bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal behaviour of highly stereoregular syndiotactic polypropene from homogeneous catalysts
Authors: Balbontin Giulio , Dainelli Dario , Galimberti Maurizio , Paganetto Guglielmo
Published: April 2003

Thermal characterization was carried out on highly stereoregular and regioregular syndiotactic polypropene (sPP) obtained with isopropylidene(cyclopentadienyl)(9‐fluorenyl)zirconium dichloride and methylaluminoxane. The influence of molecular weight and syndiotacticity degree on the thermodynamic melting point (T°m) of sPP were separately investigated by examining samples with a fully syndiotactic pentads content (rrrr) ranging from ca. 81% to ca. 94% and with an weight‐average molecular weight (M̄w) ranging from 9,6 · 104 to 17,3 · 104. Upon excluding any influence of the molecular weight, the correlation between the rrrr pentads content and the T°m of the samples led to the extrapolation of the thermodynamic melting point for a fully syndiotactic polypropene.
Synthesis of side‐chain liquid‐crystalline polyethers by chemical modification of polyepichlorohydrin
Authors: Piercourt Stéphane , Lacoudre Nelly , Borgne Alain Le , Spassky Nicolas , Friedrich Claude , Noël Claudine
Published: April 2003

Copolymers derived from polyepichlorohydrin (PECH), bearing pendant mesogenic units are obtained by chemical modification of atactic samples of PECH with sodium 4‐cyano‐4′‐biphenoxide. Rate and yield of substitution are strongly dependent on the molecular weight of the used PECH. A substantial rise (ΔT ∼ 110°C) of glass transition temperature with the percentage of incorporated cyanobiphenyl groups is observed. Copolymers with an amount of substitution higher than 60% present thermotropic liquid‐crystalline behaviour and form nematic phases. Chemical modification of PECH offers a simple method for the synthesis of new liquid‐crystalline polyethers whose transition temperatures can be adjusted by varying the amount of substitution.
Dynamics of the evolution of volatile products during laser‐induced polymer destruction
Authors: Kalontarov Lev I. , Marupov Rakhim , Bekmukhamedov Anvar T.
Published: April 2003

The dynamics of evolution of volatile products arising during destruction of poly(vinyl alcohol) and polyacrylnitrile films under the action of cw laser radiation were investigated by means of time‐of‐flight mass spectrometry. It was found that the evolution of volatiles occurs in two stages, one isothermal and the other nonisothermal. Depending on laser focusing and power, the nonisothermal stage comprises three dynamic regimes of desorption of volatile products: regime of single ejection, oscillating regime and chaotic behaviour of evolution. It is shown that the various regimes of desorption are due to inhomogeneity of laser heating and nonuniform propagation of the destruction wave from the centre of the laser beam to the periphery.
Synthesis of electrically conductive polypyrrole films by interphase oxidative polymerization
Authors: Nakata Masakazu , Shiraishi Yohtarou , Taga Megumi , Kise Hideo
Published: April 2003

Polypyrrole (PPy) films were synthesized by interface polymerization reactions between aqueous solutions of FeCl3 and solutions of pyrrole monomer in organic solvents. The polymerizations were studied using various organic solvents, and flexible and uniform PPy films were obtained using benzene or toluene as solvents. It was found that polymerization time and organic solvents strongly affect the thickness and conductivity of the films, but the atomic composition of the PPy films was independent of the reaction conditions. The mechanism of the film growth at the interface is discussed on the basis of film properties and the observation of the film surface using scanning electron microscopy.
Elementarprozesse der ziegler‐katalyse, 5. Lösungsmitteleinflüsse am Beispiel stereorigider Zirkonocen/methylaluminoxan Ziegler‐Katalysatoren
Authors: Herfert Norbert , Fink Gerhard
Published: April 2003

The syndiotactic propene polymerization was investigated by means of the Cs‐symmetric isopropylidene(fluorenyl)(cyclopentadienyl)zirconium dichloride/methylaluminoxane (iPr(Flu)‐(Cp)ZrCI2/MAO) catalyst system in toluene/methylene chloride solvent mixtures. The main result is that with increasing dielectric constant of the solvent mixture the polymerization rate increases linearly but the stereospecificity of the catalyst decreases strongly; this is revealed through a drastic decay of the rrrr‐pentads and of the melting point of the polymers. Hence, the stereospecificity of this catalyst system is connected with the existence of a polarized Zr‐CI‐AI‐complex (in toluene) or at least of a tight contact ion pair with a stereoregulating role of the counter ion. The loss of the stereospecifity in polar solvents is caused by an isomerization reaction of the solvent‐separated free zirconocene species via migration of the growing polymer chain before the next monomer insertion. But in the case of the isotactic catalyst system dimethyl‐silyl(bisindenyl)zirconium dichloride/methylaluminoxane (Me2Si(Ind)2ZrCl2/MAO) with a C2‐symmetric π‐ligand system the migration of the growing polymer chain in polar solvents causes no isomerization.
Radikalisch polymerisierbare Gallensäuren in Monoschichten, Mizellen und Vesikeln
Authors: Ahlheim Markus , Hallensleben Manfred L.
Published: April 2003

The synthesis of radically polymerizable derivatives of cholic acid containing a methacrylic group directly attached to C3 or via a C11 cinnamic ester spacer is described. The monomers form monolayers, vesicles and micells. Both in vesicles and in micells the monomers do not undergo neither photodimerization via the cinnamoyl group nor do they polymerize, but they photodimerize in an amorphous film and polymerize in isotropic solution.
Cation exchange resins based on phosphonomethyl‐substituted phenols
Authors: Kaiser Jürgen , Schied Bernd , Trautmann Norbert , Vogt Walter
Published: April 2003

Phosphonomethyl‐substituted phenols are readily obtained from o‐hydroxymethylated phenols and trialkyl phosphites. The free acids, incorporated into phenol‐formaldehyde resins, act as cation exchangers with remarkable selectivity for different metal ions.
Copolymerization of olefins with Kaminsky‐Sinn‐type catalysts
Authors: Uozumi Toshiya , Soga Kazuo
Published: April 2003

Copolymerizations of ethylene with propene, ethylene with 1‐hexene and propene with 1‐hexene were performed at 40°C under atmospheric using three kinds of Kaminsky‐Sinn‐type catalysts which differ in stereospecificity: Cp2ZrCl2‐methylaluminoxane (MAO) (aspecific); Et[IndH4]2 ZrCl2‐MAO (isopecific); i‐Pr(Cp)(Flu)ZrCl2‐MAO (syndiospecific).

