bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman analysis of formaldehyde aqueous solutions as a function of concentration
Authors: Lebrun N. , Dhamelincourt P. , Focsa C. , Chazallon B. , Destombes J. L. , Prevost D. 
Published: July 2003

AbstractRaman spectra of aqueous solutions containing up to 40 mol% of formaldehyde were recorded in the 120–4000 cm−1 spectral range. The water vibrational modes are not too heavily modified by the presence of the polymerized species in the aqueous solutions. The intensity of the bands corresponding to the C–O and C–H vibrational modes depends on the water content. Two bands are found for the C–O symmetric and antisymmetric stretching modes. The first is related to the C–O–C groups formed within the oligomer chains as the condensation increases and the second to the C–OH groups located at the end of the oligomer chains. A change in the intensity evolution of the bands corresponding to the stretching modes of the C–O–C groups occurs above 15 mol% formaldehyde concentration, corresponding to the formation of the HO(CH2O)nH oligomers with n≥3. The intensity of the stretching modes due to the C–OH groups varies linearly with concentration. A linear variation of the band intensity of the CH modes as a function of formaldehyde content is also observed. Copyright © 2003 John Wiley & Sons, Ltd.
Raman spectroscopic and DFT studies on solutions of NaBF4 in N,N‐dimethylformamide
Authors: Xuan Xiaopeng , Zhang Hucheng , Wang Jianji , Wang Hanqing 
Published: July 2003

AbstractSolutions of sodium tetrafluorobrate (NaBF4) in N,N‐dimethylformamide were investigated by Fourier transform Raman spectroscopy up to 4.30 mol kg−1 salt concentration. The new band in the N—CO deformation region arising from the bound solvent was examined in detail and a mean solvation number of 3.3 was obtained. The changes in the ν1 band of the BF4− anion indicate the presence of the contact ion pair Na+BF4−. The geometry of the contact ion pair is suggested from density functional theory calculations. Copyright © 2003 John Wiley & Sons, Ltd.
Transition Metal‐Catalyzed Ring‐Opening Polymerization of Silicon‐Bridged [1]Ferrocenophanes in the Presence of Functional Silanes: Molecular Weight Control and Synthesis of Telechelic Poly(ferrocenylsilanes)
Authors: Bartole‐Scott Alexandra , Resendes Rui , Manners Ian 
Published: July 2003

AbstractThe transition metal‐catalyzed ring‐opening polymerization of dimethyl[1]silaferrocenophane (fcSiMe2) (1), fc = Fe(η‐C5H4)2), in the presence of MePhSiH2, or the chlorosilanes ClMe2SiH, ClMePhSiH, or ClPh2SiH has been shown to allow access to poly(ferrocenylsilane)s R1R2R3Si[fcSiMe2]nH (4, 6–8), and R1[Me2Sifc]mSiR2R3[fcSiMe2]nH (5) with controlled molecular weights and which are capped by the corresponding R1R2R3Si and SiH groups (4, 5: R1 = H, R2 = Me, R3 = Ph, 6: R1 = Cl, R2 = R3 = Me, 7: R1 = Cl, R2 = Me, R3 = Ph, 8: R1 = Cl, R2 = R3 = Ph). Materials with molecular weights in the range Mn of 3.5 × 103 to 2.5 × 104 and polydispersities of 1.3–2.2 were prepared. All of the silanes examined in this study were found to be more reactive as capping agents than the previously studied Et3SiH; the order of reactivity for molecular weight control was determined to be MePhSiH2 ≈ ClMe2SiH ≈ ClMePhSiH ≈ ClPh2SiH > Et3SiH. In addition, the reactivity of the resulting SiCl end‐functionalities of poly(ferrocenylsilane)s 6 and 7 was explored, and reactions with commercial poly(ethylene glycol) methyl ether yielded poly(ethylene oxide)–block–poly(ferrocenylsilane) diblock copolymers, 10 and 11. The SiH end group, however, was much less reactive and attempts to utilize this functionality for hydrosilylation of divinyl‐terminated poly(dimethylsiloxane) to form block copolymers was ineffective.
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Syndiotactic Poly(propylene) from [Me2Si(3,6‐di‐tert‐butyl‐9‐fluorenyl)(N‐tert‐butyl)]TiCl2–Based Catalysts: Chain‐End or Enantiotopic‐Sites Stereocontrol?
Authors: Busico Vincenzo , Cipullo Roberta , Cutillo Francesco , Talarico Giovanni , Razavi Abbas 
Published: July 2003

