bluuebunny/crossref_metadata_2025 huggingface dataset:
Miscibility of phenoxy polymer/polyacrylate blends
Authors: Wu Chengpei , Wu Yiliang , Zhang Ruiyun
Published: April 2003

The miscibility of blends of phenoxy polymer 1 from bisphenol A and epichlorohydrin and polyacrylates is studied using differential scanning calorimetry (DSC) and Fouriertransform infrared (FTIR) spectroscopy. The DSC curves show that poly(alkyl acrylate)s are immiscible with phenoxy. IR spectra show that there exists weak hydrogen‐bonding interaction between poly(methyl acrylate) and phenoxy. The miscibility behavior of various phenoxy/polyacrylate blends cannot be satisfactorily explained by a non‐hydrogenbonded solubility parameter approach. It can be better explained by the polar and nonpolar solubility parameter approach.
Polymerization of propene with enantiomorphic site catalysts, 1. A statistical analysis
Authors: Di Silvestro Giuseppe , Sozzani Piero , Terragni Alberto
Published: April 2003

Recently we proposed a stereochemical classification of stereorigid metallocene catalysts according to their symmetry; statistical models of increasing complexity for the polymerization of propene based on the alternating mechanism have been developed. The general model agrees with the alternating mechanism and accounts for the most important stereochemical error (skipped insertion) and for the effect of the solvent and of polymerization temperature. Analysis of literature data of pentad concentrations for syndiotactic polypropylenes shows that the skipped insertion is more probable at high polymerization temperature, at low monomer pressure and in polar solvents.
Influence of the stretching rate on the transition front structure of uniaxially deformed isotactic poly(propylene)
Authors: Alonso Matilde , Rodríguez‐Cabello José Carlos , Merino Juan Carlos , Pastor José Maria
Published: April 2003

Recent models on the melting process of polymer crystals allow the study of semicrystalline polymer structures by calorimetric (DSC) measurements. In particular, this work is devoted to the study of those changes occurring during the deformation process of isotactic poly(propylene) samples along the transition front. By observing the evolution of the parameter of intrachain melting cooperativity in comparison with lamellar thickness, it has been possible to characterise the birth and further evolution of double fold molecules, totally extended polymer chains connecting two adjacent crystallites in the fibrillar structure, “taut tie molecules”. Furthermore, those structural changes depend on the stretching conditions. In general, low rate promotes high lamellar fragmentation and the presence of a small number of taut tie molecules. On the contrary, at higher rates crystallites coming from the original lamella show bigger size and a higher number of tie molecules are achieved.
MALDI‐TOF mass spectrometry in polymer analytics, 2. Molecular weight analysis of rigid‐rod polymers
Authors: Räder Hans Joachim , Spickermann Jochen , Kreyenschmidt Martin , Müllen Klaus
Published: April 2003

Molecular weight analysis of rigid‐rod polymers by gel permeation chromatography (GPC) is known to give overestimated values if polystyrene is used for calibration. In this work matrix‐assisted laser desorption/ionisation time of flight (MALDI‐TOF) mass spectrometry was applied for the first time toward direct molecular weight determination of a rigid‐rod type tetrahydropyrene (THP) polymer. The obtained results were supported by investigation of a homologous series of GPC‐separated oligomers with the respective structure. As opposed to common MALDI‐TOF mass spectra, monodisperse THP oligomers reveal two unusual facts: (i) Beside the formation of molecular ions fragmentation also takes place. (ii) The radical ions are detected instead of cationised species. The fully characterised THP oligomers were also used to calibrate the GPC measurements of the THP polymers. The number‐average molecular weight (M̄n), weight‐average molecular weight (M̄w) and polydispersity (M̄w/M̄n) data obtained from the oligomer‐calibrated GPC compare well to those values measured by MALDI‐TOF mass spectrometry.
Thermal behavior and spherulitic superstructures of SBC triblock copolymers based on polystyrene (S), polybutadiene (B) and a crystallizable poly(ε‐caprolactone) (C) block
Authors: Balsamo Vittoria , von Gyldenfeldt Friederike , Stadler Reimund
Published: April 2003

The dynamic crystallization and the melting behavior of polystyrene‐block‐poly(ε‐caprolactone) (PS‐b‐PCL, short notation SC), polybutadiene‐block‐poly(ε‐caprolactone) (PB‐b‐PCL, BC) and polystyrene‐block‐polybutadiene‐block‐poly(ε‐caprolactone) (PS‐b‐PB‐b‐PCL, SBC) have been studied using differential scanning calorimetry. The copolymers with high molecular weight exhibit microphase separation into microphases consisting of polystyrene, polybutadiene and poly(ε‐caprolactone) and partial crystallization of the corresponding PCL block. The crystallization occurs at temperatures below the PS glass transition. Depending on the block copolymer composition, crystallization takes place through a combination of heterogeneous and homogeneous nucleation. Isothermal crystallization was studied in order to determine the equilibrium melting point, Tm0, of the PCL block, which depends on the weight ratio wPB: wPCL. The crystallization kinetics was analyzed in terms of Avrami equation. A general decrease in the overall crystallization rate in the block copolymers relative to the equivalent PCL homopolymer was found. Additionally, the growth rate of the spherulites was followed using polarized optical microscopy. Depending on the composition and flexibility of the block connected to PCL, some copolymers showed ring‐banded spherulites.
Synthesis and thermal stability of oligourethanes based on the cycloaliphatic diisocyanate trans,trans‐4,4′‐methylenebis(cyclohexylisocyanate)
Authors: Steinlein Christian , Hernandez Laurie , Eisenbach Claus D.
Published: April 2003