The 13C NMR analysis of copolymers showed that the incorporation of higher olefins decreases in the following order: i ‐Pr(Cp)(Flu)ZrCl2‐MAO > Et[IndH4]2ZrCl2‐MAO > Cp2ZrCl2‐MAO, and that stereospecificity is retained even in the copolymerization.

The product of monomer reactivity ratios (r1 · r2) indicates that poly(propene‐co‐1‐hexene) is a statistically random copolymer whereas both poly(ethylene‐co‐propene) and poly(ethylene‐co‐1‐hexene) have somewhat alternating character regardless of catalyst stereospecificity.
Structural study of the aging and thermal evolution of polyiodide chains in doped trans‐polyacetylene
Authors: Albouy Pierre‐Antoine , Pouget Jean‐Paul , Halim John , Enkelmann Volker , Wegner Gerhard
Published: April 2003

The evolution of the structure of iodine chains in iodine‐doped polyacetylene has been followed as a function of temperature. It is shown that these chains exhibit a disorder of the second kind characterized by the lack of long‐range order in chain direction. A low‐temperature improvement of intra‐chain order demonstrates that a substantial part of this disorder is thermal in nature. A parallel is drawn to similar effects frequently observed in crystalline iodine chain organic charge transfer salts. Furthermore, fresh samples with a nominal composition CHI0,24 are unstable under the X‐ray beam. They exhibit a slow transition toward an apparently stable form corresponding to CHI0,19. The diffraction pattern in chain direction of this form can be quantitatively explained with a simple model using triiodide chains only. A comparison with other models proposed in the literature is made.
Ethylene polymerization on a high activity supported catalyst: MgCl2 (THF)2/TiCl4/AlEt2Cl
Authors: Nowakowska Maria , Bosowska Kornelia
Published: April 2003

A magnesium/electron donor complex was used as support for the synthesis of a titanium catalyst. By interaction of TiCl4 with MgCl2(THF)2 a highly active and stable catalyst for ethylene polymerization was obtained. The catalytic activity of the MgCl2(THF)2/TiCl4/AlEt2Cl system in the polymerization of ethylene was investigated as a function of Mg/Ti and Al/Ti mole ratios as well as the donor concentration in the system. Some kinetic studies of ethylene polymerization in the presence of this catalyst allowed us to determine the concentration of active centres (ca. 60 mol‐% of Ti), rate constants of elementary reactions (kp ≈ 92 dm3/(mol · s)) and kinetic equations. From these results it was possible to find further evidence for the role of the donor ligands in titanium catalysts supported on magnesium dichloride in the presence of Al‐alkyls as cocatalysts.
1‐Butene polymerization in the presence of MgCl2‐supported Ziegler‐Natta catalysts: polymer microstructure in relation to polymerization mechanism
Authors: Busico Vincenzo , Corradini Paolo , De Biasio Rosanna
Published: April 2003

1‐Butene polymerization in the presence of MgCl2‐supported Ziegler‐Natta catalyst systems was investigated under conditions such as to obtain polymer samples containing high amounts of (prevailingly) syndiotactic sequences. These were found in part to be linked to (prevailingly) isotactic sequences in stereoblock macromolecules. More clearly than in the case of the corresponding propene polymers, the spectroscopic characterization of the poly(1‐butene) samples proved that the syndiospecificity in such systems is dictated by the asymmetry of the last inserted monomer unit.
A novel route to poly(triarylcarbinols)
Authors: Zolotukhin Mikhail G. , Akhmetzyanov Shamil S. , Shishlov Nikolai M. , Latchinov Alexey N. , Sultanova Venera S. , Spirikhin Leonid V. , Khalilov Leonard M.
Published: April 2003

A novel scheme for a two‐stage synthesis of poly(triarylcarbino1)s is suggested. In the first stage, the homopolycondensation of 3‐(4‐biphenylyl)‐3‐chloro‐1,1 ‐dioxobenzo[c][1,2]‐oxathiolane (6a) via a Friedel‐Crafts reaction gives the polymeric arylene sulfophthalide 7. In the second stage, alkaline hydrolysis of the latter under mild conditions leads to linear, high‐molecular‐weight, film‐forming poly(triarylcarbino1) 8 containing sulfonate groups. The polymer films show photo‐ and thermochromism. The density of paramagnetic centres in 8 is < 1015 spins per gram, and increases on heating up to 1018 spins per gram, the initial value being restored after cooling and exposure to air.
Swelling behavior of hydrogels containing phosphate groups
Authors: Nakamae Katsuhiko , Miyata Takashi , Hoffman Allan S.
Published: April 2003

Hydrogels containing phosphate groups were prepared by copolymerization of 2‐methacryloyl‐oxyethyl dihydrogen phosphate (phosmer) and various hydrophilic monomers [N,N‐dimethyl‐acrylamide (DMAAm), acrylic acid (AAc) and 2‐hydroxyethyl methacrylate (HEMA)], and the swelling behavior was investigated. These hydrogels are thermo‐sensitive. Phosmer‐DMAAm and phosmer‐HEMA hydrogel deswell with increasing temperature, but for the phosmer‐AAc hydrogel the swelling ratio increases with temperature. Interestingly, the swelling ratio decreases with an increase in phosphate group content. This unusual behavior may arise from the phosphate group acting both as the functional group and the crosslinking agent.
Synthesis and thermotropic liquid‐crystalline properties of polyurethane‐polystyrene graft copolymers
Authors: Sato Moriyuki , Yanahara Masanobu , Kobayashi Takanori , Mukaida Ken‐ichi
Published: April 2003