AbstractThe origin of the syndiotactic selectivity in propene polymerization of a typical bridged fluorenyl‐amido catalyst, namely [Me2Si(3,6‐di‐tert‐butyl‐9‐fluorenyl)(N‐tert‐butyl)]TiCl2 (1), activated with methylaluminoxane or [HMe2N(C6H5)][B(C6F5)4]/Al(i‐butyl)3, was investigated by means of 150 MHz 13C NMR spectroscopic microstructural polymer analysis. The asymmetric induction was traced unambiguously to enantiotopic‐sites control. Compared with the better‐known cyclopentadienyl‐fluorenyl ansa‐zirconocenes, 1 turned out to be almost identically enantioselective (in agreement with computer modeling), but less stereoselective because of a higher propensity to undergo site epimerization. This results in a chain microstructure with large predominance of m over mm stereodefects, deceptively similar to that of syndiotactic poly(propylene) produced under chain‐end control.Methyl region of the 150 MHz 13C NMR spectrum of a poly(propylene) sample prepared with catalyst system 1/borate/TIBAl.magnified imageMethyl region of the 150 MHz 13C NMR spectrum of a poly(propylene) sample prepared with catalyst system 1/borate/TIBAl.
Temperature Dependent Studies of Molecular Interactions in a Low‐Molecular Weight Ester Diol Mixed with a Hyperbranched Polyester Additive
Authors: Ziemer Antje , Eichhorn Klaus‐Jochen , Adam Gudrun , Froeck Christian , Voit Brigitte , Kreitschmann Mirko , Kierkus Paul 
Published: July 2003

AbstractIn this paper the influence of the hyperbranched polyester based on 4,4‐bis(4‐hydroxyphenyl)valeric acid on the properties of an ester diol oligomer will be discussed. The hyperbranched polyester was added to an ester diol in different amounts and the resulting bulk viscosity values were measured. Surprisingly, the resulting viscosity depends on the mixing temperature of both substances. Glass transition temperatures gave an idea about the phase behavior in the blend. H bond formation in the ester diol was intensively studied by temperature dependent IR measurements. The weakening of H bonds in the ester diol oligomer with increasing temperature was proven by IR measurements and correlates with results from viscosity measurements. These changes allow increased interactions between the ester diol and the hyperbranched polyester which causes different viscosity values depending on the mixing temperature. The overall changes in the behavior of the mixture were proven by temperature dependent AFM measurements.Frequency dependent viscosity measurement for the mixture containing of 20 wt.‐% of the hyperbranched polyester.magnified imageFrequency dependent viscosity measurement for the mixture containing of 20 wt.‐% of the hyperbranched polyester.
New Functionalized Anionic Initiators Prepared from Substituted 1,1‐Diphenylethylene Derivatives with Acetal‐Protected Monosaccharides and Their Application to Chain‐Multi‐Functionalized Polymers with Glucose and Galactose Molecules
Authors: Loykulnant Surapich , Hirao Akira 
Published: July 2003

