bluuebunny/crossref_metadata_2025 huggingface dataset:
Observing artificially induced strain: implications for subglacial deformation
Authors: Hiemstra John F. , Rijsdijk Kenneth F.
Published: June 2003

By analysing a series of four successive thin‐sections from a ceramic clay that was subjected to uniaxial compression, we were able to monitor the development of microstructures in a fine‐grained sediment. The artificially induced microstructures, such as unidirectional clay reorientations and linear and circular grain arrangements, are identical to features that have been observed in thin‐sections of subglacially deformed tills, and therefore may be used as representative analogues. We argue that the structures, reflecting slip, planar shear displacements as well as rotational movements, can be explained by assuming a Coulomb‐plastic response to imposed shear. We conclude that sediments subjected to subglacial deformation behave as Coulomb materials, at least during the final stages of the deformation. The present study bridges the gap between field studies, experimental studies and theoretical modelling. The microscopic observations assist in visualising inferred subglacial processes and facilitate up‐ and downscaling between diverse methodological approaches. Copyright © 2003 John Wiley & Sons, Ltd.
Structural phase transitions in [C6H5NH3]2SiF6: differential scanning calorimetry and Raman studies
Authors: Jeghnou H. , Ouasri A. , Rhandour A. , Dhamelincourt M.‐C. , Dhamelincourt P. , Mazzah A.
Published: July 2003

Phenylammonium hexafluorosilicate, [C6H5NH3]2SiF6, crystallizes at room temperature in the orthorhombic system with probable space group Pmmm. Two structural phase transitions were detected at 226 and 280 K by means of differential scanning calorimetry and basic thermodynamic data were determined for these transitions. The internal vibrational modes of [C6H5NH3]2SiF6 were studied at room temperature and through the phase transitions by using Raman spectroscopy. These studies indicate that the vibrational state of the phenyl cations is weakly changed during these two phase transitions. Copyright © 2003 John Wiley & Sons, Ltd.
Raman spectroscopy and multivariate curve resolution of concentrated Al2O3–Na2O–H2O solutions
Authors: Schoonover Jon R. , Zhang Shuliang L. , Johnston Cliff T.
Published: July 2003

Multivariate curve resolution was applied to a series of Raman spectra for samples representing highly concentrated alkaline aluminate slurries. Factors are extracted that represent the behavior of the dominant chemical species present, including aluminate monomer, aluminate oligomers, water and hydroxide. The analysis is particularly useful in unraveling the numerous overlapping contributions in the ν(OH) region of the spectrum. These extracted factors were further examined by comparing their scores with measured physiochemical properties such as density, relative humidity and molar concentrations of components, weight fractions and water activity. Published in 2003 by John Wiley & Sons, Ltd..
Density functional and vibrational spectroscopic analysis of β‐carotene
Authors: Schlücker S. , Szeghalmi A. , Schmitt M. , Popp J. , Kiefer W.
Published: July 2003

We report a computational study on the structural, energetic and vibrational spectroscopic characteristics of β‐carotene employing density functional theory (DFT). The optimized geometry and the complete vibrational spectrum calculated at the BPW91/6–31G* level, including infrared (IR) intensities and Raman activities, are presented. The centrosymmetric structure of β‐carotene is verified both theoretically and experimentally, by identifying a stable calculated structure with Ci symmetry and the mutually exclusive occurrence of bands in the experimental Fourier transform IR and Raman spectrum, respectively. The calculated vibrational spectra reflect the major characteristic features observed experimentally. Differences in the calculated IR intensities and Raman activities for a few dominant modes of two β‐carotene configuration isomers, the all‐trans and the natural abundant (C6–C7) s‐cis form, are explained qualitatively by the corresponding eigenvectors. At the level of theory employed, s‐cis‐β‐carotene was found to be 8.8 kJ mol−1 more stable than the all‐trans form. Calculations on β‐carotene model systems were performed to separate electronic from steric contributions. The higher stability of s‐cis‐β‐carotene is explained by an energetically favored β‐ionone ring conformation, compensating for its shorter conjugation length in comparison with the all‐trans form. Copyright © 2003 John Wiley & Sons, Ltd.
Lapis lazuli as unexpected blue pigment in Iranian Lâjvardina ceramics
Authors: Colomban Philippe
Published: July 2003