New polyurethane‐graft‐polystyrenes (4) of well‐defined structures and compositions were synthesized by macromonomer technique and the structure‐liquid‐crystalline (LC) property relationship is discussed. The expected graft copolymers with polystyrene grafts were prepared by melt polycondensation of a mixture of a dihydroxy derivative of biphenyl as a mesogenic moiety (1) and a dihydroxy‐terminated styrene macromonomer (2) with diphenyl N,N′‐hexamethylenedi‐carbamate (3). Of the resulting polymers mesogenic unit‐rich graft copolymers retain the LC mesophases in spite of introduction of the polystyrene segments onto the polyurethane backbones and possess microphase‐separated structures. Polystyrene‐rich copolymers reveal no well‐defined LC mesophases and analogous thermal properties to the polystyrene segments.
Group transfer initiated polymerization of methyl methacrylate catalyzed by [((C6H5)3P)2N]+HF
Authors: Martin David T. , Bywater Stanley
Published: April 2003

Experments are reported on the group transfer polymerization of methyl methacrylate using a new bifluoride salt, bis(triphenylphosphoranylidene)ammonium hydrogendifluoride

Commonly abbreviated as PPN bifluoride (PPN HF2).

[((C6H5)3P)2N]+HF, as catalyst. Good molecular weight control was observed although a small deviation from the expected value was found. Side reactions of catalyst with initiator, and termination (cyclization) of the active centres at low monomer concentrations were investigated. The similarities between this method and classical anionic polymerization are discussed.
Synthesis of telechelic poly(p‐phenylene) derivatives
Authors: Kallitsis Joannis K. , Rehahn Matthias , Wegner Gerhard
Published: April 2003

The synthesis of oligo(2,5‐dialkyl‐p‐phenylene)s bearing terminal boronic acid, bromo‐,acetoxy‐, methoxycarbonyl‐ or carbonic acid groups is reported. Oligomers of number‐average degree of polymerization 6 ≤ Pn ≤ 20 were obtained by the palladium‐catalyzed coupling of aromatic halides with aromatic boronic acids. The same synthetic approach was used to prepare derivatives of p‐terphenyl, bearing hydroxy‐, acetoxy‐, carboxy‐ or amino‐groups in 4,4″‐position.
Synthesis and properties of polyesters derived from 2′,5′‐dialkyl‐p‐terphenyl‐4,4″‐diol
Authors: Kallitsis Joannis K. , Wegner Gerhard , Pakula Tadeusz
Published: April 2003

A series of polyesters based on 2′,5′‐dihexyl‐p‐terphenyl‐4,4″‐diol as one component and various aliphatic or aromatic diacids as the second component have been synthesized. The polyesters are soluble and film forming. Materials based on the terphenyldiol and terephthalic acid or the terphenyldiol and 2′,5′‐dihexyl‐p‐terphenyl‐4,4″‐dicarboxylic acid show a temperature dependence of the elastic modulus between 100 and 300°C resembling the behavior of hard elastic polymers, Glass transition phenomena in the conventional sense were not observed. The materials exhibit good mechanical properties up to temperatures well above 300°C.
Concerning the reaction of zirconocene dichloride and methylalumoxane: Homogeneous Ziegler‐Natta catalytic system for olefin polymerization
Authors: Cam Darinn , Giannini Umberto
Published: April 2003

The interaction of zirconocene dichloride (Cp2ZrCl2) with methylalumoxane (MAO), the two components of homogeneous catalyst for olefin polymerization, was studied by 1H NMR spectroscopy. Its was found that Cp2ZrCl2 is monoalkylated by Al2(CH3)6 present in MAO. The trimethylaluminium contained in MAO appears to be the active species in the alkylation of the zirconocene dichloride. The Cp2ZrCH3Cl likely forms, with an excess of MAO, highly polarized species. These are decomposed by a complexing agent of MAO such as KCl.
Helical amylose complexes with organic complexands, 1. Microcalorimetric and circular dichroitic investigations
Authors: Wulff Günter , Kubik Stefan
Published: April 2003

Complexation of different synthetic amyloses (Pn between 9 and 1000) with sodium dodecyl sulfate and 4‐tert‐butylphenol was investigated by means of microcalorimetry and circular dichroism. The results were compared with the complexation behaviour of α‐, β and γ‐cyclodextrins with the same guest molecules. All amyloses investigated formed complexes with sodium dodecyl sulfate in a fast reaction. In these complexes the amyloses possess a helical conformation with six glucose units per turn, which should already exist in aqueous solution before complexation. tert‐Butylphenol only forms complexes with amyloses of a Pn higher than 100. In this case apparently the amylose must adjust to complex the tert‐butylphenol in a helix with seven or eight glucose units per turn. Using these methods the complexation of sodium dodecyl sulfate with amylopectin was also demonstrated.
Cationic polymerization of 1,2‐epoxy‐3‐nitropropane in the presence of ethylene glycol, 3 Determination of the mechanism
Authors: Lagarde Florence , Reibel Leonard , Franta Emile
Published: April 2003

Cationic polymerization of 1,2‐epoxy‐3‐nitropropane was performed in the presence of ethylene glycol and borontrifluoride etherate under conditions meant to favor the Activated Monomer Mechanism. In two previous papers, we showed that the Activated Monomer Mechanism prevails until the number‐average molecular weight M̄n reaches a value of about 350. In this article, we show that beyond this value another mechanism competes effectively with the latter one: oxygen atoms of the oligomeric chains react with the protonated monomer leading to the formation of non‐cyclic tertiary oxonium ions. These ions may react with various nucleophiles during polymerization or upon deactivation, which explains the M̄n limitation as well as the excess of hydroxyl groups observed.
Copolymerization of 2,2‐dimethyltrimethylene carbonate with 2‐allyloxymethyl‐2‐ethyltrimethylene carbonate and with ε‐caprolactone using initiators on the basis of Li, Al, Zn and Sn
Authors: Kühling Steffen , Keul Helmut , Höcker Hartwig
Published: April 2003

The homopolymerization of 2,2‐dimethyltrimethylene carbonate (1), 2‐allyloxymethyl‐2‐ethyl‐trimethylene carbonate (2) and ε‐caprolactone (3) with sec‐butyllithium (sec‐BuLi), tri‐sec‐butoxyaluminium (Al(O‐secBu)3), diethylzinc (ZnEt2) and dibutyldimethoxytin ((Bu)2Sn(OMe)2) in toluene at 80°C results in a reaction product consisting of a high‐mole‐cular‐weight polymer and a homologous series of oligomers. The weight ratio polymer/oligomers, under standardized conditions, depends on the type of initiator. The sequence of monomeric units in the copolymers is statistical, for all initiators used. For sec‐BuLi and Bu2Sn(OMe)2 the distribution arises both from random addition of the monomers to the active chain end and from transesterification, while with Al(O‐secBu)3 and ZnEt2 the addition of the monomers is non‐selective.