The synthesis of molecularly uniform and isomerically pure oligourethanes is described. The compounds are models for the hard segments in polyurethane elastomers based on the aliphatic trans,trans‐4,4′‐methylenebis(cyclohexylisocyanate) (ttHMDI)/butanediol system. The thermostability of the urethanes was determined by differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and temperature‐dependent FT‐IR spectroscopy. The aliphatic urethane group was found to be more stable than urethanes based on the corresponding aromatic 4,4′‐methylenebis(phenylisocyanate) (MDI). The stability also depends on the physical properties and morphology of the oligourethane. The ttHMDI urethane group does not decompose up to the individual melting point of the oligomer, whereas in aromatic MDI diisocyanate systems decomposition occurs already significantly below the melting; the MDI‐specific transurethanization is not observed in the ttHMDI‐based urethanes.
Formation of macrocyclic polymers by intramolecular coupling of α,ω‐difunctional precursors. Numerical evaluations
Authors: Dong Dahai , Hogen‐Esch Thieo E. , Shaffer J. Scott
Published: April 2003

The end‐to‐end cyclization reaction of living monodisperse α,ω‐dianion precursors with difunctional electrophiles (EX2) in the presence of partial anion termination is described. A computer simulation was developed to establish the relationship among the initial concentration, the molecular weight of the dianion precursor, the extent of anion termination, and the yield distribution for all of the cyclic and linear polymer species. A master curve is calculated allowing the determination of the macrocycle yield as a function of MW and concentration of the dianion precursor, and degree of anion termination.
Dilute solution properties of polybutadiene modified by 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione
Authors: Bica Clara I. D. , Burchard Walther , Stadler Reimund
Published: April 2003

The dilute solution properties of 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione‐modified polybutadienes were studied in tetrahydrofuran by static and dynamic light scattering and compared with those from unmodified polybutadiene chains. For the unmodified polymer, the scaling laws were established and the coil interpenetration parameter k was determined in the thermodynamically good solvent tetrahydrofuran; the chains exhibited common flexible chain behavior. For the modified polybutadiene, the results indicate at infinite dilution a weak extent of intermolecular crosslinking via the urazole groups, coupled with a very high extent of intramolecular ring formation. In order to evaluate the fraction of rings, an analysis of the association equilibrium by Fourier‐transform infrared spectroscopy (FTIR) was performed in the absorption region of the carbonyl stretching vibration of the urazole ring.
Polynorbornene: synthesis, properties and simulations
Authors: Haselwander Thomas F. A. , Heitz Walter , Krügel Stefan A. , Wendorff Joachim H.
Published: April 2003

The vinylic polymerization of norbornenes upon catalysis with Pd2+ complexes with norbornylnitrile as ligands is reported. The polynorbornenes (M̄w = 106) display a set of unique properties including a dense packing in the amorphous state, high glass transition temperatures, large refractive index, low birefringence and significant brittleness. To test the concept that these properties can be traced back to the conformational constraints of the polymer chains, we performed ab initio calculations, semi‐empirical quantum mechanical calculations and force‐field calculations employing a force field developed by us for polynorbornenes.
Poly(methyl methacrylate)‐supported isoxazolinium permanganates: preparation and application as oxidising reagents
Authors: Shiney Abraham , Rajan Padinjare Kochampilly , Sreekumar Krishna Pillai
Published: April 2003

Divinylbenzene (DVB), ethylene glycol dimethacrylate (EGDMA) and N,N′‐methylenebis(acrylamide) (N,N′MBA) crosslinked poly(methyl methacrylate) (PMMA) was functionalised to generate isoxazolinium permanganate resins. These resins were found to selectively oxidise alcohols to the corresponding carbonyl compounds in appreciable yields. These reagents were found to possess the characteristics of polymeric reagents including operational simplicity.
New polyurethanes based on 4,4′‐diphenylmethane diisocyanate and 1,4:3,6 dianhydrosorbitol, 2. Synthesis and properties of segmented polyurethane elastomers
Authors: Cognet‐Georjon Estelle , Méchin Francoise , Pascault Jean‐Pierre
Published: April 2003

1,4:3,6‐Dianhydrosorbitol (DAS) was used as chain extender in the preparation of new segmented polyurethane elastomers, based on polyoxytetramethylene or hydrogenated polybutadiene soft segments and 4,4′‐diphenylmethane diisocyanate (MDI). These materials exhibit a two‐phase microstructure, due to the thermodynamic immiscibility between hard and soft segments, which results in an elastomeric behavior over a wide temperature range. The thermal and dynamic mechanical properties of various formulations were then examined and related to the complex morphology of the corresponding (often semi‐crystalline) materials. DAS leads to particularly stiff hard segments and provides longer rubbery plateaux, compared with a classical diol such as 1,4‐butanediol. Phase separation is favored by longer and less polar soft segments. In any case, the structure of the materials strongly depends on the composition and synthesis procedure (bulk polycondensation leads to more heterogeneous samples), and most of all on the thermal history of the samples. This latter behavior is related to the existence of a possible order‐disorder transition (ODT) which explains the change‐over from a two‐phase to a one‐phase system after specific annealing experiments.
Synthesis and characterization of new polyamides and polyimides derived from (E)‐9‐[β‐(2,4‐diaminophenyl)vinyl]anthracene
Authors: Fomine Sergei , Sànchez Carlos , Fomina L. , Alonso J. C. , Ogawa Takeshi
Published: April 2003

A new anthracene‐containing diamine, (E)‐9‐[β‐(2,4‐diaminophenyl)vinyl]anthracene, was prepared and used for the synthesis of a series of polyamides and polyimides by low temperature solution polycondensation. The polymers were highly amorphous, soluble in aprotic solvents and gave films with good optical quality on spin‐casting. The polymers showed 10% weight loss at a temperature of 415–460°C under nitrogen. The polymers exhibited an intense luminescence in the region of 450–500 nm due the emission from the excited state of the diamine moiety. It was shown that charge‐transfer (CT) interactions in polyimides were negligibly small in both the ground and the excited state, probably due to the bulky diamine fragment together with the rigid polymer backbone.
Anionic graft copolymerization of methyl methacrylate with lithium diisopropylamide‐treated poly(methacrylate)s
Authors: Akutsu Fumihiko , Inoki Mari , Takahagi Atsuko , Kasashima Yoshio , Naruchi Kiyoshi
Published: April 2003

