabilizer for propellants.
A New Method for Determining Gas Phase Heat of Formation of Aromatic Energetic Compounds
Authors: Keshavarz Mohammad H. , Tehrani Masoud K. 
Published: April 2007

AbstractA new correlation is introduced for desk calculation of gas phase heat of formation of aromatic energetic compounds that contain the elements of carbon, hydrogen, nitrogen and oxygen. Predicted gas phase heats of formation for 26 energetic compounds have a root mean square of deviation from experiment of 20.67 kJ/mol, which is in good agreement with respect to measured values of oxygen‐lean and oxygen‐rich aromatic energetic compounds.