Raman analysis of an ancient ewer (Iran, 13th century) belonging to the Lâjvardina blue glazed ceramics shows that the ultramarine colour results from the unexpected deposit of a lazurite‐rich slip at the interface between the body and a cobalt‐containing lime‐rich glaze. This confirms the use of Lâjvard (lapis lazuli) as reported in an old alchemist's treatise (Abû'l Qâsim Kâshâni, 14th century). Copyright © 2003 John Wiley & Sons, Ltd.
Raman measurements in water using a high‐power light‐emitting diode
Authors: Žukauskas A. , Novičkovas A. , Vitta P. , Shur M. S. , Gaska R.
Published: July 2003

A low‐noise Raman signal of water at 3300 cm−1 was detected using a blue (465 nm) light‐emitting diode (LED) with an output power of 0.5 W. The linewidth of the LED emission spectrum (800 cm−1) was larger than the intrinsic width of the detected Raman feature (400 cm−1). Nevertheless, the comparison of the Raman spectra from distilled and potable water demonstrated that this novel technique is applicable to the normalization of fluorescence signals in water and water‐based solutions. Copyright © 2003 John Wiley & Sons, Ltd.
Hydration of glutaraldehyde‐fixed pericardium tissue: Raman spectroscopic study
Authors: Jastrzebska Maria , Wrzalik Roman , Kocot Antoni , Zalewska‐Rejdak Justyna , Cwalina Beata
Published: July 2003

Raman spectroscopy was applied to investigate changes in the hydration state of chemically modified porcine pericardium tissue. Chemically modified tissues are used in construction of bioprostheses for replacement surgery including dermis, heart valves and blood vessels. The hydration state is a very important factor influencing specific mechanical and immunogenic properties of tissue derived materials. We analysed OH vibrational bands in the Raman spectra measured in the range 3000–3800 cm−1 for native and glutaraldehyde (GA) cross‐linked porcine pericardium tissue. For deuterated samples Raman spectra were measured in the broadened wavenumber range 2100–3800 cm−1. All spectra were deconvoluted using the minimum required three‐Gaussian fit. Peak position, integrated intensity, separation between two main peaks d1–2, integrated Gaussian OH component intensity ratio K = I1/I2 and the integrated intensity fraction R = I/Itotal were determined to analyse changes in Raman OH and OD bands of the collagenous pericardium tissue upon GA treatment. It was found that the formation of collagen–GA cross‐links causes an increase in the total water content of the tissue and an increase in the interaxial distance between collagen triple helices and introduces changes in the hydration shell surrounding the triple helix. Changes in the hydration shell are postulated to consist mainly of more sufficient formation of hexagonal than pentagonal water clusters in the space between two neighbouring triple helices. The OD and OH Raman bands measured for deuterated tissues revealed the changes in the distribution of water molecules in different subunits of collagen fibrils in the cross‐linked pericardium tissue. Copyright © 2003 John Wiley & Sons, Ltd.
Vibrational studies of alkali metal hexatungstates
Authors: Mączka M. , Hanuza J. , Waśkowska A.
Published: July 2003

Raman and IR studies of potassium, rubidium and cesium hexatungstate single crystals were performed. Assignments of the observed bands are proposed. These studies confirm that the crystal structure of hexatungstates is related to the hexagonal bronze structure but it contains a large number of W atom vacancies. The vibrational properties of these compounds are similar to those of valence‐balanced hexagonal tungsten bronzes obtained by partial substitution of W atoms by atoms with a lower valence. Copyright © 2003 John Wiley & Sons, Ltd.
Protonation, sol formation and precipitation of poly‐ and oligoanilines
Authors: Gruger A. , El Khalki A. , Colomban Ph.
Published: July 2003