The anionic grafting of methyl methacrylate onto several lithium diisopropylamide (LDA)‐treated polymers of methacrylates, such as 2‐acetoxyethyl methacrylate (1), 2‐propionyloxyethyl methacrylate (2), 2‐isobutyryloxyethyl methacrylate (3), 1‐methoxy‐carbonylethyl methacrylate (4), and methoxycarbonylmethyl methacrylate (5), or onto the LDA‐treated copolymers of the methacrylates with styrene was investigated. Graftings onto homopolymethacrylates and onto the copolymers of 1 and 2 with styrene did not occur due to the deactivation of the macromolecular lithium enolate by side reactions. Graftings onto copolymers P‐3, P‐4 and P‐5, from methacrylates 3, 4 and 5 with styrene, however, proceeded. The relative grafting efficiency decreases in the following order: P‐3 > P‐4 > P‐5. The grafting is highly influenced by the aggregation behavior of the macromolecular lithium enolates and the side reactions deactivating the lithium enolate. The aggregation behavior decreases the number of the activated points on the feed polymer, lowers the inititiation rate and the polymerization rate of the grafting, and causes a large polydispersity value (M̄w/M̄n) of the side‐chain poly(MMA).
The substitution effects of donor and acceptor on properties of poly(1,4‐phenylenevinylene) derivatives. Syntheses of poly(2‐methoxy‐5‐methylsulfinyl‐1,4‐phenylenevinylene) and its copolymers
Authors: Yoon Chong‐Bok , Shim Hong‐Ku
Published: April 2003

Electron donor and acceptor substituted poly(2‐methoxy‐5‐methylsulfinyl‐1,4‐phenylenevinylene) (PMMSPV) and a series of copolymers containing 1,4‐phenylenevinylene (PV) units were synthesized via the water‐soluble precursor pathway and cast into films. The electrical conductivity of FeCl3‐doped PMMSPV was 1.5 × 10−4 S ċ cm−1 and the copolymers showed conductivities in the range of 10−4 ∼ 10−1 S ċ cm−1 depending on the copolymer compositions. The second‐order nonlinear optical coefficient of PMMSPV was obtained with second harmonic generation method. The measured d33 value was 1.5 pm/V and gave no decay at 100°C over 40 d.
Structure of polystyrene‐block‐poly(ethylene oxide) diblock copolymer micelles in water
Authors: Jada Amane , Hurtrez Guy , Siffert Bernard , Riess Gérard
Published: April 2003

Micellization in water of two homologous series of AB‐type diblock copolymers, composed of polystyrene (PS) as the A block and poly(ethylene oxide) (PEO) as the B block, were investigated by small‐angle X‐ray scattering (SAXS) and dynamic light scattering (DLS). The copolymers have molecular weights Mn in the range 2 000—34 800, and have in a given series, the same number of repeating units of the PS block, (NPS = 10 and 38), and a variable number of repeating units of the PEO block (NPEO values in the range 23–704). In order to avoid secondary association of micelles, a dialysis technique was used to prepare the micellar systems, in the case of copolymers having high Mn values of the PS block. The experimental micelle properties such as the core radius Rc and the aggregation number N of non‐equilibrium structures, so called “frozen micelles”, obtained by dialysis, were found to be independent of the copolymer characteristics. However, for equilibrium structures, obtained by direct solubilization of the copolymers (NPS = 10) in water, Rc and N were found to decrease with increasing NPEO for the homologous series.
Radically initiated polymerization of a methacryloylamido‐terminated saccharide, 1. Monomer synthesis, homopolymerization and characterizations
Authors: Badey Bérangère , Boullanger Paul , Domard Alain , Cros Philippe , Delair Thierry , Pichot Christian
Published: April 2003

A methacrylamido‐terminated saccharide, 6‐deoxy‐6‐methacryloylamido‐D‐glucopyranose (MAG), was synthesized using a new and easy pathway. Kinetics of the radically initiated solution homopolymerization of this monomer was investigated at 50°C using 4,4′‐azobis(4‐cyanopentanoic acid); the obtained kp/kt1/2 value around 1.0 mol−1/2 ċ L1/2 ċ s−1/2 is indicative of the strong ability of MAG to polymerize (kp and kt being the rate constants of propagation and termination, respectively). The chemical structure of the homopolymer, as analyzed by 13C NMR spectroscopy shows a tacticity which is in favor of a syndiotactic configuration resulting from the bulkiness of the side group. The dimensional characteristics of the polymers were studied by light scattering as an on‐line detection in size exclusion chromatography (SEC). As expected from the kp/kt1/2 value, high weight‐average molecular weights were obtained. The small average radii of gyration were found to reflect a relatively compact structure in water due to inter‐ and intramolecular interactions; viscosity studies in various solvents as well as values of the second virial coefficient corroborate such a behavior which reflects that water is a poor solvent for poly(MAG).
Structure investigations of a crosslinkable main chain liquid crystalline copolyester by infrared spectroscopy, differential scanning calorimetry and wide‐angle X‐ray scattering
Authors: Eichhorn Klaus‐J. , Sahre Karin , Jehnichen Dieter , Tobisch Josef , Häußler Liane
Published: April 2003