AbstractLiving anionic polymerizations of methyl methacrylate, tert‐butyl methacrylate, 2‐(perfluorobutyl)ethyl methacrylate, tert‐butyl acrylate, and ethylene oxide were carried out with functionalized initiators prepared from substituted 1,1‐diphenylethylene (DPE) derivatives with two and four acetal‐protected α‐D‐glucofuranose and α‐D‐galactopyranose residues and carbanionic species such as sec‐butyllithium (sec‐BuLi), cumylpotassium, lithium and potassium naphthalenides. In certain cases, either LiCl or diethylzinc was used as an additive to control the polymerization. Several new well‐defined chain‐end‐ and in‐chain‐functionalized polymers with two and four glucose and two galactose molecules were successfully synthesized by these living polymerizations followed by deprotection. We have proposed a promising iterative methodology based on a convergent approach, with which novel two dendritic substituted DPE derivatives with four and eight acetal‐protected D‐glucofuranose residues can successively be synthesized. With use of the functionalized anionic initiators prepared from such dendritic DPE derivatives and sec‐BuLi in the polymerization of methyl methacrylate, well‐defined chain‐end‐functionalized poly(methyl methacrylate)s with four and eight glucose molecules were synthesized.magnified image
Cyclodextrins in Polymer Synthesis: Free Radical Polymerization of β‐Cyclodextrin Complexes of Photosensitive Mesoionic 6‐Oxo‐1,6‐dihydropyrimidin‐3‐ium‐4‐olates in Aqueous Medium
Authors: Theis Alexander , Ritter Helmut 
Published: July 2003

AbstractSolid mesoionic 2‐[2‐(isopropenylcarbonyloxy)ethylthio]‐1‐methyl‐6‐oxo‐3‐phenyl‐5‐propyl‐1,6‐dihydropyrimidin‐3‐ium‐4‐olate was complexed in water using β‐cyclodextrin (β‐CD) and randomly methylated β‐CD, which resulted in polymerizable complexes with 2:1 stoichiometry. The β‐CD complex was characterized using 1H NMR, ROESY NMR and UV spectroscopy. Polymerization of the complex prepared from methylated β‐CD led to a photosensitive polymer, which precipitated during polymerization and was nearly free of CD. Polymerization was carried out with a water‐soluble redox initiator. In addition, a copolymer with methyl methacrylate was prepared from the complexes, which showed a different mass‐dependent distribution in the incorporation in comparison to a copolymer prepared without CD in organic solvents.magnified image
A Comprehensive Kinetic Model for the Combined Chemical and Thermal Polymerization of Styrene up to High Conversions
Authors: Kotoulas Costas , Krallis Apostolos , Pladis Prokopis , Kiparissides Costas 
Published: July 2003

AbstractIn the present study, a comprehensive mathematical model is developed for the free‐radical polymerization of styrene to predict the polymerization rate and the molecular‐weight distribution of the polymer. The kinetic model accounts for both chemical and thermal radical generation and, thus, can be employed over an extended range of polymerization temperatures (e.g., 60–200 °C). The thermal initiation mechanism includes the reversible Diels‐Alder dimerization of styrene, radical formation via the reaction of the Diels‐Alder adduct with monomer, the formation of dead trimers, and the initiation of new polymer chains. Moreover, a comprehensive free‐volume model is employed to describe the variation of termination and propagation rate constants as well as of the initiator efficiency with respect to the monomer conversion. The cumulative molecular‐weight distribution of the polystyrene is calculated by the weighted sum of all the ‘instantaneous’ weight chain‐length distributions formed during the batch run. The capabilities of the present model are demonstrated by a direct comparison of model predictions with experimental data on monomer conversion, number‐ and weight‐average molecular weights, and molecular‐weight distribution. It should be noted that previously published kinetic models cannot describe the combined thermal and chemical free‐radical polymerization of styrene in terms of a unified, fundamental, kinetic model, which further underlines the significance of this study.Predicted and experimental weight‐average molecular weights with respect to monomer conversion (experimental conditions same as in Figure 1).magnified imagePredicted and experimental weight‐average molecular weights with respect to monomer conversion (experimental conditions same as in Figure 1).
Probing the Polarity of Various Cellulose Derivatives with Genuine Solvatochromic Indicators
Authors: Fischer Kristin , Heinze Thomas , Spange Stefan 
Published: July 2003