Raman spectrometry, UV–visible–near IR and attenuated total reflection IR absorptions are used to analyze the protonation of the emeraldine form of the phenyl/—NH2 end‐capped BQBBa tetramer and of the phenyl/—NH2 end‐capped (BQBB)4a hexadecamere in strong (H2SO4 or HCl), intermediate (CH3COOH) and weak (CH3OH) acids. Evolution of the pristine solution with aqueous dilution and time is analyzed in order to understand the formation of a sol of nanofilaments, which agglomerate and finally precipitate. Water in an acidic solution favors the precipitation of the corresponding emeraldine salt material, i.e. increases the degree of aggregation of the oligomeric species and the aromatic behavior of the rings. The secondary doping effect consists in intercalation of water molecules in the highly aggregated (paramagnetic) species, strongly bound to the oligomeric units and whose removal is always accompanied by elimination of the protonating agent (primary doping). The role of interchain interactions in charge carrier mobility appears more important than that of intrachain behavior. Copyright © 2003 John Wiley & Sons, Ltd.
Characterization of a series of sodium molybdate structures by two‐dimensional Raman correlation analysis
Authors: Chae Boknam , Jung Young Mee , Wu Xianglan , Kim Seung Bin
Published: July 2003

This paper demonstrates the use of two‐dimensional (2D) correlation spectroscopy in the characterization of the sodium molybdate structures that include and are intermediate between the hexagonal and orthorhombic forms; this series of sodium molybdates is produced by varying the preparation conditions, particularly the acid concentration and the heat‐treatment temperature. In order to verify the assignments of the vibrational modes of hexagonal sodium molybdate, 2D correlation analysis was applied to the acid concentration‐dependent Raman spectra. We can confirm from 2D Raman correlation analysis that this series of preparation conditions results in a series of sodium molybdates including and intermediate between the hexagonal and orthorhombic forms. Furthermore, 2D Raman correlation analysis elucidates the sequence of the structural transformation of hexagonal sodium molybdate into the orthorhombic form. With progression within the series from the hexagonal to the orthorhombic structures, the intensities of the oxygen–molybdenum stretching bands in sodium molybdate change in the following sequence: 973 cm−1 (terminal OMo in the hexagonal structure, decrease in intensity) → 996 cm−1 (terminal OMo in the orthorhombic structure, increase in intensity) → (897, 881) cm−1 (corner OMo2 in the hexagonal structure, decrease in intensity) → 664 cm−1 (edge OMo3 in the orthorhombic structure, increase in intensity) → 820 cm−1 (corner OMo2 in the orthorhombic structure, increase in intensity) → 692 cm−1 (edge OMo3 in the hexagonal structure, decrease in intensity). This sequence implies that the changes in the corner OMo2 and edge OMo3 structures along the series of sodium molybdates are strongly correlated. Copyright © 2003 John Wiley & Sons, Ltd.
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

Raman 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

Solutions 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

The 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

The 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.

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Methyl 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

In 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.

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Frequency 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

Living 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.

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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

Solid 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.

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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

In 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).

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Predicted 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

Kamlet‐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.

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Formulas 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

Poly(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.

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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

Propagation 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.

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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.
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

The 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.‐%.

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SEM 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

An 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.

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All‐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

Stable 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.

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Optical 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

Intercalated 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.

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TEM bright field image of intercalated polycarbonate/synthetic fluorohectorite nanocomposite.
Metallocene‐Catalyzed Solution Polymerization of Ethene at Elevated Pressure
Authors: Dornik Hans Peter , Luft Gerhard , Rau Alexander , Wieczorek Thomas
Published: July 2003

The kinetic of ethene polymerization catalyzed by (nBuCp)2ZrCl2/AliBu3/[Me2PhNH]+[B(C6F5)4]− has been investigated at 100 and 140 °C at pressures from 2 to 7 MPa. The initial polymerization rate Rp0 increases linearly with increasing catalyst concentration, whereas a second‐order dependence of Rp0 on the ethene concentration is found the number‐average molecular weight Mn increases with increasing ethene pressure (ethene concentration). The relation between Mn and ethene concentration can be explained by an equation based on a kinetic model involving a single center, two‐state catalyst system.