FTIR spectroscopy, differential scanning calorimetry (DSC) and wide‐angle X‐ray scattering (WAXS) were used for the characterization of structural properties of a cross‐linkable ternary liquid crystalline (lc) copolyester and its binary model copolyesters. The copolyesters based on itaconoylbis(4‐oxybenzoic acid), sebacoylbis(4‐oxybenzoic acid) and 2‐methylhydroquinone were annealed at different temperatures to analyse the structural changes of mesogenic and spacer segments due to their phase transitions. The results of the DSC and WAXS measurements are useful to explain the small effects in the IR spectra connected with polymer morphology. FTIR spectroscopy is able to provide information about the molecular structure along the polymer chains and also about the interactions between these chains. Micro‐ and macromolecular structures influence the orientation and crosslinking processes in dependence on temperature and time. It was shown that an increase in the ordered state and quality of crystallinity was obtained using different annealing procedures.
Heat capacities of solid, globular proteins
Authors: Zhang Ge , Gerdes Stina , Wunderlich Bernhard
Published: April 2003

In an ongoing effort to understand the thermodynamic properties of proteins, solid‐state heat capacities of poly(amino acid)s of all 20 naturally occurring amino acids and 4 copoly(amino acid)s were previously determined using our Advance Thermal Analysis System (ATHAS). Recently, poly(L‐methionine) and poly(L‐phenylalanine) were further studied with new low‐temperature measurements from 10 to 340 K. In addition, an analysis was performed on literature data of a first protein, zinc bovine insulin dimer C508H752O150N130S12Zn. Good agreement was found between experiment and calculation. In the present work, we have investigated four additional anhydrous globular proteins, α‐chymotrypsinogen, β‐lactoglobulin, ovalbumin, and ribonuclease A. The heat capacity of each protein was measured from 130 to 420 K with differential scanning calorimetry, and the data were analyzed with both the ATHAS empirical addition scheme and a fitting to computations using an approximate vibrational spectrum. For the solid state, agreement between measurement and computation scheme could be accomplished to an average and root mean square percentage error of 0.5 ± 3.2% for α‐chymotrypsinogen, −0.8 ± 2.5% for β‐lactoglobulin, −0.4 ± 1.8% for ovalbumin, and −0.7 ± 2.2% for ribonuclease A. With these calculations, it was possible to link the macroscopic heat capacities to their macroscopic causes, the group and skeletal vibrational motion. For each protein one set of parameters of the Tarasov function, Θ1 and Θ3, represent the skeletal vibrational contributions to the heat capacity. They are obtained from a new optimization procedure [α‐chymotrypsinogen: 631 K and 79 K (number of skeletal vibrators Ns = 3005); β‐lactoglobulin: 582 K and (79 K) (Ns = 2188); ovalbumin: 651 K and (79 K) (Ns = 5008) and ribonuclease A: 717 K and (79 K) (Ns = 1574), respectively]. Enthalpy, entropy, and Gibbs free energy can be derived for the solid state.
New synthesis of a highly active δ‐MgCl2 for MgCl2/TiCl4/AlEt3 catalytic systems
Authors: Di Noto Vito , Bresadola Silvano
Published: April 2003

A good supporting material for Ziegler‐Natta type catalysts was obtained by reaction between powdered metallic magnesium and 1‐chloro‐n‐CmH2m+1 (m = 3–9). This reaction affords a highly disordered form of MgCl2 which was characterized by FT‐IR spectroscopy and powder X‐ray diffraction (XRD) analysis. This MgCl2 form shows a crystallographic disorder much higher than that exhibited by the products obtained following the commercial activation procedures of α‐MgCl2, either mechanical or chemical. As shown by the XRD spectra, the synthetized MgCl2 is characterized by the typical structure of the δ‐form. Therefore, this MgCl2 form, in view of its highly disordered structure, appears as a promising material for the preparation of active supported Ziegler‐Natta type catalysts. Thus, by titanation of the obtained δ‐MgCl2 we have prepared some supported catalysts which have been tested in the slurry propene polymerizations, showing high activity (136000–138000 gPP/gTi) and good stereoselectivity (82–88% I.I.).
Ordering fractal aggregates of liquid mixtures
Authors: Zhu Peng Wei
Published: April 2003

Mixtures of liquid paraffin and polydimethylsiloxane (PDMS) were studied by small angle X‐ray scattering. The scattering patterns exhibited a single peak in finite angles and deviated from Porod's law in larger angles. The fractal dimension of mixtures was determined by power‐law analysis. The whole scattering curves were fitted well by a scattering formula. The average size and correlation distance of the aggregates were calculated from a correlation function. The fractal dimension and the static parameters were found to decrease with increasing the temperature and PDMS concentration.
Concise synthesis and characterization of 30‐membered macrocyclic monomer for poly(ether ether ketone)
Authors: Chen Mingfei , Fronczek Frank , Gibson Harry W.
Published: April 2003

A 30‐membered macrocyclic arylene ether ketone monomer for poly(ether ether ketone) was synthesized by a two‐step method. The first step involves synthesis of a long bisphenol from hydroquinone and 4,4′‐difluorobenzophenone. The second step is the cyclization of the bisphenol with 4,4′‐difluorobenzophenone. The pure macrocycle was isolated and characterized by IR, NMR, MS, TGA and DSC techniques. The X‐ray structure of the macrocycle was also determined.
Low‐temperature structural relaxation in poly(alkyl methacrylate)s and related polymers probed by photochemical hole burning
Authors: Tanaka Satomi , Machida Shinjiro , Yamashita Takashi , Horie Kazuyuki
Published: April 2003