For poly[(2,2‐dimethyltrimethylene carbonate)‐stat‐(2‐allyloxymethyl‐2‐ethyltrimethylene carbonate)] the carbonyl region of the 13C NMR spectrum is suitable for diad analysis, for poly[(2,2‐dimethyltrimethylene carbonate)‐stat‐(ε‐caprolactone)] the methyleneoxy region is most indicative. The assigment of the diads was made on the basis of model compounds.
Photoreactive chiral liquid‐crystalline side‐group copolymers containing azobenzene mesogens
Authors: Ringsdorf Helmut , Urban Claus , Knoll Wolfgang , Sawodny Michael
Published: April 2003

A series of liquid‐crystalline copolymers 1 with a chiral azobenzene moiety as photoreactive mesogenic unit was prepared. The polymers were fractionated and the mesophase behaviour of the high‐ and low‐molecular weight fractions was examined. The copolymers display smectic A and cholesteric phases. For the cholesteric phases the pitch of the helix was determined, which ranges from 3 to 20 μm. Stable monolayers at the air‐water interface were obtained from two monomers and one of the homopolymers. Multilayer assemblies of the azobenzene‐containing polymers can be used to study photo‐induced order/disorder transitions.
Functional polysiloxanes with benzophenone side‐groups: a photochemical application as radical polymerization macroinitiators
Authors: Pouliquen Lydie , Coqueret Xavier , Lablache‐Combier Alain , Loucheux Claude
Published: April 2003

Functional siloxane copolymers containing one or more ester groups derived from 2‐benzoyl‐benzoic acid (2‐BBA), 4‐dimethylaminobenzoic acid (4‐DMABA) or acrylic acid, were synthetized. These polymers were employed to prepare novel photo‐initiating systems based on the phenone/tertiary amine photogeneration of radicals. The influence of nature and relative amount of functional pendant units on the overall efficiency of the system mixed with an acrylate‐based composition was examined by quantitative IR spectroscopy. By comparing the different polymeric systems to the low‐molecular‐weight analogues, one observes a neat polymer effect inducing a greater initiation efficiency, especially when a polysiloxane containing only 2‐BBA ester groups is associated to free 4‐DMABA esters in the photosensitive composition.
Etude des propriétés microlithographiques d'une résine siliciée renfermant en mélange le poly(p‐triméthylsiloxystyrène) et le sel (C6H5)3SAsF6
Authors: Bonfils Frédéric , Giral Louis , Montginoul Claude , Sagnes René , Schué François
Published: April 2003

The study of a photoresist containing poly(p‐trimethylsiloxystyrene) (1, poly[1‐(4‐trimethyl‐siloxyphenyl)ethylene]) mixed with (C6H5)3SAsF6, which could be employed in a bilevel pattern‐transfer process, is reported. The onium salt undergoes efficient photolysis under UV radiation, to generate strong acids, responsible of the cleayage of the silicon‐containing side groups. The first results obtained show that this kind of resist could be used in microlithography, because it displays a very good sensitivity to deep UV and an excellent resistance to oxygen plasma. The syntheses of the compounds and substances used in this work are described.
Synthesis, polymerization, copolymerization, and transition‐metal coordination of 4‐(2,2′:6′,2″‐terpyridin‐4′‐yl)styrene and its polymers and copolymers
Authors: Hanabusa Kenji , Nakamura Atsushi , Koyama Toshiki , Shirai Hirofusa
Published: April 2003

Homopolymer 5 from 4‐(2,2′:6′,2″‐terpyridin‐4′‐yl)styrene (4) and copolymers 6–8 from 4 and styrene, vinyl acetate, or acrylic acid were prepared by radical‐initiated polymerization with 2,2′‐azoisobutyronitrile. These polymers containing pendent 2,2′:6′,2″‐terpyridinyl ligands readily formed monotridentate complexes with FeCl2, NiCl2, and CuCl2. By reaction of copolymer 6 with 4′‐(p‐tolyl)‐2,2′:6′,2″‐terpyridyliron(III) trichloride or 4′‐(p‐tolyl‐2,2′:6′,2″‐terpyridylruthenium(III)) trichloride in the presence of ammonium hexafluorophosphate yielded polymer‐metal complexes 11a, 11b containing the corresponding bistridentate complexes. A cyclic voltammogram of 11a containing a bis(2,2′:6′,2″‐terpyridyl)iron(II) complex showed characteristic Fe2+/Fe3+ redox couples at + 1,12 V vs. saturated calomel electrode, which was also observed as a reversible color change between purple and colorless.
Block copolymers of narrow molecular‐weight distribution with a side‐chain liquid‐crystalline polymeric block as one component
Authors: Kodaira Toshiyuki , Mori Kazumi
Published: April 2003

Syntheses of block copolymers have been undertaken by photo‐polymerization of 6‐{4‐[4‐(butoxyphenoxy)carbonyl]phenoxy}hexyl methacrylate (1) using the living propagating chain end of poly(methyl methacrylate) as an initiating species. The latter was derived from photo‐polymerization of methyl methacrylate (MMA) in the presence of methyl(5,10,15,20‐tetraphenylporphinato)aluminium. The polymerization of 1 proceeded from the propagating end of poly(MMA) with high blocking efficiency to produce poly(MMA)‐block‐poly(1) with narrow molecular‐weight distribution. The length of the block chain could be controlled by varying the amounts of monomers. An endothermic peak of the block copolymer with higher mass of liquid‐crystalline chain was observed at almost the same temperature region as that of poly(1) on differential scanning calorimetric analyses, which suggests that the former has a structure with microphase separation.
Thermodynamics of norbornene, of its polymerization process and of polynorbornene from 0 to 400 K at standard pressure
Authors: Lebedev Boris , Smirnova Natal'ya , Kiparisova Yelena , Makovetsky Kirill
Published: April 2003