AbstractKamlet‐Taft's α (hydrogen‐bond donor acidity), β (hydrogen‐bond acceptor basicity) and π* (dipolarity/polarizability) values of carboxymethyl celluloses (CMCs) and cellulose tosylates (CTs) with different degrees of substitution are reported. Fe(phen)2(CN)2 [cis‐dicyanobis(1,10‐phenanthroline)iron(II)] (1), Michler's ketone [4,4′‐bis(N,N‐dimethylamino)benzophenone] (2), and 4‐aminobenzophenone (3) have been used as solvatochromic surface polarity indicators. The three probes 1, 2, and 3, respectively, have been adsorbed onto polymer samples from 1,2‐dichloroethane (1) and cyclohexane (2, 3) solution for the UV/Vis measurements. The probe‐loaded samples have been measured by means of a special reflectance technique. Apparent ET(30) values are calculated by applying linear solvation energy relationships (LSER) using the independently determined α and π* values of the samples according to ET(30) = [ET(30)]0 + aα + sπ*, because ET(30) values are not directly available for these materials. α values of CMCs and CTs significantly decrease with increasing degree of substitution due to the decrease of the number of cellulosic OH groups (Cell‐OH). The dipolarity/polarizability π* values of the CMCs show no linear dependence on the degree of substitution. A slight increase of π* with DS is observed for CTs. The β term using 3 as the probe for CTs is not determinable, because 3 also interacts, via the carbonyl oxygen, with acidic sites of the cellulose OH groups.Formulas of the probe molecules used.magnified imageFormulas of the probe molecules used.
Propylene Polymerization with rac‐SiMe2(2‐Me‐4‐PhInd)2ZrMe2/MAO: Polymer Characterization and Kinetic Models
Authors: Lahelin Mika , Kokko Esa , Lehmus Petri , Pitkänen Päivi , Löfgren Barbro , Seppälä Jukka 
Published: July 2003

AbstractPoly(propylene)s were prepared with metallocene catalyst rac‐SiMe2(2‐Me‐4‐PhInd)2ZrMe2/MAO (rac‐dimethylsilylbis(2‐methyl‐4‐phenylindenyl)dimethylzirconium/methylaluminoxane) in heptane solution at temperatures from 50 to 80 °C with varying concentrations of monomer, hydrogen, triisobutylaluminium (TIBA) and MAO. Polymer molar mass depended on the monomer, MAO, TIBA, and hydrogen concentrations and on polymerization temperature. The isotacticity was very high (mmmm > 95%), and only a slight decrease was detected at high temperatures. Regio selectivity was also high; the total amount of 2,1‐ and 3,1‐insertions was less than 0.4 mol‐%. Lowering the monomer concentration and raising the temperature increased the amount of 3,1 defects over the amount of 2,1 defects. End‐group analysis by 13C NMR spectroscopy revealed isobutyl and allyl end‐groups. Chain transfer to aluminium and β‐CH3 elimination were concluded to be the dominating chain‐termination mechanisms. The importance of β‐CH3 elimination increased with temperature. Hydrogen addition changed both the initiation and termination mechanisms as indicated by the presence of propyl, butyl and 2,3‐dimethylbutyl end‐groups. According to modeling studies, the molar mass follows a first‐order relationship with propylene and hydrogen concentrations, and a half‐order relationship with MAO concentration. Arrhenius‐type activation energy coefficients were 125 kJ · mol−1 for β‐CH3 elimination, 66 kJ · mol−1 for chain transfer to aluminium, and 53 kJ · mol−1 for chain transfer to hydrogen. A value of 45 kJ · mol−1 was used for the propagation.magnified image
Critically Evaluated Rate Coefficients for Free‐Radical Polymerization, 4
Authors: Beuermann Sabine , Buback Michael , Davis Thomas P. , García Nuria , Gilbert Robert G. , Hutchinson Robin A. , Kajiwara Atsushi , Kamachi Mikiharu , Lacík Igor , Russell Gregory T. 
Published: July 2003