Excursion temperature dependences of spectral hole profiles in photochemical hole burning for free‐base systems porphyrin/poly(alkyl methacrylate)s are investigated to see the relationship between relaxation properties and chemical structure of the polymers. The irreversible change in hole width is a characteristic of each polymer and is very similar to the relaxation behavior measured mechanically and dielectrically. Poly(methyl methacrylate) (PMMA) shows the highest thermal stability of hole profiles among the polymers presently studied with no marked appearance of local relaxation at 20–100 K. Poly(ethyl methacrylate) (PEMA) and poly(isopropyl methacrylate) (PiPMA) show an increase in hole width even at 20 K with a plateau region at 50–70 K, which is attributed to the rotation of the ethyl or isopropyl group around the CO bond. Polymers which contain more than two serial methylene groups in the side chains (poly(propyl methacrylate), poly(butyl methacrylate), poly(isobutyl methacrylate)) show a similar relaxation behavior around 50–60 K, suggesting the onset of the rotation of the terminal ethyl or isopropyl group in the ester side chain around the CC bond. Low‐density polyethylene (LDPE) shows a similar excursion‐temperature dependence probably due to the existence of branched oligomethylene side chains. The relaxation behavior is independent of the nature of chromophores, which indicates that irreversible hole broadening is controlled mainly by the local motion of the host matrices.
p‐Toluenesulfonyl esters in cellulose modifications: acylation of remaining hydroxyl groups
Authors: Heinze Thomas , Rahn Kerstin , Jaspers Mariet , Berghmans Hugo
Published: April 2003

New soluble cellulosics with interesting molecular structures and properties were obtained by the acylation of remaining hydroxyl groups of pure, homogeneously synthesized p‐toluenesulfonylcelluloses of different degree of p‐toluenesulfonyl (tosyl) substitution (DSTosyl) ranging from 0.5 to 2.0 in pyridine and sodium acetate as a catalyst with various aliphatic, aromatic and unsaturated carbonic acid anhydrides as well as isocyanates. The reactions proceed homogeneously and yield products of a high degree of acyl substitution (DSAcyl). In the case of acetic and propionic acid anhydrides a complete functionalization of all free hydroxyl groups was achieved. Even with fatty acid anhydrides like stearic anhydride 94% of the remaining OH groups were acylated. The new polymers are readily soluble in common organic solvents such as acetone, dimethyl sulfoxide, N,N‐dimethylacetamide, N,N‐dimethylformamide, and tetrahydrofuran. They are solution processible film‐ and membrane‐forming materials. Tosylcellulose phthalates and trimellitates of appropriate DSTosyl and DSAcyl values are even soluble in aqueous NaOH. Compared to the original tosylcelluloses, the thermal degradation of tosylcellulose acylates was initiated at nearly the same temperature independent of type and degree of esterification providing an equal DSTosyl. The stability found is sufficiently high for processing.
Structures of polyethylene and copolymers of ethylene with 1‐octene and oligoethylene produced with the Cp2ZrCl2 and [(C5Me4)SiMe2N(t‐Bu)]TiCl2 catalysts
Authors: Soga Kazuo , Uozumi Toshiya , Nakamura Shuji , Toneri Tatsuya , Teranishi Toshiharu , Sano Tsuneji , Arai Takashi , Shiono Takeshi
Published: April 2003

Polymerization of ethylene and copolymerizations of ethylene with 1‐octene and oligoethylene having a vinyl end group were conducted with Cp2ZrCl2 and [(C5Me4)SiMe2N(t‐Bu)]TiCl2a as catalysts, and the structures of the resulting polymers were analyzed in detail. The Cp2ZrCl2 catalyst combined with methylalumoxane (MAO) gives polyethylene with vinyl, vinylidene and trans‐vinylene groups. The use of Al(iC4H9)3/(C6H5)3C · B(C6F5)4 as cocatalyst produces polyethylene predominantly containing trans‐vinylene groups. Polyethylene with vinyl end groups was obtained selectively with [(C5Me4)SiMe2N(t‐Bu)]TiCl2MAO as catalyst. The types and contents of CC double bonds in polyethylene markedly depend upon the metallocene compound as well as as the cocatalyst. In the copolymerizations the [(C5Me4)SiMe2N(t‐Bu)]TiCl2MAO catalyst system, on the other hand, gives poly[ethylene‐co‐(1‐octene)] with a high content of 1‐octene and a polyethylene containing an appreciable amount of long‐side‐chain oligoethylene.
Synthesis of degradable, biocompatible, and tough block‐copolyesterurethanes
Authors: Hirt Thomas D. , Neuenschwander Peter , Suter Ulrich W.
Published: April 2003

We describe the synthesis of micro‐phase‐segregated block‐copolyesterurethanes from telechelic hydroxyterminated poly{[(R)‐3‐hydroxybutyric acid]‐co‐[(R)‐3‐hydroxyvaleric acid]} (PHB‐diol) as “hard segments” (i. e., crystallizable chain sections) and hydroxyterminated poly(ε‐caprolactone)‐diethylene glycol‐poly(ε‐caprolactone) (PCL‐diol) or telechelic hydroxyterminated poly[(adipic acid)‐alt‐(1,4‐butanediol; diethylene glycol; ethylene glycol)] (Diorez®) as “soft segments”, with 2,2,4‐triethylhexamethylene diisocyanate (TMDI) or methyl (S)‐2,6‐diisocyanatohexanoate (LDI). High molecular weights were obtained with or without catalyst, the properties of the polymers depending only slightly on the presence or absence of the catalyst. The materials thus obtained were investigated also with respect to their mechanical properties and it was found that Young's modulus directly depends on the fraction of crystallizable PHB‐diol in the block copolymer while the type of non‐crystallizable segment or diisocyanate had only a minor influence: Generally, the tensile strength increases and the elongation at break decreases with increasing content of PHB‐diol. Around body temperature, these polymers exhibit only mild changes in their mechanical behavior. The chain length of the non‐crystallizable segment indirectly influences the morphology and the mechanical properties of the polymers through changes in the phase‐segregation behavior.
Kinetics of the reaction between alkaline sulfides and aryl dichlorides — model study on 4‐chloro‐ and 4,4′‐dichlorobenzophenones
Authors: Hedhli Lotfi , Lesclingant Christelle , Fradet Alain , Maréchal Ernest
Published: April 2003