Thermodynamic properties of norbornene

System: name: bicyclo[2.2.1]hept‐2‐ene.

and polynorbornene, viz. isobaric heat capacity of the monomer and polymer between 10 and 330–400 K, parameters of physical transitions of the monomer and polymer, and energy of combustion for the polymer were studied by means of precise adiabatic and isothermal calorimetry. From the experimental data, the thermodynamic functions H°(T)–H°(0), S°(T) and G°(T)–H°(0) in the range of 0 to 330–400 K as well as enthalpies of combustion and thermochemical quantities of formation ΔH, and ΔS for polynorbornene were calculated. The results were used to calculate enthalpies, entropies and Gibbs functions of bulk polymerization for norbornene between 0 and 330 K and to evaluate the ceiling temperature of polymerization.
Effects of procatalyst composition on the stereospecificity of a Ziegler‐Natta catalyst system
Authors: Chadwick John C. , Miedema Arjen , Ruisch Bart J. , Sudmeijer Olof
Published: April 2003

In propylene polymerization with MgCl2/TiCl4/phthalate ester catalysts, using 2,2,6,6‐tetramethylpiperidine as external donor, it has been found that the fraction of atactic polymer formed increased with decreasing ester content in the catalyst. At the same time, however, the stereoregularity of the isotactic polymer fraction, as measured by 13C NMR, increased. Polymerization in the absence of the external donor led to lower polymer yield and a lower stereoregularity of the isotactic fraction. The results indicate that the external donor is actively involved in the generation of isospecific sites, particularly in catalysts having relatively low ester contents.
Gas permeation through two side‐chain liquid‐crystalline polyacrylate‐based membranes containing 4‐methoxyphenyl 4‐hexyloxybenzoate or 4‐cyanophenyl 4‐hexyloxybenzoate mesogenic side groups
Authors: Chen Deng‐Shan , Hsiue Ging‐Ho , Hsu Chain‐Shu
Published: April 2003

Two kinds of side‐chain liquid‐crystalline (LC) polymers with different side‐chain mesogenic end groups were synthesized. The laminated membrane was prepared by sandwiching the side‐chain LC polymer between two porous polypropene (Celgard) films. Permeation properties for O2, N2, CO2 and CH4 through the laminated side‐chain LC polymer‐based membranes were measured using a gas‐chromatographic method at several temperatures corresponding to the stability range of the different phases of the side‐chain LC polymers. The gas permeation behaviour depends strongly on the state of the side‐chain LC polymer. The activation energy for permeation depends on the state, too. The plot of separation factor P/P versus P exhibits an unusual behaviour. P/P increases with P when the temperature rises and the phase of the side‐chain LC Polymer changes from the glassy state to the liquid‐crystalline state. The magnitude of gas permeability coefficients for the laminated membranes is rather low compared to those of some common polymers. The low gas permeability seems to originate from the low gas solubility rather than from the low gas diffusivity in the laminated side‐chain LC polymer membrane.
Arylpropenoates as photoactive units in photocontrollable polymers
Authors: Proctor Andrew D. , Gilbert Andrew , Mitchell Geoffrey R.
Published: April 2003

The synthesis of photochemical properties of a range of arylpropenoates are described and their suitability as photoactive units for the reversible manipulation of polymer properties assessed. The Z and E isomers of the 1‐naphthyl‐, 1‐(4‐methoxynaphthyl)‐ and 9‐phenanthryl‐ derivatives have sufficiently different absorption characteristics to allow their selective exciation to give photostationary states having high concentrations of each isomer. Incorporation of the photoactive units into methacrylate based polymers changes the photostationary state concentrations of the Z and E isomers but the effect on the 1‐(4‐methoxynaphthyl)‐derivative is small and here the photointerconversion is not accompanied by fatigue. The 9‐anthryl derivative undergoes facile (4π + 4π) photodimerization and this may have potential as a reversible crosslinking mechanism.
Synthesis and photosensitized homo‐ and block copolymerization of a bisphenol‐A derivative of dibenz[b, f]azepine
Authors: Alimoglu Ali K. , Bamford Clement H. , Ledwith Anthony , Yagci Yusuf
Published: April 2003

A bisphenol‐A derivative of dibenz[b,f]azepine (DBA‐Bisphenol‐DBA) was synthesized and characterized. Sensitized photopolymerization of the DBA‐Bisphenol‐DBA was studied in detail. The usefulness of N‐acyldibenz[b,f]azepine groupings in promoting photochemically induced linking of the related molecules is further demonstrated by block copolymerization of DBA‐Bisphenol‐DBA and polystyrene having terminal dibenz[b,f]azepine substituents. Those reactions arise through benzophenone‐sensitized photocyclodimerization of the central double bond of the dibenz[b,f]azepine moieties.
Reactivity of individual stereoisomers based on 4‐(3‐buten‐1‐ynyl)‐1,2,5‐trimethyl‐4‐piperidinol in radical polymerization
Authors: Aliev Nysanly U. , Kurmanaliev Oraz Sh. , Shaikhutdinov Erengaip M. , Kudaibergenov Sarkyt E. , Bekturov Esen A.
Published: April 2003

The radical polymerization of individual stereoisomers of 4‐(3‐buten‐1‐ynyl)‐1,2,5‐trimethyl‐4‐piperidinol (1) was investigated. The reaction order with respect to the monomer and the initiator, and also the kinetic and energetic parameters of the polymerization reaction were determined. The values of constants of polymerization of the stereoisomers were found with the help of the “rotating sector” method. It was established that the spatial orientation of the reactive centres with respect to the six‐membered heterocycle influences the reactivity of the monomers and leads to a change of the polymerization rate of the stereoisomers by a factor of about 1,5 to 3. To ascertain the influence of the spatial structure on the reactivity of the stereoisomers, quantum chemical calculations for model structures were performed. By means of IR and Raman spectroscopy it was established that the polymerization of 1 occurs via the double bond of the 3‐buten‐1‐ynyl groups.
Reactivity in radical and anionic copolymerizations of 4‐(trimethylsilyl)styrene. Synthesis of soluble poly{(1,4‐divinylbenzene)‐co‐[4‐(trimethylsilyl)styrene]}
Authors: Nagasaki Yukio , Han Sang Bong , Kato Masao , Tsuruta Teiji
Published: April 2003