Influence of the Zr concentration on the initial polymerization rate Rp0. pEthene = 7 MPa, solvent (toluene/ethene) = 275 mL.

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Influence of the Zr concentration on the initial polymerization rate Rp0. pEthene = 7 MPa, solvent (toluene/ethene) = 275 mL.
Sheet‐Molded Polyolefin Natural Fiber Composites for Automotive Applications
Authors: Pervaiz Muhammad , Sain Mohini M.
Published: July 2003

The use of natural fibers as reinforcing filler in thermoplastics is a relatively new application and has great potential in replacing glass fiber products in automotive industry. However, most of the research in this area has been focused primarily on flax fiber. In the first part of the work presented here, hemp fiber non‐woven mats are used exclusively in combination with a poly(propylene) matrix to study the mechanical properties of natural fiber mat thermoplastics (NMT) in the absence of binder. Film stacking was used as the method of preparation. The results show that hemp‐based NMT have comparable or even higher strength properties as compared with conventional flax‐based thermoplastics. A value of 63 MPa for the flexural strength is achieved at a fiber content of 64 wt.‐%. The influence of the compression ratio on the mechanical properties and density of NMT is also reported. A definite increase in strength is observed with increasing compression together with a much more uniform density profile. In the second part of this study, a unique combination of random hemp fibers, non‐woven mats and poly(propylene) films was employed in film stacking to evaluate strength properties and economic implications. The same fiber content (64 wt.‐%) was maintained in the final NMT by replacing 78 wt.‐% of the mats by random fibers. Preliminary tests reveal better mechanical properties especially in terms of impact energy, which is 50 to 100% higher, as compared with different mats‐only/poly(propylene) combinations. Further, a net saving of 40% in fiber cost is anticipated by replacing 78% non‐woven mats with an equivalent amount of random fibers. Overall results of this study indicate that hemp‐based NMT are promising candidates in automotive applications where high specific stiffness is required.

Tensile Strength of different NMTs and GMT.

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Tensile Strength of different NMTs and GMT.
Mechanical and Thermal Properties of Poly(L‐lactide) Incorporating Various Inorganic Fillers with Particle and Whisker Shapes
Authors: Urayama Hiroshi , Ma Chenghuan , Kimura Yoshiharu
Published: July 2003

Poly(L‐lactide) (PLLA) composites incorporating various inorganic fillers (ifR‐PLA) were prepared by the melt blending technique, and their mechanical and thermal properties were evaluated. The filler types influenced the mechanical properties of ifR‐PLA; for those incorporating particle‐ and whisker‐type fillers the tensile moduli were 3.1–3.7 and 3.7–4.5 GPa, respectively, and the flexural moduli were 4.1–4.8 and 4.8–6.1 GPa. It was found that the tensile strength and modulus, as well as the flexural modulus, of ifR‐PLA incorporating whisker‐type fillers increased in proportion to the volume percent of the fillers (Vf). The flexural strength of ifR‐PLA incorporating 9Al2O3 · 2B2O3 whiskers showed a similar increase, while that of ifR‐PLA incorporating CaCO3 whiskers showed a decrease with increasing Vf. This difference may be because the 9Al2O3 · 2B2O3 with its large aspect ratio kept its original fibrous shape, while the CaCO3 lost its fibrous shape during the blending process. However, the reinforcing effect of these fillers was relatively low compared with that known for the corresponding composites of the conventional polymeric materials, probably because of the poor surface adhesion of PLLA to the fillers.

Comparison of effect on storage moduli of different fillers.