The kinetics of the reaction between alkaline sulfides and halogenated aromatic monomers was studied using lithium sulfide and 4‐chlorobenzophenone (1a) and 4,4′‐dichlorobenzophenone (1b) as models. The release of H2S from reaction medium and the possible formation of a compound between sulfide and N‐methyl‐2‐pyrrolidone (NMP) during the preliminary dehydration step are key steps of the reaction. The reaction proceeds following two successive kinetic regimes: a first one where rapid second‐order reactions of sulfide and thiolate with 1a or 1b take place, and a second one where the slow release of sulfide from the compound formed during dehydration is rate determining and therefore governs the molecular weight of final polymer. A good agreement was found between theoretical curves calculated from this kinetic scheme and experimental data, indicating a polymerization mechanism based on an SNAr reaction mechanism.
Thermally induced radical promoted cationic polymerization using a novel N‐allyloxypyridinium salt
Authors: Reetz Ivo , Bacak Vildan , Yagci Yusuf
Published: April 2003

A system consisting of a novel N‐allyloxypyridinium salt and a radical initiator is highly appropriate for the thermal initiation of cationic polymerizations. Radicals formed upon the thermolysis (at 70°C) of initiators as 2,2′‐azoisobutyronitrile or benzoyl peroxide add to the double bond of the pyridinium salt N‐[2‐(ethoxcarbonyl)allyloxy]‐α‐picolinium hexafluoroantimonate (1). Subsequently, the pyridinium salt is fragmented yielding pyridinium‐type radical cations, species able to initiate cationic polymerizations. In the case of the radical initiator phenylazotriphenylmethane (triphenylmethaneazobenzene), the polymerization is extremely rapid, since additionally the triphenylmethyl cation formed by electron transfer initiates the polymerization. The initiation capability of the system described was demonstrated for a number of monomers, such as cyclohexene oxide, butyl vinyl ether and the bifunctional 3,4‐epoxycyclohexylmethyl 3′,4′‐cyclohexanecarboxylate. With the latter, an insoluble polymer network was readily obtained.
Ring‐opening polymerization and copolymerization of a new benzylated 1,6‐anhydro‐3‐azido‐3‐deoxy‐β‐D‐allopyranose and synthesis of amino‐polysaccharides with 1,6‐α‐allopyranosidic structure
Authors: Hattori Kazuyuki , Yoshida Takashi , Uryu Toshiyuki
Published: April 2003

Ring‐opening polymerization of a new anhydro‐hexose monomer having an azido group, 1,6‐anhydro‐3‐azido‐2,4‐di‐O‐benzyl‐3‐deoxy‐β‐D‐allopyranose (A3ABA), was carried out with Lewis acid catalysts to give a stereoregular (1→6)‐α‐D‐allopyranan derivative having the azido group at the C3 position. The number‐average molecular weights and specific rotations were 5.0 × 103 to 24.0 × 103 and +71° to +79°, respectively. Reduction of the azido groups into amino groups by lithium aluminium hydride and subsequent debenzylation of the benzyl group into hydroxyl groups by sodium in liquid ammonia gave 3‐amino‐3‐deoxy‐(1→6)‐α‐D‐allopyranan in good yield. In addition, copolymerization of A3ABA with 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranose (LGTBE) in the various feeds was carried out to afford the corresponding copolymers. The monomer reactivity ratios were calculated with the Kelen‐Tüdős method to be rA3ABA = 0.66 and rLGTBE = 1.67. After reduction of azido groups and deprotection of benzyl groups of the copolymers, new hetero‐polysaccharides having different contents of glucopyranose and 3‐amino‐allopyranose units were obtained.
Syntheses and properties of films from polymer gels based on polymer‐metal complexes
Authors: Bekturov Esen A. , Mamutbekov Galym K.
Published: April 2003

Films of poly(2‐vinylpyridine) (1), poly(allylamine hydrochloride) (2), poly(5‐methyl‐2‐vinylpyridine) (3) and poly(ethyleneimine) (4) with Ag+, Cu2+, Li+ and Ca2+ salts as well as complex transition metal ions [Fe(Cn)6]3− are prepared at the interface boundaries of immiscible solvents. The polymer/metal salt complexes exhibit highly ordered structures and high thermal stabilities as revealed by reduced viscosity, X‐ray diffraction, infrared spectrometry, thermogravimetry, differential thermal analysis as well as measurements of swelling coefficients and electroconductivity. Mole ratios of complex formation of the neat polymers as well as the polymer gels with these salts were found at [polymer] : [salt] = 1, 2, 3 and 4 referring to the repeating units of the polymers. It is suggested that the properties of the films are due to ionic bonds, ion‐coordination bonding, coordination bonds and ion‐dipole interactions between the functional groups of the polymeric hydro‐ and organic gels and the metal ions.
Aggregates of peptide‐containing block copolymers and their interactions with a lipase in aqueous solution
Authors: Naka Kensuke , Yamashita Rie , Nakamura Tohru , Ohki Akira , Maeda Shigeru , Aoi Keigo , Tsutsumiuchi Kaname , Okada Masahiko
Published: April 2003

Peptide‐containing block copolymers poly(N‐acetyliminoethylene)‐block‐poly(L‐phenylalanine)s (1) form water‐soluble large aggregates in water due to the hydrophobic and hydrogen‐bonding nature of the poly(L‐phenylalanine) block. The solution properties were studied by size exclusion chromatography, dynamic light scattering, 1H NMR spectroscopy, and transmission electron microscopy. The results were compared with those of the block copolymers poly(N‐acetyliminoethylene)‐block‐poly(N‐benzoyliminoethylene)s (2) as analogous structures of poly(L‐phenylalanine). The peptide‐containing block copolymers 1 form aggregates in water even though only short segments of poly(phenylalanine) are provided. The hydrogen‐bonding character of the amide bond in the poly(phenylalanine) segment may induce strong interactions with each polymer chain in water. The interaction of Lipase P with the polymer aggregates in water was studied by means of size exclusion chromatography. The aggregates have a strong capability of incorporating Lipase P and largely increase the hydrolysis activity of Lipase P against p‐nitrophenyl propionate compared with free Lipase. The guest‐binding ability of 8‐anilino‐1‐naphthalenesulfonic acid for the polymer aggregates was also studied.
“Living” free radical polymerization of macromonomers: Preparation of well defined graft copolymers
Authors: Hawker Craig J. , Mecerreyes David , Elce Edmund , Dao Julian , Hedrick James L. , Barakat Ibrahim , Dubois Phillippe , Jérôme Robert , Volksen Willi
Published: April 2003