Radical copolymerization of 4‐(trimethylsilyl)styrene (TMSS) with styrene were carried out to estimate the reactivity of TMSS. The monomer reactivity ratios r1 and r2 in the radical copolymerization of TMSS (M1) with styrene (M2) were evaluated as 0,28 and 0,48, respectively. The value r1 · r2 (= 0,13) being smaller than unity indicates that the trimethylsilyl group at para position behaves as an electron‐withdrawing substituent. Reactions of lithium diethylamide with TMSS in the presence of diethylamine, gave the 1:1 addition product 1‐[2‐(N,N‐diethylamino)‐ethyl]‐4‐(trimethylsilyl)benzene. Kinetic analysis showed that the second‐order rate constant (k) for this addition reaction is 34,4 · 10−4 dm3 · mol−1 · s−1, which is by a factor of 2 larger than that for the reaction with styrene (k = 16,0 · 10−4 dm3 · mol−1 · s−1). The fact is also compatible with the above consideration for the r1 · r2 values. Lithium diisopropylamide initiated anionic copolymerizations of TMSS with 1,4‐divinylbenzene (DVB) were also examined. The polymerizations proceed smoothly without any gel formation and the resulting copolymers are soluble in various common solvents such as benszene, tetrahydrofuran, chloroform, etc. Thus, novel organosilicon‐containing polymers having appropriate amounts of reactive pendent vinyl groups are easily synthesized.
MgCl2‐supported Ziegler‐Natta catalysts: A structural investigation by X‐ray diffraction and Fourier‐transform IR spectroscopy on the chemical activation process through MgCl2‐ethanol adducts
Authors: Di Noto Vito , Zannetti Roberto , Vivani Maria , Marega Carla , Marigo Antonio , Bresadola Silvano
Published: April 2003

By X‐ray diffraction on polycrystalline powders and Fourier‐transform IR spectroscopy, some adducts MgCl2(C2H5OH)x were studied, having different composition in the range from x = 0 (α‐MgCl2) to x = 6. For 2 < x ≤ 6, the structure of such adducts shows prevalently ionic MgCl bonds. For x ≤ 2, covalent bonds are observed among chlorine and magnesium atoms, which give rise to chain compounds through chlorine bridges among the Mg‐atoms. The obtained structural data are also discussed in terms of the synthesis of some MgCl2‐based supports which are very active in the Ziegler‐Natta process of olefin polymerization, after a treatment with titanium halides and a successive addition of a cocatalyst and of other suitable donors.
Polymerization of olefins with the catalyst system (RCp)TiCl3 (R = H, CH3)/SiO2‐common alkylaluminium activated with a suitable Lewis acid
Authors: Soga Kazuo , Lee Dong Hee
Published: April 2003

The silica‐supported catalyst (RCp)TiCl3 (R = H, CH3; Cp = cyclopentadienyl) was prepared by reaction of (RCp)TiCl3 with silica gel. The resulting catalyst combined with common alkylaluminium as cocatalyst does not show any activity for olefin polymerization. However, the catalyst system is easily activated by adding a strong Lewis acid like (C6H5)3C·B(C6F5)4. Polymerization of propene and ethylene‐propene copolymerization with this catalyst system gives atactic polypropene with frequent chemical inversion and a random copolymer whose structure is very similar to that produced with a homogeneous vanadium catalyst system, respectively.
1H NMR study of the kinetics of metathesis polymerization of 5‐ and 5,6‐methoxycarbonyl derivatives of bicyclo[2.2.1]‐hept‐2‐ene, initiated by
Authors: Ivin Kenneth J. , Kress Jacky , Osborn John A.
Published: April 2003

The ring‐opening metathesis polymerization of 5‐endo‐methoxycarbonyl (1), 5‐exo‐methoxy‐carbonyl (2), 5,6‐endo,endo‐bis(methoxycarbonyl) (3), 5,6‐exo,exo‐bis(methoxycarbonyl) (4) and 5,6‐endo,exo‐bis(methoxycarbonyl) (5) derivatives of norbornene, initiated by the tungsten cyclopentylidene complex , have been followed by 1H NMR in situ at 290 – 320 K. The initial metal‐carbene adduct P1 is usually distinguishable from the subsequent adducts Pn(n > 1). Initiation is generally faster than or as fast as propagation. The propagation rate constants for the monosubstituted derivatives 1 and 2 are two to four times greater than those for the 5,6‐disubstituted derivatives 3–5. Arrhenius parameters were determined for the propagation reactions of 1 and 3.
Preparation of polyaniline by oxidation of aniline using H2O2 in the presence of an iron(II) catalyst
Authors: Moon Doo Kyung , Osakada Kohtaro , Maruyama Tsukasa , Yamamoto Takakazu
Published: April 2003

Oxidative polymerization of aniline using the H2O2‐FeSO4 system gave polyaniline under mild conditions. The prepared powdery emeraldine base, a form of polyaniline, is blue black and shows high solubility in organic solvents (e.g., ca. 200 mg/mL in N‐methylpyrrolidone). The number‐average molecular weight (Mn) of the polymer obtained was 1,3–1,7 · 104 (via gel permeation chromatography vs. polystyrene) and Mw/Mn = 1,6–2,2. Poly(2‐ethylaniline) and poly‐(2‐propylaniline) with high molecular weights were also synthesized by this procedure in high yield.
Thermotropic liquid‐crystalline aromatic‐aliphatic polyimides, 1. Novel poly(imide‐carbonate)s containing pyromellitimide ring
Authors: Sato Moriyuki , Hirata Tomohiro , Mukaida Ken‐ichi
Published: April 2003