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Comparison of effect on storage moduli of different fillers.
The Cross‐Linking of Polyurethane Incorporated with Starch Granules and their Rheological Properties: Influences of Starch Content and Reaction Conditions
Authors: Ha Seung‐Kyu , Broecker Hans‐Christoph
Published: July 2003

Two series of polyurethanes were synthesized using one‐ and two‐step reactions in a bulk phase at 175 °C with polycaprolactone diol, butane‐1,4‐diol, and 4,4‐diphenylmethane diisocyanate (MDI) in a suspension of starch granules to observe cross‐linking phenomena. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) analysis, and complex viscosity η*(ω), storage G′(ω), and loss‐modulus G″(ω) as rheological measurements, were carried out to characterize the cross‐linking in the polyurethane incorporated with starch. SEM micrographs indicated that grafted polyurethane was cross‐linked between starch granules forming a three‐dimensional network. The plots of η* against ω, and log G′ against log G″ showed that the starch content increased cross‐linking, so as to induce gelation (G′ ≥ G″). However, the cross‐linked networking was decreased over the higher range of starch contents (> 33 wt.‐% for the low hard‐segment series, psb2m3 and > 27 wt.‐% for the high hard‐segment series, psb4m5). Cross‐linking is also enhanced in the high hard‐segment series compared to the low hard‐segment series. Increasing the catalyst concentration also enhanced the cross‐linking inside of the polyurethane phase.

Plots of η* against ω for p7s3b4m5(OSR C0.01) and p7s3b4m5(TSR C0.01).

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Plots of η* against ω for p7s3b4m5(OSR C0.01) and p7s3b4m5(TSR C0.01).
Mechanistic Investigation into the Unique Orientation Textures of Poly(vinylidene fluoride) in Blends with Nylon 11
Authors: Li Yongjin , Kaito Akira
Published: July 2003

Self‐seeded crystallization experiments were carried out to detect the mechanism of the unique orientation behavior of poly(vinylidene fluoride) (PVDF) in oriented PVDF/nylon 11 blends. It was found that primary nuclei have no effects on the final orientation textures adopted by PVDF. The results show that the PVDF crystal orientation in the oriented blends is determined in the early stage of crystal growth, thus a trans crystallization mechanism is preferred.

Isothermal crystallization kinetics for the self‐seeded and non‐self‐seeded crystallization at 145 °C.

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Isothermal crystallization kinetics for the self‐seeded and non‐self‐seeded crystallization at 145 °C.
An Improved Catalytic Method for Alkoxyamine Synthesis – Functionalized and Biradical Initiators for Nitroxide‐Mediated Radical Polymerization
Authors: Bothe Marc , Schmidt‐Naake Gudrun
Published: July 2003

Mn(salen)Cl was applied as a low‐cost catalyst for the formation of alkoxyamines from nitroxides and substituted styrenes. These “unimolecular initiators” for nitroxide‐mediated radical polymerization (NMRP) were synthesized using 2,2,6,6‐tetramethyl‐1‐piperidine‐1‐oxyl and 2,2,5‐trimethyl‐4‐phenyl‐3‐azahexane‐3‐oxyl. Functionalized alkoxyamines were obtained from 4‐vinylbenzyl chloride and 4‐vinylbenzyl alcohol. The divinyl compound 1,2‐bis(4‐vinylphenyl)ethane was converted to an alkoxyamine monomer and to bisaminooxy compounds, which can be used as “biradical initiators” for NMRP.

Formation of alkoxyamines using Mn(salen)Cl as the catalyst.

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Formation of alkoxyamines using Mn(salen)Cl as the catalyst.
Characterization of Chlorine‐, Amine‐ and Acrylate‐Functionalized TEMPO‐Capped and Bis‐TEMPO‐Capped Polystyrenes Using MALDI‐TOF MS
Authors: Bartsch Andreas , Dempwolf Wibke , Bothe Marc , Flakus Silke , Schmidt‐Naake Gudrun
Published: July 2003

Chlorine‐functionalized TEMPO‐capped polystyrenes were investigated using the matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) technique. Amine‐ and acrylate‐functionalized agents and bifunctional TEMPO‐capped polystyrene were also analyzed to demonstrate the applicability of this method. Using this technique allowed to analyze the conversion of the chlorine function to an acrylate function, which was previously difficult to detect with other methods.