Well defined graft copolymers have been synthesized by a nitroxide‐mediated “living” free radical process using pre‐formed macromonomers. Analysis of the graft systems revealed that the macromonomer was efficiently incorporated into the polymeric backbone to give block copolymers of controlled molecular weight and narrow polydispersities. An added benefit of the “living” free radical process is that macromonomers, such as polylactide or polycaprolactone, which contain reactive functional groups can be used to form novel graft systems using this approach. Functionalized monomers or polymeric initiators were also used in the copolymerization mixture to give graft systems with a variety of functional groups attached to the backbone.
Synthesis of poly[isobutyl (2S,3R)‐3‐benzyloxyaspartate]
Authors: García‐Martín María de Gracia , de Paz María Violante , Galbis Juan Antonio
Published: April 2003

A chiral poly(3‐substituted isobutyl D‐aspartate) 12 was synthesized by polymerization of the chiral β‐lactam 11 derived from D‐glyceraldehyde. The new polyamide was characterized by elemental analyses, and infrared, 1H‐ and 13C nuclear magnetic resonance spectroscopies. The molecular weight was estimated as 543 000 and 230 000 on the basis of viscosimetric measurements and gel‐permeation chromatography, respectively. Polyamide 12 is soluble in a variety of organic solvents including chloroform.
Syntheses of polysiloxane‐supported zirconocene catalysts and application to ethene polymerization
Authors: Arai Takashi , Ban Hoang The , Uozumi Toshiya , Soga Kazuo
Published: April 2003

Polysiloxanes with bisindenyl, bisfluorenyl, and bis(1,2,3,4‐tetramethyl)cyclopentadienyl side groups were synthesized by condensation of the corresponding dichlorosilane compounds and water to obtain supported ziroconocene catalysts. The polymerization of ethene was conducted over these catalysts combined with methylalumoxane. The polymerization activity depends markedly upon the substituents and decreases in the order: bisindenyl ≫ bisfluorenyl ≫ bis(1,2,3,4‐tetramethylcyclopentadienyl). All the supported catalysts give linear polyethene with fairly high molecular weights. The catalyst with bisindenyl groups was found to be composed of a toluene‐soluble and a toluene‐insoluble fraction. The polymerization profile (activity versus time curve) was analyzed with the toluene‐soluble and ‐insoluble fraction as well as the corresponding homogeneous system. The homogeneous system, which exerts the highest activity in the initial phase, was completely deactivated after several hours whereas the activity of the supported catalyst, especially of the toluene‐insoluble fraction, was unchanged during 12 h even at 70°C. Polysiloxanes with different content of bisindenyl groups were also synthesized via the co‐condensation with dimethyldichlorosilane and applied as the carrier. However, the activity per Zr atom decreases remarkably with an increase in dimethylsilane units.
Step growth polymerization via tandem ene and diels‐alder reactions
Authors: Mallakpour Shadpour E. , Kolshorn Heinz , Schollmeyer Dieter , Stadler Reimund
Published: April 2003

In contrast to other electron deficient enophiles or dienophiles which react with 1,4‐cyclohexadiene (1,4‐CHD) under aromatization, 1,2,4‐triazoline‐3,5‐diones react in a defined reaction sequence. In a first step the 1,4‐cyclohexadiene reacts via an ene‐reaction. The intermediately formed substituted 1,3‐cyclohexadiene immediately reacts in a Diels‐Alder reaction. The regiochemistry of the Diels‐Alder reaction is controlled by the solvent polarity. This reaction sequence can be used to synthesize polymers. Low‐molarmass model compounds were synthesized to elucidate the stereochemistry of the polymers. By varying the bistriazolinedione, polymers with backbones of different rigidity are available.
Block copolymerization of triphenylmethyl methacrylate with other methacrylates using (−)‐sparteine/9‐fluorenyllithium as an initiator
Authors: Liu Weihong , Yang Yonghong , Chen Chuanfu , Chen Yongming , Xi Fu
Published: April 2003

Diblock and triblock copolymerization of triphenylmethyl methacrylate (TrMA) with methyl methacrylate (MMA), butyl methacrylate (BuMA), benzyl methacrylate (BzMA) or diphenylmethyl methacrylate (DPMMA) in the presence of the chiral anionic complex initiator, (−)‐sparteine/9‐fluorenyllithium, were investigated. The resulting block copolymers show high specific rotation and were characterized by means of gel‐permeation chromatography, scanning electron microscopy, nuclear magnetic resonance, circular dichroism spectra and thermal analysis.
Thermal treatment of poly[ethylene‐alt‐2,2‐bis(1,4‐phenylene)propane carbonate]: A reinvestigation
Authors: Berti Corrado , Bonora Virna , Fiorini Maurizio , Pilati Francesco , Sweileh Bassam
Published: April 2003