Semi‐rigid poly(imide‐carbonate)s with high inherent viscosities were synthesized in high yields by melt polycondensation of the monomer, N,N′‐bis(6‐hydroxyhexyl)pyromellitdiimide and/or 6,6′‐(4,4′‐biphenylylenedioxy)dihexanol with alkylene bis(phenyl carbonate)s (m = 6, 8, 10 and 12). The monomer was prepared by deacetylation of an intermediate diacetylated compound derived from the condensation of pyromellitic dianhydride with 6‐aminohexanol followed by cyclization with acetic anhydride. The resulting polymers were characterized by FTIR and 13C NMR measurements and elemental analyses. The thermal and mesomorphic properties were evaluated by polarizing microscope observation, DSC measurements and powder X‐ray analyses. The polymers showed very good solubilities in organic solvents such as chloroform and 1,4‐dioxane. Flexible and tough films were cast from the chloroform solutions. All the polymers have low glass transition temperatures below room temperature which decreased with increase of the aliphatic spacer lengths. Most of the polymers display no thermotropic liquid‐crystalline properties, but only the biphenyl unit‐rich copolymer exhibits a nematic melt. It is suggested that the mesogenic character of the pyromellitimide ring is very low.
Propene polymerization with δ‐TiCl3/AlCl(C2H5)2 and δ‐TiCl3/Al(C2H5)3 catalyst systems, 1. Effect of external donors
Authors: Coutinho Fernanda , de Santa Maria Luiz Claudio
Published: April 2003

The effect of ethyl benzoate (EB), diisobutyl phthalate (DIBP), dibutyl ether (DBE) and triethoxy(phenyl)silane (EPS) as third components on the propene polymerization with the catalyst systems δ‐TiCl3/AlCl(C2H5)2 and δ‐TiCl3/Al(C2H5)3 was investigated. The influence of external donors on the isotacticity, catalyst activity and average molecular weight (Mv) was tested. If external donors are employed, Mv decreases, the insoluble fraction in boiling isooctane increases and the catalyst activity is strongly influenced by the mole ratio external donor/TiCl3. The results indicate that all external donors employed have the same qualitative effect on catalytic active centers.
End‐functionalized polymers of p‐alkoxystyrenes by living cationic polymerization, 2.p‐tert‐butoxystyrene
Authors: Shohi Hajime , Sawamoto Mitsuo , Higashimura Toshinobu
Published: April 2003

A series of end‐functionalized polymers of p‐tert‐butoxystyrene (tBOS), with an acetoxy, an ethyl malonate, or a methacryloxy group, were synthesized by living cationic polymerization with the use of hydrogen iodide/zinc iodide (HI/ZnI2) as initiating system: XCH2CH2OCH(CH3)‐(tBOS)nOCH3 (4) [X:(C2H5OCO)2CH (4a); CH3COO (4b)]; H(tBOS)nOCH2CH2Z (8) [Z: OCOC(CH3)CH2 (8a), OCOCH3 (8b)]. For the synthesis of these polymers, the following two methods were employed: (i) living polymerization of tBOS initiated with a functional vinyl ether‐hydrogen iodide adduct 2 [XCH2CH2OCH(CH3)I] in conjunction with ZnI2 to give “αend”‐functional polymers 4 and (ii) quenching the HI/ZnI2‐initiated living poly(tBOS) with a functional alcohol 7[HOCH2CH2Z] to give “ωend”‐functional polymers 8. All these polymers were shown to possess controlled molecular weights (number‐average degree of polymerization DPn=[tBOS]0/[initiator]0), narrow molecular weight distributions (Mw/Mn < 1,1), and end‐functionalities close to one. The end groups of the polymers 4a and 4b were converted into carboxy (5a) and hydroxy (5b) functions.
A novel synthetic route to rigid‐rod polyimides
Authors: Helmer‐Metzmann Freddy , Rehahn Matthias , Schmitz Ludwig , Ballauff Matthias , Wegner Gerhard
Published: April 2003

A new synthetic approach to soluble, rigid‐rod, aromatic polymides is described. The polycondensation is done by a Pd‐catalyzed aryl‐aryl coupling of N,N′‐bis(4‐bromo‐2,5‐didodecyl‐phenyl)‐1,2:4,5‐pyromellitic diimide (2) and 2,5‐didodecyl‐1,4‐benzenediboronic acid (3). Here, the imide structure is already preformed in monomer 2. A structurally identical polymer is synthesized by the classical procedure condensing 1,2:4,5‐pyromellitic dianhydride (PMDA) (4) and 4,4″‐diamino‐2,5,2′,5′,2″,5″‐hexadodecyl‐p‐terphenyl (5). Both polymers are characterized in detail by 1H and 13C NMR spectroscopy, membrane osmometry and size exclusion chromatography. The average degree of polycondensation is of the order of 15. The thermal behaviour of the polymers is studied by differential scanning calorimetry and thermogravimetrical analysis.
1H NMR investigation of some aromatic copolyester
Authors: Abis Luigi , Po' Riccardo , Spera Silvia , Bachilega Giancarlo , Occhiello Ernesto , Garbassi Fabio
Published: April 2003

The microstructure of aromatic copolyesters prepared by bulk polymerization was investigated by means of 1H NMR spectroscopy. The aromatic region of the spectra appears to be sensitive to the sequence distribution of aromatic rings. Line shape simulation and resolution enhancement of the time domain spectra with a Gaussian window function allow a quantitative evaluation of the relative intensities. Sequence distribution in terms of triads and diads formed by aromatic rings was then derived and compared with the one calculated on the basis of a random distribution. The results show that the distribution, as expected for this class of copolymers, is random.
Liquid‐crystalline polyethers and copolyethers of 4‐hydroxy‐acetophenone azine with a homologous series of flexible methylene spacers
Authors: Cimecioglu A. Levent , Weiss R. A.
Published: April 2003