MALDI‐TOF mass spectrum of a polystyrene described in this article, as obtained with DHB as the matrix.

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MALDI‐TOF mass spectrum of a polystyrene described in this article, as obtained with DHB as the matrix.
Correlation between Polymer Particle Size and in‐situ NIR Spectra
Authors: Reis Marlon M. , Araújo Pedro H. H. , Sayer Claudia , Giudici Reinaldo
Published: July 2003

This work describes the estimation of polymer particle size from NIR spectra collected in situ and online in an automated reactor. A good linearity between spectra and average polymer particle diameter is found. The multivariate linear model is also tested with an independent data set not used in the model fitting. Despite varying monomer and polymer concentrations and temperature changes along the process, the average particle sizes are well predicted and can be monitored by NIR spectroscopy during emulsion polymerization reactions.

Evolution of average particle diameter with polymer content for three different BA/Sty semi‐continuous emulsion polymerization reactions. Open symbols correspond to spectra used in the model fitting and solid symbols to the test data set. The different symbol types correspond to the three different reactions.

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Evolution of average particle diameter with polymer content for three different BA/Sty semi‐continuous emulsion polymerization reactions. Open symbols correspond to spectra used in the model fitting and solid symbols to the test data set. The different symbol types correspond to the three different reactions.
Ring and Disk‐Like CdSe Nanoparticles Stabilized with Copolymers
Authors: Wagih Fahmi Amir , Oertel Ulrich , Steinert Volker , Froeck Christian , Stamm Manfred
Published: July 2003

CdSe nanoparticles stabilized with the amphiphilic diblock copolymer polystyrene‐block‐poly(4‐vinylpyridine) were spread from toluene dispersion on the water surface. Monolayers could be transferred onto solid substrates using the Langmuir‐Blodgett technique. By means of atomic force and scanning electron microscopy highly symmetric ring and disk‐like structures with diameters ranging between 150 nm and 1200 nm were observed.

AFM image of a mixed monolayer of copolymer 12 and CdSe nanoparticles stabilized with polystyrene‐block‐poly(4‐vinylpyridine).

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AFM image of a mixed monolayer of copolymer 12 and CdSe nanoparticles stabilized with polystyrene‐block‐poly(4‐vinylpyridine).
New Star‐Shaped Metallo‐Polymeric Chromophores
Authors: Viau Lydie , Even Michael , Maury Olivier , Haddleton David M. , Le Bozec Hubert
Published: July 2003

The synthesis of new star‐shaped polymers, prepared by atom transfer radical polymerization of methyl methacrylate with tris(dialkylaminostyryl‐2,2′‐bipyridine) zinc(II) and iron(II) metalloinitiators, is reported. Their thermal and optical (absorption and emission) properties are discussed.

Structure of the star‐shaped polymers.

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Structure of the star‐shaped polymers.
Alternating Diene Metathesis Polycondensation (ALTMET) – A Versatile Tool for the Preparation of Perfectly Alternating AB Copolymers
Authors: Demel Sandra , Slugovc Christian , Stelzer Franz , Fodor‐Csorba Katalin , Galli Giancarlo
Published: July 2003

Perfectly alternating copolymers can be synthesised by reacting diacrylates with terminal dienes using alternating diene metathesis polycondensation (ALTMET). This novel method is very versatile and allows preparation of diverse structures of polymers, including main‐chain liquid crystalline polymers.

Main‐chain liquid crystalline polymer obtained by ALTMET.

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Main‐chain liquid crystalline polymer obtained by ALTMET.
State‐of‐the‐Art and Future of Combinatorial Polymer Research: 2nd DPI Workshop on Automated Synthesis and High‐Throughput Experimentation in Polymer and Materials Research
Authors: Schubert Ulrich S. , Meier Michael A. R.
Published: July 2003

This section contains reports on topical conferences. Reports are usually written at the request of the editorial office, but unsolicited contributions are also welcome. Suggestions should be sent to the editorial office of the Macromolecular journals, preferably by E‐mail to macromol@wiley‐vch.de.