AbstractPropagation rate coefficients, kp, which have been previously reported by several groups for free‐radical bulk polymerizations of cyclohexyl methacrylate (CHMA), glycidyl methacrylate (GMA), benzyl methacrylate (BzMA), and isobornyl methacrylate (iBoMA) are critically evaluated. All data were determined by the combination of pulsed‐laser polymerization (PLP) and subsequent polymer analysis by size‐exclusion chromatography (SEC). This so‐called PLP‐SEC technique has been recommended as the method of choice for the determination of kp by the IUPAC Working Party on Modeling of Polymerisation Kinetics and Processes. The present data fulfill consistency criteria and the agreement among the data from different laboratories is remarkable. The values for CHMA, GMA, and BzMA are therefore recommended as constituting benchmark data sets for each monomer. The data for iBoMA are also considered reliable, but since SEC calibration was established only by a single group, the data are not considered as a benchmark data set. All kp data for each monomer are best fitted by the following Arrhenius relations: CHMA: $k_{\rm p} = 10^{6.80} \;{\rm L} \cdot {\rm mol}^{ - 1} \cdot {\rm s}^{ - 1} \exp \left( {{{ - 23.0\;{\rm kJ} \cdot {\rm mol}^{ - 1} } \over {{\rm R} \cdot T}}} \right)$, GMA: $k_{\rm p} = 10^{6.79} \;{\rm L} \cdot {\rm mol}^{ - 1} \cdot {\rm s}^{ - 1} \exp \left( {{{ - 22.9\;{\rm kJ} \cdot {\rm mol}^{ - 1} } \over {{\rm R} \cdot T}}} \right)$, BzMA: $k_{\rm p} = 10^{6.83} \;{\rm L} \cdot {\rm mol}^{ - 1} \cdot {\rm s}^{ - 1} \exp \left( {{{ - 22.9\;{\rm kJ} \cdot {\rm mol}^{ - 1} } \over {{\rm R} \cdot T}}} \right)$, iBoMA: $k_{\rm p} = 10^{6.79} \;{\rm L} \cdot {\rm mol}^{ - 1} \cdot {\rm s}^{ - 1} \exp \left( {{{ - 23.1\;{\rm kJ} \cdot {\rm mol}^{ - 1} } \over {{\rm R} \cdot T}}} \right)$. Rather remarkably, for the methacrylates under investigation, the kp values are all very similar. Thus, all data can be fitted well by a single Arrhenius relation resulting in a pre‐exponential factor of 4.24 × 106 L · mol−1 · s−1 and an activation energy of 21.9 kJ · mol−1. All activation parameters refer to bulk polymerizations at ambient pressure and temperatures below 100 °C. Joint confidence intervals are also provided, enabling values and uncertainties for kp to be estimated at any temperature.95% joint confidence intervals for Arrhenius parameters A and EA for cyclohexyl (CHMA), glycidyl (GMA), benzyl (BzMA), and isobornyl (iBoMA) methacrylate; for details see text.magnified image95% joint confidence intervals for Arrhenius parameters A and EA for cyclohexyl (CHMA), glycidyl (GMA), benzyl (BzMA), and isobornyl (iBoMA) methacrylate; for details see text.
Molecular Structure, Crystallinity, and Morphology of Uncompatibilized and Compatibilized Blends of Polyethylene/Nylon 12
Authors: Sato Harumi , Sasao Shigehiro , Matsukawa Kimihiro , Kita Yasuo , Yamaguchi Hiroshi , Siesler Heinz W. , Ozaki Yukihiro 
Published: July 2003

AbstractThe present study is aimed at investigating differences in molecular structure, crystallinity, and morphology between uncompatibilized and compatibilized blends of high‐density polyethylene (HDPE) and Nylon 12 by using Fourier‐transform (FT) Raman spectroscopy, wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Uncompatibilized and compatibilized blends of HDPE/Nylon 12 with a Nylon 12 content ranging from 10 to 90 wt.‐% with an increment of 10 wt.‐% were prepared. The compatibilized polymer blends were prepared by adding a small amount of maleic anhydride (MAH) and it was found that 0.5 wt.‐% MAH yielded a good dispersion. SEM images show that both kind of blends have a different miscibility behavior. The uncompatibilized and compatibilized blends yield quite different X‐ray diffraction patterns; the latter blends with a Nylon 12 content > 70 wt.‐% show orientational effects in the X‐ray pattern of the HDPE. The crystallinity of the HDPE of both blends was evaluated by the full width at half intensity of the (110) reflection of HDPE. To do that, the diffraction peaks were analyzed by a curve‐fitting method. To evaluate the crystallinity from Raman spectra, the intensity ratio of the two bands at 1 129 and 1 110 cm−1 was used. Of note is that the 1 129 cm−1 band is caused by a symmetric CC stretching mode of all‐trans (CH2)n groups arising only from HDPE. The Raman spectra and X‐ray diffraction measurements revealed that when the Nylon 12 content reaches 70 wt.‐%, the crystallinity of HDPE in the compatibilized blends becomes higher than that of HDPE in the uncompatibilized blends. This result is different from the general trend of crystallinity of HDPE in polymer blends. The difference suggests that the effect of the high viscosity of the Nylon‐rich phase on the crystallinity is more significant than the effect of the impurity (MAH‐grafted PE). It seems that the extension of the Nylon 12‐rich phase during the extrusion process leads to orientational effects because of the increase in the interaction between MAH and HDPE.SEM images of HDPE/Nylon 12 compatibilized (top) and uncompatibilized (bottom) blends with a Nylon 12 content of 20 wt.‐%.magnified imageSEM images of HDPE/Nylon 12 compatibilized (top) and uncompatibilized (bottom) blends with a Nylon 12 content of 20 wt.‐%.
All‐Solid Actuator Consisting of Polyaniline Film and Solid Polymer Electrolyte
Authors: Yan Hu , Tomizawa Kazuhisa , Ohno Hiroyuki , Toshima Naoki 
Published: July 2003