The synthesis of high‐molecular‐weight polyethers and copolyethers based on 4‐hydroxyacetophenone azine and α,ω‐dibromoalkanes was carried out in N‐methyl‐2‐pyrrolidone via Williamson etherification using the caesium salt of the diol. Polyethers were composed of a homologous series of flexible methylene spacers with m = 5−12, while the copolyethers contained a 1:1 mole ratio of two different spacers with m = 5/7, 6/8, 7/9, 8/10, 9/11 and 10/12. Polymers with relatively short spacers (m = 5−8 methylene groups) exhibit enantiotropic mesomorphism, whereas those having m = 8−11 are tentatively identified to be monotropic. The polyether with m = 12 is crystalline. Copolyethers are enantiotropic and their mesophase ranges are considerably wider than those of the homopolyethers. The mesophases were identified to be nematic by polarised light microscopy. The transition temperatures of both the homopolymers and copolymers show classical even‐odd variations as a function of the spacer length.
Studies on the polymerization of ethylene using a high‐yield MgCl2‐supported titanium catalyst, 1. Effects of synthesis parameters on catalyst activity and polymer properties
Authors: Fuhrmann Hans , Bredereck Hartmut , Pracht Heinz
Published: April 2003

The preparation of a highly active Ti‐Mg catalyst in two steps is reported. the first step is a Grignard reaction conducted in hexane with an under‐stoichiometric amount of tetrahydrofuran. In the second step the Grignard suspension is treated with a TiCl4/CCl4 mixture. Owing to optimized synthesis conditions after a thermal activation the catalyst suspension is ready for use in combination with an alkylaluminium cocatalyst without further separation and drying operations. Because of its high response to H2 the catalyst may preferably be used for the production of polyethylene (PE) for injection moulding. Depending on the Ti content the catalyst shows an activity of between 184 and 250 kg PE per g Ti per h and per bar for a PE with melt flow index between 20 and 30 g/10 min. The content of Ti4+ in the catalyst is high (up to 72 wt.‐%). The catalyst suspension shows a marked resistance against reduction by the cocatalyst. The catalytic activity not only depends on the mole ratio of the individual catalyst components but even more on their actual concentration in the reaction medium.
Polymeric phthalocyanines and their precursors, 17. Structure and photoelectrochemical properties of thin films of polymeric phthalocyanines from bridged diphthalonitriles
Authors: Yanagi Hisao , Wada Minoru , Ueda Yasukiyo , Ashida Micho , Wöhrle Dieter
Published: April 2003

Thin films of polymeric phthalocyanines 4a–c were prepared by in‐situ syntheses from oxy‐and phenoxy‐bridged diphthalonitriles 3a–c with copper layers deposited on Ti plates and KCI crystals. The structure of the polymers was characterized by VIS, IR and photoelectron spectra, and scanning electron microscopy. The most uniform structure was obtained for polymer 4c, in which phthalocyanine rings were linked two‐dimensionally by flexible bridges of phenoxy groups. Polymers 4a and 4b are structurally not uniform, and formation of phthalocyanine rings was incomplete especially in polymer 4a. Photoelectrochemical properties of polymeric phthalocyanine electrodes were investigated in Ti/4a–c/Fe(CN)63−/4−/Pt cells. The electrode of 4a shows n‐type semiconducting behavior under illumination. The current‐voltage curve for the electrode of 4b did not show remarkable rectification or photocurrents. On the other hand, cathodic photocurrents were obtained for the electrode of 4c, indicating a p‐type semiconducting behavior under illumination. The photoelectrochemical properties were related to the structural uniformity of the polymers.
Polymerization of monomers containing functional silyl groups, 12. Free‐radical polymerization of 2‐silyl‐substituted 1,3‐butadienes
Authors: Takenaka Katsuhiko , Hirao Akira , Nakahama Seiichi
Published: April 2003

Free‐radical polymerizations of five 2‐silyl‐substituted 1,3‐butadienes, 2‐trimethoxysilyl‐1,3‐butadiene (1), 2‐triisopropoxysilyl‐1,3‐butadiene (2a), 2‐[diisopropoxy(methyl)silyl]‐1,3‐buta‐diene (2b), 2‐[isopropoxy(dimethyl)silyl]‐1,3‐butadiene (2c), and 2‐trimethylsilyl‐1,3‐butadiene (3), were carried out in bulk. Considerable amounts of Diels‐Alder dimers as well as polymers were obtained at 80°C with AIBN as an initiator. Formation of the dimer was suppressed completely at 15°C with a redox type initiator, a combination of benzoyl peroxide and N,N‐dimethylaniline. In these cases, the polymerization rates were extremely low, resulting in low polymer yield, at most 50%. The microstructures of the resulting polymers were predominantly E‐1,4, regardless of the polymerization conditions and the substituents at the silicon atom. The results of copolymerizations of silyl‐butadienes (M1) and styrene (M2) show that the former monomers have higher reactivity than the latter (r1 = 4,1 − 2,2;r2 = 0,4 − 0,5). The r1 values decrease with an increase in the number of methyl groups at the silicon atom.
Synthesis of polystyrene‐poly(tert‐butyl acrylate) diblock copolymers bearing fluorescent groups at the junctions
Authors: Hruska Zdenek , Vuillemin Bruno , Riess Gérard , Katz Aviva , Winnik Mitchell A.
Published: April 2003

AB‐type diblock copolymers composed of polystyrene as the A block and poly(tert‐butyl acrylate) as the B block were synthesized by sequential anionic polymerization. 1‐(2‐Anthryl)‐1‐phenylethylene, a new fluorescent monomer, and 1‐(9‐phenanthryl)‐1‐phenylethylene were used to introduce fluorescent moieties at the block junctions. Ultraviolet (UV) spectroscopy and gelpermeation chromatography (GPC) analyses were used to characterize the prepared copolymers.
Synthèse de polyquinazolones à chaîne latérale fluorée
Authors: Boutevin Bernard , Ranjalahy‐Rasoloarijao Laurent , Rousseau Alain , Garapon Jacques , Sillion Bernard
Published: April 2003

Bis(4H‐3,1‐benzoxazin‐4‐one) substituted in 2‐ and 2′‐position with CH2CH2RF, where RF is a perfluorinated alkyl group, have been prepared. Polycondensation with 4,4′‐oxydianiline and with 4,4′‐methylenedianiline led to polyquinazolones which have different inherent viscosities according to the solvent of polycondensation and to the proportions of reactants used. The thermal behavior of these polymers characterized by differential scanning calorimetry or thermogravimetry was studied. The polyquinazolones are thermostable and exhibit a fluorine content of 50 mass‐%.