The final product of the thermal treatment of poly[ethylene‐alt‐2,2‐bis(1,4‐phenylene)‐propane carbonate] (polymer 1) at 280°C under vacuum was characterized as a random copolymer containing both ether and carbonate groups and not as pure bisphenol A polycarbonate as reported previously by other authors. Infrared and NMR spectroscopy were used to detect the changes of the polymer structure during the thermal treatment; the resulting polymers were also characterized by measuring their intrinsic viscosity. During the thermal treatment different reactions occur: exchange reactions (which would lead to a random copolycarbonate), and intramolecular elimination of ethylene carbonate and carbon dioxide. This last elimination is responsible for the formation of ether groups which, being stable under the reactions conditions, prevent the complete elimination of the aliphatic moieties. The final random copolymer was also prepared by reacting pure bisphenol A polycarbonate (PC) and ethylene carbonate; this confirms the occurrence of exchange reactions, which lead to a random copolycarbonate having a structure similar to the polymer deriving from polymer 1. Surprisingly, in the presence of a typical exchange reaction catalyst such as dibutyltin dimethoxide or titanium tetrabutoxide, the final product of the thermal treatment of polymer 1 is pure PC.
Polymers from multifunctional isocyanates, 12. Alternating copolymers from isocyanatoalkenes and electron deficient 1,2‐disubstituted alkenes
Authors: Mormann Werner , Schmalz Kerstin , Grimm Axel
Published: April 2003

The free radical copolymerization of the electron rich monomers vinyl isocyanate, isopropenyl isocyanate, trans‐1‐propenyl isocyanate, and trans‐β‐styryl isocyanate with maleic anhydride has been investigated. The copolymerization behaviour of different electron deficient monomers like maleic anhydride, citraconic anhydride, N‐phenylmaleimide and fumaronitrile with isopropenyl isocyanate or vinyl isocyanate has also been studied. Polymerization in benzene is accompanied by precipitation of polymer, while the polymerization proceeds in solution in 2‐butanone. Alternating copolymers were obtained in all cases. The alternating behaviour is favoured by the very low tendency of all monomers except maleimides to undergo homopolymerization. From the reaction with maleic anhydride the reactivity of electron donating monomers was found to be vinyl isocyanate ≈ isopropenyl isocyanate ≫ β‐styryl isocyanate ≈ ≫ 1‐propenyl isocyanate, while the reactivity of electron accepting monomers with isopropenyl isocyanate was: maleic anydride > N‐phenylmaleimide > fumaronitrile.
New monomers and photosensitive polymers: the synthesis and polymerization of 2‐, 3‐ and 4‐vinylphenyl thiocyanate
Authors: Kern Wolfgang , Hobisch Josefine , Hummel Klaus
Published: April 2003

The new monomers 2‐vinylphenyl thiocyanate (6a), 3‐vinylphenyl thiocyanate (6b) and 4‐vinylphenyl thiocyanate (6c) were prepared from 2‐, 3‐ and 4‐aminoacetophenone (1a–c) as starting materials. The homopolymers (7a–c) and the copolymers 8a–c of the monomers 6a–c with styrene were prepared via free radical polymerization. The polymers, which were obtained as fully soluble and stable materials, were sensitive to UV light. The crosslinking of the polymers 7a–c and 8a–c was investigated under 254 nm UV radiation. From the sensitivity curves of the polymers, gel doses Eg between 2,6 and 95 mJ · cm−2 were derived.
Transmission electron microscopy of free standing thin films of poly(ether ether ketone)
Authors: Plummer Christopher John George , Kausch Hans‐Henning
Published: April 2003

Free standing thin films of poly(ether ether ketone) crystallized in situ by heating from the glassy state have been shown to be suitable for high resolution transmission electron microscopy lattice imaging. Films mounted on coarse‐mesh copper grids could also be observed in the deformed state, allowing lattice imaging of regions of strain induced crystallization at temperatures in the neighbourhood of the glass transition temperature.
Influence of configuration upon heterogeneity in anisotropic glasses as determined by thermally stimulated current
Authors: Liu Shur‐Fen , Lee Yu‐Der
Published: April 2003

Thermally stimulated current (TSC) as well as differential scanning calorimetry (DSC) was used to determine the glass transition temperature of anisotropic glasses for semiflexible polyesters with polymethylene spacers. The highly sensitive technique of thermal‐windowing polarization or relaxation map analysis (RMA) was used to further study the relaxation behavior of the anisotropic glasses as well as the heterogeneity of the samples. Experimental results indicate that phase separation is dependent upon the length of the polymethylene chain, i.e., the configuration of polymethylene segments and the number (n value) of methylene groups. The longer the polymethylene segment the larger the difference in the two transition temperatures, the higher transition temperature (Tg,H) and lower transition temperature (Tg,L). For a polymer with even value of n, ΔTg (Tg,H minus Tg,L) of the anisotropic glass is lower than that for the neighboring two polymers with odd n values. In addition, the distortion effect of the polymethylene segment with even number of methylene groups on the polymer chains under polarization was studied by the Vogelian relaxation behavior of the ρ‐peak. These results indicated that the maximum fractional volume of the polymethylene segments of the anisotropic glass for a polymer with even n value would be smaller than that for a polymer with odd n value under polarization.
Synthesis of simple main‐chain type polyimides derived from aliphatic diamines and 4,4″‐terphenyltetracarboxylic acid, and their thermotropic liquid crystalline behavior
Authors: Inoue Tatsuo , Kakimoto Masa‐aki , Imai Yoshio , Watanabe Junji
Published: April 2003

We have synthesized a series of aliphatic‐aromatic polyimides by high pressure polycondensation of monomer salts derived from diaminoalkanes and diethyl 4,4″‐terphenyl‐tetracarboxylates. The polyimides, designated as P‐nTPE, were obtained with n, the number of methylene units in the spacer, ranging from 6 to 12. Among these, the P‐nTPE polyimides with 8⩽n⩽12 from mesophases. The mesophases of P‐8TPE and P‐11TPE are enantiotropic, whereas those of the other polyimides are monotropic. The nematic phase was identified for all polyimides from X‐ray and microscopic observations; only P‐11TPE exhibits polymorphism, in which a nematic phase is followed by a smectic phase upon cooling. The ability for liquid crystal formation in main‐chain polyimides is discussed.