AbstractAn all‐solid actuator, consisting of a polyaniline (PANI) film and a solid polymer electrolyte (SPE) of poly(ethylene oxide) derivative (STO288), clearly showed a reversible displacement in an atmosphere when a voltage was applied between the PANI film and the SPE layer. The displacement and the response rate are mainly dependent on the applied voltage and the employed supporting salt, but are influenced by the humidity and temperature of the environment. The results of the present experiments have revealed that the influences of the humidity and temperature on the performance of the actuator are predominantly through the ionic conductivity of the SPE.All‐solid actuator consisting of PANI and SPE.magnified imageAll‐solid actuator consisting of PANI and SPE.
Colloidal Crystalline Arrays of β‐Polymorphic Poly(vinylidene fluoride)
Authors: Habibur Rahman M. , Nandi Arun K. 
Published: July 2003

AbstractStable layers of nearly monodisperse spheres of β‐polymorphic poly(vinylidene fluoride) with iridescent properties are prepared. The colloidal crystalline arrays (CCAs) were characterized by optical microscopy, differential scanning calorimetry (DSC), and FT‐IR spectroscopy. FT‐IR spectroscopic and wide‐angle X‐ray scattering (WAXS) studies revealed a β‐polymorphic PVF2 structure, the DSC study showed that the level of crystallinity in the CCA was much higher than that in the melt‐crystallized sample, and UV‐visible spectroscopy showed extinction peaks at 323 and 510 nm in the CCAs. The β‐polymorphic PVF2 structure, along with the optical extinction properties of these CCAs, raises the prospect of their application in optical filters and/or piezoelectric sensors.Optical micrograph of PVF2 CCA films cast on glass substrates.magnified imageOptical micrograph of PVF2 CCA films cast on glass substrates.
Intercalated Polycarbonate/Clay Nanocomposites: Nanostructure Control and Foam Processing
Authors: Mitsunaga Masaki , Ito Yasuhito , Ray Suprakas Sinha , Okamoto Masami , Hironaka Katsuhiko 
Published: July 2003

AbstractIntercalated polycarbonate (PC)/clay nanocomposites (PCCN)s have been prepared successfully through the melt intercalation method in the presence of a compatibilizer. The internal structure and morphology of the PCCNs has been established by using wide‐angle X‐ray diffraction (WAXD) analyses and transmission electron microscopic (TEM) observations. The morphology of these nanocomposites and degradation of the PC matrix after nanocomposites preparation can be controlled by varying surfactants used for the modification of clay and compatibilizer. The intercalated PCCNs exhibited remarkable improvements of mechanical properties when compared with PC without clay. We also discuss foam processing of one representative PCCN using supercritical CO2 as a foaming agent.TEM bright field image of intercalated polycarbonate/synthetic fluorohectorite nanocomposite.magnified imageTEM bright field image of intercalated polycarbonate/synthetic fluorohectorite nanocomposite.